The objective of this study was to evaluate the effect of a reduced-carbohydrate (reduced-CHO) diet on the rate of perceived exertion (RPE) curve during an incremental test. Nine physically active men performed a progressive incremental test on a cycle ergometer (25 W·2 min−1) after 72 hr on either a control diet (60% CHO) or a reduced-CHO diet (30% CHO). Lactate and RPE thresholds were identified using the Dmax method (DmaxLa and DmaxRPE, respectively). Power output, heart rate and RPE scores in DmaxLa and DmaxRPE were similar between the diets and were not different from each other, regardless of the diet. Lactate values were consistently higher (p < .05) in the control diet compared with the reduced-CHO diet during power output after the lactate breakpoint; however, they were not accompanied by a proportional increase in RPE scores. These results suggest that DmaxRPE and DmaxLa are not dissociated after a short-period reduced-CHO diet, whereas the lactate values after the lactate threshold are reduced with a reduced-CHO diet, although they are not accompanied by alterations in RPE.
Guilherme Assuncao Ferreira, Raul Osiecki, Adriano Eduardo Lima-Silva, Michel Cardoso de Angelis-Pereira and Fernando Roberto De-Oliveira
Patricia Guimaraes Couto, Romulo Bertuzzi, Carla Caroline de Souza, Hessel Marani Lima, Maria Augusta Peduti Dal Molin Kiss, Fernando Roberto de-Oliveira and Adriano Eduardo Lima-Silva
This study analyzed the pacing employed by young runners in 10,000 m time-trials under 3 dietary regimens of different carbohydrate (CHO) intakes. Nineteen boys (13–18 years) ate either their normal CHO diet (56% CHO), high (70% CHO), or low (25% CHO) CHO diets for 48 hr; the boys then performed a 10,000 m run (crossover design). The high CHO diet led to faster final sprint (14.4 ± 2.2 km·h-1) and a better performance (50.0 ± 7.0 min) compared with the low CHO diet (13.3 ± 2.4 km·h-1 and 51.9 ± 8.3 min, respectively, p < .05). However, the final sprint and performance time in the high CHO or low CHO diets were statistically not significantly different from the normal CHO diet (13.8 ± 2.2 km·h-1 and 50.9 ± 7.4 min; p > .05). CHO oxidation rate during the constant load exercise at 65% of VO2max was elevated in high CHO diet (1.05 ± 0.38 g·min-1) compared with low CHO diet (0.63 ± 0.36 g·min-1). The rating of perceived exertion increased linearly throughout the trial, independently of the dietary regimen. In conclusion, the high CHO diet induced higher CHO oxidation rates, increased running speed in the final 400 m and enhanced overall running performance, compared with low CHO.