Lipid and lipoprotein changes in premenstrual women following step aerobic dance training.

Exercise training can improve lipid and lipoprotein concentrations and reduce the risk of heart disease. Little information is available concerning aerobic dance training and lipoprotein concentration changes in women. The purpose of this study was to compare the effects of two different methods of step bench training on cardiorespiratory fitness, body composition, and lipoprotein concentrations in college-aged females. Subjects were assigned to one of three groups: a traditional continuous step (CS), an interval step group (IS), or a non-exercise control group (C). The CS and the IS groups participated in three 50-minute sessions for 12 weeks. The CS session included a warm-up, 30-35 min of continuous bench stepping, 10-15 min of calisthenic exercises, and a 5-min cool-down. The IS sessions included a 5-7-min warm-up, 35-40 min of alternating intervals of bench stepping and non-step aerobic dance, and a 5-7-min cool-down. Target heart rates were maintained within 70 to 85% of maximal heart rate. Results showed increases in HDL-C concentrations in the IS group (p<0.05). Decreases in percent body fat were evident in both dance groups (p<0.05) and cardiovascular fitness increased in both groups (p<0.01). No changes were evident in the control group. In college-aged women, 12 weeks of IS or CS training improved cardiorespiratory fitness and body composition. In addition, IS training appears to have a greater effect on HDL-C concentrations than CS training.

Exercise in a hot environment: comparison of two different fluid intake patterns.

AIM: Extensive research has been undertaken in the area of exercise and hydration. Most work has focused on prehydration. Less is known about different fluid intake patterns during exercise and its effect in thermoregulatory variables in hot environments. This study attempted to determine if ingesting fluid either in a single bolus or intermittently during exercise had different results in thermoregulatory parameters and thirst in a hot environment. METHODS: Six moderately trained men and women (n=6, 5 male, 1 female; mean+/-SD: age 28.5+/-2.5 y; weight 74.4+/-3.3 kg, VO2max 45.9+/-3.7 ml.kg.min-1) completed 2 exercise sessions in a randomized, counterbalanced order. Treatment 1 (bolus) consisted of 60 minutes of bicycling at 50% of VO2max in a climatic chamber (dry bulb temperature, 35 degrees C, 45% relative humidity). Subjects consumed 1 000 ml of plain cool (22 degrees C) water immediately before exercise. During treatment 2 (intermittent) the same environmental conditions were present, but subjects consumed 250 ml of water immediately before exercise. During the bicycle ride, subjects consumed 250 ml of cool water at minutes 15, 30, and 45 of exercise for a total trial volume of 1,000 ml. Tympanic ear temperatures, heart rates, rating of perceived exertion (RPE), and thirst scale data were collected immediately before exercise and at minutes 10, 20, 30, 40, 50, and 60 of exercise. RESULTS: No statistical differences were noted in temperature between treatments (P>0.05). Lower heart rates and thirst scores were noted for the bolus treatment at various time points (P<0.05). Little differences were noted between treatments for RPE during exercise. CONCLUSIONS: These results suggest that consumption of water in a single bolus is more beneficial for some aspects of thermoregulatory control and delaying thirst during exercise in the heat. Additional mechanistic studies with larger sample sizes are warranted.

Plasma lipid and lipoprotein responses during exercise.

The purpose of this study was to examine the effect of prolonged exercise on plasma lipid and lipoprotein concentrations and to identify caloric time-points where changes occurred. Eleven active male subjects ran on a treadmill at 70% of maximal fitness (VO2max) and expended 6278.7 kilojoules (Kj) energy (1500 kcal). Blood samples were obtained at the 4185.8 Kj (1000 kcal) timepoint during exercise and at each additional 418.6 Kj (100 kcal) expenditure until 6278.7 Kj was expended. After correcting for plasma volume changes, decreases in low-density lipoprotein cholesterol (LDL-C) were observed during exercise at time-points corresponding to 4604.4 and 5441.5 Kj (1100 and 1300 kcal) of energy expenditure, and immediately after exercise. Total cholesterol concentrations decreased significantly at exercise kilojoule expenditures of 4604.4, 5441.5 and 5860.1 (1100, 1300 and 1400 kcal). There were also exercise induced increases in high-density lipoprotein cholesterol (HDL-C) and HDL2-C concentrations immediately after exercise. Although acute lipid and lipoprotein changes are typically reported in the days following exercise, the current data indicate that some lipoprotein concentrations change during acute exercise. Our data suggest that a threshold of exercise may be necessary to change lipoproteins during exercise. Future work should identify potential mechanisms (lipoprotein lipase, cholesterol ester transport protein, LDL uptake) that alter lipoprotein concentrations during prolonged exercise.

Aerobic circuit exercise training: effect on adolescents with well-controlled insulin-dependent diabetes mellitus.

OBJECTIVES: To test the safety and effects of exercise conditioning on cardiorespiratory fitness, body composition, muscle strength, glucose regulation, and lipid/cholesterol levels. SUBJECTS: Ten male adolescents with insulin-dependent diabetes mellitus (IDDM) and 10 adolescent nondiabetic (ND) subjects. DESIGN: Pretest, posttest intervention trial with control group. SETTING: University-based human performance laboratory. INTERVENTION: Mixed endurance and calisthenic/strength activities performed at a rapid pace three times weekly for 12 weeks. RESULTS: Only one subject with IDDM experienced hypoglycemia after a single exercise session. Both subject groups improved their cardiorespiratory endurance (p < .05). Lean body mass of IDDM subjects increased by 3.5% (p < .05). Subjects with and without IDDM lowered their percent body fat (p < .05 and .001, respectively). Strength improvement of IDDM subjects ranged from 13.7% (p < .001) to 44.4% (p < .01), depending upon the maneuver. Fasting blood plasma glucose for all subjects was unchanged by training, but glycosylated hemoglobin A1c of IDDM subjects was reduced by .96 percentage point (p < .05). Reductions of HbA1c benefitted subjects exhibiting poor preconditioning glycemic control. Low-density lipoprotein cholesterol was decreased in subjects with IDDM (p < .05), but not total cholesterol or triglycerides. CONCLUSION: Adolescents with IDDM undergoing aerobic circuit training improve their cardiorespiratory endurance, muscle strength, lipid profile, and glucose regulation. Aerobic circuit training is safe for properly trained and monitored adolescent diabetics.

Microcomputer servo-controlled bicycle ergometer system for psychophysiological research.

Steady state exercise is widely used for psychophysiological studies in which a constant heart rate at a predetermined level is desired. We have developed a microcomputer servo-controlled bicycle ergometer system that can be used for administering steady state exercise. Fourteen healthy male subjects, with a wide range of fitness levels (measured by VO2max) were exercised to either a fixed workload (130 watts) or a predetermined heart rate level (servo-heart rate) of 122 bpm (i.e., 65% of maximum calculated heart rate for the sample). Servo-heart rate was implemented using a feedback loop that automatically adjusted workload to compensate for immediate variations in heart rate, resulting in a more consistent heart rate. Heart rate varied from the predetermined value by 17 bpm during fixed workload but only 3 bpm during servo-heart rate (p less than .05). Therefore, by using the microcomputer servo-controlled bicycle ergometer, heart rate was maintained at a predetermined level regardless of the subject's fitness level. VO2max and workload during servo-heart rate were significantly correlated (r = .85, p less than .05). Therefore, the workload necessary to maintain heart rate at a constant level may provide an approximate index of aerobic fitness level.