Sports Science Division, Division of Equine Research Institute, Japan Racing Association, Shimotsuke, Tochigi, Japan.
PLoS One. 2024 Jun 14;19(6):e0305622. doi: 10.1371/journal.pone.0305622. eCollection 2024.
Understanding how muscle activity changes with different surface grades during canter is essential for developing training protocols in Thoroughbreds because canter is their primary gait in training and races. We measured the spatiotemporal parameters and the activation of 12 surface muscles in the leading limb side of 7 Thoroughbreds. Horses were equipped with hoof strain gauges and cantered at 10 m/s on a treadmill set to grades of -4%, 0%, 4%, and 8%, randomly, for 30 seconds each without a lead change. Integrated electromyography (iEMG) values during stance and swing phases were calculated and normalized to mean iEMG values during stride duration at 0% grade in each muscle. The iEMG values at each grade were compared using a generalized mixed model. Stride duration significantly decreased due to shorter swing duration on an 8% grade (P < 0.001) compared to all other grades, where no significant changes were observed. Compared to a 0% grade, the normalized iEMG values during the stance phase on an 8% grade in five muscles significantly increased (Musculus infraspinatus; +9%, M. longissimus dorsi (LD); +4%, M. gluteus medius (GM); +29%, M. biceps femoris; +47%, M. flexor digitorum lateralis; +16%). During the swing phase, the normalized iEMG values in six muscles significantly increased on an 8% grade compared to a 0% grade (M. splenius; +21%, M. triceps brachii; +54%, LD; +37%, GM; +24%, M. semitendinosus; +51%, M. extensor digitorum longus; +10%). No significant changes were observed in iEMG values on -4% and 4% grades compared to the 0% grade. Although +/- 4% grades had little effect on neuromuscular responses, 8% uphill canter reduced stride duration due to decreased swing duration and required increase of muscle activation during either stance and swing phase. Canter on an 8% grade might strengthen equine muscles to increase propulsive force and stride frequency.
了解在不同表面坡度下，马在跑步时肌肉活动的变化对于发展纯血马的训练方案至关重要，因为跑步是他们在训练和比赛中的主要步态。我们测量了 7 匹纯血马的前肢侧 12 块表面肌肉的时空参数和激活情况。马被装备了蹄应变计，并在跑步机上以 10 m/s 的速度以-4%、0%、4%和 8%的坡度随机运行 30 秒，每个坡度都没有改变方向。在每个肌肉的 0%坡度的步幅持续时间内，计算并归一化了支撑和摆动阶段的积分肌电图（iEMG）值。使用广义混合模型比较每个坡度的 iEMG 值。与所有其他坡度相比，8%的坡度下，由于摆动时间缩短，步幅持续时间显著缩短（P < 0.001），而在其他坡度下则没有观察到显著变化。与 0%坡度相比，在 8%坡度下，五个肌肉在支撑阶段的归一化 iEMG 值显著增加（肩胛下肌；+9%，最长肌（LD）；+4%，臀中肌；+29%，股二头肌；+47%，趾外侧伸肌；+16%）。在摆动阶段，与 0%坡度相比，六个肌肉的归一化 iEMG 值在 8%坡度下显著增加（多裂肌；+21%，肱三头肌；+54%，LD；+37%，臀中肌；+24%，半腱肌；+51%，趾长伸肌；+10%）。与 0%坡度相比，在-4%和 4%坡度下，iEMG 值没有明显变化。虽然 +/- 4%的坡度对神经肌肉反应影响不大，但 8%的上坡跑步由于摆动时间缩短而减少了步幅持续时间，这需要在支撑和摆动阶段增加肌肉激活。8%的坡度跑步可能会增强马的肌肉力量，以增加推进力和步频。
