Fazzari Camille, Macchi Robin, Ressam Camélia, Kunimasa Yoko, Nicol Caroline, Martha Cécile, Bolmont Benoît, Sainton Patrick, Hays Arnaud, Vercruyssen Fabrice, Lapole Thomas, Bossard Martin, Casanova Rémy, Bringoux Lionel, Chavet Pascale
Aix-Marseille Université, CNRS, ISM, Marseille, France.
French Institute of Sport (INSEP), Laboratory Sport, Expertise and Performance (EA 7370), Paris, France.
Front Physiol. 2023 Jun 2;14:1212198. doi: 10.3389/fphys.2023.1212198. eCollection 2023.
Originally developed for astronauts, lower body positive pressure treadmills (LBPPTs) are increasingly being used in sports and clinical settings because they allow for unweighted running. However, the neuromuscular adjustments to unweighted running remain understudied. They would be limited for certain lower limb muscles and interindividually variable. This study investigated whether this might be related to familiarization and/or trait anxiety. Forty healthy male runners were divided into two equal groups with contrasting levels of trait anxiety (high, ANX, = 20 vs. low, ANX, = 20). They completed two 9-min runs on a LBPPT. Each included three consecutive 3-min conditions performed at 100%, 60% (unweighted running), and 100% body weight. Normal ground reaction force and electromyographic activity of 11 ipsilateral lower limb muscles were analyzed for the last 30 s of each condition in both runs. Unweighted running showed muscle- and stretch-shortening cycle phase-dependent neuromuscular adjustments that were repeatable across both runs. Importantly, hamstring (BF, biceps femoris; STSM, semitendinosus/semimembranosus) muscle activity increased during the braking (BF: +44 ± 18%, < 0.001) and push-off (BF: +49 ± 12% and STSM: +123 ± 14%, < 0.001 for both) phases, and even more so for ANX than for ANX. During the braking phase, only ANX showed significant increases in BF (+41 ± 15%, < 0.001) and STSM (+53 ± 27%, < 0.001) activities. During the push-off phase, ANX showed a more than twofold increase in STSM activity compared to ANX (+119 ± 10% vs. +48 ± 27, < 0.001 for both). The increase in hamstring activity during the braking and push-off phases may have accelerated the subsequent swing of the free-leg, likely counteracting the unweighting-induced slowing of stride frequency. This was even more pronounced in ANX than in ANX, in an increased attempt not to deviate from their preferred running pattern. These results highlight the importance of individualizing LBPPT training and rehabilitation protocols, with particular attention to individuals with weak or injured hamstrings.
下身正压跑步机（LBPPTs）最初是为宇航员开发的，由于其允许无负重跑步，越来越多地应用于体育和临床环境。然而，对无负重跑步的神经肌肉调整仍研究不足。它们在某些下肢肌肉中可能受限且个体间存在差异。本研究调查了这是否可能与熟悉程度和/或特质焦虑有关。40名健康男性跑步者被分为两组，特质焦虑水平不同（高焦虑组，ANX，=20；低焦虑组，ANX，=20）。他们在LBPPT上完成了两次9分钟的跑步。每次跑步包括在100%、60%（无负重跑步）和100%体重下连续进行的三个3分钟阶段。在两次跑步的每个阶段的最后30秒，分析了11块同侧下肢肌肉的正常地面反作用力和肌电图活动。无负重跑步显示出与肌肉和拉长缩短周期阶段相关的神经肌肉调整，且在两次跑步中均可重复。重要的是，腘绳肌（BF，股二头肌；STSM，半腱肌/半膜肌）在制动（BF：+44±18%，<0.001）和蹬离（BF：+49±12%，STSM：+123±14%，两者均<0.001）阶段的肌肉活动增加，高焦虑组比低焦虑组增加得更多。在制动阶段，只有高焦虑组的BF（+41±15%，<0.001）和STSM（+53±27%，<0.001）活动有显著增加。在蹬离阶段，高焦虑组的STSM活动比低焦虑组增加了两倍多（+119±10%对+48±27，两者均<0.001）。在制动和蹬离阶段腘绳肌活动的增加可能加速了自由腿随后的摆动，可能抵消了失重引起的步频减慢。在高焦虑组中这种情况比低焦虑组更明显，他们更努力地不偏离自己喜欢的跑步模式。这些结果强调了个性化LBPPT训练和康复方案的重要性，尤其要关注腘绳肌薄弱或受伤的个体。
