64093
document
Activation of the carotid chemoreflex secondary to muscle metaboreflex stimulation in men . Recent work has shown that the carotid chemoreceptor ( CC ) contributes to sympathetic control of cardiovascular function during exercise , despite no evidence of increased circulating CC stimuli , suggesting enhanced CC activity/sensitivity . As interactions between metaboreceptors and chemoreceptors have been previously observed , the purpose of this study was to isolate the metaboreflex while acutely stimulating or inhibiting the CC to determine whether the metaboreflex increased CC activity/sensitivity . Fourteen young healthy men ( height : 177.0 ± 2.1 cm , weight : 85.8 ± 5.5 kg , age : 24.6 ± 1.1 yr ) performed three trials of 40 % maximal voluntary contraction handgrip for 2 min , followed by 3 min of postexercise circulatory occlusion ( PECO ) to stimulate the metaboreflex . In random order , subjects either breathed room air , hypoxia ( target SPo2 = 85 % ) , or hyperoxia ( FiO2 = 1.0 ) during the PECO to modulate the chemoreflex . After these trials , a resting hypoxia trial was conducted without handgrip or PECO . Ventilation ( Ve ) , heart rate ( HR ) , blood pressure , and muscle sympathetic nervous activity ( MSNA ) data were continuously obtained . Relative to normoxic PECO , inhibition of the CC during hyperoxic PECO resulted in lower MSNA ( P = 0.038 ) and HR ( P = 0.021 ) . Relative to normoxic PECO , stimulation of the CC during hypoxic PECO resulted in higher HR ( P < 0.001 ) and Ve ( P < 0.001 ) . The ventilatory and MSNA responses to hypoxic PECO were not greater than the sum of the responses to hypoxia and PECO individually , indicating that the CC are not sensitized during metaboreflex activation . These results demonstrate that stimulation of the metaboreflex activates , but does not sensitize the CC , and help explain the enhanced CC activity with exercise .
64094
Outcome_Physical
muscle metaboreflex stimulation
64095
Participant_Sex
men