Effects of oral creatine and resistance training on myosin heavy chain expression

Purpose: This study examined 12 wk of creatine (Cr) supplementation and hea vy resistance training on muscle strength and myosin heavy chain (MHC) isof orm mRNA and protein expression. Methods: Twenty-two untrained male subject s were randomly assigned to either a control (CON), placebo (PLC), or Cr (C RT) group in a double-blind fashion. Muscle biopsies were obtained before a nd after 12 wk of heavy resistance training. PLC and CRT trained thrice wee kly using three sets of 6-8 repetitions at 85-90% 1-RM on the leg press, kn ee extension, and knee curl exercises. CRT ingested 6 g.d(-1) of Cr for 12 wk, whereas PLC consumed the equal concentration of placebo. Results: There were no significant differences for percent body fat (P>0.05). However, fo r total body mass, fat-free mass, thigh volume, muscle strength, and myofib rillar protein, CRT and PLC exhibited significant increases after training when compared to CON (P<0.05), whereas CRT was also significantly greater t han PLC (P<0.05). For Type I, Ha, and IIx MHC mRNA expression, CRT was sign ificantly greater than CON and PLC, whereas PLC was greater than CON (P<0.0 5). For MHC protein expression, CRT was significantly greater than CON and PLC for Type I and IN (P<0.05) but was equal to PLC for Ha. Conclusion: Lon g-term Cr supplementation increases muscle strength and size, possibly as a result of increased MHC synthesis.