Diabetes and exercise

Evaluation of skeletal muscle activity during foot training exercises using positron emission tomography

The foot exercises “rock-paper-scissors” and “towel gathering” are widely used in patients with lower limb disorders; however, there are no detailed reports on muscle activity during such training. We quantitatively evaluated the difference in skeletal muscle activity between the two exercises using positron emission tomography. Eight university student athletes were included. Four participants each were assigned to the foot rock-paper-scissors and towel gathering groups. Participants in each group underwent continuous training for 15 min, and received an intravenous injection of 18F-fluorodeoxyglucose. After retraining for 15 min, participants rested for 45 min. Regions of interest were defined in 25 muscles. The standardized uptake value (SUV) in the trained limb was compared with that in the non-trained control limb. SUVs increased in four skeletal muscles (tibialis anterior, peroneus brevis, extensor hallucis brevis, and abductor hallucis) in the rock-paper-scissors group, and in four muscles (flexor digitorum longus, extensor hallucis brevis, extensor digitorum brevis, and quadratus plantae) in the towel gathering group. Thus, foot rock-paper-scissors and towel gathering involved skeletal muscles related to the medial longitudinal arch and toe grip strength, respectively. Given that the two exercises target different skeletal muscles, they should be taught and implemented according to their respective purposes.

Risk Factors for Coronary Heart Disease in Hispanic Populations: A Review

Epidemiological studies of coronary heart disease (CHD) risk factors among Hispanics were examined. Hispanics as compared with Anglo Americans and blacks appear to have somewhat lower mortality rates of CHD. This suggests that Hispanics may have lifestyle patterns which reduce CHD risk in the areas of stress, diet, exercise, hypertension, and smoking. However, independent studies report that their samples of Mexican American subjects, but not Puerto Rican subjects, had higher blood lipid levels, greater rates of being overweight, and participate in less aerobic exercises as compared with same sex and aged Anglo American cohorts. By contrast, adult Mexican Americans and Puerto Ricans tend to smoke less than do Anglo American cohorts, although some evidence suggests that Hispanic adolescents may smoke more than do their Anglo American peers. The CHD risk status of Hispanics is summarized and recommendations for future research and health promotion programs are made.

Evaluation of individual skeletal muscle activity by glucose uptake during pedaling exercise at different workloads using positron emission tomography

Skeletal muscle glucose uptake closely reflects muscle activity at exercise intensity levels <55% of maximal oxygen consumption (V̇o2max). Our purpose was to evaluate individual skeletal muscle activity from glucose uptake in humans during pedaling exercise at different workloads by using [18F]fluorodeoxyglucose (FDG) and positron emission tomography (PET). Twenty healthy male subjects were divided into two groups (7 exercise subjects and 13 control subjects). Exercise subjects were studied during 35 min of pedaling exercise at 40 and 55% V̇o2max exercise intensities. FDG was injected 10 min after the start of exercise or after 20 min of rest. PET scanning of the whole body was conducted after completion of the exercise or rest period. In exercise subjects, mean FDG uptake [standardized uptake ratio (SUR)] of the iliacus muscle and muscles of the anterior part of the thigh was significantly greater than uptake in muscles of control subjects. At 55% V̇o2max exercise, SURs of the iliacus muscle and thigh muscles, except for the rectus femoris, increased significantly compared with SURs at 40% V̇o2max exercise. Our results are the first to clarify that the iliacus muscle, as well as the muscles of the anterior thigh, is the prime muscle used during pedaling exercise. In addition, the iliacus muscle and all muscles in the thigh, except for the rectus femoris, contribute when the workload of the pedaling exercise increases from 40 to 55% V̇o2max.

Impact of the short-term, intense exercise on postprandial glycemia in type 2 diabetic patients treated with gliclazide

BACKGROUND

Physical activity is crucial for treatment of diabetes. However, intensive exercise brings the risk for metabolic decompensation; therefore, predicting its effect on glycemia is of great importance.

MATERIALS AND METHODS

Fourteen type 2 diabetic patients (47.9+/-1.6 years; mean+/-S.E.M.), treated with gliclazide, and 14 healthy controls (45.1+/-1.0 years) were subjected to standard graded submaximal (90% HR(max)) exercise treadmill testing for 2 h after standardized breakfast. Blood glucose, lactate, insulin, and proinsulin concentrations were measured on fasting and during the periexercise period up to 120 min after the effort. Glucagon, growth hormone, cortisol, and catecholamines were determined up to 60 min of the recovery period.

RESULTS

After exercise, glycemia decreased from the preexercise value of 11.3+/-1.4 to 8.0+/-1.1 mmol/l at 120 min (P<.001) in the diabetic group, while in controls, it did not change significantly. Shift in glycemia during and after exercise in the diabetic group was dependent on preexercise glycemia, according to the quadratic polynomial regression model, whereas a simple negative correlation between these indices was found in the control group. Insulinemia tended to decrease from the midexercise maximum of 488+/-116 to 261+/-71 pmol/l at the 120th min in diabetic patients. Neither hypoglycemia nor deficit in response of counterregulatory hormones was observed.

CONCLUSIONS

In the type 2 diabetic patients treated with gliclazide, short-term, intensive, submaximal exercise, performed 2 h after a meal, causes reduction of hyperglycemia during the recovery period. Preexercise glycemia was found to be a primary predictor of the shift in glycemia under the exercise, according to the polynomial regression model.

Walking decreased risk of cardiovascular disease mortality in older adults with diabetes

OBJECTIVE

This study examines the association of walking with mortality in persons with type 2 diabetes compared to those with normal glucose tolerance.

