||Neuromuscular function during knee extension exercise after cold water immersion
Wakabayashi, Hitoshi ,
Wijayanto, TitisTochihara, Yutaka
Journal of physiological anthropology
36p.28 , 2017-06-23 , BioMed Central
Background: Human adaptability to cold environment has been focused on in the physiological anthropology and related research area. Concerning the human acclimatization process in the natural climate, it is necessary to conduct a research assessing comprehensive effect of cold environment and physical activities in cold. This study investigated the effect of cold water immersion on the exercise performance and neuromuscular function during maximal and submaximal isometric knee extension. Methods: Nine healthy males participated in this study. They performed maximal and submaximal (20, 40, and 60% maximal load) isometric knee extension pre-and post-immersion in 23, 26, and 34 degrees C water. The muscle activity of the rectus femoris (RF) and vastus lateralis (VL) was measured using surface electromyography (EMG). The percentages of the maximum voluntary contraction (% MVC) and mean power frequency (MPF) of EMG data were analyzed. Results: The post-immersion maximal force was significantly lower in 23 degrees C than in 26 and 34 degrees C conditions (P < 0.05). The post-immersion % MVC of RF was significantly higher than pre-immersion during 60% maximal exercise in 23 and 26 degrees C conditions (P < 0.05). In the VL, the post-immersion % MVC was significantly higher than pre-immersion in 23 and 26 degrees C conditions during 20% maximal exercise and in 26 degrees C at 40 and 60% maximal intensities (P < 0.05). The postimmersion % MVC of VL was significantly higher in 26 degrees C than in 34 degrees C at 20 and 60% maximal load (P < 0.05). The postimmersion MPF of RF during 20% maximal intensity was significantly lower in 23 degrees C than in 26 and 34 degrees C conditions (P < 0.05), and significantly different between three water temperature conditions at 40 and 60% maximal intensities (P < 0.05). The post-immersion MPF of VL during three submaximal trials were significantly lower in 23 and 26 degrees C than in 34 degrees C conditions (P < 0.05). Conclusions: The lower shift of EMG frequency would be connected with the decrease in the nerve and muscle fibers conduction velocity. To compensate for the impairment of each muscle fibers function, more muscle fibers might be recruited to maintain the working load. This might result in the greater amplitude of EMG after the cold immersion.