Effect of exercise to rest ratio on plasma lactate concentration at work rates above and below maximum oxygen uptake.
The metabolic and physiological responses to different exercise to rest ratios (E:R) (2:1, 1:1, 1:2) of eight subjects exercising at work rates approximately 10% above and below maximum oxygen uptake (VO2max) were assessed. Each of the six protocols consisted of 15 1-min-long E:R intervals. Total work (kJ), oxygen uptake (VO2), heart rate (fc) and plasma lactate concentrations were monitored. With increases in either E:R or work rate, VO2 and fc increased (P < 0.05). The average (15 min) VO2 and fc 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 VO2max and ranged from a low of 1.8 mmol.l-1 (1:2-90) to a high of 10.7 mmol.l-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.