STUDY DESIGN AND SETTING

This prospective study included community-dwelling adults from the Rancho Bernardo Study aged 50-90 years in 1984-86 who had type 2 diabetes (n=347) or normal glucose tolerance (n=1,317). During the 10-year follow up, Cox proportional hazards modeling was used to model time until death from all causes (n=538), coronary heart disease (CHD, n=143), other cardiovascular disease (non-CHD CVD, n=138), and other causes (n=257) while adjusting for multiple potential confounders.

RESULTS

After adjusting for sex, age, smoking, body mass index, alcohol, exercise, history of CHD, and other covariates, adults with diabetes who walked > or =1 mile per day were half as likely to die from all causes combined (hazard ratio [HR]=0.54; 95% confidence interval [CI]: 0.33, 0.88), and less than one-fifth as likely to die from non-CHD CVD (HR=0.19; 95% CI: 0.04, 0.86) compared to adults with diabetes who did not walk. Walking was also protective among adults with normal glucose tolerance (HR=0.55; 95% CI: 0.32, 0.96).

CONCLUSION

Results suggest walking > or =1 mile per day may provide strong protection from all-cause and non-CHD CVD mortality in older adults with diabetes.

Influence of aerobic treadmill exercise on blood glucose homeostasis in noninsulin dependent diabetes mellitus patients

The role of treadmill exercise on blood glucose homeostasis in noninsulin dependent diabetes mellitus (NIDDM) were studied using males between age of 45 and 60 years (X-52), who were clinically and biochemically-confirmed cases of NIDDM were taken into study group. Control group comprised of 10 males between age group of 45 to 60 (X-53) years. All the subjects were assessed by physician and were investigated to confirm diabetic status. The whole study period was extended for 6 weeks. The significant decrease in postprandial blood sugar (44.4 mg% for the study group and 32.2mg% for the control group) with a significant inter group difference (P<0.05) was observed. The mean decrease in fasting blood sugar (39.4mg% for the study group and 27.4mg% for the control group), with a marginal inter group difference (P<0.05) was observed. The treadmill exercise was found to be a definite tool in addition to drug and diet in glycemic control.

America's obesity epidemic: measuring physical activity to promote an active lifestyle

The incidence of overweight and obesity in the United States and worldwide has reached epidemic proportions. To effectively intervene, dietetics professionals and other health care practitioners need to address both sides of the energy balance equation when counseling clients and patients. Often, the focus on energy intake supersedes the promotion of a physically active lifestyle. Incorporating appropriate and sufficient physical activity into one's life is an essential component of achieving and maintaining a healthful body weight. This review summarizes background knowledge on the benefits of physical activity for health and provides an overview of available tools for measuring physical activity and energy expenditure. The physical and mental health benefits of an active lifestyle, current physical activity recommendations for the US public, the prevalence of inactivity in the United States, and components of energy expenditure are reviewed. Additionally, tools for estimating total energy expenditure, resting metabolic rate, and physical activity are evaluated and suitable approaches for applying these tools are provided.

Alcohol and postexercise metabolic responses in type 2 diabetes

The objective was to investigate the impact of the combination of exercise and alcohol on the metabolic response in nonfasting and fasting type 2 diabetic subjects. In part 1, 12 untrained middle-aged type 2 diabetic subjects participated on 3 test days. On each day, they ingested a light meal (1,824 kJ) containing 48 energy percent (E%) carbohydrate, 38 E% fat, and 14 E% protein. The meal was followed by either (A) rest or (B) 30 minutes of exercise (40% of maximum O2 consumption [VO2max]) or (C) taken with alcohol (0.4 g/kg body weight) followed by 30 minutes of exercise (40% of VO2max). In part 2, 11 untrained middle-aged type 2 diabetic subjects participated on 4 test days without a meal. The subjects were either (A) resting, (B) drinking alcohol (0.4 g/kg body weight), (C) exercising 30 minutes (40% of VO2max), or (D) drinking alcohol (0.4 g/kg body weight) and exercising 30 minutes (40% of VO2max). On each test day, regular blood samples were drawn for 4 hours for analysis of glucose, insulin, lactate, triglycerides, nonesterified fatty acid (NEFA), and ethanol. Comparing exercise and rest following a light meal (part 1, no change (7%) occurred in the plasma glucose response area (642 +/- 119 v 724 +/- 109 mmol x L(-1) x 240 min, NS). However, it was significantly reduced (by 27%) in response to exercise and alcohol (509 +/- 98 v 724 +/- 109 mmol x L(-1) x 240 min; P = .03). Similar serum insulin response areas were obtained. After exercise and alcohol, plasma lactate increased compared with the resting state (2.2 +/- 0.2 v 1.6 +/- 0.1 mmol x L(-1), P = .004) and with exercise alone (2.2 +/- 0.2 v 1.8 +/- 0.2 mmol x L(-1), P = .04). Serum NEFAs were significantly reduced by exercise and alcohol compared with the resting state (0.50 +/- 0.04 v 0.65 +/- 0.06 mmol x L(-1), P = .008) and with exercise alone (0.50 +/- 0.04 v 0.61 +/- 0.05 mmol x L(-1), P = .02). Similar serum triglycerides were found. During the fasting state (part 2), similar plasma glucose response areas were obtained in the four situations. The insulin response area to exercise and alcohol increased significantly compared with the resting state (3,325 +/- 744 v 882 +/- 295 pmol x L(-1) x 240 min, P = .02) and with exercise alone (3,325 +/- 744 v 1,328 +/- 422 pmol x L(-1) x 240 min, P = .007). No difference was found compared with alcohol alone. Plasma lactate was higher after alcohol intake versus the resting state (1.9 +/- 0.1 v 1.3 +/- 0.1 mmol x L(-1), P = .003), as well as after exercise and alcohol (1.9 +/- 0.1 v 1.3 +/- 0.1 mmol x L(-1), P = .01). After exercise and alcohol serum NEFAs were significantly reduced compared with the resting state (0.43 +/- 0.02 v 0.64 +/- 0.02 mmol x L(-1), P < .001), alcohol alone (0.43 +/- 0.02 v 0.51 +/- 0.02 mmol x L(-1), P < .001), and exercise alone (0.43 +/- 0.02 v 0.64 +/- 0.02 mmol x L(-1), P < .001). Serum triglycerides were similar in the four situations. We conclude that moderate exercise with or without moderate alcohol intake does not cause acute hypoglycemia either after a light meal or in the fasting state in untrained overweight type 2 diabetic subjects.

