Physiological responses to cold water immersion following cycling in the heat.

UNLABELLED 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 approximately 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 repeated 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 (Tre), and skin temperatures (Tsk) were measured throughout recovery. RESULTS CWI elicited a significantly lower HR (CWI: Delta 116 +/- 9 bpm vs. CONT: Delta 106 +/- 4 bpm; P = .02), Tre (CWI: Delta 1.99 +/- 0.50 degrees C vs. CONT: Delta 1.49 +/- 0.50 degrees C; P = .01) and Tsk. 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.