Creatine Supplementation Does Not Influence the Ratio Between Intracellular Water and Skeletal Muscle Mass in Resistance-Trained Men.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 32916658 · doi:10.1123/ijsnem.2020-0080
What was done
Twenty-seven resistance-trained men received either creatine (n = 14) or placebo (n = 13) for 8 weeks while performing a 4-day-per-week split resistance training routine. Skeletal muscle mass (SMM) was estimated from appendicular lean soft tissue measured via dual-energy X-ray absorptiometry. Total body water, intracellular water (ICW), and extracellular water (ECW) were assessed via spectral bioelectrical impedance.
What was found
Both groups showed significant increases (p < .05) in SMM, total body water, and ICW, with greater improvements in the creatine group than in the placebo group (exact numerical values not reported in the abstract). ECW increased similarly in both groups (p < .05). The SMM/ICW ratio did not change in either group (p > .05), but the SMM/ECW ratio decreased only in the creatine group (p < .05). A positive correlation was observed between SMM and ICW changes (r = .71, p < .05).
Why it matters
This study indicates that creatine-induced muscle mass gains accompany proportional increases in intracellular water rather than creating a disproportionate intracellular fluid expansion relative to muscle mass.
Limits
The abstract does not provide absolute values, effect sizes, or confidence intervals. The sample size is small (n = 27) and limited to resistance-trained men. Muscle mass and body fluid compartments were estimated using indirect methods (DXA and bioimpedance spectroscopy) rather than direct tissue measurements.
Cited by
- contradicts A creatine loading phase (20-30 g/day for 5-7 days) acutely increases water retention for 3-5 days, after which maintenance dosing of 3-5 g/day moves the water intracellularly into muscle.