Diabetes mellitus and predisposition to athletic pedal fracture

The purpose of this project was to study the epidemiology of pedal fractures among diabetic athletes and to determine whether diabetic athletes have a higher prevalence of pedal fractures than athletes from the general population. Questionnaire results were obtained from 120 athletes, 60 with diabetes mellitus and 60 without the disease. Subjects answered questions regarding gender, age, duration of disease (if present), presence of Type I or Type II diabetes, daily activity level, types of physical activity, and the admission or denial of athletically induced pedal fracture, including which bones were affected. Statistical significance was achieved with the following parameters: the presence of diabetes and increased prevalence of fracture (p < 0.025) maleness and diabetes and increased prevalence of fracture (p < 0.05), duration of diabetes greater than 25 years and increased prevalence of fracture (p < 0.005), control subjects greater than 30 years of age and increased prevalence of fracture (p = 0.007), moderate correlation between diabetes and prevalence of multiple fractures (r = 0.55, p < 0.025), and moderate correlation between daily activity level and prevalence of fracture among control subjects (r = 0.73, p < 0.05). The most frequently fractured bone was the fifth metatarsal. Until now the literature available on the topic has been sparse, confusing and inconclusive; the results of this study was enable individuals with diabetes to be informed of the risks of pedal fracture associated with active lifestyles.

Relationship of co-morbidities of obesity to weight loss and four-year weight maintenance/rebound

This study examined the effect of weight loss (separate from energy restriction) and weight maintenance/rebound over time on blood pressure, serum lipids, and body composition in 24 obese (mean 137% ideal body weight (IBW)) females with mild to moderate hypertension. Weight loss was induced under tightly controlled General Clinical Research Center conditions until each subject had lost at least 10 kg (mean 13 kg) and attained normal body weight (< 120% IBW). After 4 years subjects returned for repeat evaluation. Weight changes were compared with 24 pair-matched normal weight controls who were also followed for 4 years. With weight loss, significant improvements were seen in standing mean arterial pressure (MAP), serum total cholesterol, low-density lipoprotein cholesterol, and triglycerides. Subjects regained 11 kg (87% of the weight lost) over the 4 year follow-up period while control subjects gained only 2 kg. Subjects who chose self-selected exercise gained less weight than nonexercisers (6 kg vs. 13 kg, P < 0.05). With weight regain there were significant increases in standing and supine MAP, total cholesterol, and high-density lipoprotein (HDL) cholesterol. The amount of weight regained was significantly correlated with standing MAP (r = 0.73), triglycerides (r = 0.43), and HDL cholesterol (r = -0.47). The percentage fat of the weight regained was no greater than that of the weight previously lost. Weight loss, distinct from energy restriction, was associated with improvements in blood pressure and serum lipid levels. The ability to sustain these improvements in the co-morbidities of obesity was directly related to the persistence and magnitude of weight loss maintenance.

Glutamate-arginine salts and hormonal responses to exercise

Hormonal changes during exercise is of growing interest because of their role in adaptation, and performance. The production of amino acids (AA) due to the degradation of muscle protein increases during exercise and some AA may be utilized for energy expenditure or as hormonal secretagogues. Thus, one can propose a strategy to reduce muscle protein breakdown and regulate hormones involved in energy metabolism by dietary AA supplementation. We assessed the effects of glutamate-arginine salt (AGs) ingestion on exercise-induced hormonal alterations in highly trained cyclists (age 18-22 yrs). Using an indwelling catheter, we collected multiple blood samples at rest, during warm up, during and after an intense exercise session. Plasma growth hormone (hGH), insulin and cortisol were measured by radioimmunoassay. As reported in previous studies, we observed a marked increase in plasma hGH and cortisol levels during and after exercise in the placebo (Pl) condition as well as a slight decrease in insulin concentration. In addition, we found that the ingestion of AGs had significant effects on some dynamic hormonal changes. AGs had no effect on resting plasma levels of hGH, insulin or cortisol. However, the marked elevation in cortisol and hGH during and after exercise in the placebo condition, was greatly diminished when subjects ingested AGs. Our results show that AGs can modify exercise-induced hormonal changes and raise the possibility that it may be used to alter energy metabolism during endurance exercise.

Exercise prescription for individuals with metabolic disorders. Practical considerations

Regular exercise has been recognised as an important component in the management of patients with diabetes mellitus. In addition to acutely lowering blood glucose, exercise training improves glucose tolerance and peripheral insulin sensitivity, contributes to weight loss and reduces several risk factors for cardiovascular disease. When proper precautions are taken to prevent hypoglycaemia, individuals with diabetes can enjoy the same benefits from exercise as nondiabetic healthy individuals. As a guideline, moderate intensity, aerobic endurance activities should be performed for 20 to 40 minutes at least 3 times a week. Blood glucose should be monitored, and insulin dose and carbohydrate intake adjusted based on the blood glucose response to the type and duration of exercise. This review will summarise current understanding of the therapeutic role of exercise in the treatment of diabetes and will present guidelines for prescribing exercise in diabetic patients.

