Type II diabetes mellitus (T2DM) is a condition that is characterised by chronically elevated blood glucose. Research indicates that exercise interventions involving aerobic, resistance-training, combined-training and alternative modalities are all useful in the prevention and treatment of T2DM, although exercise programs should be tailored to the individual’s specific comorbidities and risk of injury.
- 1 CONTENTS
- 2 What is type II diabetes?
- 3 How can we determine the presence of T2DM?
- 4 What is the prevalence of T2DM?
- 5 What is the incidence of T2DM?
- 6 What are the problems with untreated T2DM?
- 7 What are the risk factors for T2DM?
- 8 What is the economic burden of T2DM?
- 9 Is aerobic exercise useful for the treatment of T2DM?
- 10 Is resistance training useful for the treatment of T2DM?
- 11 Is combined training useful for the treatment of T2DM?
- 12 Are alternative exercise interventions useful for the treatment of T2DM?
- 13 What are the effects of exercise on glycaemic control?
- 14 Are combined exercise and lifestyle interventions useful for the treatment of T2DM?
- 15 What long term effect does exercise have in T2DM?
- 16 What have reviews of exercise interventions for T2DM found?
- 17 Evidence-based recommendations for exercise
- 18 Conclusions
- 19 References
What is type II diabetes?
Type II diabetes mellitus (T2DM) is a condition that is characterised by chronically elevated blood glucose (hyperglycaemia) due to inadequate insulin secretion relative to the body’s need. The pathophysiology of the disease results from a combination of impaired insulin secretion due to insulin resistance in the liver and beta-cell damage and insulin resistance in the muscle tissue (Bock et al. and Defronzo). The development of T2DM seems to be closely related with the development of obesity, coinciding with a genetic predisposition for beta cell dysfunction (Kahn, 2003).
How can we determine the presence of T2DM?
T2DM is usually diagnosed by the level of glucose in the blood after a night fast in the morning (i.e. fasting blood glucose or FBG), in response to an oral glucose tolerance test (OGTT) where a glucose load is administered and the blood glucose is measured usually 2 hours after, or determined by the average blood sugar of the last 2 – 3 months measured as the percentage of glucose bound to haemoglobin (A1C). The definitions of T2DM using each of these tests are shown in the following table:
|Normal||<100 mg/dL or <5.6 mmol/L||2hrs <140 mg/dL or 7.8 mmol/L||<6.4%|
|Pre-diabetes||100 – 125mg/dL or 5.6 – 6.9 mmol/L||141 – 199mg/dL or 7.9 – 11mmol/L||5.7 – 6.4%|
|Diabetes||>126mg/dL or 7.0mmol/L||>200mg/dL or 11.1mmol/L||>6.5%|
What is the prevalence of T2DM?
Various researchers have assessed the prevalence of T2DM including world population data and specific to country and ethnic race. In 2008, there were 250 million T2DM sufferers worldwide, with another 57 million individuals with an at risk pre-diabetic state. In the US alone, 24 million people have been diagnosed as living with T2DM, or 8% of the population (Smith, 2010). It was been estimated that there will be 430 million people with T2DM worldwide by 2030 (Shaw et al. 2010).
|Dunstan et al.||Australia||7.4%|
|Dunstan et al.||Males in Australia||8%|
|Dunstan et al.||Females in Australia||6.8%|
|Wild et al.||World||2.8%|
|Drivsholm et al.||Males >60 years in Denmark||12.3%|
|Mokdad et al.||United States||7.9%|
|Harris et al.||United States adults aged >20 years||5.1%|
|Harris et al.||United States adults aged 40 – 74 years||12.3%|
|Yang et al.||Chinese adults||9.7%|
|Yang et al.||Chinese adults aged 20 – 39||3.2%|
|Yang et al.||Chinese adults aged 40 – 59||11.5%|
|Yang et al.||Chinese adults aged >60 years||20.4%|
|Legro et al.||Females with diagnosed PCOS||7.5%|
|Cowie et al.||United States adults||9.3%|
|Ramachandran et al.||Urban Indian adults >20 years||12.1%|
Based on these studies, the prevalence of T2DM can range from 2.8 – 20.4%, depending on the population studied. Older populations tend to display greater prevalence of T2DM than younger populations. The prevalence of T2DM in whole populations can range from 2.8 – 10.4%.
What is the incidence of T2DM?
The incidence of T2DM in the US has doubled in the last 30 years with 3 million new patients between 2007-2009.
|Magliano et al.||Australian male adults||0.8%|
|Magliano et al.||Australian male adults||0.7%|
|Fox et al.||United States males in the 1990s||3.7%|
|Fox et al.||United States females in the 1990s||5.8%|
|Fox et al.||United States males in the 1970s||2.0%|
|Fox et al.||United States females in the 1970s||2.7%|
|Geiss et al.||adults surveyed in 1997||0.49%|
|Geiss et al.||adults surveyed in 2003||0.69%|
|Gregg et al.||individuals with a BMI >35 kg/m2||15.1%|
|Mason et al.||United States women aged 34 – 59 years||1.5%|
Based on these studies, it appears that the incidence of T2DM has increased over the last 2 decades and can range from 0.5 – 15.1% depending on the exact population. Studies also indicate that individuals who are physically sedentary or obese have a higher incidence.
What are the problems with untreated T2DM?
The mismanagement of hyperglycaemia in patients with T2DM can result in complications such as micro-vascular damage such as retinopathy, nephropathy and neuropathy (Smith et al. 2010), as well as macro-vascular complications and all-cause mortality (Dormandy et al., 2005). Cardiovascular disease is the leading cause of death in the US and T2DM is a major risk factor for that disease. A fundamental goal of managing T2DM is glycaemic control because of the complications associated with chronically elevated blood glucose.
What are the risk factors for T2DM?
