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

This study examined 12 wk of creatine (Cr) supplementation and heavy resistance training on muscle strength and myosin heavy chain (MHC) isoform mRNA and protein expression.

Twenty-two untrained male subjects were randomly assigned to either a control (CON), placebo (PLC), or Cr (CRT) group in a double-blind fashion. Muscle biopsies were obtained before and after 12 wk of heavy resistance training. PLC and CRT trained thrice weekly using three sets of 6-8 repetitions at 85-90% 1-RM on the leg press, knee extension, and knee curl exercises. CRT ingested 6 g.d-1 of Cr for 12 wk, whereas PLC consumed the equal concentration of placebo.

There were no significant differences for percent body fat (P > 0.05). However, for total body mass, fat-free mass, thigh volume, muscle strength, and myofibrillar protein, CRT and PLC exhibited significant increases after training when compared to CON (P < 0.05), whereas CRT was also significantly greater than PLC (P < 0.05). For Type I, IIa, and IIx MHC mRNA expression, CRT was significantly greater than CON and PLC, whereas PLC was greater than CON (P < 0.05). For MHC protein expression, CRT was significantly greater than CON and PLC for Type I and IIx (P < 0.05) but was equal to PLC for IIa.

Long-term Cr supplementation increases muscle strength and size, possibly as a result of increased MHC synthesis.