Can J Diabetes 37 (2013) 359–360
Contents lists available at ScienceDirect
Canadian Journal of Diabetes journal homepage: www.canadianjournalofdiabetes.com
Guest Editor’s Note
Physical Activity, Exercise and Diabetes
Regular physical activity has been recommended for people with diabetes for hundreds of years. Historically, Susruta, a physician in India, was the first to recommend exercise for health reasons roughly 2600 years ago (1). He highlighted exercise as a strategy to promote a reduction in the sweetness of urine in patients with diabetes. Although he believed that diabetes was a disease of the urinary tract, he linked it with obesity and recommended dietary changes along with long walks and engaging in sports such as wrestling and riding on a horse or elephant (1). Early in our careers as researchers on physical activity and diabetes in the 1990s, we were sometimes asked, “Why did you choose to study such an old science?” or “Don’t we already know pretty much everything about exercise and diabetes?” Ironically, most of the highest-quality evidence on exercise and diabetes has been published in the past 10 years or so (i.e. subsequent to when our interrogators thought we already knew everything there was to know on this topic). In this special issue focusing on exercise and physical activity in diabetes, 7 articles cover a wide range of exercise-related topics. These range from short-term effects of exercise, to the health and fitness benefits of resistance and aerobic type exercise training to the challenges in implementation of exercise programming at the community level. The commentary by Armstrong and Sigal highlights changes in the Canadian Diabetes Association’s Clinical Practice Guidelines on Physical Activity/Exercise between 2008 (2) and 2013 (3). One key change in the updated recommendations is a softening of the previous recommendation for exercise stress testing in asymptomatic previously sedentary patients who are about to initiate a new exercise regimen. This change reflects new evidence that screening for cardiovascular disease with exercise stress testing (4) or nuclear imaging (5) may not alter prognosis. Other new elements of the Clinical Practice Guidelines discussed in the commentary include minimizing risk of heat-related illness, new strategies to reduce exercise-related hypoglycemia in patients with type 1 diabetes, exercise in people with peripheral neuropathy and motivating people with diabetes to be more physically active. Two articles by Yardley et al in this special issue highlight the health benefits of resistance exercise (weight lifting) and intermittent high-intensity anaerobic exercise in patients with type 1 diabetes. Among the most important recent discoveries in this area is the finding that resistance exercise does not cause nearly the same magnitude of reduction in glucose levels as aerobic exercise, which may be helpful from a hypoglycemia prevention point of view. Moreover, when both types of activities are performed in the same session, performing the resistance exercise before (rather than after) the aerobic exercise results in greater stability in glucose 1499-2671/$ – see front matter Ó 2013 Canadian Diabetes Association http://dx.doi.org/10.1016/j.jcjd.2013.10.001
levels, and less hypoglycemia, both during the exercise session and after its completion. As highlighted in the review article by Yardley et al on intermittent high-intensity exercise, it remains to be determined whether the reduced hypoglycemia risk during this type of exercise will translate to improved blood glucose control as measured by A1C level in the long term. One theory is that strategies allowing exercise to occur with more glucose stability and with less hypoglycemia might translate to a lower A1C level because patients would have less fear of hypoglycemia, and would perceive less need to consume excessive carbohydrates or make very aggressive reductions in insulin doses. In two of the articles published in this special issue, refinements in the exercise prescription for type 2 diabetes are presented along with examination of a new potential mechanism for the benefits of exercise. In a small randomized crossover study, Eshghi et al tested the hypothesis that aerobic exercise increases the plasma concentrations of glucagon like peptide-1 (GLP-1) and glucosedependent insulinotropic polypeptide in patients with type 2 diabetes, which would be a potential mechanism for improved glucose tolerance with exercise. They found patients had higher GLP-1 levels during periods when on metformin vs. placebo, but levels of GLP-1 and glucose-dependent insulinotropic polypeptide were not different on exercise days vs. sedentary days. In the other original research article, Drs. Yang and Oh performed a retrospective analysis of the results of a 6-month partially supervised, primarily home-based exercise program for people with type 2 diabetes. Impressively, more than 500 patients completed the program over a 5-year period, and the program produced a very significant improvement in cardiorespiratory fitness (by w15%). They also found that participants who were prescribed exercise in the form of longer walking distances and at faster walking paces had greater