Effects of dehydration and rehydration on the one-repetition maximum bench press of weight-trained males.

Dehydration, a common practice among competitive athletes in sports including weight classes, has uncertain effects on strength. This study examined the effects of passive dehydration (D, approximately 2 hours in a sauna) followed by rehydration (R, approximately 2 hours of rest with water ad libitum) on bench press one-repetition maximum (1RM). Ten weight-trained males (x +/- SE; age = 25 +/- 1 years; mass = 85.5 +/- 5.2 kg; height = 173.5 +/- 1.7 cm; body fat = 17.8 +/- 2.2%; 1RM = 118 +/- 8 kg) completed 2 testing sessions (E1/E2 and D/R) consisting of, respectively, 2 euhydration 1RM measurements separated by 2 hours of rest; and D 1RM followed by R 1RM. Testing sessions were administered in counterbalanced order and separated by 1 week. D resulted in increases (p < 0.005) in body temperature, urine specific gravity, hematocrit, and hemoglobin (calculated 8% decrease in plasma volume) as well as decreased body mass (p < 0.005). 1RM was decreased following D (111.4 +/- 7.2 kg) compared to both E1 (118 +/- 7.6 kg, p = 0.0015) and R (117.3 +/- 7.8 kg, p = 0.0023), with no significant difference between E1 and R. A significant association (r = -0.67, p < 0.05) was observed between percent lean body mass (%LBM) and the change in 1RM following D. In conclusion, passive dehydration resulting in approximately 1.5% loss of body mass adversely affects bench press 1RM performance. The adverse affects of dehydration seem to be overcome by a 2-hour rest period and water consumption.

Effect of 14 weeks of resistance training on lipid profile and body fat percentage in premenopausal women.

OBJECTIVES: To study the effects of a supervised, intensive (85% of one repetition maximum (1-RM)) 14 week resistance training programme on lipid profile and body fat percentage in healthy, sedentary, premenopausal women. SUBJECTS: Twenty four women (mean (SD) age 27 (7) years) took part in the study. Subjects were randomly assigned to either a non-exercising control group or a resistance exercise training group. The resistance exercise training group took part in supervised 45-50 minute resistance training sessions (85% of 1-RM), three days a week on non-consecutive days for 14 weeks. The control group did not take part in any structured physical activity. RESULTS: Two way analysis of variance with repeated measures showed significant (p < 0.05) increases in strength (1-RM) in the exercising group. There were significant (p < 0.05) decreases in total cholesterol (mean (SE) 4.68 (0.31) v 4.26 (0.23) mmol/1 (180 (12) v 164 (9) mg/dl)), low density lipoprotein (LDL) cholesterol (2.99 (0.29) v 2.57 (0.21) mmol/l (115 (11) v 99 (8) mg/dl), the total to high density lipoprotein (HDL) cholesterol ratio (4.2 (0.42) v 3.6 (0.42)), and body fat percentage (27.9 (2.09) v 26.5 (2.15)), as well as a strong trend towards a significant decrease in the LDL to HDL cholesterol ratio (p = 0.057) in the resistance exercise training group compared with their baseline values. No differences were seen in triglycerides and HDL cholesterol. No changes were found in any of the measured variables in the control group. CONCLUSIONS: These findings suggest that resistance training has a favourable effect on lipid profile and body fat percentage in healthy, sedentary, premenopausal women.

Relationship between % heart rate reserve and % VO2 reserve in treadmill exercise.

