Effects of pre-exercise snack bars with low- and high-glycemic index on soccer-specific performance: An application of continuous glucose monitoring

This study aimed to investigate the effects of pre-exercise snack bars with different glycemic indices (GI) on soccer-specific performance. In a randomised crossover study design, 12 recreational soccer players consumed either low- or high-GI snack bars 1 h before 25 min small-sided game (SSG) training. Following the SSG training, the players' passing abilities were assessed using the Loughborough Soccer Passing Test (LSPT), followed by aerobic endurance capacities YOYO Intermittent Recovery Test Level 1 (YYIRT), respectively. Continuous glucose monitors (CGM) were used to track the glycemic response during SSG training and all tests. The result showed that participants' performance was significantly better in the low-GI trial compared with the high-GI trial for the LSPT movement (58.27 ± 10.99 vs. 62.27 ± 7.63 s, <i>p</i> < 0.05), LSPT total (74.64 ± 22.66 vs. 83.18 ± 18.29 s, <i>p</i> < 0.05), and YYIRT (1196 ± 657 vs. 993 ± 536 m, <i>p</i> < 0.01). The CGM data indicated a lower mean (6.2 ± 0.7 vs. 7.1 ± 0.6 mmol/L, <i>p</i> < 0.01) and lower glycemic variability in postprandial interstitial glucose levels in the low-GI trial, compared with the high-GI trial. In conclusion, pre-exercise low-GI snacks could result in more stable glycemic responses and enhance soccer-specific performance.