This study evaluated magnesium-creatine (MgCre) supplementation on body water and quadriceps torque. Maltodextran (Placebo), Mg oxide plus Cre (MgO-Cre), and Mg-creatine chelate (MgC-Cre) at 800 mg Mg and 5 g Cre per day were used for 2 weeks in 35 subjects in a random assignment, blinded study. Pre-post measures were completed with bioimpedance to determine total body water (TBW), extracellular water (ECF), and intracellular water (ICF), and an isokinetic device at 180 degrees per second for knee extension peak torque (T), total work (W), and power (PWR). Body weights increased for both treatment groups, MgO-Cre Delta 0.75 kg (P <.05) and MgC-Cre Delta 0.4 kg (P =.07). Significant pre-post differences (P <.05) were noted only for MgC-Cre in ICW (26.29 v 28.01 L) and ECW (15.75 v 14.88 L). MgC-Cre had significant peak T (Nm) increase (124.5 v135.8, P <.05), while MgO-Cre (116.4 v 124.9, P =.06) and placebo (119.8 v 123.7, P =.343) did not. Both treatment groups had increased PWR (P <.05). MgC-Cre affects cellular fluid compartments. The peak torque changes were significant only in the MgC-Cre group, which had increases in ICW that may infer more muscular creatine due to its osmotic effect, and with increased cellular hydration, perhaps increased protein synthesis.