For exercise prescription purposes, it is often assumed that % heart rate reserve (%HRR) provides equivalent intensities to %VO2max. However, a recent study from this laboratory demonstrated that during cycling exercise %HRR is not equivalent to %VO2max, but is instead equivalent to a percentage of the difference between resting and maximal VO2, i.e., % VO2reserve (%VO2R). The current study examined these relationships during treadmill exercise. Fifty adults performed Bruce protocol treadmill tests to exhaustion. For each subject, data obtained at rest, at the end of each stage, and at maximum were used to determine linear regressions of %HRR versus %VO2max, and of %HRR versus %VO2R. For %HRR versus %VO2max the mean intercept and slope were -6.1+/-0.7 and 1.10+/-0.01, respectively, with a mean r of 0.990+/-0.002. For %HRR versus %VO2R, the mean intercept and slope were 1.5+/-0.6 and 1.03+/-0.01, respectively, with a mean r of 0.990+/-0.002. Both regressions differed statistically from the line of identity (i.e., intercept of 0 and slope of 1). However, the regression of %HRR versus %VO2R was significantly closer (P < 0.001 ) to the line of identity than was the regression of %HRR versus %VO2max. We conclude that %HRR should be considered as an indicator of %VO2R, not %VO2max, when prescribing treadmill exercise, as was previously concluded for cycling exercise.

Heart rate reserve is equivalent to %VO2 reserve, not to %VO2max.

Percentage of heart rate reserve (%HRR) is widely considered to be equivalent to % of maximal oxygen consumption (%VO2max) for exercise prescription purposes. However, this relationship has not been established in the literature, and a theoretically stronger case can be made for an equivalency between %HRR and %VO2 Reserve (%VO2R) (i.e., the difference between resting and maximal VO2). The current study hypothesized that %HRR is equivalent to %VO2R, not %VO2max, and that the discrepancy between %HRR and %VO2max would be inversely proportional to fitness level. Sixty-three adults performed incremental maximal exercise tests on an electrically braked cycle ergometer. HR and VO2 at rest, at the end of each stage of exercise, and at maximum were used to perform linear regressions on %HRR versus %VO2max, and %HRR versus %VO2R for each subject. For %HRR versus %VO2max, the mean intercept and slope were -11.6 +/- 1.0 and 1.12 +/- 0.01, respectively, which were significantly different (P < 0.001) from 0 and 1, respectively. For %HRR versus %VO2R, the mean intercept and slope were -0.1 +/- 0.6 and 1.00 +/- 0.01, respectively, which were not distinguishable from the line of identity. There was a significant (P < 0.01) inverse relationship between fitness level (VO2max) and the discrepancy between %HRR and %VO2max. In conclusion, %HRR should not be considered equivalent to %VO2max. Rather, %HRR is equivalent to %VO2R, and this relationship should be used in exercise prescription.

Exercise training and severe caloric restriction: effect on lean body mass in the obese.

The purpose of this study was to investigate the effects of exercise intensity on the body composition of obese subjects during severe caloric restriction. Forty obese subjects (33 women, 7 men; 41 +/- 7.7 years; 106 +/- 26kg; body fat > 25% men, > 30% women) on a commercially prepared OPTIFAST 420kcal/day supplemented fast were randomized into groups that exercised at target heart rates corresponding to 40% and 60% of the heart rate reserve (HRR) at the start of the program. Training volume was similar for both groups at approximately 300kcal per session three times per week for 12 weeks. Body weight, body fat, and lean weight were similar for both exercise intensity groups at week one. Overall, body weight decreased by 15.3 +/- 6.7 kg (p < or = .05), and body fat decreased by 14.9 +/- 5.0 kg (p < or = .05) for the 40 subjects, whereas lean weight remained unchanged. No significant differences in body weight, body fat, or lean weight were observed between the two groups. The results of the current study indicated that while on a supplemented 420-kcal/day fast, exercise at 40% and 60% of the HRR affected body composition similarly when total training volume was held constant at 900kcal/week. Lean weight remained unchanged and accompanied a 14.9 +/- 5.0-kg decrease in body fat, which may have resulted when the volume of exercise (ie, 900kcals/wk) was factored into the exercise prescriptions. These results suggest that exercising at 60% of the HRR offers no advantages for body composition changes over those obtained from exercising at 40% of HRR when the total volume of exercise training is controlled.