Sweating response to passive stretch of the calf muscle during activation of 1 forearm muscle metaboreceptors in heated humans

29 Activation of muscle metaboreceptors and mechanoreceptors has been shown to independently 30 influence the sweating response, while their integrative control effects remain unclear. We 31 examined the sweating response when the two muscle receptors are concurrently activated in 32 different limbs as well as the blood pressure response. In total, 27 young males performed 33 passive calf muscle stretches (muscle mechanoreceptor activation) for 30 s in a semi-supine 34 position with and without post-isometric handgrip exercise muscle ischemia (PEMI, muscle 35 metaboreceptor activation) at exercise intensities of 35 and 50% of maximum voluntary 36 contraction (MVC) under hot conditions (ambient temperature, 35°C, relative humidity, 50%). 37 Passive calf muscle stretching alone increased the mean sweating rate significantly on the 38 forehead, chest, and thigh (SRmean) and mean arterial blood pressure (MAP), but not the heart 39 rate (HR), from pre-stretching levels by 0.04±0.01 mg/cm/min, 4.0±1.3 mmHg (P < 0.05), 40 and -1.0±0.5 beats/min (P > 0.05), respectively. The SRmean and MAP during PEMI were 41 significantly higher than those at rest. The passive calf muscle stretch during PEMI increased 42 MAP significantly, by 3.4±1.0 and 2.0±0.7 mmHg for 35 and 50% of MVC, respectively (P < 43 0.05), but not that of SRmean or HR at either exercise intensity. These results suggest that 44 sweating and blood pressure respond to concurrent activation of the two muscle receptors in 45 different limbs differ, and that the influence of calf muscle mechanoreceptor activation alone 46 on the sweating response disappears during forearm muscle metaboreceptor activation. 47 48