Introduction: The haemodynamic responses of skeletal muscle to localised changes in tissue temperature are still poorly understood, despite the widespread therapeutic use of heating and cooling. We aimed to systematically identify these responses both at rest and during one-legged exercise over a wide range of physiologically relevant temperatures. Methods: Leg tissue temperatures in 7 males (age 22±1 years) were altered at rest over 1hr through the use of frozen gel packs (cooling) or a water perfused suit (heating). Core, skin and deep muscle (Tm) temperatures were measured throughout. Haemodynamic alterations in 3 major arteries of the leg (common, superficial, and profunda femoral arteries: CFA, SFA, and PFA) were assessed using duplex Doppler ultrasound, with the contralateral leg providing control measures. Systemic haemodynamic responses were measured non-invasively using infrared plethysmography. Following each intervention, CFA flow was measured during incremental single-legged knee extensor exercise in the experimental or control leg (10±1, 16±1, 23±2, and 30±2W). All values are means ± SEM, with Tm and flows analysed using RM-ANOVA and conductance using linear regression. Results: At rest, 1hr of localised cooling (Tm 34.9±0.3°C to 29.5±0.6°C;p<0.05) led to small but significant decreases in blood flow to all three vessels (40-60ml.min-1 or 15-25%;p<0.05), with heating (Tm 34.5±0.5°C to 36.8±0.1°C;p<0.05) leading to significant increases (100-360ml.min-1 or 63-99%;p<0.05). Blood flow through the PFA (the major supply artery of the thigh skeletal muscle and therefore representative of muscle blood flow) showed significant alterations following both interventions (25% decrease and 63% increase respectively;p<0.05). PFA vascular conductance showed a strong linear relationship with muscle temperature during both interventions (R2=0.95 and 0.96;p<0.01), with the sensitivity of the response increasing considerably at ~35 °C (i.e. normal resting muscle temperature; 0.11±0.03 to 0.70±0.07ml.min-1.mmHg-1.°C-1). Systemic and control leg values remained unchanged. During exercise, prior cooling of the leg had no effect on CFA flows. In contrast, exercise following heating resulted in significantly higher CFA flows throughout the duration of the protocol (~500ml.min-1;p<0.05). Conclusions: These findings suggest that local temperature exerts significant effects on skeletal muscle haemodynamics both at rest and during exercise over a wide range of temperatures, but with significantly increased sensitivity observed at temperatures ≥ 35°C. The maintenance of an increased blood flow throughout exercise following heating suggests an independent role for temperature in the hyperaemic exercise response, potentially mediated through the rapid increases in local muscle and blood temperature experienced when undertaking dynamic muscular contractions.
|Publication status||Published - 2013|
|Event||International Union of Physiological Sciences - Birmingham, United Kingdom|
Duration: 21 Jul 2013 → 26 Jul 2013
|Conference||International Union of Physiological Sciences|
|Period||21/07/13 → 26/07/13|