Many studies have documented an observation of risk factors for the development of T2DM. The development of T2DM may be influenced by genetics, age, acute exercise, physical fitness, dietary nutrients, medications, obesity and body fat distribution, as shown by the following studies:
|Hu et al.||The researchers performed a prospective cohort study including 84,941 female nurses to investigate the associations of lifestyle variables and development of T2DM between 1980 – 1996.||The researchers found that overweight and obesity was the single most important predictor of developing T2DM. A lack of exercise, poor diet and smoking were all associated with the risk of T2DM after controlling for body mass index.|
|Levine et al.||The researchers investigated the effect of overfeeding and obesity in free-living walking distance.||The researchers reported that lean counterparts walked 3.5 miles/day more than obese individuals for short durations (<15 minutes) and low velocity (around 1mph). Furthermore, free-living walking reduces with spontaneous overfeeding.|
|Veneables et al.||The researchers performed a review to investigate the effect of obesity and lack of physical activity in the development of T2DM in the UK.||The researchers found that a lack of physical activity and obesity are two major risk factors for T2DM.|
|Wei et al.||The researchers reported data about the fitness of 8,633 participants.||They reported that the least fit 20% of the cohort had a 1.9 and 3.7 times greater risk for developing impaired fasting glucose and T2DM respectively compared with the most fit 40% of the cohort.|
|Colditz et al.||The researchers performed a prospective cohort study in female nurses including 114,281 participants aged 30 – 55 years between 1976 – 1990 to investigate the relationship between adult weight gain and the risk of T2DM.||The researchers found that the risk of T2DM was significantly associated with body mass index (BMI). Compared to women that maintained weight or lost less than 5kg during the study, women who gained 5 – 7.9kg or 8 – 10.9kg had a 1.9 or 2.7 times greater likelihood of developing T2DM. In women who lost more than 5kg during the study period reduced their risk of T2DM by 50% or more.|
|Chan et al.||The researchers performed a prospective cohort study of male health professionals including 51,529 participants between 1987 – 1992 to investigate the relation between obesity, fat distribution and weight gain on the development of T2DM.||The researchers found that obesity measured as body mass index was a major predictor of developing T2DM, amounting to a 42% greater likelihood for men with a BMI of >35 kg/m2 compared to men with a BMI <23 kg/m2. BMI at age 21 and weight gain were also related to T2DM. Fat distribution measured as waist-to-hip ratio was a poorer predictor than waist circumference for T2DM risk.|
|Pradhan||The researchers performed a nested case control study of women who developed T2DM during the Women’s Health Study between 1992-1996. The researchers used 188 women who developed T2DM and 362 control participants to investigate the relation between markers of inflammation and T2DM risk.||The researchers found that women in the highest quartile for inflammatory markers were more likely to develop T2DM than those in the lowest quartile.|
|Yang et al.||The researchers performed a cross sectional study of a nationally representative sample of 46,239 Chinese adults >20 years to investigate the prevalence of diagnosed and undiagnosed T2DM. Diagnosis of T2DM was considered either fasting glucose level of ≥126 mg/dl, 2-hour glucose level ≥200/l, or both.||The researchers found that T2DM prevalence increased with increasing body mass index (BMI).|
|Ramanchandran et al.||The researchers performed a cross-sectional stratified random sampling study to investigate the prevalence and risk factors for T2DM in urban living Indians above the age of 20 years.||The researchers found that T2DM prevalence increased with body mass index, sedentary physical activity, monthly income, family history, hip to waist ratio and age.|
|Mohan et al.||The researchers performed a cross-sectional study of 11 existing cohort studies of 4 Asian countries including 24,335 participants to investigate the prevalence of T2DM and glucose tolerance.||The researchers found that T2DM prevalence increased with age and reached a peak at 70-89 years for Chinese, compared with 60-69 years for Indian adults. Indian adults had the highest prevalence of T2DM among the cohorts.|
Based on these studies, it appears that the main risk factors for developing T2DM are: overweight or obesity, having a high body mass index (BMI), following a sedentary lifestyle, having a high waist-to-hip ratio and being of advanced age.
What is the economic burden of T2DM?
A number of studies have investigated the economic burden of T2DM, which is considerable. It is estimated that T2DM incurred an estimated cost of $174 billion in the US in 2007 (CDC) of which $116 billion is medical expenditures and $58 billion is reduced national productivity (American Diabetes Association). Since the current estimate for the number of individuals with T2DM in the US is 23.7 million, this is a per capita cost of around $4,895 per year. It is projected that the number of people with diagnosed and undiagnosed T2DM will increase from 23.7 to 44.1 million over the next 25 years, thereby bringing costs to $336 billion per annum (Huang et al.). In other countries, the costs are lower. Chan et al. found that individual annual costs of Hong Kong residents with T2DM were $1,725, of which 78.4% was government expenditure. For individuals with T2DM and subsequent micro- or macro-vascular comorbidities, the costs were found to be 1.1 fold greater. In Europe, Jönsson et al. found that the estimated cost of T2DM in 8 European countries combined was €29 billion in 1999 and the annual per patient cost was estimated to be €2,834. Overall, it appears that T2DM-related spending is set to increase because of an increasing population size and age. Moreover, the per-patient cost in the Western world is around $3,000 – 5,000 per year.
Is aerobic exercise useful for the treatment of T2DM?
A great number of studies have assessed the utility of various types of aerobic exercise for T2DM, with generally very positive results, as shown in the following table:
|Winnick et al.||The researchers assessed the effect of aerobic exercise training on short-term whole body insulin sensitivity in 18 obese diabetic individuals. Both groups had energy intake and macronutrient ratio’s controlled and one group performed aerobic exercise at 70% of their maximal oxygen consumption over a 7-day period.||The researchers found that after 1 week, the exercise group displayed significantly improved whole body and peripheral insulin sensitivity.|
|Cauza et al.||The researchers assessed the effect of either resistance training or endurance training on blood glucose responses 48 hours post exercise, before and after a 4 month training intervention on 15 adults with T2DM.||The researchers reported that glycaemic control was improved in the resistance training group only, where mean post exercise blood glucose was reduced by 15% after the 4 month intervention. The researchers reported no change in 48 hour mean blood glucose values following the endurance training intervention.|
|Raz et al.||The researchers assessed the effect of a 12-week long aerobic exercise intervention in which the subjects exercised 3 times per week for 45 minutes. The subjects were 40 patients aged 56.6 ± 6.6 years. They were randomly allocated to either an exercise or control group.||Following the intervention, the exercise group demonstrated significant reductions in plasma glycol-haemoglobin (A1C) as well as triglycerides and fructosamine, which persisted to the 12-month follow-up in those who continued exercise.|
|Rönnemaa et al.||The researchers assessed the effect of 4 months of physical activity on metabolic control. They randomly allocated 25 patients to either an exercise of control group.||Following the intervention, the researchers reported a significant reduction in glycosylated haemoglobin A1C and 2-hour plasma glucose following a glucose tolerance test as well as a non-significant reduction in fasting glucose.|
|Eriksson et al.||The researchers assessed the benefits of either circuit-type resistance training or aerobic endurance training on glucose disposal. They recruited 7 subjects for the aerobic training programme and 8 for the circuit-type resistance training, while a further 7 served as control subjects.||Following the intervention, the aerobic training group displayed significant improvements in peak oxygen consumption and HDL lipoprotein levels but they did not show improvements in glucose disposal or insulin secretion.|
