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, VO2peak: 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 (˜10 g 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 1 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.