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The purpose of this study was to compare the effects of cold water immersion (CWI) and active recovery (ACT) on resting limb blood flow, rectal temperature and repeated cycling performance in the heat.
- 10 subjects (endurance-trained male cyclists) completed two testing sessions separated by 1 week;
- Each trial consisted of an initial all-out 35-min exercise bout. Five minutes after the completion of the first exercise bout (Ex1), subjects performed randomised either a standardised ACT protocol (cycling at 40% individual PPO = peak power output (test with a kind of calconi test; 125 W and increased by 25 W every 3 min until exhaustion)) for 15 min or a full body (excluding head and neck).
- Followed by a 40-min passive recovery period before repeating the 35-min exercise bout.
- Performance was measured as the change in total work completed during the exercise bouts.
- Resting limb blood flow, heart rate, rectal temperature and blood lactate were recorded throughout the testing sessions.
Performance: There was a significant decline in performance after ACT compared with CWI where performance remained unchanged.
Rectal temperature (RT): RT was significantly reduced immediately after CWI (36.8°C (1.0°C)) after 40 minuts passive recovery compared with ACT (38.3°C (0.4°C)).
Limb blood flow (LBF): A key aim of this study was to examine the effect of CWI and ACT recovery on limb blood flow. LBF during the passive recovery phase was lower after CWI than ACT. Resting blood flow was initially elevated in both the arms and legs above normal resting levels. This reflects the influence of the hot ambient conditions on skin temperature, which leads to increased cutaneous blood flow and therefore increased LBF.
It is not possible to differentiate between skin and muscle blood flow in the present study, the elevated leg-to-arm blood flow ratio during CWI is likely to reflect an altered distribution of blood flow, while the absolute leg blood flow was reduced during CWI, it is likely that there was a relative reduction in skin blood flow, and this redistribution of blood flow was related to rectal temperature and performance.
Future studies should aim to differentiate muscle and skin blood flow, and the associated muscle and skin temperatures, after CWI to verify these findings.
These findings indicate that CWI recovery leads to better maintenance of performance during high intensity cycling in hot conditions than ACT .The reduction in rectal temperature during CWI was negatively correlated with the performance benefit, indicating that there may be a need to individualise cooling protocols to maximise the performance benefits for individual athletes. The reduction in limb blood flow during CWI was greater in the non-active limbs (arms) compared with the active limbs (legs), suggesting that CWI also leads to a redistribution of blood flow. This adds support to the hypothesis that CWI leads to a redirection of blood flow from the periphery to the core, thereby improving venous return, cardiac efficiency and exercise performance. Overall CWI is an effective intervention for maintaining repeat cycling performance in the heat and this performance benefit is associated with alterations in core temperature and limb blood flow.