Near-infrared Spectroscopy (NIRS) Measurements in Cold Water Immersion.

One of the most popular recovery strategies utilised by elite and amateur athletes is a form of cryotherapy called cold-water immersion (CWI). CWI is suggested to augment recovery from exercise induced muscle damage (EIMD) through temperature induced reductions in microvascular blood flow and tissue metabolism. However, a review of CWI literature highlights a lack of physiologic data regarding muscle blood flow and muscle metabolic responses to its application (Chapter 1). In addition, an overview of the near-infrared spectroscopy (NIRS) technique and measurements is then discussed, highlighting its ability to measure muscle blood flow and tissue metabolism during CWI. Subsequently, a systematic review investigates the application of NIRS measurements during CWI (Chapter 2). Contrasting changes in local muscle blood volume (ΔtHb) were reported during and following post-exercise CWI, with an increase in tHb explained as a cold-induced vasodilatory response whilst a decrease in tHb suggested the occurrence of peripheral vasoconstriction. The measurement of local muscle oxygen saturation (ΔTSI %) was also common during and following post-exercise CWI but arguably was inadequate for providing useful insight into muscle metabolic activity as there tended to be no change in TSI (%), or it was reported as a standalone measure. An experimental study using male university level long distance runners (n = 11) investigated the utility of a NIRS occlusion procedure to quantify measures of muscle blood flow (mBF) and muscle oxygen consumption (mVO2) (Chapter 3). Measures were obtained pre- and post-CWI at two different temperatures (10 ° and 15 °C). By performing arterial occlusion, a similar reduction in mVO2 was shown in both CWI temperatures. This is consistent with the notion that CWI is capable of reducing muscle metabolism. NIRS derived mBF and mVO2 extends current findings and understanding of the muscle physiological response to CWI.