Štirn Igor, Garcia-Ramos Amador, Feriche Belen, Strojnik Vojko, Tomažin Katja
Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia.
Department of Physical Education and Sport, Faculty of Sport Sciences, University of Granada, Granada, Spain.
Front Physiol. 2022 Apr 25;13:861927. doi: 10.3389/fphys.2022.861927. eCollection 2022.
The aim of the study was to test whether ascending to a moderate real altitude affects motoneuron pool excitability at rest, as expressed by a change in the H-reflex amplitude, and also to elucidate whether a possible alteration in the motoneuron pool excitability could be reflected in the execution of lower-body concentric explosive (squat jump; SJ) and fast eccentric-concentric (drop jump; DJ) muscle actions. Fifteen participants performed four experimental sessions that consisted of the combination of two real altitude conditions [low altitude (low altitude, 690 m), high altitude (higher altitude, 2,320 m)] and two testing procedures (H-reflex and vertical jumps). Participants were tested on each testing day at 8, 11, 14 and 17 h. The only significant difference ( < 0.05) detected for the H-reflex was the higher H-reflex response (25.6%) obtained 15 min after arrival at altitude compared to baseline measurement. In terms of motor behavior, DJ height was the only variable that showed a significant interaction between altitude conditions (LA and HA) and time of measurement (8, 11, 14 and 17 h) as DJ height increased more during successive measurements at HA compared to LA. The only significant difference between the LA and HA conditions was observed for DJ height at 17 h which was higher for the HA condition ( = 0.04, ES = 0.41). Although an increased H-reflex response was detected after a brief (15-20 min) exposure to real altitude, the effect on motorneuron pool excitability could not be confirmed since no significant changes in the H-reflex were detected when comparing LA and HA. On the other hand, the positive effect of altitude on DJ performance was accentuated after 6 h of exposure.
本研究的目的是测试上升到适度的实际海拔高度是否会影响静息时运动神经元池的兴奋性，这通过Hoffmann反射（H反射）幅度的变化来表示，同时还要阐明运动神经元池兴奋性的任何可能变化是否会在下肢向心爆发力（深蹲跳；SJ）和快速离心-向心（跳深；DJ）肌肉动作的执行中体现出来。15名参与者进行了四个实验环节，这些环节由两种实际海拔条件[低海拔（690米）、高海拔（2320米）]和两种测试程序（H反射和垂直跳跃）的组合构成。参与者在每个测试日的8、11、14和17时接受测试。检测到的H反射唯一显著差异（P<0.05）是到达海拔高度15分钟后获得的H反射反应比基线测量值高（25.6%）。在运动行为方面，DJ高度是唯一在海拔条件（低海拔和高海拔）与测量时间（8、11、14和17时）之间表现出显著交互作用的变量，因为与低海拔相比，在高海拔连续测量期间DJ高度增加得更多。在17时观察到低海拔和高海拔条件之间的唯一显著差异，即高海拔条件下的DJ高度更高（P = 0.04，效应量ES = 0.41）。尽管在短暂（15 - 20分钟）暴露于实际海拔高度后检测到H反射反应增加，但由于比较低海拔和高海拔时未检测到H反射的显著变化，因此无法确认对运动神经元池兴奋性的影响。另一方面，暴露6小时后，海拔对DJ表现的积极影响更加明显。
