衰竭運動後增補牛奶對耐力運動表現之影響

Abstract

目的：探討在肝醣耗竭運動後，增補不同脂肪含量（全脂、脫脂）牛奶，對隨後耐力運動表現之影響。方法：以9名大學體育系男性學生為受試對象（年齡為20.6 ± 1.2歲，身高為177.5 ± 3.5公分，體重為72.9 ± 6.8公斤）。以重覆量數、平衡次序原則的實驗設計，受試者分別接受3種實驗處理，實驗處理間至少間隔7天。首先，每位受試者必須先接受最大攝氧量 (maximal oxygen uptake, VO2max) 測驗，並推算出最大功率 (power at VO2max, Pmax) 作為後續實驗處理之強度依據。在每次實驗處理中需依序接受肝醣耗竭運動測驗、恢復期4小時以及70% Pmax耐力運動的測驗。在恢復期期間，受試者必須飲用實驗處理增補飲料（全脂牛奶、脫脂牛奶、水）。評估實驗處理增補後之耐力運動耗竭時間 (TTE) 以及心肺功能與代謝的影響。結果：在耐力運動之耗竭時間中，3種實驗處理間沒有顯著差異 (p > .05) ，但是若以水實驗處理為基準值，全脂牛奶實驗處理的進步率顯著高於脫脂牛奶 (WFM vs. NFM, 53.9% ± 72.0% vs. 27.5% ± 52.1%, p = .035) 。在70% Pmax耐力運動中的平均心跳率，全脂牛奶實驗處理顯著高於脫脂牛奶 (WFM vs. NFM, 160 ± 16 vs. 152 ± 14 bpm, p< .05) 。在呼吸交換率中，水實驗處理在耐力運動時的25%TTE顯著低於之後的50-100%TTE (p < .05) ，醣類氧化速率上，全脂牛奶與水實驗處理的25%TTE顯著低於之後的50-100%TTE (p < .05) 。在游離脂肪酸上，在4小時恢復後的立即 (WFM vs. NFM vs. W, 0.23 ± 0.09 vs. 0.13 ± 0.05 vs. 0.66 ± 0.26 mmol•L-1, p < .05) 及70%Pmax耐力運動後 (WFM vs. NFM vs. W, 0.73 ± 0.24 vs. 0.77 ± 0.34 vs. 1.40 ± 0.55 mmol•L-1, p < .05) ，水實驗處理顯著高於全脂牛奶與脫脂牛奶。結論：本研究結果顯示，與脫脂牛奶相較下，增補全脂牛奶，在肝醣耗竭運動後，可能可以提昇非最大耐力的自行車運動至衰竭時間，並且節省肝醣的使用。而由於運動時間的延長，因此有心跳率較高的情形。Purpose: To investigate the effects of milk-based drinks with different fat (whole- and non-fat) on the endurance performance following an exhaustive interval workout. Methods: Nine male collegiate athletes (age, 20.6 ± 1.2 yrs; height, 177.5 ± 3.5 cm; weight, 72.9 ± 6.8 kg) were recruited in this repeated measured and counter-balance designed study, and completed 3 trials separated by at least 7 days. All subjects were asked to perform incremental cycling exercise test for calculating the power output at 70% maximal oxygen uptake (70%Pmax). In each treatment, subjects performed a glycogen-depleting exercise followed by 4 hours of recovery, and a subsequent endurance trial to volitional exhaustion at 70%Pmax. During the recovery period, subjects consumed the experimental drinks: whole-fat milk (WFM), non-fat milk (NFM), or water (W). The effects of the drink on time to exhaustion (TTE) and the cardiovascular and metabolic responses to endurance trial were examined. Results: No significant differences on the TTE were observed among treatments (p > .05). However, the change of TTE between WFM and W was significantly higher than that in NFM (WFM vs. NFM, 53.9% ± 72.0% vs. 27.5% ± 52.1%, p = .035). The average heart rate during endurance trial at 70%Pmax was significantly higher in WFM than that in NFM (WFM vs. NFM, 160 ± 16 vs. 152 ± 14 bpm, p< .05). In the W treatment, the respiratory exchange ratio and fat oxidation rate at 25%TTE were significantly higher than those at 50%–100%TTE (p < .05). The glucose oxidation rates at 25%TTE were also significantly lower than those at 50%–100%TTE (p < .05) in the WFM and W, respectively. The free fatty acids concentrations immediately after the 4 hours of recovery (WFM vs. NFM vs. W, 0.23 ± 0.09 vs. 0.13 ± 0.05 vs. 0.66 ± 0.26 mmol•L-1, p < .05) and after the endurance trial at 70%Pmax (WFM vs. NFM vs. W, 0.73 ± 0.24 vs. 0.77 ± 0.34 vs. 1.40 ± 0.55 mmol•L-1, p< .05) in W were significantly higher than those in WFM and NFM. Conclusion: These results suggest that milk-based drink with whole-fat, while comparing the non-fat milk, might improve the TTE and induce the glycogen sparing effect during the submaximal cycling exercise following the glycogen-depleting workout, however, this improvement might also increase the heart rate responses during exercise.