Physiological Responses to Cold Water Immersion Following Cycling in the Heat

Cold water immersion (CWI) has become a popular means of enhancing recovery from various forms of exercise. However, there is minimal scientific information on the physiological effects of CWI following cycling in the heat. Purpose: To examine the safety and acute thermoregulatory, cardiovascular, metabolic, endocrine, and inflammatory responses to CWI following cycling in the heat. Methods: Eleven male endurance trained cyclists completed two simulated similar to 40-min time trials at 34.3 +/- 1.1 degrees C. All subjects completed both a CWI trial (11.5 degrees C for 60 s repealed three times) and a control condition (CONT; passive recovery in 24.2 +/- 1.8 degrees C) in a randomized cross-over design. Capillary blood samples were assayed for lactate, glucose, pH, and blood gases. Venous blood samples were assayed for catecholamines, cortisol, testosterone, creatine kinase. C-reactive protein, IL-6, and IGF-1 on 7 of the 11 subjects. Heart rate (HR), rectal (T(re)), and skin temperatures (T(sk)) were measured throughout recovery. Results: CWI elicited a significantly lower HR (CWI: Delta 116 +/- 9 bpm vs. CONT: Delta 106 +/- 4 bpm; P = .02), T(re) (CWI: Delta 1.99 +/- 0.50 degrees C vs. CONT: Delta 1.49 +/- 0.50 degrees C; P = .01) and T(sk). However, all other measures were not significantly different between conditions. All participants subjectively reported enhanced sensations of recovery following CWI. Conclusion: CWI did not result in hypothermia and can be considered safe following high intensity cycling in the heat, using the above protocol. CWI significantly reduced heart rate and core temperature; however, all other metabolic and endocrine markers were not affected by CWI.