Effect of Isotonic Resistance Training and Creatine and/or Protein Supplementation on Isokinetic Muscle Function in Older Men

Strength training with one mode of exercise (isotonic) usually results in neuromuscular improvements evidenced in other forms of muscle contraction (isokinetic or isometric), especially in young, healthy subjects. It is unclear if older muscle has the same adaptive ability between the different forms of contraction. If resistance training is performed by older individuals, it has been suggested that protein supplementation might be necessary to maximize potential improvements. Additionally, creatine supplementation is generally considered a positive ergogenic aid, however, its effectiveness has not been established in an older population. Therefore, the purpose of this randomized, placebo-controlled study was to assess the effectiveness of protein and/or creatine supplementation in combination with an isotonic resistance training program on isokinetic muscle function in men aged 48-72 years. Forty-two male subjects were randomly assigned to one of four training groups: 1) resistance training placebo (RTP, n=10); 2) resistance trained creatine supplemented (RTCr, n=10); 3) resistance trained protein supplemented (RTPr, n=11); and 4) resistance trained creatine and protein supplemented (RTCrPr, n=11). The intervention consisted of a 16-week progressive overload resistance training protocol (3 days/week), designed to improve strength and muscle mass. Subjects consumed their blinded drinks immediately following each training session. Isokinetic peak torque at 60, 180, and 240^o新ec^-1 and isokinetic muscle endurance for both the knee flexors and extensors were measured pre, mid, and post training. Repeated measures ANOVA indicated a significant training effect (p < .05) for both the knee extensor and flexor muscle groups' peak torque, average power, and acceleration at 60^o新ec^-1, 180^o新ec^-1, and 240^o新ec^-1, whereas only the knee flexor muscle group had significant improvements (p < .05) in time to peak torque at 60^o新ec^-1, 180^o新ec^-1, and 240^o新ec^-1. The knee extensors had significant (p < .05) improvements in total work and average power, as well as a significant reduction in force decline, during the isokinetic muscle endurance test. Interestingly, there were no differences between treatment groups or any trial by group interactions for any of the isokinetic parameters. In conclusion, older males improved isokinetic muscle function following isotonic strength training, however, there was no additional benefit from either the protein or creatine supplementation.