Physical activity in Minnesota physicians

METHODS

A survey inquiring about physical activity was mailed to a random sample of 500 physicians who were current members of the Minnesota Medical Association.

RESULTS

Overall, 65.6% of the 393 respondents reported performing regular exercise, while 38.2% participated in exercise vigorous enough to be of cardiovascular benefit (at least three times per week, at least 15-30 min per session, and strenuous enough to cause sweating or shortness of breath). Men reported a significantly higher prevalence of regular exercise and cardiovascular exercise than did women. There was no significant relationship between the prevalence of either regular exercise or cardiovascular exercise and age, specialty, the percentage of primary care performed, the number of patients seen per day, or the number of hours worked per week.

CONCLUSIONS

The prevalence of physical activity was higher among physicians in this survey compared with levels reported for the general population.

Insulin and glucagon in prevention of hypoglycemia during exercise in humans

To assess the roles of decrements in insulin and increments in glucagon in the prevention of hypoglycemia during moderate exercise (approximately 60% peak O2 consumption for 60 min), normal young men were studied during somatostatin infusions with insulin and glucagon infused to 1) hold insulin and glucagon levels constant, 2) decrease insulin, 3) increase glucagon, and 4) decrease insulin and increase glucagon during exercise. In contrast to a comparison study (saline infusion), when insulin and glucagon were held constant, glucose production did not increase and plasma glucose decreased from 5.5 +/- 0.2 to 3.4 +/- 0.2 mmol/l (P less than 0.001) initially during exercise. Notably, plasma glucose then plateaued and was 3.3 +/- 0.2 mmol/l at the end of exercise. This decrease was at most only delayed when either insulin was decreased or glucagon was increased independently. However, when insulin was decreased and glucagon was increased simultaneously, there was an initial increase in glucose production, and the glucose level was 4.5 +/- 0.2 mmol/l at 60 min, a value not different from that in the comparison study. Thus we conclude that both decrements in insulin and increments in glucagon play important roles in the prevention of hypoglycemia during exercise and do so by signaling increments in glucose production. However, since hypoglycemia did not develop during exercise when changes in insulin and glucagon were prevented, an additional counterregulatory factor, such as epinephrine, must be involved in the prevention of hypoglycemia during exercise, at least when the primary factors, insulin and glucagon, are inoperative.

A review of five major community-based cardiovascular disease prevention programs. Part I: Rationale, design, and theoretical framework

Major community-based cardiovascular disease prevention programs have been conducted in North Karelia, Finland; the state of Minnesota; Pawtucket, Rhode Island; and in three communities and more recently in five cities near Stanford, California. These primary prevention programs aim to reduce cardiovascular disease incidence by reducing risk factors in whole communities. These risk factors are smoking, high blood cholesterol, diet high in cholesterol and saturated fat, hypertension, sedentary lifestyle, and obesity. This strategy may be contrasted with secondary prevention programs directed at patients who already have symptomatic cardiovascular disease and "high risk" primary prevention programs directed at individuals found through screening to have one or more risk factors. The design of the five major programs is similar in that intervention communities are matched for purposes of evaluation with nearby comparison communities. Underlying these programs are theories of community health education, social learning, communication, social marketing, and community activation, as well as more traditional biomedical and public health disciplines. This is Part I of a two-part article.

Hormonal and metabolic changes during exercise in cirrhotic patients

The metabolic response to exercise was compared in 10 cirrhotic patients (P) in a stable clinical condition and in 6 sedentary, age-matched, normal subjects (C) performing 32 minutes of treadmill exercise with the same constant workload corresponding to three to four times their resting oxygen uptake. Taking indirect calorimetry as reference, respiratory exchanges indicated that cirrhotic patients consumed carbohydrates almost exclusively, unlike the normal controls, who consumed lipids and glucids in about the same proportions (RQ: 0.98 +/- 0.04 v 0.87 +/- 0.04, P less than .0001). In the patients, this carbohydrate path of exercise metabolism lowered glycemia from the resting value of 5.23 +/- 0.16 mmol/L to 4.03 +/- 0.37 mmol/L (P less than .0001) and raised the plasma lactate concentration from 2.08 +/- 0.24 mmol/L at rest to 3.48 +/- 0.32 mmol/L at the eighth minute of exercise (P less than .001), thus suggesting defective liver glyconeogenesis. Fatty free acids and glycerol remained almost constant during exercise, whereas catecholamines increased. Insulin levels were high in patients at rest (67.1 +/- 14.5 U/mL v 15.1 +/- 3.5 U/mL); they declined sharply at the onset of exercise but nevertheless remained high compared to those observed in the controls (P less than .0001). Glucagon increased in exercising patients from 88.3 +/- 21.3 pg/mL to 127.4 +/- 30.6 pg/mL (NS). Esterified plasma carnitine declined in the patients from 13.0 +/- 2.2 mumol/L to 8.6 +/- 1.5 mumol/L (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Managing the Diabetic Athlete

In brief: Being in good diabetic control-ie, having a blood glucose level near the normal range-is possible for almost any diabetic athlete whose sport allows consistent and predictable energy expenditure. For example, the physiologic demands of cycling or marathon running can easily be anticipated. But even sports such as football that may wreak havoc on blood glucose levels can be managed by the diabetic who frequently self-tests for glucose and then makes appropriate adjustments in insulin and food intake. The author discusses the metabolic responses to exercise in the non-diabetic vs the diabetic and offers practical advice on specific problems, such as managing the obese diabetic who wants to start an exercise program.

