Effect Of High-concentration Artificial Co2-water Lower Legs Bath On The Rate Of Force Development In Plantar Flexion And Dorsiflexion Muscle

Facilitation of the blood supply and oxygen consumption in the muscle by a local immersion of the extremities into high-concentration carbon dioxide water (CO2-water, CO2 ≥ 1000 ppm) suggests an improvement in muscle performance. PURPOSE: In the present study, we investigated whether the lower legs bath into the CO2-water influences the rate of force development (RFD) in plantar flexion and dorsiflexion muscle. METHODS: Healthy male college students (n = 6, 19-24 yrs, 170.4 ± 4.7 cm, 63.8 ± 9.1 kg) participated in this study. The subjects were randomly divided into the tap-water group and the CO2-water group, and a crossover test was conducted. The subjects immersed their lower legs up to below the knee into tap-water or CO2-water at 35 °C for 10 minutes. Subjective thermal sensation (TS) during the lower leg bath were recorded by every two minutes. The medial head of gastrocnemius muscle (MG) dominant muscle hardness was evaluated using ultrasound real-time tissue elastography and maximum isometric plantar flexion and dorsiflexion strength using our developed muscle strength measuring device at pre and post lower legs bathing. The strain ratio (SR) between the MG and the subcutaneous adipose tissue of the calf was calculated. In addition, the RFD was also measured. We compared the variables after the tap water bath and after the CO2-water bath using a paired Student's t-test. The significance level was set at p < 0.05. RESULTS: TS in the CO2-water was significantly higher than in the tap-water (tap-water vs. CO2-water at 10 minutes in the bath, -0.50 ± 0.55 vs. 1.17 ± 0.41, p < 0.001). After the lower leg bath, in the CO2-water compared with the tap-water, SR significantly increased (3.26 ± 1.52 vs. 7.82 ± 3.91, p < 0.05). Ankle joint peak strength and RFD (0-200 ms) were not significantly difference between pre and after tap-water bathing. However, mean right ankle dorsiflexion strength increased significantly more CO2-water than tap-water (14.4 ± 10.0 Nm vs. 15.8 ± 7.3 Nm, p < 0.05). CONCLUSIONS: The present results suggested that the CO2-water lower leg bath improves the muscle elasticity of the immersion part. No significant change in RFD was observed with the lower leg bath. However, muscle strength tended to improve slightly. It was suggested that CO2-water bathing might contribute to muscle strength improvement. This study was funded in part by a Japan Society for Promotion of Science Grant-in-Aid for Scientific Research (C)#:21 K11450.