ABSTRACT
A study was conducted to ascertain the relationship between oxygen uptake (Vo<SUB>2</SUB>) and vertical velocity using a pedal-stepping stair simulator. Ten healthy volunteers performed fbur kinds of graded exercise using a stair simulator (SS), whose pitches were set at 80, 100, and 120 beat⋅min<SUP>-1</SUP>, and also an electrically braked bicycle ergometer (BE) . Work rate on the SS was detemined on the basis of the vertical pedal velocity, in accord with the climbingvelocity for stairs. The incremental rate was set at 0.34 W⋅kg<SUP>-1</SUP> every 3 min. Heart rate and Vo<SUB>2</SUB> were measured during the final minute of every stage. Both heart rate and Vo<SUB>2</SUB> during SS were significantly lower than those on BE at the same level of work intensity. Regression equations between Vo<SUB>2</SUB> (m<I>l</I>⋅kg<SUP>-1</SUP>⋅min<SUP>-1</SUP>) and velocity (<I>v</I>: m⋅s<SUP>-1</SUP>) were as follows;<BR>pitch 80: Vo<SUB>2</SUB>=1.00×<I>v</I>+0.06<BR>pitch 100: Vo<SUB>2</SUB>=0.88×<I>v</I>+1.58<BR>pitch 120: Vo<SUB>2</SUB>=0.84×<I>v</I>+2.13<BR>These equations give a lower value of Vo<SUB>2</SUB> than the previous equation based on stair-climbingvelocity reported by the American College of Sports Medicine. Although the individual relationship between Vo<SUB>2</SUB> and heart rate was closely linear, there was a significant effect ofexercise mode and stepping pitch. These results indicate that the work intensity of pedalstepping exercise with a stair simulator is overestimated if it is calculated based on theprevious equation for stair-climbing.
ABSTRACT
Gas exchange kinetics during constant-load exercise were measured to investigate the possibility that excess CO<SUB>2</SUB> output during exercise might not be dependent on hyperventilation. Five healthy males performed twelve minutes of cycle exercise, including two minutes of 0 W pedaling, at 20, 40, 50, 60, 70, and 80% of their maximal work rate (WRmax) determined on the basis of preliminary ramp exercise of 30 W/min. Minute ventilation, O<SUB>2</SUB> uptake, and CO<SUB>2</SUB> output were measured breath-by-breath. Excess CO<SUB>2</SUB> output and CO<SUB>2</SUB> stores were calculated, assuming that the respiratory quotient (RQ) in tissue is constant during constant-load exercise and that the respiratory exchange ratio at the mouth level is equal to the RQ during the steady-state phase. Excess CO<SUB>2</SUB> output was observed at levels of WR greater than 40% WRmax after initial CO<SUB>2</SUB> storage, where VC<SUB>O2</SUB>/V<SUB>E</SUB> decreased gradually as though in parallel with the kinetics of CO<SUB>2</SUB> storage. VO<SUB>2</SUB>/V<SUB>E</SUB>, however, appeared to be constant after the initial peak. These data suggest that V<SUB>E</SUB> is closely correlated with V<SUB>O2</SUB> rather than V<SUB>CO2</SUB> during constant-load exercise, indicating that excess CO<SUB>2</SUB> output to compensate lactate production is independent of hyperventilation.