The effects of antioxidant vitamin supplementation on expiratory flow rates at rest and during exercise.

PURPOSE: Previous studies suggest that pulmonary function is associated with fruit and vegetable consumption and plasma concentrations of antioxidant vitamins. Also, expiratory flow limitation (EFL) has been reported to limit ventilation during exercise in healthy individuals. We hypothesized antioxidant vitamin supplementation (AVS) would increase resting expiratory flow rates in healthy subjects and reduce EFL during exercise. METHODS: Ten healthy, nonsmoking subjects (5 M/5 W), consuming <5 servings of fruit and vegetables per day, participated in a randomized, single-blinded crossover design study with subjects receiving a placebo (PLA) or AVS [vitamins C (500 mg), E (400 IU), beta-carotene (15,000 IU), zinc (7.5 mg), selenium (50 mg), copper (1 mg), and manganese (2.5 mg)] for 4 weeks. After a minimum 4-week washout period, subjects received the alternate supplementation. Pulmonary function tests and total antioxidant status (TAS) from plasma were measured pre- and post-supplement period. Subjects completed a pre- and post-supplement treadmill test for 20 min at 70% [Formula: see text] followed by increasing workload until exhaustion. RESULTS: AVS increased (p < 0.05) TAS by ~21% and resting expiratory flow rates (FEF25-75, FEF50) by ~9%. Following AVS, %EFL was significantly reduced by ~15% at minute 15, 20, and end-exercise with no change (p > 0.05) in end-expiratory lung volumes. Breathing frequency and ratings of perceived exertion and dyspnea were also lower (p < 0.05) at min 20 of exercise. No changes (p > 0.05) were evident at rest or during exercise with PLA. CONCLUSIONS: These results suggest that AVS can increase TAS, improve resting expiratory flow rates and reduce EFL during exercise in healthy subjects who are not meeting fruit and vegetable recommendations.

Effects of inspiratory muscle training on exercise responses in normoxia and hypoxia.

The purpose of this study was to determine the effects of inspiratory muscle training (IMT) on exercise in hypoxia (H) and normoxia (N). A 4-week IMT program was implemented with 12 healthy subjects using an inspiratory muscle trainer set at either 15% (C; n=5) or 50% (IMT; n=7) maximal inspiratory mouth pressure (PImax). Two treadmill tests (85% VO2max) to exhaustion and measures of diaphragm thickness (Tdi) and function were completed before and after training in H and N. Significant increases of 8-12% and 24.5+/-3.1% in Tdi and PImax, respectively, were seen in the IMT group. Time to exhaustion remained unchanged in all conditions. Inspiratory muscle fatigue (downward arrowPImax) following exercise was reduced approximately 10% (P<0.05) in IMT after both N and H. During H, IMT reduced (P<0.05) VO2 by 8-12%, cardiac output by 14+/-2%, ventilation by 25+/-3%; and increased arterial oxygen saturation by 4+/-1% and lung diffusing capacity by 22+/-3%. Ratings of perceived exertion and dyspnea were also significantly reduced. These data suggest that IMT significantly improves structural and functional physiologic measures in hypoxic exercise.