Background In sports, warm-up is used for injury prevention and performance improvement. However, many questions remain about the effect of warm-up on performance, and the motor nerves associated with performance have not been clarified.
Objective This study aims to understand the effect of warm-up on the motor nerve conduction velocity (MCV) of the lower limbs, and obtain further information on evidence-based warm-up.
Method This study had the approval of the Ethical Committee Aomori University of Health and Welfare. The subjects were healthy male college students free from any neurological injury or major disease. The MCV and latencies were measured with an electromyogram and evoked potential testing device (Neuropack X1). The right tibial nerve was measured at rest just before starting the warm-up and at intervals of 10 minutes after starting the warm-up. The reference electrode was placed on the distal lateral first metatarsal bone at the hallux fundus, and the leading electrode was placed on the abductor hallucis muscle belly. The distal stimulation site was directly above the tibial nerve at the bottom of the medial malleolus, and the proximal stimulation site was the popliteal centre. For stimulation intensity, a maximum upper intensity that was 15–20% more than required for causing maximum reaction was used. The room temperature of the warm-up environment was set at 26ºC, and using a treadmill and a heart rate monitor, 30 minutes of running at an aerobic level was performed. For analysis, Tukey’s test was used for multiple comparisons, and significance level was set at less than 5%.
Result The MCV before starting the warm-up was 49.1 ± 6.0 m/sec, distal latency was 4.6 ± 0.93 m/sec, and proximal latency was 12.9 ± 1.41 m/sec. The MCV showed a value significantly higher by 9.1% after 30 minutes of warm-up than before warm-up (p < 0.05). On the other hand, the distal latency showed values significantly lower by 16.9% and 19.1% after 20 minutes and 30 minutes of warm-up, respectively, than before warm-up (p < 0.001, in each). Further, the proximal latency showed significantly lower values of 10.4% and 12.4% after 20 minutes and 30 minutes of warm-up, respectively, than before warm-up (p < 0.001, in each).
Discussion The MCV increased and the latency decreased over time with warm-up. In particular, the reaction time of the lower limbs of the motor nerves showed a significant change 20 minutes after starting the warm-up. Moreover, the change in the proximal latency was larger than that in the distal latency, which is believed to be due to the usage of the muscles in the foot and knee when running. From these observations, we conclude that a warm-up by running needs to be performed for at least 20 minutes, and a warm-up that considers muscle usage could lead to greater performance improvements.
Acknowledgment This study was performed with the support of a 2015 research grant from Aomori University of Health and Welfare.
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