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 total, high-speed and sprint distances covered in football matches are lower when Wet-Bulb Globe Temperature is higher [1], likely due to increased physiological and perceptual strain during exercise in the heat [2]. In laboratory-based football simulations, pre-match and half-time cooling interventions reduced core body temperature and thermal sensation and improved endurance performance [3]. However, a recent field-based study showed that cold towels covering the head, neck, shoulders and upper back (5–7°C) and cool fluid ingestion (5°C, 1 L) did not increase total, moderate-speed running, high-speed running and sprinting distances compared with no-cooling condition in the heat [4]. To improve match running performance in hot environments, a greater cooling power of combined internal and external body cooling may be necessary. Therefore, this study examined whether a combined internal (ice slurry ingestion) and external (cold water immersion of the hand and forearm, cold towel) cooling during 3-min cooling breaks and half-time improves running performances in a football match in a hot environment. METHODS: Twenty highly trained male footballers (goalkeepers excluded) from a university football club played a 90-min match in a hot environment (30.5°C, 40% relative humidity) receiving either a body cooling (COOL) or no-cooling (CON). Players were split into pairs of two by the teams’ coaches based on playing position and skill to create two teams of similar strength. One team received a large cold towel (19°C) covering the neck and ice slurry ingestion (200 g, -1.2°C) during 3-min cooling breaks in both halves and the same towels covering the neck, chest and abdominal region, back, and sides, ice slurry ingestion (400 g, -1.2°C) and cold water immersion of the hand and forearm (5 min, 19°C) during a 15-min half-time. The other team performed a passive rest and were given the same fluids at 24°C. Match running performance was recorded at 100 Hz using a global positioning system. The estimated core body temperature and heart rate were measured using a heat flux system. RESULTS: Two participants were excluded due to injuries. Moreover, six and seven participants in the COOL and CON groups, respectively, were excluded due to heat flux system failures. No significant differences were observed for all match running, estimated core body temperature and heart rate responses between groups (p > 0.05). CONCLUSION: This study revealed that combined internal and external cooling during 3-min cooling breaks and half-time did not improve running performances during a football match in a hot environment. Given the high match-to-match variability in the absolute match running performance [5], further research is needed to re-investigate the effect of body cooling using relative match running performance (e.g., speed relative to maximal aerobic speed). REFERENCES: 1. Schwarz et al., 2025a; 2. Périard et al., 2021; 3. Aldous et al., 2019; 4. Schwarz et al., 2025b; 5. Carling et al., 2016
Read CV Takuma YanaokaECSS Paris 2023: CP-PN19