cardiorespiratory fitness at 6 months in comparison with those prescribed shorter-duration and lower-intensity exercise. The regression analysis by Yang and Oh suggested that walking distance might be more important than walking speed for increasing cardiorespiratory fitness. However, the nonrandomized uncontrolled study design, and the fact that exercise prescription was determined by fitness at baseline, limit the certainty of this conclusion. Although the benefits of aerobic and resistance training are now widely known, adherence to such training often is challenging. In their original research article, Tulloch et al conducted a qualitative investigation of patient’s perceived barriers and facilitators at several time points during the previously published Diabetes and Aerobic and Resistance Exercise trial (6), which evaluated the effects of supervised, facility-based aerobic and resistance training in type 2 diabetes. They found that social support from family members and an overall greater sense of well-being and fitness
360
Guest Editor’s Note / Can J Diabetes 37 (2013) 359–360
were the main factors associated with higher exercise adherence. Interestingly, participants who performed either resistance exercise alone or combined resistance and aerobic exercise had higher long-term adherence than those randomized to only aerobic exercise. Those participants performing resistance exercise also reported a greater sense of enjoyment and more support from their trainers, factors that might explain their greater long-term exercise adherence. Participants who remained adherent to exercise over time had the same barriers to exercise (e.g. work commitments, weather and illness/injury), but more facilitators (e.g. perceived health benefits, support from family and use of strategies to maintain activity level), compared with those whose exercise adherence diminished over time. Also in this issue are two articles describing attempts to implement exercise programming in community settings. Rowan et al provides a commentary on the successes and challenges of their Pre-Diabetes Detection and Physical Activity Intervention Delivery program. The Pre-Diabetes Detection and Physical Activity Intervention Delivery program focuses on culturally specific exercise options for people at high risk of prediabetes in a diverse urban Canadian city. The researchers shared their strategies for community engagement and some of their preliminary research findings. Shields et al described the effectiveness for Diabetes Educators in attending a workshop on Physical Activity/Exercise and using the Physical-activity and Exercise Toolkit. This toolkit was developed by Drs. Jonathon Fowles and Chris Shields with input from numerous stakeholders. Interestingly, after attending the workshop and using the toolkit, educators reported greater knowledge about physical activity and a greater sense of competence in prescribing exercise, but they also developed a greater appreciation of the complexity of exercise prescription. As we learn more about the effects of exercise on patients with diabetes, we become increasingly aware of how much more there is to learn. We still need to determine the effects of different exercise
modalities, exercise durations and intensities and different means of delivery for exercise training in different populations. We have made progress in developing strategies to minimize exerciseassociated hypoglycemia risk in patients with type 1 diabetes, but more can be done. There has been little research using continuous glucose monitoring to optimize diabetes management during and after exercise. Finally, to maximize the impact of physical activity on population health, we need to make considerably more progress in helping people of all ages and from all walks of life to incorporate more physical activity in their lives, and to continue doing so in the long term. Michael C. Riddell, PhD Ronald J. Sigal, MD, MPH, FRCPC Guest Editors-in-Chief E-mail address: [email protected] (M.C. Riddell) References 1. Tipton CM. Susruta of India, an unrecognized contributor to the history of exercise physiology. J Appl Physiol 2008;104:1553–6. 2. Canadian Diabetes Association Expert Committee. Canadian Diabetes Association Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada: physical activity and diabetes. Can J Diabetes 2008;32(suppl 1): S37–9. 3. Sigal RJ, Armstrong MJ, Colby P, et al. Canadian Diabetes Association 2013 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada: physical activity and diabetes. Can J Diabetes 2013;37(suppl 1):S40–4. 4. Lievre M, Moulin P, Thivolet C, et al. Detection of silent myocardial ischemia in asymptomatic patients with diabetes: results of a randomized trial and metaanalysis assessing the effectiveness of systematic screening. Trials 2011;12:23. 5. Young LH, Wackers FJ, Chyun DA, et al. Cardiac outcomes after screening for asymptomatic coronary artery disease in patients with type 2 diabetes: the DIAD study: a randomized controlled trial. JAMA 2009;301:1547–55. 6. Sigal RJ, Kenny GP, Boule NG, et al. Effects of aerobic training, resistance training, or both on glycemic control in type 2 diabetes: a randomized trial. Ann Intern Med 2007;147:357–69.