|Poirier et al.||The researchers assessed the effect of a 12-week endurance cycling intervention on insulin sensitivity and fasting glucose in 7 obese and 6 non-obese subjects. The intervention consisted of 3 x 1-hour aerobic cycling sessions each week at 60% of V02-max.||The researchers found that V02-max significantly improved following the intervention. They found no change in fat mass, per cent body fat, fasting glucose or insulin sensitivity when the participants were treated as one group. Treated as separate groups, they found an improvement in insulin sensitivity in the non-obese group only.|
|Reitman et al.||The researchers assessed the effects of 6 – 10 weeks of intensive aerobic training on glucose tolerance, insulin secretory capacity, and insulin-induced glucose disposal in 6 obese recently-diagnosed patients with non-insulin dependant T2DM. The participants performed exercise 5 or 6 days weekly and performed 20 – 40 minutes of interval-type exercise involving 5 minutes of work followed by 2 minutes of rest at 60 – 90% of maximal aerobic capacity.||The researchers reported that fasting glucose reduced in every single participant and oral glucose tolerance improved in 5 of the 6 participants. They reported that the average insulin induced glucose disposal rate in the group did not reach statistical significance.|
|Trovati et al.||The researchers assessed the effect of physical training for 1 hour/day, 7 days/week for 6 weeks at 50 – 60% maximum oxygen uptake on glucose uptake, insulin secretion and action.||The researchers reported that there were significant improvements in blood glucose control, glucose tolerance and insulin action.|
|Segal et al.||The researchers investigated the effect of a 12-week aerobic training program that lead to an improvement in cardiorespiratory fitness on glucose control and insulin action when body composition changes and proximity to the exercise bout were controlled. The subjects performed aerobic training for a total of 4 hours per week, comprising aerobic cycling at 60% of maximum capacity, while caloric expenditure during the bouts was compensated for with additional food in order to maintain body composition.||The researchers reported significant improvements in cardiorespiratory fitness (+27%) while hepatic glucose production was reduced by 22% in the obese group. The researchers reported that insulin action measured by euglycaemic clamp was not altered following the training intervention in either the diabetic, obese or non obese groups.|
|Holten et al.||The researchers assessed the effect of a 10-week long aerobic exercise intervention that consisted of training 3 times per week for 20 – 45 minutes. The researchers measured physiological variables (lactate threshold, body composition and acute vascular changes) as well as quality of life indices.||The researchers found significant improvements in lactate threshold and a reduction in body fat percentage. No changes in interstitial nitric oxide levels or changes in the physical or mental components of the quality of life survey were observed.|
|Bruce et al.||The researchers assessed the effect of an aerobic training intervention lasting 8 weeks on insulin sensitivity and muscle lipids in type 2 diabetic participants and healthy controls. The subjects performed aerobic exercise 3 times per week.||The researchers reported that pre-training insulin sensitivity was lower in the T2DM group, and remained lower following the intervention, although both groups improved insulin sensitivity to the same extent (30%). The researchers reported that muscle triglyceride content reduced and was associated with the increase in insulin sensitivity.|
|Tessier et al.||The researchers investigated the effect of an aerobic training programme of 16 weeks in duration on the treatment of metabolic control, physical capacity and quality of life in a group of participants with T2DM.||The researchers reported that exercise capacity (measured as total time on the treadmill) and glucose excursion (measured during an oral glucose tolerance test) significantly improved after 16 weeks of aerobic training.|
|Boule et al.||The researchers investigated the effects of a 20 week endurance training programme on healthy, previously sedentary participants on measures of an intravenous glucose tolerance test.||The researchers found that mean insulin sensitivity increased significantly following the training but was transient, disappearing 72hrs after the last training bout. They also reported significant improvements in glucose disappearance index (3%), measures of glucose tolerance and insulin response to glucose (insulin secretion) in both the participants with the lowest glucose tolerance (-7%) and in the highest (14%).|
|King et al.||The researchers investigated glucose tolerance and insulin action immediate following exercise and the time course in which the improvements in glucose homeostasis persisted in 9 subjects with a mean age of 51 years. The subjects performed 45 minutes of exercise at 73% of their peak VO2 for 5 days, followed by 7 days of inactivity in which an oral glucose tolerance test was performed immediately following the last exercise bout and 1, 3, 5, and 7 days after exercise.||The researchers found that the glucose area under the curve was significantly higher in days 5 and 7 compared to days 1 and 3 and immediately following the exercise bout. They found that the incremental insulin area compared to days 1 and 3 was 43% and 66% higher in day 5 and 7, respectively. Finally, they reported that glucose tolerance was significantly better within 3 days of exercise compared to at 5 and 7 days.|
|Braun et al.||The researchers investigated the effect of low- vs. high-intensity aerobic exercise on glucose control in 8 women staying in a metabolic ward. The subjects performed 3 conditions, 1) low-intensity exercise (50% of V02-max), 2) high-intensity exercise (75% of V02-max) and 3) a control, in which no exercise was performed. The exercise conditions were energy-matched.||The researchers reported that plasma glucose and glucose clearance was significantly greater after both exercise conditions that the control condition. They reported that plasma insulin response was lower after the high-intensity exercise compared with after the low-intensity exercise.|
|Duncan et al.||The researchers investigated the effect of a 6-month intervention of aerobic walking exercise (at 45 – 55% to 65 – 75% HRR) without weight-loss on glucose control, fat clearance and fasting lipids in 18 sedentary adults. The participants performed 3 – 4 to 5 – 7 weekly bouts of 30 minutes.||The researchers found that the walking programme improved insulin sensitivity and markers of free fatty acid utilisation without changes in waist circumference, BMI, fat clearance and fasting lipids. The researchers concluded that even modest amounts of exercise affect glucose and fat metabolism.|
|Houmard et al.||The researchers investigated the effect of 6 months of different aerobic walk/jogging training interventions comprising of 1) low-volume-moderate-intensity (12 miles/week 40 – 55% of V02-max = 170 minutes/week ) 2) low-volume-high-intensity (12 miles/week 65 – 80% of V02-max = 115 minutes/week), and 3) high-volume-high-intensity (20 miles/week 65 – 80% of V02-max = 170 minutes/week) on insulin sensitivity in 154 sedentary overweight and obese individuals.||The researchers reported that all exercise groups improved insulin sensitivity with the greatest improvements following the low-volume-moderate-intensity and high-volume-high-intensity exercise. The researchers concluded that weekly duration of exercise may be an important mediating factor.|
|Jeon et al.||The researchers performed a systematic review of 10 prospective cohort studies including 301,221 participants and 9,367 incidence cases investigating the effect of moderate intensity, 5 of which specifically investigated the role of walking.||The researchers found that adherence to moderate intensity programmes produced a 31% reduction in the risk of T2DM. Among the walking exercise interventions, a 30% reduction was observed in individuals participating in >2.5 hours/week of brisk walking, compared to individuals performing almost no walking and was independent of body mass index.|
|Tudor-Locke et al.||The researchers assessed the effectiveness of the ‘First Step’ programme that consists of increasing individual’s daily walking distance on individuals with T2DM. The researchers assessed anthropometric and glucose control measures after the 16-week intervention period and a 24 week follow up assessment.||The researchers reported that the intervention significantly improved steps per day, producing approximately 30 minutes of walking. However, they reported no significant changes in any of the other variables measured between the intervention and control.|
Based on these studies, it appears that aerobic exercise in T2DM has beneficial effects on cardiorespiratory fitness and lipid levels. Aerobic exercise can improve long term glucose control (measured by A1C) and short term glucose and insulin responses, although the improvement in glucose tolerance appears to drop substantially within 3 days. The intensity and volume of aerobic exercise may correlate with greater improvements in acute glycaemic responses.
Is resistance training useful for the treatment of T2DM?
