ECSS Paris 2023: CP-PN19
INTRODUCTION: Cold exposure elevates arterial blood pressure; however, the relative contributions of central circulatory response and vascular resistance to blood pressure regulation during exercise remain unclear. Sinusoidal workload allows the assessment of dynamic cardiovascular responses through amplitude and phase shift analyses (Fujita et al., 2022, 2023). Therefore, this study aimed to distinguish the control characteristics of central and peripheral cardiovascular responses during sinusoidal walking under thermoneutral and mild cold conditions in the absence of shivering. METHODS: Fifteen healthy young adults (14 men and 1 female) performed sinusoidal walking on a treadmill under two ambient temperature conditions: mild cold condition (19℃; T19) and thermoneutral condition (28℃; T28). The treadmill speed varied sinusoidally between 3 and 6 km•h-1. Beat-by-beat heart rate (HR) and mean arterial pressure (MAP) were continuously measured. Stroke volume (SV) was estimated by model-flow method, and cardiac output (CO) was calculated by multiplying HR and SV. Forearm skin blood flow (SkBf) was continuously measured using a laser tissue blood flowmeter. Total peripheral resistance (TPR) and cutaneous vascular conductance (CVC) were calculated. Core temperature (tympanic) and mean skin temperature (chest, upper arm, thigh, and lower leg) were recorded throughout the protocol. Each variable was fitted to a sinusoidal model to determine amplitude (Amp) and phase shift (PS). RESULTS: Mean skin and core temperature were significantly lower under the T19 condition compared to the T28 condition (both p<0.05). MAP was significantly higher under the T19 condition (p<0.01), whereas HR, SV, CO and SkBf did not significantly change between conditions (all p>0.05). CVC was significantly decreased and TPR was significantly increased under the T19 condition compared to the T28 condition (both p<0.05). Moreover, SkBf exhibited larger PS values than cardiovascular variables (HR, SV, and CO), and this delay was more pronounced in the T19 condition. In contrast, Amp did not significantly differ between conditions for any cardiovascular variables. CONCLUSION: The elevation in MAP under mild cold condition with unchanged CO and increased TPR indicates that blood pressure regulation was primarily mediated by vascular resistance rather than central circulatory control. Furthermore, the slower dynamics of SkBf with larger PS values, particularly in the T19 condition, suggest that cutaneous blood flow contributes minimally to blood pressure regulation under mild cold conditions. These findings demonstrate distinct control characteristics between central hemodynamics and peripheral vascular resistance during sinusoidal walking in mild cold environments.
Read CV Mako FujitaECSS Paris 2023: CP-PN19
INTRODUCTION: The Cold Pressor Test (CPT) is widely used to assess sympathetic-mediated vascular responses (1). Traditionally, CPT involves immersing the hand in ice water; however, this procedure can be technically demanding and may induce severe pain, limiting its clinical applicability (2). Ice bag application provides practical advantages, by mechanically fixing the contact area, reducing discomfort related to wetness, and improving experimental reproducibility. However, it remains unclear whether it elicits hemodynamic responses comparable to the traditional immersion method. Therefore, this study aimed to compare the brachial artery blood flow and shear rate responses induced by two CPT modalities: ice water immersion and ice bag application. METHODS: Eleven healthy young adults (7 males, 4 females; 22 ± 3 years) participated in this study. Right radial artery blood pressure and electrocardiograms were recorded using a tonometry-based automated system. Participants completed two CPT trials in random order: 1) immersion of the left hand in ice water (WI trial), and 2) placement of the left hand between ice bags (IB trial) for 3 min. Brachial artery blood flow was evaluated using Doppler ultrasound. Flow-mediated dilation (FMD) was also assessed using a 5-min ischemic stimulus applied to the right forearm. RESULTS: Skin temperature of the middle finger decreased more during WI than during IB (-24.0 ± 2.2 ºC vs. -19.8 ± 3.4ºC, p < 0.05). This greater reduction in local skin temperature during WI may reflect a stronger peripheral stimulus. In contrast, the increase in mean arterial pressure was similar between trials (WI: +15.2 ± 10.9 mmHg vs. IB: +16.2 ± 8.9 mmHg). WI increased brachial artery blood velocity from 6.0 ± 4.0 cm/s to 7.5 ± 6.3 cm/s, whereas the IB produced a smaller change (5.8 ± 3.3 to 6.5 ± 3.2 cm/s). Although 9 of 11 participants exhibited an increase in blood velocity during WI, 2 demonstrated marked reductions despite substantial increases in blood pressure, indicating heterogeneous vascular responses. CONCLUSION: Ice water immersion elicited a greater increase in brachial artery blood velocity compared with ice bag application, despite similar pressor responses. These findings indicate that although both modalities effectively elevate arterial pressure, only immersion may produce a substantial local shear stimulus. The greater reduction in local skin temperature during immersion may contribute to differences in peripheral vascular signaling. The presence of divergent responses in a subset of participants highlights the complexity and inter-individual variability of vascular regulation during cold pressor stimulation. REFERENCES: (1) Victor RG, Leimbach WN Jr, Seals DR, Wallin BG, Mark AL. Effects of the cold pressor test on muscle sympathetic nerve activity in humans. Hypertension. 1987;9(5):429-436. (2) Mitchell LA, MacDonald RA, Brodie EE. Temperature and the cold pressor test. J Pain. 2004;5(4):233-237.
Read CV Megumi KajiECSS Paris 2023: CP-PN19
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
Read CV victor FRIGNATIECSS Paris 2023: CP-PN19