Contents lists available at ScienceDirect
Canadian Journal of Diabetes journal homepage: www.canadianjournalofdiabetes.com
Guest Editor’s Note
Physical Activity, Exercise and Diabetes
Regular physical activity has been recommended for people with diabetes for hundreds of years. Historically, Susruta, a physician in India, was the first to recommend exercise for health reasons roughly 2600 years ago (1). He highlighted exercise as a strategy to promote a reduction in the sweetness of urine in patients with diabetes. Although he believed that diabetes was a disease of the urinary tract, he linked it with obesity and recommended dietary changes along with long walks and engaging in sports such as wrestling and riding on a horse or elephant (1). Early in our careers as researchers on physical activity and diabetes in the 1990s, we were sometimes asked, “Why did you choose to study such an old science?” or “Don’t we already know pretty much everything about exercise and diabetes?” Ironically, most of the highest-quality evidence on exercise and diabetes has been published in the past 10 years or so (i.e. subsequent to when our interrogators thought we already knew everything there was to know on this topic). In this special issue focusing on exercise and physical activity in diabetes, 7 articles cover a wide range of exercise-related topics. These range from short-term effects of exercise, to the health and fitness benefits of resistance and aerobic type exercise training to the challenges in implementation of exercise programming at the community level. The commentary by Armstrong and Sigal highlights changes in the Canadian Diabetes Association’s Clinical Practice Guidelines on Physical Activity/Exercise between 2008 (2) and 2013 (3). One key change in the updated recommendations is a softening of the previous recommendation for exercise stress testing in asymptomatic previously sedentary patients who are about to initiate a new exercise regimen. This change reflects new evidence that screening for cardiovascular disease with exercise stress testing (4) or nuclear imaging (5) may not alter prognosis. Other new elements of the Clinical Practice Guidelines discussed in the commentary include minimizing risk of heat-related illness, new strategies to reduce exercise-related hypoglycemia in patients with type 1 diabetes, exercise in people with peripheral neuropathy and motivating people with diabetes to be more physically active. Two articles by Yardley et al in this special issue highlight the health benefits of resistance exercise (weight lifting) and intermittent high-intensity anaerobic exercise in patients with type 1 diabetes. Among the most important recent discoveries in this area is the finding that resistance exercise does not cause nearly the same magnitude of reduction in glucose levels as aerobic exercise, which may be helpful from a hypoglycemia prevention point of view. Moreover, when both types of activities are performed in the same session, performing the resistance exercise before (rather than after) the aerobic exercise results in greater stability in glucose 1499-2671/$ – see front matter Ó 2013 Canadian Diabetes Association http://dx.doi.org/10.1016/j.jcjd.2013.10.001
levels, and less hypoglycemia, both during the exercise session and after its completion. As highlighted in the review article by Yardley et al on intermittent high-intensity exercise, it remains to be determined whether the reduced hypoglycemia risk during this type of exercise will translate to improved blood glucose control as measured by A1C level in the long term. One theory is that strategies allowing exercise to occur with more glucose stability and with less hypoglycemia might translate to a lower A1C level because patients would have less fear of hypoglycemia, and would perceive less need to consume excessive carbohydrates or make very aggressive reductions in insulin doses. In two of the articles published in this special issue, refinements in the exercise prescription for type 2 diabetes are presented along with examination of a new potential mechanism for the benefits of exercise. In a small randomized crossover study, Eshghi et al tested the hypothesis that aerobic exercise increases the plasma concentrations of glucagon like peptide-1 (GLP-1) and glucosedependent insulinotropic polypeptide in patients with type 2 diabetes, which would be a potential mechanism for improved glucose tolerance with exercise. They found patients had higher GLP-1 levels during periods when on metformin vs. placebo, but levels of GLP-1 and glucose-dependent insulinotropic polypeptide were not different on exercise days vs. sedentary days. In the other original research article, Drs. Yang and Oh performed a retrospective analysis of the results of a 6-month partially supervised, primarily home-based exercise program for people with type 2 diabetes. Impressively, more than 500 patients completed the program over a 5-year period, and the program produced a very significant improvement in cardiorespiratory fitness (by w15%). They also found that participants who were prescribed exercise in the form of longer walking distances and at faster walking paces had greater cardiorespiratory