The external costs of a sedentary life-style

Using data from the National Health Interview Survey and the RAND Health Insurance Experiment, we estimated the external costs (costs borne by others) of a sedentary life-style. External costs stem from additional payments received by sedentary individuals from collectively financed programs such as health insurance, sick-leave coverage, disability insurance, and group life insurance. Those with sedentary life-styles incur higher medical costs, but their life expectancy at age 20 is 10 months less so they collect less public and private pensions. The pension costs come late in life, as do some of the medical costs, and so the estimate of the external cost is sensitive to the discount rate used. At a 5 percent rate of discount, the lifetime subsidy from others to those with a sedentary life style is $1,900. Our estimate of the subsidy is also sensitive to the assumed effect of exercise on mortality. The subsidy is a rationale for public support of recreational facilities such as parks and swimming pools and employer support of programs to increase exercise.

Effects of exercise on cardiovascular disease risk in women with NIDDM

The effect of a 4-month exercise program on measures of cardiovascular disease (CHD) risk was observed in women (mean age = 59.2 +/- 3.9 years) of postmenopausal years with NIDDM, who demonstrated fair to normal control of blood glucose control. The women were randomly assigned to either an exercise (n = 5) or control (n = 5) group. Initially, both groups had a similar body mass index, resting heart rate and blood pressures, blood glucose and hemoglobin A1. After 4 months, the exercise group demonstrated a 32% increase (P less than 0.03) in both absolute and relative maximum oxygen uptake (VO2) while the control group remained unchanged. Significant differences were found between the exercisers and non-exercisers for absolute (F(1,8) 4.94, P = 0.057) and relative (F(1,8) 7.67, P = 0.024) maximum VO2 from pretest to posttest. Body weight (kg) and body fat (%) remained unchanged for both groups. Although total cholesterol was found to be reduced by 13% for the exercise group (P less than 0.03) and 11% for the controls (P less than 0.01), a 15% decrease (P less than 0.03) in high-density lipoprotein (HDL) was observed for the control group, only. Hence, a marked difference (P less than 0.03) in the risk ratio was observed between the exercise and control groups. These data suggest that physical exercise may play an important role in the maintenance of HDL mass and in the reduction of CHD risk factors in women of postmenopausal years with NIDDM.

Exercise and the intensively treated IDDM patient

Individuals with IDDM can benefit from an exercise program in the same way nondiabetic individuals can. In addition to lowering insulin requirements and reducing the risk for cardiovas cular disease, exercise can produce many of the same physical adaptations in IDDM patients that nondiabetic individuals achieve. When used in combination with diet and insulin, exercise can produce beneficial effects on metabolic control.

Effects of physical training on the myocardium of streptozotocin-induced diabetic rats

Effects of endurance swimming training on myocardial contractility and left ventricular myosin isoenzymes were examined in diabetic rats. A diabetic condition was induced in 15-week-old male Wistar rats, by intravenous injection of streptozotocin (50 mg/kg). Swimming training was carried out for five to six weeks (90 min/day, 6 days/week). In order to estimate myocardial contractility, the isometric developed tension of the isolated left ventricular papillary muscle was measured. Myosin isoenzymes were obtained by pyrophosphate gel electrophoresis. Fasting blood glucose of the trained group was significantly lower than that of the sedentary group (sedentary vs. trained = 409.6 +/- 25.9 vs. 266.3 +/- 20.5 mg/dl, p less than 0.001). There was no significant difference in isometric developed tension (T) between the two groups, and the dT/dtmax of the trained group showed a tendency to increase (sedentary vs. trained, T: 2.8 +/- 0.8 vs. 2.9 +/- 0.8 g/mm2, dT/dtmax: 23.1 +/- 3.6 vs. 26.2 +/- 3.5 g/mm2.s, p less than 0.1). Myocardial mechanical responses to isoproterenol and dibutyryl cAMP were increased in the trained group. Left ventricular myosin isoenzyme pattern was shifted towards VM-1 by endurance swimming (sedentary vs. trained, VM-1: 5.6 +/- 4.5 vs. 19.6 +/- 8.8%, p less than 0.001, VM-3: 75.1 +/- 10.0 vs. 54.9 +/- 14.7%, p less than 0.001). These results indicate that endurance swimming can improve disordered glucose metabolism and also influence myocardial contractility, myocardial catecholamine responsiveness, and energetics in myocardial contraction.

Exercise-Related Sudden Death: Risks and Causes (Part 1 of 2)

In brief: Exercise-related sudden death is a clinical syndrome that is well known both to the general public and to the medical community. Autopsy studies of victims have identified multiple structural cardiovascular diseases underlying sudden death in young athletes (aged 30 years and younger). These diseases include myocardial, coronary arterial, aortic, valvular, and cardiac conduction system disorders. In athletes over 30 years of age, the underlying cause is almost invariably severe coronary artery disease. The author discusses these diseases, along with apparent mechanisms of sudden death, clinical points, risks of exercise stress testing, and cardiac rehabilitation, as a basis for attempts to prevent these tragic events.

The effects of muscular exercise on glucose, free fatty acids, alanine and lactate in type I diabetic subjects in relation to metabolic control

Metabolic effects of muscular exercise were studied in eleven subjects with type I diabetes mellitus during poor metabolic control, and again during good metabolic control, and in ten healthy control subjects. All the subjects were submitted to a submaximal gradual triangular test on an electrically braked bicycle ergometer; glucose, FFA, alanine and lactate were measured at rest, and after exercise. In poorly controlled patients, glucose and FFA were unchanged after exercise, whereas blood alanine and lactate increased by a percentage similar to that of the controls, and well-controlled diabetic patients. Baseline alanine concentrations were lower and lactate concentrations higher than in the controls and well-controlled patients. After adequate metabolic control was achieved, in the well-controlled diabetic patients a normalization of pre-exercise alanine and lactate levels and a decrease in blood glucose and FFA after exercise was observed.

