Background: Creatine supplementation (Cr) increases strength during resistance training, but the time course of this strength increase is unclear. The aim was to determine the precise time course by which Cr could increase strength and whether Cr prevents muscle damage during eight weeks of resistance training.
Methods: Young males were randomized (double blind) to Cr (N.=9, 0.07g/kg/d) and placebo (N.=9) during 8-weeks of resistance training (3 d/week). Strength was assessed across six exercises every two weeks. Venous blood samples obtained at baseline, and 24 and 48 hours after the final resistance training session were assessed for creatine kinase [CK] and lactate dehydrogenase [LDH] as measures of muscle damage.
Results: Strength was significantly higher in the Cr versus placebo group (P<0.05) after two weeks of training for three of the six exercises (bench press, leg press, shoulder press). By the end of the eight weeks of training, strength was significantly higher in the Cr versus placebo group (P<0.05) for four of the six exercises (bench press, leg press, shoulder press, and triceps extension, but not biceps curl or lat-pulldown). Creatine supplementation did not prevent muscle damage. Indeed, muscle damage markers increased in the Cr compared to placebo group (P<0.05).
Conclusions: Cr increased muscular strength in as little as two weeks during a resistance training program; however, this was not accompanied by decreased muscle damage. Greater muscle damage with Cr may be due to a greater training intensity enabled by Cr supplementation. This might lead to greater protein turnover and enhanced muscle adaptation.