Effect of Low- and High-Glycemic-Index Meals on Metabolism and Performance During High-Intensity, Intermittent Exercise

Abstract

Consuming carbohydrate-rich meals before continuous endurance exercise improves performance, yet few studies have evaluated the ideal preexercise meal for high-intensity intermittent exercise, which is characteristic of many team sports. The authors' purpose was to investigate the effects of low- and high-glycemic-index (GI) meals on metabolism and performance during high-intensity, intermittent exercise. Sixteen male participants completed three 90-min high-intensity intermittent running trials in a single-blinded random order, separated by ~7 d, while fasted (control) and 2 hr after ingesting an isoenergetic low-GI (lentil), or high-GI (potato and egg white) preexercise meal. Serum free fatty acids were higher and insulin lower throughout exercise in the fasted condition (p < .05), but there were no differences in blood glucose during exercise between conditions. Distance covered on a repeated-sprint test at the end of exercise was significantly greater in the low-GI and high-GI conditions than in the control (p < .05). Rating of perceived exertion was lower in the low-GI condition than in the control (p = .01). In a subsample of 5 participants, muscle glycogen availability was greater in the low-and high-GI conditions versus fasted control before the repeated-sprint test (p < .05), with no differences between low and high GI. When exogenous carbohydrates are not provided during exercise both low- and high-GI preexercise meals improve high-intensity, intermittent exercise performance, probably by increasing the availability of muscle glycogen. However, the GI does not influence markers of substrate oxidation during high-intensity, intermittent exercise.

Effects of carbohydrate, branched-chain amino acids, and arginine in recovery period on the subsequent performance in wrestlers

“…The lack of effect of carbohydrate supplementation, with or without BCAA and arginine, on the performance of high-intensity intermittent exercise is in contrast to previous studies in which low muscle glycogen content contributed to the development of fatigue in such type of exercise [2,4,54,55]. Although muscle biopsy was not performed, the exercise protocol used in our study would significantly reduce the glycogen content in the working muscles.…”

The Effect of Ergogenic Supplements and Mediterranean Diet on Cycling Performance. Differences According to Duration and Intensity.

“…Accordingly, in the present study, carbohydrates showed a positive impact on athletic performance during the endurance test (p = 0.001), similar with other experimental studies in cyclists [20,46]. However, regarding the speed test of 200m, the consumption of carbohydrates from our cyclists did not have any ergogenic benefit (p = 0.163), which is suggested by [13].…”

Comparison between Preexercise Meals Intake Effect with Different Glycemic Load on Exercise Performance in Female Athletes

“…They observed that participants' run time was higher after intaking LGI foods than the mentioned time after HGI foods; and the end of the exercise, serum FFA concentrations were higher after LGI than HGI meal [11]. There are some studies in support of these beneficial effects [14,15], however several studies found no different effect in TTE of athletes [16,17,18]. A study by Jamurtas and colleagues showed that ingestion of foods with LGI or HGI at 30 minutes prior to one-hour cycling did not show any significant changes in TTE values [16].…”