Effect of physical exercise on sensitivity and responsiveness to insulin in humans

The effect of acute physical exercise on insulin sensitivity and responsiveness of glucose uptake and hepatic glucose production was studied. Seven untrained men were subjected to four sequential euglycemic hyperinsulinemic clamps after rest (R), immediately after exercise (E), as well as 48 h after 60 min of 150 W ergometer exercise (ER). Insulin-mediated glucose uptake was higher on E and ER days compared with R days. Apparent Km decreased after exercise (52 +/- 3 R vs. 43 +/- 4 E and 40 +/- 3 ER microU/ml, means +/- SE) and Vmax increased (9.5 +/- 0.8 R vs. 10.9 +/- 0.7 E and 10.7 +/- 0.8 ER mg.min-1.kg-1). Glucose oxidation increased with the increasing insulin infusion rate, and maximal glucose oxidation rate was lower on E days compared with R days. The maximal conversion rate of glucose to glycogen was higher on E and ER days (8.0 +/- 0.3 and 7.2 +/- 0.2, respectively) than on R days (5.7 +/- 0.6 mg.min-1 kg-1). Muscle glycogen synthase I activity was higher immediately after exercise and remained higher for the next 48 h. No change in any glucoregulatory hormone or metabolite could explain the increased insulin action seen after exercise. In additional experiments (n = 3), no remaining effect existed 5 days after exercise. Both insulin and exercise suppressed the pancreatic secretion of insulin and proinsulin. The conclusions drawn are that prolonged moderate exercise increases insulin action on glucose uptake in humans by reducing apparent Km and increasing Vmax. This effect lasts 48 h but not 5 days. The increased insulin action may be related to an exercise-induced increase in glycogen synthase activity.

Exercise for patients with chronic disease

Most patients with chronic disease can benefit from rehabilitation efforts to optimize their functioning within the limitations placed on them by the disease and/or treatment and to increase their responsibility in their health care. Rehabilitation should include education and counseling in nutrition, behavioral change, exercise conditioning, and clinical concerns. The exercise portion can be accomplished in a supervised or unsupervised setting, depending on the patient's clinical status and needs. The exercise prescription must be modified to meet the clinical needs of the patient. Supervised settings may increase compliance and provide the primary care physician with valuable follow-up information that will assist in long-term medical care. The primary care physician has the responsibility of carefully screening patients, referring them into the appropriate exercise setting, and incorporating the rehabilitation results into the patient's long-term care. Physician support can dramatically enhance the success of the rehabilitation efforts.

Effects of muscular exercise on erythrocyte adenosine triphosphate concentration in patients with insulin-dependent diabetes mellitus

Type I diabetes mellitus represents a metabolic disorder in which intracellular glycolytic pathway is inhibited by insulin deficiency, with the subsequent decreased availability of energetic substrates such as ATP. Some aspects of the energetic metabolism in response to an intensive demand (muscular exercise) were investigated, in a group of 10 ketotic diabetic patients, by measuring erythrocyte adenosine triphosphate (ATP) and blood glucose, free fatty acids (FFA) and lactate levels. In the diabetic subjects, in comparison with normal subjects, the decreased levels of erythrocyte ATP at rest did not increase after exercise, while the increased levels of FFA at rest did not diminish after exercise. The results show that the impaired erythrocyte glycolysis may produce reduced levels of ATP not only at rest, but also after exercise, when muscular contraction results in a manifold increase in cellular energy requirements. In addition, other metabolic systems providing energy for the exercising muscle, such as FFA utilization, are impaired in the ketotic diabetic patients.

What is "tight control" of diabetes? Goals, limitations, and evaluation of therapy

Complete normalization of the blood glucose concentration is the ideal goal in patients with diabetes. Because of deficiencies in therapeutic modalities for diabetes, achievement of approximation of normoglycemia is usually a satisfactory result. Generally, blood glucose ranges of 70 to 120 mg/dl preprandially and less than 160 to 180 mg/dl 90 minutes postprandially in nonpregnant patients with diabetes are considered appropriate. Diurnal variations in glycemia can be caused by the size and composition of meals, the time of day a meal is eaten, stress, and exercise. Self-monitoring of blood glucose by the patient and measurement of glycosylated hemoglobin have been useful in achieving control of diabetes.

Diabetes, insulin and exercise

The metabolic and hormonal adaptations to single exercise sessions and to exercise training in normal man and in patients with insulin-dependent as well as non-insulin-dependent diabetes mellitus are reviewed. In insulin-dependent (type I) diabetes good metabolic control is best obtained by a regular pattern of life which will lead to a fairly constant demand for insulin from day to day. Exercise is by nature a perturbation that makes treatment of diabetes difficult: Muscle contractions per se tend to decrease the plasma glucose concentration whereas the exercise-induced response of the so-called counter-regulatory hormones tend to increase plasma glucose by increasing hepatic glucose production and adipose tissue lipolysis. If the pre-exercise plasma insulin level is high, hypoglycaemia may develop during exercise whereas hyperglycaemia and ketosis may develop if pre-exercise plasma insulin levels are low. Physical activity is often difficult to carry out on a precise schedule and the exercise-induced changes in demand for insulin and calories vary according to the intensity and duration of exercise, time of day, and differ within and between individuals. Thus, physical training can not be recommended as a means of improving metabolic control in insulin-dependent diabetes. However, our present knowledge and technology allows the well-informed and cooperative patient to exercise and even to reach the elite level. To achieve this, pre-exercise metabolic control should be optimal and knowledge of the patient's reaction to exercise is desirable, which necessitates frequent self-monitoring of plasma glucose. It may often be necessary to diminish the insulin dose before exercise, and/or to ingest additional carbohydrate during or after exercise. In non-insulin-dependent (type II) diabetes, exercise is associated with less risk of metabolic derangement, and in genetically disposed individuals physical training may prevent development of overt diabetes possibly by diminishing the strain on the pancreatic beta cell. The latter, however, is only achieved if exercise is not accompanied by increased caloric intake. Whether physical training in diabetes can reduce cardiovascular morbidity and mortality is at present unknown, but training has in diabetic patients been shown to lessen some risk factors for development of arteriosclerosis. However, training of diabetics (especially in the less well-regulated patient) may not lessen coronary risk factors to the same extent as in healthy subjects.