fitness at 6 months in comparison with those prescribed shorter-duration and lower-intensity exercise. The regression analysis by Yang and Oh suggested that walking distance might be more important than walking speed for increasing cardiorespiratory fitness. However, the nonrandomized uncontrolled study design, and the fact that exercise prescription was determined by fitness at baseline, limit the certainty of this conclusion. Although the benefits of aerobic and resistance training are now widely known, adherence to such training often is challenging. In their original research article, Tulloch et al conducted a qualitative investigation of patient’s perceived barriers and facilitators at several time points during the previously published Diabetes and Aerobic and Resistance Exercise trial (6), which evaluated the effects of supervised, facility-based aerobic and resistance training in type 2 diabetes. They found that social support from family members and an overall greater sense of well-being and fitness
360
Guest Editor’s Note / Can J Diabetes 37 (2013) 359–360
were the main factors associated with higher exercise adherence. Interestingly, participants who performed either resistance exercise alone or combined resistance and aerobic exercise had higher long-term adherence than those randomized to only aerobic exercise. Those participants performing resistance exercise also reported a greater sense of enjoyment and more support from their trainers, factors that might explain their greater long-term exercise adherence. Participants who remained adherent to exercise over time had the same barriers to exercise (e.g. work commitments, weather and illness/injury), but more facilitators (e.g. perceived health benefits, support from family and use of strategies to maintain activity level), compared with those whose exercise adherence diminished over time. Also in this issue are two articles describing attempts to implement exercise programming in community settings. Rowan et al provides a commentary on the successes and challenges of their Pre-Diabetes Detection and Physical Activity Intervention Delivery program. The Pre-Diabetes Detection and Physical Activity Intervention Delivery program focuses on culturally specific exercise options for people at high risk of prediabetes in a diverse urban Canadian city. The researchers shared their strategies for community engagement and some of their preliminary research findings. Shields et al described the effectiveness for Diabetes Educators in attending a workshop on Physical Activity/Exercise and using the Physical-activity and Exercise Toolkit. This toolkit was developed by Drs. Jonathon Fowles and Chris Shields with input from numerous stakeholders. Interestingly, after attending the workshop and using the toolkit, educators reported greater knowledge about physical activity and a greater sense of competence in prescribing exercise, but they also developed a greater appreciation of the complexity of exercise prescription. As we learn more about the effects of exercise on patients with diabetes, we become increasingly aware of how much more there is to learn. We still need to determine the effects of different exercise
modalities, exercise durations and intensities and different means of delivery for exercise training in different populations. We have made progress in developing strategies to minimize exerciseassociated hypoglycemia risk in patients with type 1 diabetes, but more can be done. There has been little research using continuous glucose monitoring to optimize diabetes management during and after exercise. Finally, to maximize the impact of physical activity on population health, we need to make considerably more progress in helping people of all ages and from all walks of life to incorporate more physical activity in their lives, and to continue doing so in the long term. Michael C. Riddell, PhD Ronald J. Sigal, MD, MPH, FRCPC Guest Editors-in-Chief E-mail address: [email protected] (M.C. Riddell) References 1. Tipton CM. Susruta of India, an unrecognized contributor to the history of exercise physiology. J Appl Physiol 2008;104:1553–6. 2. Canadian Diabetes Association Expert Committee. Canadian Diabetes Association Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada: physical activity and diabetes. Can J Diabetes 2008;32(suppl 1): S37–9. 3. Sigal RJ, Armstrong MJ, Colby P, et al. Canadian Diabetes Association 2013 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada: physical activity and diabetes. Can J Diabetes 2013;37(suppl 1):S40–4. 4. Lievre M, Moulin P, Thivolet C, et al. Detection of silent myocardial ischemia in asymptomatic patients with diabetes: results of a randomized trial and metaanalysis assessing the effectiveness of systematic screening. Trials 2011;12:23. 5. Young LH, Wackers FJ, Chyun DA, et al. Cardiac outcomes after screening for asymptomatic coronary artery disease in patients with type 2 diabetes: the DIAD study: a randomized controlled trial. JAMA 2009;301:1547–55. 6. Sigal RJ, Kenny GP, Boule NG, et al. Effects of aerobic training, resistance training, or both on glycemic control in type 2 diabetes: a randomized trial. Ann Intern Med 2007;147:357–69.
