Japan Institute of Sports Sciences, Nishigaoka, Kitaku, Tokyo, JAPAN.
Department of Budo and Sport Studies, Tenri University, Tenri, Nara, JAPAN.
Med Sci Sports Exerc. 2020 Jan;52(1):187-195. doi: 10.1249/MSS.0000000000002098.
The present study investigated the effects of three consecutive days of endurance training under conditions of low energy availability (LEA) on the muscle glycogen content, muscle damage markers, endocrine regulation, and endurance capacity in male runners.
Seven male long-distance runners (19.9 ± 1.1 yr, 175.6 ± 4.7 cm, 61.4 ± 5.3 kg, maximal oxygen uptake [V˙O2max]: 67.5 ± 4.3 mL·kg·min) completed two trials consisting of three consecutive days of endurance training under LEA (18.9 ± 1.9 kcal·kg FFM·d) or normal energy availability (NEA) (52.9 ± 5.0 kcal·kg FFM·d). The order of the two trials was randomized, with a 2-wk interval between trials. The endurance training consisted of 75 min of treadmill running at 70% of V˙O2max. Muscle glycogen content, respiratory gas variables, and blood and urine variables were measured in the morning for three consecutive days of training (days 1-3) and on the following morning after training (day 4). As an indication of endurance capacity, time to exhaustion at 19.0 ± 0.8 km·h to elicit 90% of V˙O2max was evaluated on day 4.
During the training period, body weight, fat-free mass, and skeletal muscle volume were significantly reduced in LEA (P = 0.02 for body weight and skeletal muscle volume, P = 0.01 for fat-free mass). Additionally, muscle glycogen content was significantly reduced in LEA (30%, P < 0.001), with significantly lower values than those in NEA (P < 0.001). Time to exhaustion was not significantly different between the two trials (20 min, P = 0.39).
Three consecutive days of endurance training under LEA decreased muscle glycogen content with lowered body weight. However, endurance capacity was not significantly impaired.
本研究旨在探讨连续 3 天低能量状态下的耐力训练对男性跑步运动员肌肉糖原含量、肌肉损伤标志物、内分泌调节和耐力能力的影响。
7 名男性长跑运动员（19.9±1.1 岁，175.6±4.7cm，61.4±5.3kg，最大摄氧量[V˙O2max]：67.5±4.3mL·kg·min）完成了两项试验，分别为连续 3 天低能量状态下的耐力训练（18.9±1.9kcal·kg FFM·d）或正常能量状态下的耐力训练（52.9±5.0kcal·kg FFM·d）。两项试验的顺序是随机的，两次试验之间间隔 2 周。耐力训练包括 75 分钟以 70%V˙O2max 的速度在跑步机上跑步。在连续 3 天的训练（第 1-3 天）和训练后的第二天早上（第 4 天）测量肌肉糖原含量、呼吸气体变量以及血液和尿液变量。以 19.0±0.8km·h 的速度耗尽 90%V˙O2max 的时间作为耐力能力的指标，在第 4 天进行评估。
在训练期间，低能量状态下体重、去脂体重和骨骼肌体积明显下降（体重和骨骼肌体积下降 P=0.02，去脂体重下降 P=0.01）。此外，低能量状态下肌肉糖原含量明显下降（约 30%，P<0.001），明显低于正常能量状态下的水平（P<0.001）。两次试验的耐力时间无明显差异（约 20 分钟，P=0.39）。
连续 3 天低能量状态下的耐力训练会降低肌肉糖原含量，导致体重下降。然而，耐力能力并没有受到明显的损害。
