Effect of Cold Water Immersion on Metabolic Rate in Humans

Background: Cold water immersion is a widely used form of cryotherapy in the active population despite the limited knowledge on its physiological effects. From an injury standpoint, reducing metabolic rate is advantageous to prevent secondary injury. In contrast, increased metabolism can be beneficial in ridding the body of unwanted metabolites. This study looked to determine the effect of cold water immersion on metabolic rate.  Understanding this phenomenon will help determine appropriate clinical applications of cold water immersion and lead to a better understanding of cryotherapy in general. This study looked to determine the effect of cryotherapy in the form of waist deep cold water immersion at 9° C on metabolic rate. Methods: 10 participants from a university student population volunteered and completed a 15-minute treatment of waist deep cold water (9° C) immersion. Metabolic rate measurements were taken using a Jaeger Oxycon Mobile Unit for 5 minutes prior to treatment, 15 minutes of treatment, and 5 minutes post treatment for a total of 25 minutes. Statistical analysis was completed using a one way repeated measures ANOVA test to compare treatment intervals to baseline intervals. Results: Cold water immersion resulted in elevated metabolic rates for 8 of 10 participants during the first 5 minutes of treatment and for 6 of 10 in the 5 minute post treatment (p < 0.05). A second statistical analysis excluding the first 30 second data point in the 5-10 and 20-25 minute treatments was used to account for movement in and out of the whirlpool. The second analysis showed the same results as the first with the exception of one participant who no longer displayed a statistically significant change in the 20-25 minute interval. Conclusion: These results indicate that cold water immersion should not be used as a measure of reducing secondary injury because of its potential to increase metabolic rate, but instead may have potential benefits in exercise recovery