RESUMO
BACKGROUND: To examine whether short-term, ie, five daily sessions, vigorous dynamic cycling exercise and heat exposure could achieve heat acclimation in trained athletes and the effect of heat acclimation on cutaneous blood flow in the active and nonactive limb. METHODS: Fourteen male badminton and table tennis athletes (age = 19.6 ± 1.2 years) were randomized into a heat acclimation (EXP, n = 7) or nonheat acclimation (CON, n = 7) group. For 5 consecutive days, the EXP group was trained using an upright leg cycle ergometer in a hot environment (38.4°C ± 0.4°C), while the CON group trained in a thermoneutral environment (24.1°C ± 0.3°C). For both groups, the training intensity and duration increased from a work rate of 10% below ventilatory threshold (VT) and 25 minutes per session on day 1, to 10% above VT and 45 minutes per session on day 5. Subjects performed two incremental leg cycle exercise tests to exhaustion at baseline and post-training in both hot and thermoneutral conditions. Study outcome measurements include: maximum oxygen uptake (VO2max); exercise heart rate (HR); O2 pulse; exercise time to exhaustion (tmax); skin blood flow in the upper arm (SkBFa) and quadriceps (SkBFq); and mean skin (Tsk). RESULTS: The significant heat-acclimated outcome measurements obtained during high-intensity leg cycling exercise in the high ambient environment are: (1) 56%-100% reduction in cutaneous blood flow to the active limbs during leg cycling exercise; (2) 28% drop in cutaneous blood flow in nonactive limbs at peak work rate; (3) 5%-10% reduction in heart rate (HR); (4) 10% increase in maximal O2 pulse; and (5) 6.6% increase in tmax. CONCLUSION: Heat acclimation can be achieved with five sessions of high-intensity cycling exercise in the heat in trained athletes, and redistribution of cutaneous blood flow in the skin and exercising muscle, and enhanced cardiovascular adaptations provide the heat-acclimated athletes with the capability to increase their endurance time in the hot environment.
RESUMO
UNLABELLED: To examine the effect of a 10-week upper-body resistance training program on bone turnover markers and site-specific bone mineral density (BMD) in the wrist and distal half of the ulna and radius in untrained and healthy young premenopausal women. METHODS: Twenty-two subjects (aged 22.1 ± 1.8 years) were randomly assigned to a resistance training (n = 12) or no training control (n = 10) group. The following outcome variables were measured before and after 10 weeks of resistance training: (1) bone formation biomarker osteocalcin, and bone resorption biomarker tartrate-resistant acid phosphatase isoform 5b; (2) BMD in the wrist and distal half of the ulna and radius; (3) isokinetic strength of the elbow and knee extensors and flexors; (4) dynamic strength of the arm extensors and flexors; and (5) maximum number of push-ups. RESULTS: The 10-week upper body resistance training intervention resulted in improved strength performance in push-ups (resistance training versus control: P < 0.05), chest presses (P < 0.05), and pulldowns (P < 0.05). However, there was no improvement in the BMD of the wrist (P > 0.05), BMD of the distal half of the ulna and radius (P > 0.05), and metabolic biomarkers osteocalcin (P > 0.05) and tartrate-resistant acid phosphatase isoform 5b (P > 0.05), except for the osteocalcin/tartrate-resistant acid phosphatase isoform 5b ratio. Also, no improvement in the resistance training group was observed for isokinetic strength of the knee and elbow flexion/extension. CONCLUSION: Upper-body muscular strength performance, but not bone metabolic markers and BMD of the wrist, can be improved with a 10-week upper body resistance training program of the nonweight-bearing limbs in untrained young premenopausal women.
