Artificial CO2-water Leg-bath Facilitates Recovery From Muscle Hardness Caused By Resistance Exercise

Abstract

Facilitation of the blood stream and oxygen consumption of the muscle by a local immersion of the extremities into high concentration carbon dioxide water (CO2-water, CO2≥1000ppm), suggests an improvement of muscle performance and joints flexibility. PURPOSE: In the present study, we investigated whether the immersion of extremities including agonist muscles into artificially made CO2-water influenced recovery of the increased muscle hardness induced by a resistance exercise. METHODS: The healthy male college students (n=11, age; 18-19 yrs, height; 168.6±4.5 cm, weight; 66.2±9.3 kg) participated in this study. The subjects performed 100 times calf raise resistance exercise and immersed lower legs into tap-water or artificial CO2-water at 35 °C for 10 minutes immediately after the exercise. Blood flow in the immersed skin (BFskin) and electrocardiogram (ECG) were recorded continuously throughout the experiment. Hardness of the gastrocnemius medialis (MG) was evaluated using ultrasound real-time tissue elastography. Visual analog scale test on muscle pain (VAS) and muscle hardness measurements were performed at 3 time points (prior to exercise, immediately after exercise, at 10 min after exercise). The strain ratio (SR) between the MG and a reference material was calculated. RESULTS: BFskin in the CO2-water leg-bath was significantly higher than that in the tap-water leg-bath (CO2 -water vs. tap-water, 5.5±1.8 vs. 2.1±1.2 ml·min-1·100g-1, p<0.05). At 10 min after exercise, CO2 -water treatment compared with the tap-water treatment, SR decreased significantly quicker (1.37±0.28 vs. 0.67±0.08, p<0.05). In addition, VAS at recovery 10 min became smaller in the CO2-water than the tap-water (18.1±10.2 vs. 33.9±16.2 mm, p<0.05). CONCLUSIONS: We reported previously that the muscle blood flow in the immersed part was larger in CO2-water than tap-water of a same temperature. In addition to a local effect of CO2, suppression of muscular sympathetic activity may also contribute to the increase in local blood flow. Facilitation of muscle hardness recovery shown in this study might be caused by the increased muscle blood flow. The present study suggested that high concentration artificial CO2-water immersion may contribute to rapid recovery from the high intensity exercise-induced muscle fatigue.