高溫環境對臨界負荷、運動耐受性與肌肉氧合作用之影響

Abstract

目的：本研究旨在觀察不同環境溫度對臨界負荷、運動耐受性和肺部、腿部肌肉氧合作用的影響。方法：以12名男性自行車運動員為受試對象，採隨機交叉之實驗設計，受試者須在高溫 (35°C, HT) 和常溫 (22°C, NT)，分別執行遞增負荷運動測驗 (IET)、3分鐘衰竭測驗 (3MT)、高強度和激烈強度固定負荷運動測驗。測驗間至少間隔48小時。測驗過程中，使用能量分析儀收集攝氧量，並分析最大攝氧量 (VO2max)、第一換氣閾值 (VT1)、第二換氣閾值 (VT2) 並各別對應其輸出功率 (wVO2max、wVT1和wVT2) 及攝氧動力學數據，同時監測心跳率、肺部和腿部作用肌群的肌肉氧合濃度 [包含總血紅素、含氧血紅素 (O2Hb)、去氧血紅素 (HHb) 及組織氧合指標 (TSI)]，運動表現記錄包括結束功率 (EP)、高於EP之總作功 (WEP)、功率峰值和平均功率，以及高強度和激烈強度的運動持續時間。結果：IET顯示，VO2max在HT明顯高於NT (NT vs. HT, 59.3 ± 7.6 vs. 61.3 ± 8.0 ml·kg-1·min-1, p< .05)，但VT1、VT2和最大心跳率則沒有明顯差異。然而，wVO2max (NT vs. HT, 355 ± 42 vs. 335 ± 44 W)、wVT1 (NT vs. HT, 205 ± 22 vs. 190 ± 23 W) 和wVT2 (NT vs. HT, 243 ± 27 vs. 230 ± 32 W) 在NT明顯高於HT (p < .05)。而在NT 時的3MT運動表現 (NT vs. HT，EP，228 ± 34 vs. 219 ± 33 W；功率峰值，606 ± 82 vs. 588 ± 87 W；平均功率，308 ± 32 vs. 300 ± 34 W) 都明顯高於HT (p < .05)，而WEP除外。此外，在相同環境溫度的wVT2和EP (NT, r = .674; HT, r = .672) 以及VO2max和VO2peak (NT, r = .877; HT, r = .893)，皆具顯著相關 (p < .05)。在高強度運動部分，HT的生理反應和肌肉氧飽和度在腿部O2Hb和TSI，皆明顯低於NT，而HHb則明顯較高。在激烈強度部分發現，雖然HT的運動耐受性明顯較短於NT，但仍符合激烈強度所需達到的運動持續時間。結論：雖然HT會造成運動時生理壓力的增加，不利運動表現，但不論是在高溫或常溫下，3MT所測得之EP可以適當地評估有氧適能，且均可作為劃分高強度和激烈強度運動區間之強度界線。Purpose: To investigate the effects of heat condition on critical power (CP), exercise tolerance, and muscle oxygenation in respiratory and locomotor muscles. Methods: Twelve male cyclists were recruited in the randomized crossover design study. Each subject was required to perform incremental exercise tests, 3-min all-out tests (3MT), and high-intensity and severe-intensity constant load exercises in both high-temperature (HT, 33°C) and neutral-temperature (NT, 22°C) environments. All trials were conducted at least 48 hours apart. Physiological responses, such as maximal oxygen uptake (VO2max), first and second ventilatory thresholds (VT1 and VT2) against the power output (wVO2max, wVT1, and wVT2), and VO2 kinetics were measured during the tests. During each trial, heart rate (HR) and muscle oxygenation in respiratory and locomotor muscles were continuously monitored, including total hemoglobin, oxygenated hemoglobin (O2Hb), deoxygenated hemoglobin (HHb), and tissue saturation index (TSI). End power (EP), anaerobic capacity (WEP), and time to exhaustion were recorded during the tests. Results: VO2max under HT was significantly higher than that under NT (NT vs. HT: 59.3 ± 7.6 vs. 61.3 ± 8.0 ml·kg−1·min−1, p< .05), but no significant difference was noted between these conditions for VT1, VT2, or HRmax. However, wVO2max (NT vs. HT: 355 ± 42 vs. 335 ± 44 W), wVT1 (NT vs. HT: 205 ± 22 vs. 190 ± 23 W), and wVT2 (NT vs. HT: 243 ± 27 vs. 230 ± 32 W) were significantly higher under NT than HT (p < .05). During the 3MT, exercise performance (NT vs. HT: EP, 228 ± 34 vs. 219 ± 33 W; peak power, 606 ± 82 vs. 588 ± 87 W; mean power, 308 ± 32 vs. 300 ± 34 W) was significantly higher under NT than HT (p < .05),with the exception of WEP. Furthermore, significant correlations were observed both between wVT2 and EP (NT, r = .674; HT, r = .672, p< .05), and between VO2max and VO2peak (NT, r = .877; HT, r = .893, p < .05) under the same conditions. During high-intensity exercise sessions, physiological responses and muscle oxygenation of locomotor muscles were significantly higher (HHb) and lower (O2Hb and TSI) under HT than NT. Exercise tolerance during severe-intensity exercise was significantly lower under HT than NT; nevertheless, the exercise duration was sufficient for practical application. Conclusion: Although the increased physiological stress resulted from HT might impair exercise performance, the EP derived from 3MT can accurately estimate aerobic capacity and distinguish high- from severe-intensity exercise, regardless of NT or HT conditions.