Graded Venous Occlusion of the Lower Limbs Contributes to the Exercise Pressor Response in Healthy Humans

Abstract

BackgroundLocomotor muscle group III/IV afferent feedback contributes to sympathoexcitation. Sub‐systolic lower limb occlusion may stimulate this reflex. PurposeTo examine the cardiovascular response to lower limb venous occlusion in healthy humans during rest and exercise.MethodsNineteen adults (9 men, 25±5 yr; mean±SD) participated in two visits. V1: 3 min seated rest followed by randomized bilateral thigh tourniquet inflation to 20, 40, 60, 80, 100 mmHg for 2 min with 2 min deflation between occlusions. V2: Recumbent cycle ergometer exercise at 30% peak work with occlusion described in V1. We measured mean, systolic and diastolic pressure, cardiac output, heart rate, and stroke volume (MAP, SBP, DBP, CO, HR, and SV, respectively). ResultsAt rest, MAP (85±18 mmHg) increased at 100 mmHg (Δ4±5, p<0.05) mediated by increased DBP (71±15 mmHg) at 100 mmHg (Δ5±4, p<0.05) with no change in SBP. During exercise, MAP (89±11 mmHg) increased at 60 (Δ7±7), 80 (Δ14±8), and 100 (Δ16±8) mmHg occlusions via increased SBP (133±22 mmHg) at 60 (Δ12±14), 80 (Δ20±13), and 100 (Δ26±13) mmHg and DBP (68±9 mmHg) at 60 (Δ5±5), 80 (Δ10±7), and 100 (Δ12±7) (p<0.05, all). Although, CO and SV did not change, HR (108±11 bpm) increased at 40 (Δ5±4), 60 (Δ8±5), 80 (Δ13±7), and 100 mmHg (Δ15±7) (p<0.05, all).ConclusionStimulation of locomotor muscle group III/IV afferents via sub‐systolic occlusion contributes to cardiovascular control.