Effect of exercise to rest ratio on plasma lactate concentration at work rates above and below maximum oxygen uptake

Summary

The metabolic and physiological responses to different exercise to rest ratios (E: R) (2:1, 1: l, 1:2) of eight subjects exercising at work rates approximately 10% above and below maximum oxygen uptake ($\dot VO_{2 max}$) were assessed. Each of the six protocols consisted of 15 1-min-long E : R intervals. Total work (kJ), oxygen uptake ($\dot VO_2$), heart rate (f _c and plasma lactate concentrations were monitored. With increases in either E : R or work rate,$\dot VO_2$ andf _c increased (P <0.05). The average (15 min)$\dot VO_2$ andf _c ranged from 40 to 81 %, and from 62 to 91% of maximum, respectively. Plasma lactate concentrations nearly doubled at each E : R when work rate was increased from 90 to 110% of$\dot VO_{2 max}$ and ranged from a low of 1.8 mmol -I⁻¹ (1: 2–90) to a high of 10.7 mmol·1⁻¹ (2:1–110). The 2:1–110 protocol elicited plasma lactate concentrations which were approximately 15 times greater than that of rest. These data suggest that plasma lactate concentrations during intermittent exercise are very sensitive to both work rate and exercise duration.