Tyler C M, Golland L C, Evans D L, Hodgson D R, Rose R J
Equine Performance Laboratory, The University of Sydney, Rural Veterinary Centre, PMB 4, Werombi Rd., Camden, NSW 2570 Australia.
Pflugers Arch. 1998 Aug;436(3):391-7. doi: 10.1007/s004240050648.
Thirteen standard-bred horses were trained intensively for 34 weeks and detrained for 6 weeks to study skeletal muscle adaptations to prolonged training, overtraining and detraining. Training included endurance (phase 1, 7 weeks), high-intensity (phase 2, 9 weeks) and overload training (OLT) (phase 3, 18 weeks). During phase 3, horses were divided into two groups, OLT and control (C), with OLT horses performing greater intensities and durations of exercise than C horses. Overtraining was evident in OLT horses after week 31 and was defined as a significant reduction in treadmill run time in response to a standardised exercise test (P<0.05). Relationships between peripheral (skeletal muscle) and whole body (maximum O2 uptake, V.O2, max, treadmill run time) adaptations to training were determined. Prolonged training resulted in significant adaptations in morphological characteristics of skeletal muscle but the adaptations were limited and largely completed by 16 weeks of training. Fibre area increased in all fibres while the number of capillaries per fibre increased and the diffusional index (area per capillary) decreased. Mitochondrial volume density continued to increase throughout 34 weeks of training and paralleled increases in V.O2,max and treadmill run time. Significant correlations were noted between mitochondrial volume and V.O2,max (R=0.71), run time and V.O2,max (R=0.83) and mitochondrial volume and run time (R=0.57). We conclude that many of adaptive responses of muscle fibre area and capillarity occur in the initial training period but that markers of oxidative capacity of muscle indicate progressive increases in aerobic capacity with increases in training load. The lack of differences between C and OLT groups indicated that there may be an upper limit to the ability of training stimulus to evoke skeletal muscle adaptive responses. There was no effect of overtraining or detraining on any of the adaptive responses measured.
13匹标准赛马接受了为期34周的强化训练，随后停训6周，以研究骨骼肌对长期训练、过度训练和停训的适应性变化。训练包括耐力训练（第1阶段，7周）、高强度训练（第2阶段，9周）和超负荷训练（OLT）（第3阶段，18周）。在第3阶段，马匹被分为两组，即OLT组和对照组（C组），OLT组马匹的运动强度和持续时间均高于C组马匹。在第31周后，OLT组马匹出现明显的过度训练，表现为在标准化运动测试中跑步机跑步时间显著减少（P<0.05）。研究了外周（骨骼肌）和全身（最大摄氧量、V.O2、max、跑步机跑步时间）对训练的适应性之间的关系。长期训练导致骨骼肌形态特征发生显著适应性变化，但这些变化有限，且在训练16周时基本完成。所有纤维的纤维面积增加，每根纤维的毛细血管数量增加，而扩散指数（每根毛细血管的面积）降低。在34周的训练过程中，线粒体体积密度持续增加，并与V.O2、max和跑步机跑步时间的增加平行。线粒体体积与V.O2、max（R=0.71）、跑步时间与V.O2、max（R=0.83）以及线粒体体积与跑步时间（R=0.57）之间存在显著相关性。我们得出结论，肌肉纤维面积和毛细血管密度的许多适应性反应发生在训练初期，但肌肉氧化能力的指标表明，随着训练负荷的增加，有氧能力逐渐提高。C组和OLT组之间没有差异，这表明训练刺激引发骨骼肌适应性反应的能力可能存在上限。过度训练或停训对所测量的任何适应性反应均无影响。
