Purpose: Eight subjects, aged 27.0 ± 1.6 yr, performed incremental workload cycling to investigate the contribution of skeletal muscle mechano- and metaboreceptors to ventilatory control during dynamic exercise. Methods: Each subject performed four bouts of exercise: exercise with no intervention (CON); exercise with bilateral thigh cuffs inflated to 90 mm Hg (CUFF); exercise with application of lower-body positive pressure (LBPP) to 45 torr (PP); and exercise with 90 mm Hg thigh cuff inflation and 45 torr LBPP (CUFF+PP). Ventilatory responses and pulmonary gas exchange variables were collected breath-by-breath with concomitant measurement of leg intramuscular pressure. Results: Ventilation (V̇(E)) was significantly elevated from CON during PP and CUFF+PP at workloads corresponding to ≥ 60% CON peak oxygen uptake (V̇O(2peak)) and during CUFF at workloads ≥ 80% CON V̇O(2peak), P < 0.05. The V̇O2 at which ventilatory threshold occurred was significantly reduced from CON (2.17 ± 0.28 L · min-1) to 1.60 ± 0.19 L · min-1, 1.45 ± 0.15 L · min-1, and 1.15 ± 0.11 L · min-1 during CUFF, PP, and CUFF+PP, respectively. The slope of the linear regression describing the V̇E/CO2 output relationship was increased from CON by approximately 22% during CUFF, 40% during PP, and 41% during CUFF+ PP. Conclusions: As intramuscular pressure was significantly elevated immediately upon application of LBPP during PP and CUFF+PP without a concomitant increase in V̇(E), it seems unlikely that LBPP-induced increases in V̇(E) can be attributed to activation of the mechanoreflex. These findings suggest that LBPP-induced reductions in perfusion pressure and decreases in venous outflow resulting from inflation of bilateral thigh cuffs may generate a metabolite sensitive intramuscular ventilatory stimulus.
- Carotid chemoreceptors
- Central command
- Lower-body positive pressure
ASJC Scopus subject areas
- Orthopedics and Sports Medicine
- Physical Therapy, Sports Therapy and Rehabilitation