Repeated muscle glycogen supercompensation with four days' recovery between exhaustive exercise

Objectives: To determine if a 4 d period of high carbohydrate intake can supercompensate muscle glycogen and exercise work capacity on back-to-back occasions. Design: Seven trained cyclists (6 male, VO(2)peak: 57 +/- 4 mL kg(-1) min(-1)) completed a 9-d experimental period, consisting of three intermittent exhaustive cycling trials on days 1 (trial 1), 5 (trial 2) and 9 (trial 3). Following trial 1 cyclists were fed a high carbohydrate diet ((1) over tilde 0g kg(-1) day(-1)) for eight days to assess their capacity to repeatedly supercompensate muscle glycogen with 4 d recovery. Methods: A resting muscle biopsy was obtained prior to each trial consisting of 2 min work intervals (90-60% peak power output) interspersed with 2 min recovery (40% peak power output) repeated until exhaustion. Each 72-h period between trial days included two days of low volume cycling and a rest day. Resting muscle glycogen and total work completed was determined for each trial day. Results: Baseline muscle glycogen on day 1 (583.6 +/- 111.0 mmol kg(-1) dry mass)was supercompensated on day 5 (835.1 +/- 112.8 mmol kg(-1) dry mass; p= 0.04, d = 2.25) and again on day 9 (848.3 +/- 111.4 mmol kg(-1) dry mass; p = 0.01, d = 2.38). Total cycling work capacity increased from trial l to trial 2 (+8.7 +/- 5.4 kJ kg(-1); p = 0.01; d =1.41); a large effect was observed in trial 3 compared to trial 1 (+6.4 +/- 6.8 kJ kg(-1); p = 0.10; d=1.10). Conclusions: A 4 d high carbohydrate feeding strategy is sufficient to repeatedly supercompensate muscle glycogen content following exhaustive exercise and results in enhanced work capacity. (C) 2019 Published by Elsevier Ltd on behalf of Sports Medicine Australia.