A great number of studies have assessed the utility of various types of resistance exercise for T2DM, with generally very positive results, as shown in the following table:
|Baum et al.||The researchers assessed the effects of a 12-week exercise intervention on glycaemic control and A1C. The researchers randomly allocated 40 diabetic patients into: resistance training, vibration training, and flexibility training groups. Each training group performed 3 weekly training bouts. The resistance training program consisted of 8 exercises performed for 12 repetitions for 1 set (70% 1RM) for the first 6 weeks, increasing to 2 sets in week 7-9, followed by 3 sets of 10 repetitions in week 10-12.||The researchers reported that following the resistance training intervention the subjects displayed significantly improved glycaemic control by -5.6% at the 150-minute mark following an oral glucose tolerance test compared to baseline. The researchers reported that the patients’ A1C and fasting blood glucose was no different post-training from pre-training.|
|Dunstan et al.||The researchers assessed the effects of a 6-month resistance-training intervention (plus a weight loss diet) in 36 overweight adults aged 60 – 80 years with T2DM. The researchers randomly allocated the participants into: a progressive high-intensity resistance-training program plus weight-loss diet, and a control program plus weight-loss diet.||The researchers reported significant improvements in A1C in the resistance training group (-1.2%) compared to the weight-loss only group (-0.4%). The researchers reported that the resistance-training group also significantly improved their strength and lean body mass (+0.5kg) and reduced their fat mass (-2.4kg).|
|Castaneda et al.||The researchers assessed the effect of a 16-week progressive resistance-training intervention in 62 Latino older adults (aged 66 years) with T2DM. The researchers randomly allocated the adults into: a progressive resistance training group or a control group. They performed testing for glycaemic control, glycogen storage, metabolic syndrome abnormalities and body composition.||The researchers reported a significant improvement in A1C (8.7% to 7.6%), muscle glycogen storage (+24%) and lean body mass (+1.2kg). The researchers also reported that 72% of exercisers reduced their medication following the training intervention and displayed a significant reduction in trunk fat mass and systolic blood pressure.|
|Baldi & Snowling||The researchers assessed the effect of a 10-week moderate resistance-training intervention in 18 obese men with T2DM. The researchers randomly allocated the participants to: moderate resistance training, or a control group.||The researchers reported that the resistance training intervention significantly reduced fasting blood glucose and insulin, and produced a non-significant reduction in A1C. The researchers further reported that the resistance-training intervention increased fat free mass by 3.5% and that changes in A1C and fasting blood glucose were inversely proportional to the changes in fat free mass.|
|Brooks et al.||The researchers performed a randomised controlled trial to assess the effect of a 16-week resistance-training intervention on muscle quality and measures of glycaemic control in 62 Hispanics aged >52 years with T2DM. The resistance-training intervention consisted of 5 exercises performed for 3 sets of 8 repetitions, 3 times per week with the intensity of exercise increasing at weeks 10 – 14.||The researchers reported that resistance training improved muscle quality and type I and II fibre area and reduced insulin resistance, inflammation and adiponectin levels.|
|Dunstan et al.||The researchers assessed the effect of a 2-month supervised resistance-training program followed by a 12-month period of either a maintenance program at home or at a community fitness centre. The researchers assessed A1C after the 2 and 14 month intervention period in 58 overweight T2DM adults between the ages of 40 – 80 years.||The researchers reported a reduction in A1C (-0.4%) following the supervised intervention that persisted for the remaining maintenance program in the community fitness centre group only. After the initial decrease in A1C in the home program group, levels almost returned to baseline (-0.1%). The researchers noted that the decrease in A1C was positively associated with the program compliance.|
|Cauza et al.||The researchers assessed the effect of a 4-month resistance or endurance training intervention on metabolic control, muscle strength and cardiovascular endurance in 22 older T2DM patients (aged 56 years).||The researchers reported that A1C, insulin resistance, total cholesterol, LDL and HDL all significantly improved in the resistance training group but there was no change in the subjects following the endurance intervention.|
|Dunstan et al.||The researchers performed a randomised control trial to investigate whether the improvements following a 6-month supervised high-intensity resistance-training intervention can be maintained after a 6-month home-based resistance-training period in 36 adults between the ages of 60 – 80 years with T2DM.||The researchers reported that the improvements in upper and lower body strength and muscle mass were maintained following the 6-month home-based resistance training intervention. However, they report that the improvements in A1C did not persist after the 6-month supervised training period.|
|Colberg et al.||The researchers conducted a controlled trial to assess the effectiveness of an 8-week moderate-intensity resistance-training program in enhancing cutaneous perfusion in patients with T2DM and control subjects.||The researchers reported that following the 8 week training program, both groups displayed no change in dorsal foot cutaneous perfusion.|
|Fenicchia et al.||The researchers evaluated the ability of both acute and chronic resistance training to enhance glycaemic control in women with T2DM. The subjects performed 6 weeks of progressive resistance-training where glycaemic control was measured before resistance training, 12 – 24 hours following the first resistance-training session and 60 – 72 hours after the final resistance-training session.||The researchers reported that glycaemic control was enhanced 12 – 24 hours following the resistance-training bout but did not persist to the 60 – 72 hour mark after the training intervention. The researchers also reported that insulin concentrations were not different following any of the training bouts.|
|Fluckey et al.||The researchers assessed the effect of a single resistance-training bout on glucose tolerance in T2DM adults with a mean age of 53.3 years, age-matched and younger control participants. Following a resistance-training bout consisting of 7 exercises performed for 10 repetitions for a total of 3 sets, the participants were given a glucose load at the 18 hour mark to assess glucose and insulin responses.||The researchers reported that glucose response was unchanged from pre to post in any of the groups but insulin response was significantly lower following the exercise bout in the diabetic older adults.|
|Ibañez et al.||The researchers evaluated the effect of a 16-week, twice-weekly progressive resistance-training intervention without a weight-loss diet on abdominal fat and insulin sensitivity in older men with a mean age 66.6 ± 3.1 years with T2DM.||The researchers reported that following the progressive resistance-training program, the participants experienced significant decreases in visceral and subcutaneous abdominal fat, increase in insulin sensitivity and fasting blood glucose. They also found that subjects’ energy intake did not decrease during the intervention.|
|Honkola et al.||The researchers conducted a randomised control trial to assess the effectiveness of circuit-based resistance-training on glycaemic control, blood pressure and lipids in individuals with T2DM. The researchers recruited 18 participants to a 5-month, twice-weekly moderate-intensity and high-volume circuit-based resistance-training program, while 20 participants served as controls.||The researchers reported that the resistance-training intervention produced a significant reduction in A1C of -0.5% and improved total cholesterol, low density lipoprotein and triglycerides.|
|Eriksson et al.||The researchers assessed the effectiveness of a twice weekly resistance-training program, (moderate-intensity, high-volume) on long term glycaemic control, muscle endurance and size.||The researchers reported that following the intervention A1C, muscle endurance and muscle size all significantly improved.|
|Misra et al.||The researchers assessed the effectiveness of a 12-week supervised progressive resistance-training intervention in Asian Indians with T2DM on glycaemic control, body composition, insulin sensitivity and lipids.||The researchers reported that following the intervention, there were significant declines in A1C (-0.5%), fasting blood glucose (-2.7mmol/l), total cholesterol and total triglycerides. The researchers reported no significant changes in total body fat, BMI, truncal fat or CRP levels.|
|Dunstan et al.||The researchers performed a randomised control trial to assess the effect of an 8-week circuit-based resistance-training intervention on adults with a mean age of 51 years with T2DM.||The researchers reported that the intervention produced significant reductions in self-monitored glucose levels and insulin area under the curve.|
|Cheng et al.||The researchers assessed the association between muscle-strengthening activities and insulin sensitivity among 4m504 American adults between the ages of 20 – 79 years without T2DM.||The researchers reported that self-reported weekly frequencies of muscle-strengthening activities independently predicted greater insulin sensitivity but not fasting glucose.|
