Muscle glycogen depletion does not alter segmental extracellular and intracellular water distribution measured using bioimpedance spectroscopy

Abstract

Although each gram of glycogen is well known to bind 2.7-4.0 g of water, no studies have been conducted on the effect of muscle glycogen depletion on body water distribution. We investigated changes in extracellular and intracellular water (ECW and ICW) distribution in each body segment in muscle glycogen-depletion and glycogen-recovery condition using segmental bioimpedance spectroscopy technique (BIS). Twelve male subjects consumed 7.0 g/kg body mass of indigestible (glycogen-depleted group) or digestible (glycogen-recovered group) carbohydrate for 24 h after a glycogen-depletion cycling exercise. Muscle glycogen content using ¹³C-magnetic resonance spectroscopy, blood hydration status, body composition, and ECW and ICW content of the arm, trunk, and leg using BIS were measured. Muscle glycogen content at the thigh muscles decreased immediately after exercise (glycogen-depleted group, 71.6 ± 12.1 to 25.5 ± 10.1 mmol/kg wet wt; glycogen-recovered group, 76.2 ± 16.4 to 28.1 ± 16.8 mmol/kg wet wt) and recovered in the glycogen-recovered group (72.7 ± 21.2 mmol/kg wet wt) but not in the glycogen-depleted group (33.2 ± 12.6 mmol/kg wet wt) 24 h postexercise. Fat-free mass decreased in the glycogen-depleted group ( P < 0.05) but not in the glycogen-recovered group 24 h postexercise. However, no changes were observed in ECW and ICW content at the leg in both groups. Our results suggested that glycogen depletion per se does not alter body water distribution as estimated via BIS. This information is valuable in assessing body composition using BIS in athletes who show variable glycogen status during training and recovery. NEW & NOTEWORTHY Segmental bioimpedance spectroscopy analysis reveals the effect of muscle glycogen depletion on body segmental water distribution in controlled conditions. Despite the significant difference in the muscle glycogen levels at the leg, no difference was observed in body resistance and the corresponding water content of the extracellular and intracellular compartments.

Keywords: bioimpedance; body composition; glycogen.