D. C. Casal

The effects of exercise and weight loss on plasma lipids in young obese men

We studied the independent and combined effects of exercise training and weight loss on blood lipids under fixed diet and exercise conditions. Twenty-one obese sedentary men were randomly allocated to one of four treatment groups: (1) inactive and constant weight (control), (2) exercise training and constant weight, (3) inactive and weight loss, and (4) exercise training and weight loss. There were three study periods: a 3 week baseline period inactive and on an isocaloric diet, a 12 week treatment period, and a 3 week weight stabilization period. Exercise consisted of treadmill walking at an energy cost of 3500 kcal/wk for groups 2 and 4 with replacement caloric intake only in group 2. Group 3 reduced caloric intake by 3500 kcal/wk during the treatment period. Weight loss for groups 3 and 4 were 13.4 pounds and 13.7 pounds, respectively. Maximal oxygen uptake (mL/min) increased 6% in both exercise groups (2 and 4), and percent body fat decreased only in these groups. Regression analysis by group assignment on HDL cholesterol (HDL-C) showed that the inactivity-weight loss modality (group 3) and the exercise-constant weight modality (group 2) each significantly increased HDL-C, with an additive effect of exercise and weight loss (group 4). The rate of HDL-C change differed significantly between groups (P = 0.01). HDL-C increased 0.63, 0.61, and 1.89 mg/dL per 3 weeks or 2%, 2.4%, and 5.5% above baseline levels in groups 2, 3, and 4, respectively, while the control group decreased 0.11 mg/dL. Plasma triglycerides and very low-density lipoprotein (VLDL) cholesterol increased with exercise at constant weight (group 2) and decreased with exercise associated with weight loss (group 4). In conclusion, exercise and weight loss separately and independently increase HDL-C, and their effects are additive.

Failure of caffeine to affect substrate utilization during prolonged running.

Nine sub-3-h male marathoners performed three 45-min monitored treadmill runs at approximately 75% of VO2max during a 2-wk period. The men were assigned in a random, double-blind fashion following the control run to receive either 350 ml of decaffeinated coffee or 350 ml of decaffeinated coffee with 400 mg of caffeine added 1 h before the second run with crossover to the other beverage for the third run. Venous blood was analyzed for free fatty acids, triglycerides, glucose, and lactic acid before beverage consumption and before and after each run. Oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory exchange ratio (R), ventilation (VE), and perceived exertion were measured at 15, 30, and 45 min of each run. Of the blood parameters, free fatty acid and lactic acid concentration increased following caffeine ingestion. There was no difference in VO2, VCO2, or R between the three runs. Perceived exertion showed a significant decrease (P less than 0.05) at each time point in caffeine added and decaffeinated compared to control. Triglycerides, glucose, and lactic acid increased similarly in all three runs. In these well-trained marathoners, although plasma free fatty acids were elevated significantly prior to exercise after caffeine ingestion, there was no indirect evidence of altered substrate utilization during subsequent treadmill running.

Effects of 2,000 kcal per week of walking and stair climbing on physical fitness and risk factors for coronary heart disease

BACKGROUND Epidemiologic evidence suggests that 8,368 kJ or 2000 kcal per week of moderate physical activity, including walking and stair climbing, can reduce risk of coronary heart disease (CHD). The goal of this study was to assess the effects of this amount of these two activities on physical fitness and risk factors for CHD. METHODS Twenty-two healthy, slightly overweight, sedentary, normotensive, normolipemic men, age 22 to 44 years, were randomly assigned to an exercise or control group for 12 weeks followed by a 4-week washout period. The subjects then were crossed-over to the alternate group for an additional 12-week period. Exercise consisted of 5 days per week of supervised treadmill exercise plus stair climbing. Treadmill exercise consisted of walking for 45 minutes at 5.15 km per hour at 2% grade for a total of 19.3 km per week. Subjects also climbed 10 floors of stairs at a time at their own pace without prescribed target heart rates for a total of 50 floors per week. The estimated total weekly energy cost of the treadmill walking plus stair climbing was 8,368 kJ or 2,000 kcal. Mean observed heart rates were 55% and 82% of maximal heart rate during treadmill walking and stair climbing, respectively. Data from the two exercise periods and two control periods were pooled and compared by analysis of variance. RESULTS Sixteen subjects completed all phases of the study. Maximal oxygen uptake (VO2max) by the Bruce treadmill exercise protocol with metabolic gas measurements was below average for age at baseline, and was not significantly affected by 12 weeks of training. No significant changes were noted between groups in body weight or percent body fat (hydrostatic weighing), although there was a trend for loss of weight and fat with exercise training. Mean systolic blood pressure (119 mm Hg) was unchanged in both groups. However, diastolic blood pressure (72 mm Hg and 78 mm Hg for the treatment and control groups, respectively) showed an unexpected 6 mm Hg increase during the exercise period and a 5 mm Hg decline during the control period. Mean plasma lipid and lipoprotein levels were unaffected by training, except for a 16% reduction in triglycerides (P < .05). However, a 28% increase in plasma high density lipoprotein (HDL)-cholesterol (P < .01) was noted during the initial 12-week training period, which regressed during the washout period, and was not replicated during the second 12-week exercise period. CONCLUSIONS Twelve weeks of walking and stair climbing at a moderate pace and intensity at an energy cost of about 2,000 kcal per week failed to improve physical fitness or risk factors for CHD. A reduction in physical activities other than the prescribed exercise program, as reported by a physical activity recall questionnaire, probably contributed to an absence of an exercise response. A longer and/or a more intense activity program is apparently required to improve these modalities.

Skeletal muscle creatine kinase MB alterations in women marathon runners

SummaryTotal creatine kinase (CK) and CK MB activities were determined in gastrocnemius muscle and serum obtained from 14 female marathon runners. The level of CK MB in muscle increased significantly (p<0.05) after chronic exercise training from 5.3% to 10.5% of the total CK activity, but not after acute exercise (post-marathon 8.9%). No significant differences in total CK activities were detected. However, the total CK activity in the muscles were significantly (p<0.05) less than those previously reported from the muscle of men runners (1800 U/g, 3000 U/g respectively). No significant correlation existed between fiber type and muscle CK MB activity. Additionally, trace amounts of mitochondrial CK and CK BB were present in muscle homogenates. A significant correlation was observed in the increase in mean serum total CK (597 UL−1) and CK MB (23 UL−1) activities 24 h after the race (r=0.97,P<0.05). These results suggest that gastrocnemius muscle in women adapts to training with increased CK MB activities and imply that skeletal muscle is the major source of elevated serum CK MB activities in women marathon runners.

CREATINE KINASE MB ISOENZYME ADAPTATIONS IN STRESSED HUMAN SKELETAL MUSCLE

The creatine kinase (CK) isoenzyme composition was determined in serial gastrocnemius muscle biopsies obtained from 12 male marathon runners. The mean muscle CK-MB composition significantly increased after chronic exercise (training) from 5.3% (pretraining) to 7.7% (premarathon) as well as after acute exercise (postmarathon) to 10.5% of the total CK activity (P less than 0.05). However, no significant differences in total CK activities were detected. Additionally, mitochondrial CK and CK-BB isoenzymes were present in muscle homogenates. A significant correlation was observed in the increase in mean serum total CK (3,322 U/l) and CK-MB (174 U/l) activities 24 h after the race (r = 0.98, P less than 0.05). These results show that gastrocnemius muscle adapts to long-distance training and racing with increased CK-MB activities and imply that skeletal muscle is the major source of elevated serum CK-MB activities in marathon runners.