|Holten et al.||The researchers performed a controlled trial to assess the effectiveness of resistance-training 3 times per week on muscle insulin action and Glut4 content in individuals with T2DM.||The researchers reported that following the 6-week resistance-training intervention, they observed increased glucose extraction and this was explained by greater leg muscle mass of the trained leg. They also reported that muscle content of Glut4 and insulin receptors were significantly increased post-intervention, suggesting that resistance-training enhances insulin action in skeletal muscle.|
|Miller et al.||The researchers investigated the effect of a 16-week resistance training program in 11 older males (50 – 63 years) on changes in insulin action.||The researchers reported that the program induced a strength increase of 47% and while fasting insulin decreased, fasting glucose levels did not. During the oral glucose tolerance test the researchers reported that glucose infusion rates increased 20 – 24% during the low and high infusion rates and plasma insulin levels decreased.|
|Eriksson et al.||The researchers assessed the benefits or either circuit-type resistance training or aerobic training on glucose disposal. For the study, 7 subjects followed the aerobic training program, while 8 subjects performed the circuit-type resistance training, and a further 7 served as control subjects.||Following the intervention, the aerobic training produced significant improvements in peak oxygen consumption (V02), and HDL lipoprotein but caused no change in glucose disposal. On the other hand, the circuit-based resistance training intervention improved glucose disposal by 23%.|
|Smutok et al.||The researchers assessed the effect of exercise modality after a 20-week training intervention of either aerobic or resistance training on glucose tolerance in 1) T2DM, 2) impaired glucose tolerance or 3) hyper-insulinaemic subjects.||The researchers found that there was no difference in glucose tolerance results following either the resistance or aerobic training interventions, suggesting that resistance-training has similar effects on acute glucose control than aerobic training.|
|Black et al.||The researchers investigated the effect of both volume and intensity of resistance-training on subsequent insulin sensitivity in 17 individuals with impaired fasting glucose. The participants performed 4 separate exercise bouts of either single or multiple set exercise of moderate intensity (65% 1-repetition max) or high intensity (85% 1-repetition max) and fasting glucose and insulin was taken 24hrs after each bout with 3 days washout between bouts.||The researchers reported that all exercise bouts improved fasting glucose and insulin, but in comparison to single-set bouts, multiple-set exercise bouts demonstrated significantly greater reductions in fasting glucose and insulin. The researchers conclude that the greatest reduction in fasting glucose and insulin was observed following high-intensity multiple-set resistance exercise.|
|Kwon et al.||The researchers investigated the effect of low-intensity resistance-training with elastic bands (or a control group) on fat body mass, fat free mass and insulin sensitivity. The training group exercised twice-weekly with exercises performed for 3 sets and the total duration lasting 60 minutes.||The researchers reported significant gains in fat free mass and reductions in body fat mass and abdominal fat mass despite no change in insulin sensitivity.|
|Gordon et al.||The reviewers conducted a systematic review to assess the effect of resistance training on glycaemic control and insulin sensitivity. The reviewers found 20 studies including 13 randomised control trials.||The reviewers reported that supervised resistance training produces improvements in both glycaemic control and insulin sensitivity. The reviewers reported, however, that without supervision, compliance and subsequent glycaemic control are decreased.|
|Irvine and Taylor||The reviewers produced a systematic review and meta-analysis to assess the effect of resistance-training as a safe and effective intervention for glycaemic control in patients with T2DM. The reviewers found 9 randomised control trials that included a total of 372 patients.||The reviewers reported that resistance-training significantly improves glycaemic control (A1C) to the extent of a -0.3% reduction. Compared to aerobic training, however, the reviewers reported no significant effect of resistance training.|
Based on these studies, it appears that resistance-training can increase muscle strength and lean mass, and reduce subcutaneous and visceral fat in T2DM. Resistance-training may also improve glucose disposal, insulin response and long term glycaemic control, as well as improving these outcomes in conjunction with weight loss.
Is combined training useful for the treatment of T2DM?
A great number of studies have assessed the utility of various types of combined exercise for T2DM, with generally very positive results, as shown in the following table:
|Sigal et al. 2007.||The researchers performed a randomised control trial to assess the effect of aerobic or resistance training alone, or combined in 251 patients with T2DM. The researchers randomly allocated the subjects to a either an aerobic-only group, resistance-training only group, a combined training group, or a control group. The training groups trained 3 times per week for 22 weeks.||The researchers reported significant improvements in glycaemic control following both aerobic exercise and resistance-training. However, they also reported that the combined training resulted in superior improvements than aerobic (0.46%) or resistance training (0.59%) alone.|
|Tokmakidis et al.||The researchers assessed the effect of combined strength and aerobic training on short and long term effects of glycaemic control, insulin action and exercise capacity in post menopausal women aged 55.2 ± 6.7 years. The exercise programme consisted of 2 days per week strength training (60% of maximal voluntary force), and 2 days per week aerobic exercise (60 – 70% months 0 – 2 months, and 70 – 80% months 3 – 4) and measurements were taken at both 4 and 16 weeks.||After 4 weeks, the participants had significantly reduced glucose and insulin area under the curve, as well as A1C (-0.6%). After 16 weeks, glucose and insulin area under the curve were improved further (glucose 12.5%, insulin 38%) and A1C also decreased further (7.1% to 6.9%).|
|Wallace et al.||The researchers assessed the effects of either endurance training, resistance-training or a combined endurance and resistance training protocol (performed in the same session) for 14 weeks (3 times per week) on markers of insulin resistance in hyper-insulinaemic adults.||The researchers reported that the combined training intervention produced significantly improved body fat reductions (6.9 vs. 1.4%), changes in insulin concentrations (8.5 vs. 3 uU.mL-1), reductions in glucose levels (11.1 vs. 5.9 mg/dl), improvements in blood lipids and reductions in blood pressure.|
|Maiorana et al.||The researchers assessed the effect of a circuit style exercise programme 8 weeks in duration consisting of both aerobic and resistance training on glycaemic control, cardiorespiratory fitness, muscular strength and body composition in 16 subjects (aged 52 ± 2 years), using a prospective, randomised crossover design.||The researchers found that the combined training programme produced favourable effects in cardiorespiratory fitness, body fat mass and muscle strength. They also observed significant reductions in glycosylated haemoglobin (A1C) and fasting blood glucose.|
|Balducci et al.||The researchers investigated the effect of a multicentre supervised aerobic and resistance-training programme on glucose control and heart disease risk factors in 606 Italian patients. The subjects received either twice-weekly supervised aerobic and resistance training plus exercise counselling vs. counselling alone.||The researchers found that the supervised exercise group significantly improved their glucose control (A1C = -0.3%), and improved systolic (-4.2mmHg) and diastolic (-1.7mmHg) blood pressure, waist circumference (-3.6cm), body mass index, lipid profile and insulin resistance.|
|Cuff et al.||The researchers investigated the effect of a combined resistance and aerobic training programme compared to aerobic training alone in post menopausal women with T2DM. 28 women were assigned to one of three 16-week training intervention groups, either 1) combined training, 2) aerobic only, or 3) a control group. The researchers reported that both exercise interventions improved abdominal subcutaneous and visceral adipose tissue, whereas the combined training group increased muscle density compared to all other groups.||The researchers reported that glucose disposal was independently associated with changes in abdominal subcutaneous and visceral adipose tissue and muscle density. Further, they reported that muscle density maintained a relationship with glucose disposal after controlling for abdominal fat.|
|Marcus et al.||The researchers performed a randomised control trial investigating the effect of aerobic training plus high force eccentric resistance-training or aerobic-only training on measures on thigh lean tissue and intramuscular fat, glycosylated haemoglobin, body mass index (BMI) and 6-minute walk distance in 15 participants with a mean age of 50.7 years.||The researchers reported that both groups experienced a reduction in glycosylated haemoglobin but the combined training group experienced a trend towards greater reductions (-0.59 vs. -0.31%). Whereas the combined training intervention increased thigh lean tissue (15.1cm2), the aerobic only group experienced a reduction in thigh lean mass (-5.6 cm2). Lastly, a greater reduction in BMI was observed in the combined training intervention, and no difference was observed in the increase of 6-minute walk distance between groups.|
Based on these studies, it appears that combined training offer additional benefits to either aerobic or resistance exercise alone in terms of improved long term glycaemic control, body composition and lipid profiles.
