Peripheral blood flow changes in response to postexercise cold water immersion

This study compared the effect of postexercise water immersion (WI) at different temperatures on common femoral artery blood flow (CFA), muscle (total haemoglobin; tHb) and skin perfusion (cutaneous vascular conductance; CVC), assessed by Doppler ultrasound, near-infrared spectroscopy (NIRS) and laser Doppler flowmetry, respectively. Given that heat stress may influence the vascular response during cooling, nine men cycled for 25 min at the first ventilatory threshold followed by intermittent 30-s cycling at 90% peak power until exhaustion at 32·8 ± 0·4°C and 32 ± 5% RH. They then received 5-min WI at 8·6 ± 0·2°C (WI₉ ), 14·6 ± 0·3°C (WI₁₅ ), 35·0 ± 0·4°C (WI₃₅ ) or passive rest (CON) in a randomized, crossover manner. Heart rate (HR), mean arterial pressure (MAP), muscle (T_mu ), thigh skin (T_thigh ), rectal (T_re ) and mean body (T_body ) temperatures were assessed. At 60 min postimmersion, decreases in T_re after WI₃₅ (-0·6 ± 0·3°C) and CON (-0·6 ± 0·3°C) were different from WI₁₅ (-1·0 ± 0·3°C; P<0·05), but not from WI₉ (-1·0 ± 0·3°C; P = 0·074-0·092). WI₉ and WI₁₅ had reduced T_body , T_thigh and T_mu compared with WI₃₅ and CON (P <0·05). CFA, tHb and CVC were lower in WI₉ and WI₁₅ compared with CON (P<0·05). tHb following WI₉ remained lower than CON (P = 0·044) at 30 min postimmersion. CVC correlated with tHb during non-cooling (WI₃₅ and CON) (r²  = 0·532; P<0·001) and cooling recovery (WI₉ and WI₁₅ ) (r²  = 0·19; P = 0·035). WI₉ resulted in prolonged reduction in muscle perfusion. This suggests that CWI below 10°C should not be used for short-term (i.e. <60 min) recovery after exercise.