呼吸肌與耐力型運動表現

Respiratory muscles and endurance performance

耐力性運動項目的運動表現，可能會受到許多因素的影響，包括心血管系統的氧氣運送、工作肌群的氧氣萃取能力、機械效率，以及情緒因素等。呼吸肌群具有高度的有氧能力，且具有極佳的抗疲勞能力。許多運動生理學家並不認為呼吸是限制運動表現的因子之一。既然呼吸肌群屬於骨骼肌的一種，先前的研究顯示呼吸功能可透過特殊的阻力訓練方式而獲得改善。再者，目前有許多研究顯示，呼吸不僅會限制運動表現 (特別是在激烈強度時)，而且強化呼吸肌的功能可改善運動表現。運動引起的呼吸肌疲勞會導致呼吸肌代謝反射的誘發，進而增加運動肌群的疲勞程度。透過吸氣肌訓練與特殊的吸氣肌熱身活動，可促進吸氣肌功能，進而可降低或延遲呼吸肌疲勞的程度。除此之外，由於呼吸肌具有高比例的I型肌纖維與高度的氧化能力，因此，可能有助於加速運動後乳酸的移除。本文在探討呼吸肌疲勞是如何影響運動表現，以及特殊的吸氣肌訓練、熱身與恢復策略的增能效益。整體而言，吸氣肌訓練課程 [50%-80% PImax (maximum inspiratory pressure，最大吸氣肌力)、約6週、每週6天、每天2組 × 30次吸氣] 可改善運動員的運動耐受性。特殊的吸氣肌熱身活動 (40% PImax，2組 × 30次吸氣)，也可提升隨後的衰竭性間歇運動表現。不過，目前仍需要更多的研究，加以釐清吸氣肌熱身活動對於受過良好訓練運動員的專項耐力運動表現之影響。雖然，低負荷 [15公分水柱 (cmH2O)] 的吸氣肌動態恢復活動，可作為激烈運動後，協助移除乳酸的恢復策略；然而，其下可能的生理機轉以及對於隨後運動表現的增能效果，仍須未來進一步地探究。

Performance in endurance events can be limited by the oxygen deliverability of cardiovascular system, oxygen extraction of working muscles, mechanical efficiency, and emotional factors. The respiratory muscle groups have a very high aerobic capacity and a substantial fatigue resistance. Most exercise physiologists do not consider the breathing to be a limiting factor for exercise performance. Since the respiratory muscle groups belong to the skeletal muscles, previous studies showed that the respiratory functions could be enhanced by specific resistance training programs. Furthermore, there were many evidences to support that breathing not only limits exercise performance, especially at intense intensity, but that strengthened respiratory muscle functions improve exercise performance. The respiratory muscle fatigue induced by exercise results in respiratory muscle metaboreflex, thus increasing contractile failure of locomotor muscles. The respiratory muscle fatigue could be attenuated or delayed by improving the inspiratory muscle functions through inspiratory muscle training and specific inspiratory muscle warm-up strategies. In addition, the respiratory muscles, which has oxidative potential and high proportion of type I fibers, might accelerate the post-exercise lactate clearance. This review described how the respiratory muscle fatigue affects exercise performance, and the possible ergogenic effects of specific inspiratory muscle training, warm-up, and recovery strategies. Overall, the inspiratory muscle training program [50%-80%PImax (maximum inspiratory pressure), 6 days per weeks for 6 weeks, 2 sets of 30 breaths per day] could improve exercise tolerance in athletes. The specific inspiratory muscle warm-up activity (40% PImax, 2 sets of 30 breaths) might enhance subsequent exhaustive intermittent exercise performance. However, further studies are needed to clarify the effects of inspiratory muscle warm-up activity on the specific endurance performance of well-trained athletes. Although the inspiratory loading at 15 cmH2O might be used as a recovery strategy to eliminate the lactate accumulated by intense exercise, the possible physiological mechanism and the ergogenic effects on subsequent performance are needed to be determined in future.