Title

Peripheral blood flow changes in response to post-exercise cold water immersion

Date of Award

2014

Degree Type

Thesis

Degree Name

Master of Science (Sports Science)

School

School of Exercise and Health Sciences

Faculty

Health, Engineering and Science

First Advisor

Professor Ken Nosaka

Second Advisor

Dr Chris Abbiss

Third Advisor

Dr Jeremiah Peiffer

Abstract

A reduction in body temperature is considered to be the primary mechanism by which cold water immersion (CWI) enhances short-term (h) recovery and improves exercise capacity in the heat. However, improvement in exercise performance may be optimised at a given cooling magnitude. Water temperature and immersion duration influence the magnitude of cooling in the core body, muscle and skin. Given the role of blood flow in convective heat flux, substrate delivery and metabolic waste clearance, it is important to understand the influence of different water temperatures on compartmental distribution of limb blood flow during CWI. Therefore, the purpose of this study was to compare blood flow changes in the common femoral artery, vastus lateralis muscle, and thigh skin induced by 5 min of post-exercise water immersion at 8°C, 14°C, 35°C or passive rest. In a randomised manner, nine recreationally active men performed exhaustive cycling in a climate control chamber (32.8 ± 0.4°C and 32 ± 5%rh), followed by 5 min of water immersion at 8.6 ± 0.2°C (WI8), 14.6 ± 0.3°C (WI14), 35.0 ± 0.4°C (WI35) or passive rest (CON). The exercise task involved 25 min of cycling at a power output equivalent to first ventilatory threshold, followed by high-intensity intermittent cycling (30 s at 90% of peak power output to 30 s at 70 W). Measurement of blood flow in thigh skin (laser Doppler flowmetry), vastus lateralis muscle (near infrared spectroscopy), and common femoral artery (Doppler ultrasound), heart rate, mean arterial pressure, skin, muscle, rectal, and mean body temperatures were obtained prior to exercise and up to 60 min post-immersion.

Both WI14 and WI8 reduced mean body, calf and thigh skin, and muscle temperatures, compared with WI35 and CON (p0.05). Relative to pre-immersion, differences were observed in the magnitude of reduction between skin, muscle, and common femoral blood flow. Decreases in muscle and skin blood flow were similar (p>0.05), but to a lesser extent when compared with femoral blood flow (p

Therefore, 5 min of CWI at 8°C and 14°C effectively reduced temperatures, when compared with CON and WI35. Although WI8 was more effective than WI14 in reducing mean body temperature, there was no influence on the decreases in skin, muscle and femoral blood flow. Furthermore, WI8 did not result in significant reduction in muscle blood flow compared to WI35, despite significant muscle cooling. Given that mean arterial blood pressure was elevated, it is possible hydrostatic effects during WI35, coupled with shivering thermogenesis during WI8 confounded extent of muscle blood flow reduction in the present study. As such, influence of hydrostatic pressure per se on peripheral blood flow cannot be ruled out although blood flow changes were similar between WI35 and CON. Additionally, current findings indicate unknown vascular beds, other than measured sites in the vastus lateralis muscle and thigh skin, contribute to overall changes in the limb blood flow. It appears that vasoconstriction in skin and muscle vasculatures are associated with the interaction between suppressed vasodilatory substances (e.g. nitric oxide) and altered baroreflex mediated sympathetic nerve activity. However, underlying mechanisms warrant further investigation.

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