Are alternative exercise interventions useful for the treatment of T2DM?
Several studies have assessed the utility of various alternative types of exercise for T2DM, with generally very positive results, as shown in the following table:
|Baum et al.||The researchers assessed the effects of a 12-week exercise intervention on glycaemic control and A1C. The researchers randomly allocated 40 diabetic patients into: resistance training, vibration training, and flexibility training. Each training group performed 3 weekly training bouts. The vibration training program consisted of 8 different exercises performed on a vibration training device for 30-seconds each, and the frequency was increased during the last 3 weeks.||The researchers reported that following the vibration training intervention fasting blood glucose significantly reduced and at 150 minutes following an oral glucose tolerance test, while blood glucose was reduced by 6.3% compared to baseline. The researchers reported that A1C following the vibration training intervention significantly reduced by -0.3%.|
|Innes et al.||The researchers performed a systematic review of 25 eligible studies investigating the efficacy of yoga in improving clinical outcomes in T2DM patients.||The researchers reported that the studies suggest that yoga may confer beneficial changes in several risk indices such as glucose and insulin management, lipid profile, body composition, stress and inflammatory measures and pulmonary function.|
|Sacco et al.||The researchers investigated the effect of a cost effective telephone ‘coaching’ intervention by a para-professional on glycaemic control, adherence and T2DM-related symptoms and depression.||The researchers reported that the intervention improved the participant’s diet, physical activity frequency, reduced medical symptoms and depression symptoms.|
|Tsang et al.||The researchers performed a randomised control trial investigating the effect of a form of Tai Chi (Tai Chi for Diabetes) on insulin resistance and long term glucose control in 38 participants aged 65 years, of which 79% were women.||The researchers reported no changes in insulin resistance or long term glucose control between the sham training and experimental condition.|
Based on these studies, it appears that some alternative exercise interventions may confer beneficial effects on risk indices for patients with T2DM and in some circumstances impart small but significant effects on glycaemic control.
What are the effects of exercise on glycaemic control?
There are generally very beneficial effects of exercise on glycaemic control, as shown by the studies in the following table:
|Baynard et al.||The researchers investigated the effect of a single bout (30 minutes), multiple bouts (3 x 10 minutes) or no exercise on glucose control to an oral glucose tolerance test in 9 women with T2DM with a mean age of 53 years and 6 age-matched controls. The women exercised at 60% of V02-max for the allotted time the day prior to the oral glucose tolerance test.||The researchers reported that the aerobic exercise bouts performed the day prior had no effect on glucose control or compared to no exercise at all. The only differences observed between the T2DM patients and the control were that the diabetic patients demonstrated significantly greater glucose responses and had greater fasting insulin levels.|
|Goulet et al.||The researchers investigated the effect of 6 months of aerobic or resistance-training on insulin sensitivity outside of the residual effect of the last training bout on 18 non-obese older women aged 54 – 78 years.||The researchers reported that the aerobic training reduced body fat mass whereas aerobic training and resistance-training increased fat-free mass. They found that neither training intervention improved glucose disposal outside of the residual effect of the last training bout.|
|Kang et al.||The researchers investigated the effect of 7 days of aerobic exercise for either 1) 50 minutes at 70% of V02-max or 2) 70 minutes at 50% of V02-max on subsequent glucose tolerance and insulin responses to an OGTT in 6 obese and 6 T2DM patients.||The researchers found that glucose tolerance and insulin response were improved to the greatest extent following the higher-intensity exercise in the obese group. No significant changes in glucose or insulin responses were observed between the exercise interventions in the T2DM patients. The researchers explain their T2DM patients may have been relatively hypo-insulinaemic.|
|Kirwin et al.||The researchers investigated the effect of 7 days of aerobic training on the suppression of hepatic glucose production and whether improvements were observed in either insulin sensitivity, responsiveness, or both in 14 obese T2DM patients aged 64 years. The aerobic training comprised both cycling and treadmill walking each day at 70% of V02-max for 30 minutes.||The researchers reported that 7 days of aerobic exercise improved glucose disposal rates during low and high hyper-insulinaemic clamp procedures and reduced hepatic glucose production following exercise. The researchers conclude that vigorous exercise can have significant impact on insulin action and hepatic glucose suppression in T2DM patients.|
Based on these studies, it appears that an exercise bout increases glucose disposal and decreases plasma insulin, thereby normalising blood glucose. However, this response to exercise appears to be transient. It also appears that exercise intensity may aid in augmenting the transient response to exercise by improving glucose tolerance and reducing plasma insulin in response to blood glucose. However, sustained improvements in glycaemic control may not occur in exercising individuals outside of the residual effect of an exercise bout.
Are combined exercise and lifestyle interventions useful for the treatment of T2DM?
