The Effects of Low- and High-Glycemic Index Sport Nutrition Bars on Metabolism and Performance in Recreational Soccer Players.

Mojtaba Kaviani,Jennifer Jochim,Spencer Gall,Gordon A Zello,Philip D Chilibeck

doi:10.3390/nu12040982

Abstract

Consumption of low-glycemic index (GI) carbohydrates (CHO) may be superior to high-GI CHO before exercise by increasing fat oxidation and decreasing carbohydrate oxidation. We compared the effects of pre-exercise feeding of a low-GI lentil-based sports nutrition bar with a high-GI bar on metabolism and performance during a simulated soccer match. Using a randomized, double-blind, counterbalanced, crossover design, participants (n = 8) consumed 1.5 g/kg available CHO from a low-GI bar (GI = 45) or high-GI bar (GI = 101) two hours before a 90 min simulated soccer match, and 0.38 g/kg body mass during a 15 min half-time break. The test involved alternating 6 min intervals of paced jogging, running, walking, and sprinting, and 3 min intervals of soccer-specific skills (timed ball dribbling, agility running, heading, kicking accuracy). Carbohydrate oxidation rate was lower during the match after consuming the low-GI compared to high-GI bar (2.17 ± 0.6 vs. 2.72 ± 0.4 g/min; p < 0.05). Participants performed better during the low-GI versus high-GI bar condition on the agility test (5.7 ± 0.4 versus 6.1 ± 0.6 s; p < 0.01) and heading (i.e., jumping height 24.7 ± 4.3 versus 22.2 ± 4.5 cm; p < 0.01) late in the soccer match (72 min). A low-GI lentil-based sports nutrition bar provides a metabolic benefit (lower carbohydrate oxidation rate) and a modest improvement in agility running and jumping height (heading) late in the test.

Highlights

IntroductionCarbohydrate (CHO) is an important source of energy throughout strenuous prolonged exercise
Carbohydrate (CHO) is an important source of energy throughout strenuous prolonged exercise.Premature fatigue during prolonged exercise is linked with depletion of carbohydrate stores
We showed that low-glycemic index (GI) foods consumed before a simulated soccer match on a treadmill reduced carbohydrate oxidation [20], increased fat oxidation [21], and tended to reduce glycogen usage [22] compared to conditions where high-GI foods were consumed before exercise

Summary

Introduction

Carbohydrate (CHO) is an important source of energy throughout strenuous prolonged exercise. Premature fatigue during prolonged exercise is linked with depletion of carbohydrate stores (i.e., blood glucose and liver and muscle glycogen stores). Muscle glycogen concentrations are directly correlated to time to fatigue during moderately strenuous exercise ranging from 60%–80% of maximal oxygen uptake (VO2max ) [1]. Endurance and high-intensity intermittent exercise will be adversely affected by reduced glycogen stores. During soccer matches, this would most likely occur in the second half of a game [3,4,5]. Soccer players with lower levels of muscle glycogen cover less distance and run at lower speeds during the last 15 min of a match [6]. Total number of sprints and markers of acceleration and deceleration capacity are reduced in the last 15 min of the Nutrients 2020, 12, 982; doi:10.3390/nu12040982 www.mdpi.com/journal/nutrients

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