Monitoring Changes in Skeletal Muscle Blood Flow During Contrast Water Therapy.
Authors:   , Williams Biju 
Published: September 2024

Background: Contrast water therapy (CWT) is a popular recovery modality, expected to enhance recovery and reduce muscle damage. CWT is proposed to produce benefits through increased muscle blood flow (mBF). However, to date, no studies have investigated mBF during CWT. Therefore, it is envisaged that monitoring mBF during CWT, using near infrared spectroscopy (NIRS) and venous occlusion (VO) might provide some useful data. Objective: The objectives of the study were: Study 1: Identify an appropriate duration of immersion in each water temperature (hot= 40° C and cold= 10°); Study 2: Based on the findings, design a CWT protocol and monitor mBF kinetics during CWT vs hot water. General Methods: In a randomised crossover design, mBF in forearm extensor digitorum communis during water immersion (either hot (40° C), cold (10° C) or CWT (cold/hot)) was measured using NIRS and VO. Skin temperatures were monitored in both studies. Central haemodynamic parameters were monitored in Study 2. After ascertaining normality of data, two-way repeated measures ANOV A was performed to determine the mBF changes affected by water temperature and time. If a significant interaction effect was found, post-hoc tests were carried out using one-way ANOV As with Bonferroni. Statistical significance was set at P < 0.05 and Eta2 was used to report the effect size. Methods (Study 1): Male participants (n = 12) attended two sessions to complete 10-minute water immersion in either hot or cold water. mBF were measured using NIRS during VOs applied at the last 20 s of every minute. Methods (Study 2): Male participants (n = 9) attended two water immersion trials of 12-minute (alternated 6 x 2 min) in either alternated hot and cold or hot water. mBF were measured using NIRS during VOs applied at the last 20 s of every two minutes (during water immersion) and every minute (for baseline). Results (Study 1): Significant (P < 0.05, Eta2 = 0.506) condition*time interaction effects. Posthoc tests revealed that during hot water immersion the significant rate of increase in mBF ( - 82%) occurred within the first 2 minutes (P < 0.05). The significant change with cold water was a drop in mBF (- 58%) from baseline, at minute 10 (P < 0.05). Results (Study 2): Significant (P < 0.05 , Eta2 = 0.360) condition*time interaction. Post-hoc tests revealed significant increase in mBF (- 124% from baseline) by minute 12 (P < 0.05). No significant changes in mBF occurred with CWT. Discussion & Conclusion: Study 1: Results suggest that a duration of 2 minutes would be appropriate for the hot water immersion in a CWT protocol. Immersion duration with cold water would need to follow a time scale from the previous studies that comply with the greatest non-significant rate of change observed in Study 1, which was around 2 minutes. Therefore, for the CWT in Study 2, a 2 min cold and 2 min hot combination seems appropriate. Study 2: The hot water sessions in the CWT might have not penetrated the muscle to increase the muscle temperature to induce vasodilation. Considering the results, it is postulated that to stimulate an increase in mBF, CWT protocol if applied in resting conditions might require a longer duration of hot water immersion (compared to cold). These findings might be useful while designing CWT protocols to target enhanced recovery through improved mBF.