There are generally very beneficial effects of combined exercise and lifestyle interventions on T2DM, as shown by the studies in the following table:
|Tuomilehto et al.||The researchers performed a randomized control trial in 522 participants, overweight and with impaired fasting glucose. The individuals were assigned to either an intervention that was aimed at inducing weight loss of >5% body weight, increasing physical activity to 30 minutes/per day and dietary changes such as increasing fiber intake and managing dietary fat intake.||The researchers reported that participants in the intervention group lost 4.5kg in the first year and a net loss of 3.5kg was observed by 2 years. The participants reported adherence to the lifestyle changes (where physical activity adherence was 86%) during follow up periods, which related to changes in weight loss and T2DM incidence. The researchers report that T2DM incidence in the intervention group and control group were 6% and 14% respectively, and the cumulative incidence of T2DM was 58% lower in the intervention group compared to the control group.|
|Barnard et al.||The researchers investigated the effect of the ‘Pritikin’ program of diet and exercise on 60 non-insulin dependant diabetics during a 26 day residential programme. The researchers reported that all but 2 subjects were taken off their medication by the end of the program.||During the intervention, the subjects lost an average of 4.3kg and decreases of fasting blood glucose (195 vs. 145 mg/dl) and triglycerides (284 vs. 186 mg/dl) were observed. The daily walking duration increased from 12 to 103 minutes. The researchers further reported that the reduction in fasting blood glucose was not correlated with weight-loss, walking time or increase in aerobic capacity. The researchers concluded that the total program was effective at improving glucose control.|
|Clark et al.||The researchers investigated the effect of a brief tailored lifestyle self management intervention which included follow up calls, or a usual care control group in 100 patients (aged 40 – 70 years) with T2DM.||The researchers reported that the intervention was successful in reducing dietary fat intake and to a lesser extent increasing physical activity.|
|Lindstrom et al.||The researchers reported data from 1 and 3 years of the Finnish T2DM prevention study of 522 middle-aged overweight individuals. The intervention group received individualised nutritional counselling and were offered circuit-type resistance-training sessions, which was most intensive in the first year, followed by a maintenance period.||The researchers reported that after 1 and 3 years weight reductions were 4.5kg and 3.5kg respectively, compared to 1.0kg and 0.9kg in the control group. Further, measures of glycaemia and lipaemia improved more in the intervention group compared with the control group.|
|Glasgow et al.||The researchers investigated the effect of a computer-assisted self-management program to produce changes in lifestyle and dietary behaviours that affect weight, glucose control, quality of life, lipid profiles and depression in patients with T2DM. The researchers assigned 335 patients to either a cognitive theory-based intervention program or a computer-enhanced usual care program and took follow-up measurements at 2-months.||The researchers reported that the cognitive theory-based intervention significantly reduced weight and dietary fat compared to the computer-enhanced intervention. The researchers demonstrated a non-significant trend towards improved A1C, lipids and depression measures in those with elevated measures at baseline. They concluded that the computer-enhanced intervention was feasible and produced improvements in target behaviours.|
|Hamman et al.||The researchers investigated the effect of each lifestyle change in weight, diet and physical activity on the risk of developing T2DM of data from 1,079 participants from the Diabetes Prevention Program.||The researchers reported that weight-loss was the major predictor of T2DM prevention and that physical activity and dietary changes were associated with weight loss and important to maintain weight loss. Among the 495 participants who did not meet their weight loss goal, those who achieved the physical activity goal had a 44% reduction in T2DM incidence.|
|Lifshitz et al.||The researchers investigated the effect of metformin, placebo or a lifestyle intervention including a 7% weight reduction and 150 minutes/week of exercise on reducing the incidence of T2DM in 3,234 individuals with impaired fasting glucose levels (aged 51 years and 34 BMI).||In the average 2.8 year follow up the incidence of T2DM was 11, 7.8 and 4.8 cases per 100 person-years in the placebo, metformin and lifestyle groups respectively. The lifestyle intervention reduced the incidence by 58 per cent compared to 31 per cent following metformin therapy. The researchers concluded that a lifestyle intervention was significantly more effective at reducing the incidence of T2DM than metformin.|
|Li et al.||The researchers investigated follow-up data from the China Da Qing Diabetes Prevention Study of 577 participants who were randomly assigned to either a diet, exercise, diet + exercise or control group. The active intervention period lasted for 6 years, and the researchers have performed a 20 year follow-up, investigating the risk of T2DM, cardiovascular disease events and mortality.||The researchers reported that in the diet + exercise group there was a 51% and 43% lower incidence rate of T2DM than the control group at 6 and 20 year follow periods. Similarly, the average annual incidence of T2DM was 7% for the intervention groups compared with 11% of the control group. The researchers report no differences in the rate of first cardiovascular disease event, cardiovascular disease mortality or all-cause mortality between groups, but lacked statistical power for these outcomes.|
|Lindstrom et al.||The researchers provided additional follow-up data from the Finnish Diabetes Prevention Study after a median of 7 years after first participation (3 years after the active intervention period) to investigate changes in risk reduction after the discontinuation of active intervention and counselling and to assess any changes in previously established lifestyle changes.||The researchers reported that during the total follow up the incidence of T2DM was 4.3 and 7.4 per 100-person years in intervention and control participants respectively. They reported that the risk reduction was related with successful adherence to lifestyle changes such as weight loss, dietary changes and physical activity participation. During the post-follow up period after the intervention had stopped, relative risk was 36% in the intervention group.|
Based on these studies, it appears that exercise is an important adjunct to weight-loss and lifestyle interventions to reduce the incidence of T2DM and to improve outcomes in those already with T2DM. It appears that successful weight maintenance is correlated with adherence to exercise and improved weight loss during supervised exercise interventions.
What long term effect does exercise have in T2DM?
The following studies have explored the long-term effects of exercise in individuals with T2DM:
|Castaneda et al.||The researchers performed a randomised control trial to assess the effect of resistance training on glucose transporter expression (Glut4/hSGLT3) in Hispanic older adults (65 years) with T2DM. The researchers reported that following 16 weeks of resistance training, hSGLT3 but not Glut4 expression is increased in skeletal muscle.||The researchers reported that resistance training was the only independent predictor of hSGLT3 expression among the participants and was associated with increased glycogen stores and exercise intensity.|
|Gordon et al.||The researchers performed a randomised control trial to assess the changes in cytokine expression and muscle fibre size following 16 weeks of resistance training and usual care or a control group receiving only usual care in 30 adults with a mean age of 67 years.||The researchers reported that type I and II muscle fibre cross sectional area increased following the training intervention as well as interleukin 1 beta (IL-1beta), and both groups experienced increases in TNF-a and TGF-beta1 transcripts following the 16-week experiment. The researchers concluded that resistance training results in muscle fiber hypertrophy and affects the source of inflammation expressed in muscle.|
|O’Gorman et al.||The researchers investigated the effect of 7 days of exercise on insulin-mediated glucose disposal and changes in molecular signalling in 7 non-diabetic and 8 diabetic obese men.||The researchers found that insulin-mediated glucose disposal was increased in the diabetic men but not the non-diabetic men after the 7 day period. They found that the increase in glucose disposal was associated with an increase in glut4 content following the short-term exercise intervention.|
|Christ-Roberts et al.||The researchers investigated the effect of 8 weeks of aerobic exercise training on insulin mediated glucose disposal in 16 insulin resistance non diabetic men and 6 T2DM patients.||The researchers found that glycogen storage was 46% and 45% higher than baseline in the non-diabetic and diabetic participants respectively. They found that glut4 protein content was increased by 38% and 22% respectively. No changes in the ability of insulin to stimulate insulin receptor 1-associated PI3–kinase.|
Based on these studies, it appears that changes in muscle quality and quantity occur in response to exercise in individuals with T2DM.
What have reviews of exercise interventions for T2DM found?
A number of reviews have assessed the use of various different exercise interventions for the treatment of T2DM, as follows:
|Hu and Tuomilehto||The reviewers assessed the available literature for the role of physical activity and lifestyle modifications in the prevention of cardiovascular disease in patients with T2DM.||As well as certain nutritional interventions, they concluded that physical activity was associated with greater longevity in patients with T2DM regardless of body fat percentage, blood pressure, total cholesterol and smoking and alongside modifying diet and lifestyle factors is an appropriate preventative strategy.|
|Zanuso et al.||The reviewers conducted a review of 37 of the most relevant randomised control trials, meta-analyses and cohort studies investigating the relationship between exercise interventions and metabolic outcomes in T2DM. The review covers the effect of aerobic only and resistance only exercise interventions and the effects of combined aerobic and resistance training.||The reviewers found that there was a positive outcome of aerobic training programs and that more vigorous intensity aerobic exercise elicits superior improvements in A1C, V02max and insulin sensitivity. They also found that resistance-training also confers positive improvements in glycaemic control and similar in magnitude to aerobic training which makes resistance training an efficacious exercise modality. They reported based on limited research that combined training may have synergistic and incremental effects on glycaemic control, and offer greater improvements in A1C than either aerobic or resistance training alone.|
|Boule et al.||The reviewers performed a systematic review and meta analysis to assess the effect of exercise for glycaemic control in patients with T2DM. The reviewers found 14 studies, 11 of which were randomised and 3 of which were non-randomised control trials.||The reviewers reported that exercise produced changes in markers of glycaemic control by an amount that would significantly reduce T2DM complications, but without a significant change in body mass.|
|Snowling and Hopkins||The reviewers produced a meta-analysis to assess the effect of different modes of exercise training on glycaemic control. The meta-analysis included 27 randomised control trials with a total of 1,003 patients with T2DM.||The reviewers reported that the difference in improvement between aerobic training, resistance training or combined training was minimal, all producing a small (0.8%) reduction in A1C. The reviewers reported that combined training generally produced superior benefits in glycaemic control than either training mode alone. The effect of exercise training on other risk factors was generally unclear or trivial and exercise appears to produce greater improvements with increasing disease severity.|
|Umpierre et al.||The reviewers conducted a systematic review and meta-analysis on the effect of structured exercise training (aerobic, resistance or combined) compared to physical activity advice in patients with T2DM. The reviewers found 48 randomized controlled trials including 5,385 patients.||The reviewers reported that structured exercise training significantly improves A1C levels following combined (-0.67%), aerobic (0.73%) and resistance-training (-0.57%). The reviewers reported that exercise training of more than 150min per week produces superior results than less than 150 minutes per week. The reviewers also report than physical activity advice (without dietary advice) appears to have no affect on glycaemic control.|
Based on these reviews, it appears that exercise confers important benefits for patients with T2DM, significant enough in magnitude to reduce T2DM-related complications. It also appears that combined modality exercise may be superior due to synergistic effects on glycaemic control.