Glucoregulation during exercise: hypoglycemia is prevented by redundant glucoregulatory systems, sympathochromaffin activation, and changes in islet hormone secretion

During mild or moderate nonexhausting exercise, glucose utilization increases sharply but is normally matched by increased glucose production such that hypoglycemia does not occur. To test the hypothesis that redundant glucoregulatory systems including sympathochromaffin activation and changes in pancreatic islet hormone secretion underlie this precise matching, eight young adults exercised at 55-60% of maximal oxygen consumption for 60 min on separate occasions under four conditions: (a) control study (saline infusion); (b) islet clamp study (insulin and glucagon held constant by somatostatin infusion with glucagon and insulin replacement at fixed rates before, during and after exercise with insulin doses determined individually and shown to produce normal and stable plasma glucose concentrations prior to each study); (c) adrenergic blockage study (infusions of the alpha- and beta-adrenergic antagonists phentolamine and propranolol); (d) adrenergic blockade plus islet clamp study. Glucose production matched increased glucose utilization during exercise in the control study and plasma glucose did not fall (92 +/- 1 mg/dl at base line, 90 +/- 2 mg/dl at the end of exercise). Plasma glucose also did not fall during exercise when changes in insulin and glucagon were prevented in the islet clamp study. In the adrenergic blockade study, plasma glucose declined initially during exercise because of a greater initial increase in glucose utilization, then plateaued with an end-exercise value of 74 +/- 3 mg/dl (P less than 0.01 vs. control). In contrast, in the adrenergic blockade plus islet clamp study, exercise was associated with glucose production substantially lower than control and plasma glucose fell progressively to 58 +/- 7 mg/dl (P less than 0.001); end-exercise plasma glucose concentrations ranged from 34 to 72 mg/dl. Thus, we conclude that: (a) redundant glucoregulatory systems are involved in the precise matching of increased glucose utilization and glucose production that normally prevents hypoglycemia during moderate exercise in humans. (b) Sympathochromaffin activation, perhaps sympathetic neural norepinephrine release, plays a primary glucoregulatory role by limiting glucose utilization as well as stimulating glucose production. (c) Changes in pancreatic islet hormone secretion (decrements in insulin, increments in glucagon, or both) are not normally critical but become critical when catecholamine action is deficient. (d) Glucoregulation fails, and hypoglycemia can develop, both when catecholamine action is deficient and when changes in islet hormones do not occur during exercise in humans.

Dissociation of effects of insulin and contraction on glucose transport in rat epitrochlearis muscle

The effects of insulin and contraction on glucose transport and metabolism were investigated in rat epitrochlearis muscles in vitro. Insulin dose-response curves showed a threshold (approximately 50 microunits/ml) and saturation-type (approximately 1 mU/ml) kinetics, whereas isometric contraction activated glucose transport and metabolism in a linear fashion with no evidence of a threshold. Insulin and contraction increased the apparent maximal rate of uptake of the hexose transport system with minimal effect on its apparent Km. The stimulatory effects of insulin and contraction were additive; similar results were obtained with 2-deoxy-D-glucose. Contraction stimulated glucose transport in three different preparations of muscles depleted of insulin: 1) exhaustively washed for 2 h, 2) rats infused with anti-insulin serum, and 3) chronically (streptozotocin-induced) diabetic rats. Prostaglandin E2 augmented the effect of a submaximal concentration of insulin on glucose transport without exerting any effect by itself but had no effect on contraction-augmented glucose transport. It is concluded that insulin and contraction activate glucose transport and metabolism via independent mechanisms.

Glucose counterregulation, hypoglycemia, and intensive insulin therapy in diabetes mellitus

The prevention or correction of hypoglycemia is the result of both dissipation of insulin and activation of counterregulatory systems. In the models studied to date, glucagon and epinephrine have been shown to be the key counterregulatory factors; the potential roles of other hormones, neural factors, or substrate mechanisms in other models and during more gradual recovery from hypoglycemia remain to be defined. Deficient glucagon responses to decrements in plasma glucose, which are common in patients with IDDM and occur in some patients with NIDDM, result in altered counterregulation. But counterregulation is generally adequate, because epinephrine compensates for it. Defective glucose counterregulation due to combined deficiencies of glucagon and epinephrine secretory responses occurs in many patients, typically those with longstanding diabetes, and must be added to the list of factors known to increase the risk of hypoglycemia, at least during intensive therapy. From the material reviewed, it should be apparent that much has been learned about glucose counterregulation. It should be equally clear that much remains to be learned. Among the many possibilities, we consider four worthy of emphasis. First of all, we need to examine the physiology and pathophysiology of glucose counterregulation in additional models (e.g., during exercise) and over longer periods. Secondly, we need to determine whether central nervous system adaptation to antecedent glycemia occurs and, if so, identify its mechanisms. Thirdly, we need to develop better methods of insulin delivery or learn to correct or compensate for defective counterregulatory systems, if we are to achieve euglycemia safely in diabetic patients with defective glucose counterregulation. Finally, we need to know whether effective control of diabetes mellitus prevents development of defective glucose counterregulation.

