RESUMEN
PURPOSE: To determine the effects of magnesium (Mg2+) supplementation on performance and recovery in physically active women using the sensitive and recently advanced measure of ionic Mg2+ (iMg). METHODS: Participants (N = 121) were screened for [iMg] in plasma, with 44 (36.4%) exhibiting [iMg] below the normal range of 0.53-0.67 mmol.L-1 (4). Thirty-two subjects (21 +/- 3 yr) representing a broad range of [iMg] (0.54 +/- 0.04 mmol.L-1) completed the main 14-wk study. At baseline, participants submitted to a resting blood pressure measurement, and they completed both an anaerobic treadmill test and an incremental (aerobic) treadmill test. For the latter, values for workload, oxygen uptake, and heart rate were obtained at both anaerobic threshold and maximal effort. Blood samples for iMg, total serum Mg2+ (TMg), erythrocyte Mg2+ (EMg), Ca2+, K+, Na+, hemoglobin, hematocrit, lactate, and glucose were also collected pretest, and 4, 10, 30 min, and 24 h posttest. Subjects received 212 mg.d-1 Mg oxide or placebo in a double-blind fashion and were retested after 4 wk. After a 6-wk washout period, the testing was repeated with a treatment crossover. RESULTS: Ionic Mg2+ increased with Mg2+ treatment versus placebo (P < 0.05); however, performance and recovery indices were not significantly affected. CONCLUSION: Four weeks of 212 mg.d-1 Mg oxide supplementation improves resting [iMg] levels but not performance or recovery in physically active women.
Asunto(s)
Antiácidos/farmacología , Suplementos Dietéticos , Óxido de Magnesio/farmacología , Resistencia Física , Adolescente , Adulto , Estudios Cruzados , Método Doble Ciego , Prueba de Esfuerzo , Femenino , Frecuencia Cardíaca , Humanos , Magnesio/sangre , Consumo de Oxígeno , PlacebosRESUMEN
This study investigated the efficacy of SPORT (a popular dietary supplement) in improving performance and assisting recovery in 9 trained athletes. In a double-blind, crossover experiment, subjects ran at workloads of 60 and 80% of peak oxygen uptake (Peak VO2) for 5 min each with 5 min recovery after each bout and at 100% Peak VO2 until exhaustion. Two capsules of either SPORT or a gelatin placebo were administered 1 hr prior to exercise and immediately after each workload. Heart rate (HR) and blood lactate (BLa) were measured at 1 hr prior to exercise, immediately after the 100% exercise bout and at 5, 10, 20, and 45 min during recovery. No significant differences between treatments on HR and BLa measures at any of the 6 time periods, or on subjects' time to exhaustion were found. Under the conditions of this experimental design, SPORT had no beneficial effects on performance or recovery in trained athletes.