Ventilatory and Gas Exchange Responses under Spontaneous and Fixed Breathing Modes during Arm Exercise

抄録

To evaluate the difference of ventilatory and gas exchange response differences between arm and leg exercise, six healthy young men underwent ramp exercise testing at a rate of 15 W·min⁻¹ on a cycle ergometer separately under either spontaneous (SPNT) or fixed (FIX) breathing modes, respectively. Controlled breathing was defined as a breathing frequency (f_b; 30 breaths·min⁻¹) which was neither equal to, nor a multiple of, cranking frequency (50 rev·min⁻¹) to prevent coupling of locomotion and respiratory movement, i.e., so-called locomotor-respiratory coupling (LRC). Breath-by-breath oxygen uptake (VO₂), ventilation (VE), CO₂ output (VCO₂), tidal volume (VT), f_b and end-tidal PCO₂ (PETCO₂) were determined using a computerized metabolic cart.
Arm exercise engendered a higher level of VO₂ at each work rate than leg exercise under both FIX and SPNT conditions. However, FIX did not notably affect the VO₂ response during either arm or leg exercise at each work rate compared to SPNT. During SPNT a significantly higher f_b and lower PETCO₂ during arm exercise was found compared with leg exercise up to a f_b of 30 breaths·min⁻¹ while VE and VT were nearly the same. During fixed breathing when f_b was fixed at a higher rate than during SPNT, a significantly lower PETCO₂ was observed during both exercise modes. These results suggest that: 1) FIX breathing does not affect the VO₂ response during either arm or leg exercise even when non-synchronization between limb locomotion movement and breathing rate was adopted; 2) at a f_b of 30 breaths·min⁻¹ FIX breathing induced a hyperventilation resulting in a lower PETCO₂ which was not associated with the metabolic rate during either arm or leg exercise, showing that VE during only leg exercise under the FIX condition was significantly higher than under the SPNT condition.