Author(s): FRIGNATI, V., MARTIN, G., BOURENNE, J., PRIEUR-BLANC, N., BREGEON, F., GARDAREIN, J.L., HAYS, A., GIRAUD, D., Institution: AIX-MARSEILLE UNIVERSITÉ , Country: FRANCE, Abstract-ID: 2439

INTRODUCTION:
The increase in heat waves is accompanied by a rise in heat-related illnesses [1]. Cold water immersion (CWI) is the gold standard method for rapidly reducing core temperature [2]. However, whole body CWI is not very compatible with intensive care and its use in the field remains limited, justifying the exploration of alternative strategies. This study aimed to compare the effects of different partial immersion strategies (arms [A], legs [L], arms+legs [AL], or no immersion [NI]) on reducing gastrointestinal temperature (TGI).
METHODS:
Twenty-six participants (12 men and 14 women) completed four experimental sessions (A, L, AL, and NI) consisting of rowing exercise until TGI>38.5 °C, immersion for 15 minutes, a 15 minute post-immersion rest period, and then a second 10 minutes exercise session. The variables measured included: TGI, skin temperature, popliteal and brachial arterial blood flow, heart rate, ventilatory flow and oxygen consumption.
RESULTS:
At the end of the immersion phase, no significant difference in TGI was observed between the four conditions (p>0.05). At the same time, arterial flow was lower than in the NI condition in all immersion conditions, at the brachial (A: -87.3 ± 14.03 mL/min, p<0.001; L: -55.67 ± 13.88 mL/min, p<0.01; AL: -80.84 ± 14.41 mL/min, p<0.001) and popliteal (A: -57.69 ±14.08 mL/min, p<0.01; L : -66.94 ± 13.76 mL/min, p<0.001; AL : -55.85 ± 14.25 mL/min, p<0.01). At the end of the rest period, TGI was still not different between the four conditions (p>0.05). At the same time, arterial flow was lower than the NI condition for conditions A and AL at the brachial level (A: -65.72 ± 14.23 mL/min, p<0.001; AL: -58.67± 14.41 mL/min, p<0.01) and for all conditions at the popliteal level (A: -57.23 ± 14.27 mL/min, p<0.01; L: -50.66 ± 13.92 mL/min, p<0.05; AL: -85.34 ± 14.45 mL/min, p<0.001). During the second rowing exercise: at 5 minutes, the TGI was lower in AL than in NI and L (NI: 0.27 ± 0.06 °C, p<0.001; L: 0.24 ± 0.06 °C, p<0.05) and was higher in NI compared to A and L (A: -0.27 ± 0.06 °C, p<0.001; L: -0.23 ± 0.06 °C, p<0.05). At 10 minutes, TGI was lower in AL compared to the other conditions (L: 0.33 ± 0.07 °C, p<0.001; NI: 0.63 ± 0.07 °C, p<0.001; A: 0.40 ± 0.07 °C, p<0.001) and in L compared to NI (-0.31 ± 0.06 °C, p<0.001).
CONCLUSION:
During immersion, regardless of conditions, cold seems to be stored in the immersed limbs and does not appear to spread to the central body compartment. This seems to be due to the redistribution of blood mass caused by vasoconstriction. Resuming physical exercise, known to cause vasodilation of active muscles, redirects blood to the immersed limbs, causing a drop in TGI. As a result, the greater the volume of the body immersed, the greater the storage. Thus, AL condition maximises the drop in TGI during the second exercise. These results could improve cooling techniques and promote the development of innovative tools targeting the limbs.
[1]Adélaïde 2022/[2] Barletta 2024