Evidence-based recommendations for exercise
The following studies have set out current guidelines or position statements in respect of the use of exercise for the treatment of T2DM, as follows:
|Hordern et al.||The researchers formed the position statement from Exercise and Sport Science Australia. The authors made 5 suggestions for exercise training."||The researchers recommend 1) a weekly exercise volume of either 210 minutes per week of moderate intensity or 125 minutes per week of vigorous intensity, 2) exercise should be performed with no more than 2 consecutive days between bouts, 3) vigorous intensity exercise may be more beneficial than moderate intensity in patients without contraindication, 4) At least 2 resistance training sessions should be included in the total weekly exercise volume comprising 2 – 4 sets of 8 – 10 repetitions for 8 – 10 exercises, and 5) because of the presence of co-morbidities, exercise training programs should be written and delivered by appropriately qualified professionals.|
|Colberg et al.||The researchers formed the joint position statement for the American Diabetes Association and the American College of Sports Medicine.||The researchers suggest that exercise interventions (with modest weight loss) can lower the risk of T2DM by 58% in high-risk populations and has positive affects on lipids, blood pressure, cardiovascular events, mortality and quality of life. The researchers suggest that a combined approach of aerobic and resistance exercise offers the most benefit. The researchers also suggest that participants should take part in at least 150 minutes per week of moderate to vigorous intensity exercise and moderate to vigorous resistance training 2 – 3 times per week, with no more than 2 consecutive days between exercise bouts.|
|Madden.||The author offers several clinical recommendations for exercise interventions for patients with T2DM.||The recommendations are: 1) a combined approach of aerobic and resistance exercise should be taken, and the ratio should be determined based on the participants comorbidities, 2) although vigorous exercise intensity has superior impact on insulin sensitivity, the risk of injury should be considered, and patients should undertake the highest intensity exercise possible that is safe and tolerable, 3) the role of low-volume-high-intensity training may be an effective intervention for patients if their comorbidities allow for it, especially if compliance is poor due to perceived time constraints.|
|Duclus et al.||The authors form the recommendations of the Francophone Diabetes Society.||The researchers recommend 1) the use of aerobic endurance exercises like walking, cycling and swimming, as well as resistance training, 2) either longer duration moderate intensity exercise (>30 minutes @ 40 – 60% of HRM) for at least 150 minutes per week or vigorous intensity shorter duration (20 minutes @ >60% HRM) for 90 minutes per week, 3) to exercise at least 3 times per week with no more than 2 consecutive days between bouts.|
Based on these guidelines, it appears that exercise interventions to help treat T2DM should revolve around combined modality aerobic and resistance exercise between 120 – 210 minutes per week dependant on exercise intensity, and tailored to the individual’s specific comorbidities and risk of injury.
|Prevalence||The prevalence of T2DM can range from 2.8 – 20.4%, depending on the population studied. Older populations tend to display greater prevalence of T2DM than younger populations. The prevalence of T2DM in whole populations can range from 2.8 – 10.4%.|
|Incidence||The incidence of T2DM has increased over the last 2 decades and can range from 0.5 – 15.1% depending on the exact population. Studies also indicate that individuals who are physically sedentary or obese have a higher incidence.|
|Risk Factors||The main risk factors for developing T2DM are: being overweight or obesity, having a high body mass index (BMI), following a sedentary lifestyle, having a high waist-to-hip ratio and being of advanced age.|
|Aerobic exercise||Aerobic exercise in T2DM has beneficial effects on cardiorespiratory fitness and lipid levels. Aerobic exercise can improve long term glucose control (measured by A1C) and short term glucose and insulin responses, although the improvement in glucose tolerance appears to drop substantially within 3 days. The intensity and volume of aerobic exercise may correlate with greater improvements in acute glycaemic responses.|
|Resistance-training||Resistance-training can increase muscle strength and lean mass, and reduce subcutaneous and visceral fat in T2DM. Resistance-training may also improve glucose disposal, insulin response and long term glycaemic control, as well as improving these outcomes in conjunction with weight loss.|
|Combined training||Combined training offer additional benefits to either aerobic or resistance exercise alone in terms of improved long term glycaemic control, body composition and lipid profiles.|
|Alternative exercise||Some alternative exercise interventions may confer beneficial effects on risk indices for patients with T2DM and in some circumstances impart small but significant effects on glycaemic control.|
|Effects of exercise on glycemic control||An exercise bout increases glucose disposal and decreases plasma insulin, thereby normalising blood glucose. However, this response to exercise appears to be transient. It also appears that exercise intensity may aid in augmenting the transient response to exercise by improving glucose tolerance and reducing plasma insulin in response to blood glucose. However, sustained improvements in glycaemic control may not occur in exercising individuals outside of the residual effect of an exercise bout.|
|Combined exercise and lifestyle interventions||Exercise is an important adjunct to weight loss and lifestyle interventions to reduce the incidence of T2DM and to improve outcomes in those already with T2DM. It appears that successful weight maintenance is correlated with adherence to exercise and improved weight loss during supervised exercise interventions.|
|Long-term effect of exercise||Changes in muscle quality and quantity occur in response to exercise in individuals with T2DM.|
|Reviews of exercise interventions||exercise confers important benefits for patients with T2DM, significant enough in magnitude to reduce T2DM-related complications. It also appears that combined modality exercise may be superior due to synergistic effects on glycaemic control.|
|Current guidelines||Exercise interventions to help treat T2DM should revolve around combined modality aerobic and resistance exercise between 120 – 210 minutes per week dependant on exercise intensity, and tailored to the individual’s specific comorbidities and risk of injury.|
In summary, it appears that exercise interventions involving aerobic, resistance-training, combined-training and alternative modalities are all useful in the prevention and treatment of T2DM. An exercise program designed to help treat T2DM should involve combined exercise modalities lasting 120 – 210 minutes per week dependant on exercise intensity, and tailored to the individual’s specific comorbidities and risk of injury.
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