Effects of carbohydrate supplementation on the RPE-blood lactate relationship.

PURPOSE

To examine the effects of carbohydrate (CHO) ingestion on the RPE-blood lactate relationship during incremental and constant-effort exercise.

METHODS

Six male and three female subjects (mean age = 27.2 +/- 8.2 yr, height [ht] = 174.5 +/- 13.5 cm, weight [wt] = 68.9 +/- 12.5 kg, body fat = 18.5 +/- 8.3%), completed two incremental cycling lactate threshold (LT)/(.)VO2peak tests followed by two 45-min production trials. Two hundred and forty milliliters of either carbohydrate or placebo (PL) was ingested before and every 15 min during exercise.

RESULTS

No differences were observed between conditions at LT, 2.5 and 4.0 mM, and peak. Within the CHO condition: V O2 = 25.0, 32.6, 37.5, 47.2 mL x kg x min(-1); power output = 123.3, 170.7, 200.1, 241.7 W; RPE = 12.8, 15.4, 17.2, 19.3; and HR = 137.4, 156.8, 168.7, 187.7 beats x min(-1) at LT, 2.5 mM, 4.0 mM, and peak, respectively. Within PL: V O2 = 24.7, 32.5, 36.8, 45.7 mL x kg x min(-1); power output = 130.0, 175.4, 201.9, 240.0 W; RPE = 12.1, 15.0, 17.0, 19.3; and HR = 134.9, 157.9, 169.6, 187.2 beats x min(-1), respectively. In the CHO condition, blood glucose was higher (P < 0.001), and a trend was observed for lower RPE over time (P = 0.07). During the production trials (RPE of 16) in the CHO condition, higher blood glucose area under the curve (AUC) (PL: 204.1 +/- 79.3 mM; CHO: 220.6 +/- 18.5 mM; P = 0.039) and a trend for greater total work (PL: 448.5 +/- 73.8 kJ; CHO: 470.5 +/- 65.6 kJ; P = 0.089) were observed.

CONCLUSIONS

We conclude that 1) CHO ingestion does not alter the blood lactate-RPE relationship during incremental LT/(.)VO2peak cycling; and 2) carbohydrate supplementation during exercise, eliciting high RPE, may increase work output during training sessions.