Outpatient pediatric diabetes--I. Current practices

A survey of pediatric diabetologists in the U.S. was made in an attempt to define current outpatient practices in diabetes subspecialty clinics. Survey questions addressed clinic organization, health care team members, content of histories and physical examinations, use of laboratory studies, patient education, therapeutic recommendations, self-management practices and screening procedures used to identify early diabetes-related complications. The results of the survey suggested similar clinic organization and operation in most settings; a high degree of reliance on glycosylated hemoglobin determinations; a preference for the use of NPH insulin; and a lack of credence given urinary glucose determinations. Additionally, screening tests for the development of complications are not performed with regularity.

Decrease in ventricular beta-adrenergic receptors in trained diabetic rats

The effects of physical training on beta-adrenergic receptors were evaluated in heart ventricular tissue of diabetic rats. Mild diabetes mellitus was induced in rats with streptozotocin (45 mg/kg, iv). They were then submitted to a progressive 10-week running programme on a treadmill. Binding studies were done at six different concentrations of (-) [3H]dihydroalprenolol (0.5 to 14.4 nM) with ventricular membrane preparations from control (n = 13), sedentary diabetic (n = 9) and trained diabetic rats (n = 10). Direct linear plot analysis of the data revealed that the total number of beta-adrenoceptors was reduced in sedentary diabetic rats as compared to control (2231 +/- 207 vs 2922 +/- 211 fmol/ventricles; P less than 0.05); however, there was no significant change in the receptor density expressed as fmol/mg of membrane protein (40 +/- 3 vs 43 +/- 3; P greater than 0.05). On the other hand, the beta-adrenergic binding sites were decreased in training diabetic rats, either expressed as the total number of receptors (1920 +/- 179 vs 2922 +/- 211; P less than 0.01), or as fmol/mg of membrane protein (30 +/- 3 vs 43 +/- 3; P less than 0.01). There was no significant change in the dissociation constant (KD) of these receptors between groups (KD = 4.08 +/- 0.51, 4.69 +/- 0.93 and 2.88 +/- 0.39 nM respectively for control, sedentary diabetic and diabetic trained animals). The basal epinephrine concentration was significantly increased in trained diabetic rats (102 +/- 21 pg/ml vs 47 +/- 7 for control (P less than 0.05) and vs 49 +/- 9 for sedentary diabetic (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on the mechanism of improved glucose control during regular exercise in type 2 (non-insulin-dependent) diabetes

The effects of 6 weeks of thrice weekly training on glycaemic control were assessed in 20 sedentary Type 2 (non-insulin-dependent) diabetic patients and 11 control subjects matched for previous physical activity. Maximal oxygen uptake was lower in the diabetic patients than in control subjects before training (26.2 +/- 1.1 versus 32.6 +-/ 1.7 ml X kg-1 X min-1; p less than 0.001). Glycosylated haemoglobin levels decreased in the diabetic patients during the training programme (12.2 +/- 0.5 to 10.7 +/- 0.4%; p less than 0.02). Oral and intravenous glucose tolerance determined 72 h after the last exercise period showed only minimal improvement. Plasma glucose levels were, however, significantly lower at 12 h than 72 h after exercise in eight subjects tested at both time points. These data suggest than an exercise programme can produce a significant decrease in glycosylated haemoglobin levels in Type 2 diabetic males probably due, in great measure, to the cumulative effect of transient improvements in glucose tolerance which follow each individual period of exercise.

Exercise: a vital component for patients on the Biostator

Exercise was incorporated into the treatment of diabetic patients on the Biostator. As the purpose of the Bio stator is to determine the patient's in sulin requirements over a 24 hour pe riod, activity and exercise are impor tant to normalize that 24-hour period as much as possible.

Individual exercise programs were developed for each of the patients on the Biostator. The most common ex ercise vehicle chosen was a bicycle ergometer. Physical Therapy devel oped these programs based on the pa tient's "Home Activity Assessment. " Nursing and Physical Therapy then monitored the patient's compliance with the exercise program during the "run" on the Biostator.

The Biostator print-out (see Table I, p. 13) was used in a retrospective study of the effect of exercise on the patient's blood glucose levels. It was found that the median decrease in blood sugar immediately after cessa tion of exercise was - 6mgldl and for 15 minutes after cessation of exercise was — 12mg/dl. Empirical data is im portant to the patient so that they may balance exercise, diet, and insulin to keep blood glucose levels in control.

Exercise for optimal health: strategies and motivational considerations

It appears that most people who engage in exercise for 20-60 min per day, 3 days per week, at an intensity level of 70-80% of maximal heart rate will derive at least some health-related benefits associated with improved cardiorespiratory fitness and optimal body weight. Individuals exhibiting extremely low cardiorespiratory fitness can probably derive benefits from even less exercise, while higher intensity and/or longer duration may be required to optimize some desired changes, particularly in areas associated with metabolic adaptation relative to blood lipids, diabetes, and psychological affect. While there is some evidence that it may take less exercise to maintain fitness levels already attained, a lifelong pattern of regular physical activity is recommended to optimize health-related benefits. Strategies which have been successful in combating high attrition rates in exercise programs include educational efforts to increase the participants' awareness pf exercise benefits; assessment procedures which determine the participants' needs, provide continuous motivational reinforcement, and accurately record improvement; and written contracts which hold participants accountable for reaching realistic goals within specified time periods.