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The Effects of Training with Free Weights or Machines on Muscle Mass, Strength, and Testosterone and Cortisol Levels

Shane Schwanbeck

Free weights are generally preferred over machines by practitioners of strength training because they involve incorporation of greater muscle mass because of the greater stabilization that is required. Using free weights may therefore allow one to gain more muscle mass and strength with chronic training; however, this has not been thoroughly addressed. The purpose of this study was to compare the effect of training with free weights or machines on muscle mass, testosterone and cortisol concentrations, and strength.

Fifteen males and twenty-one females aged 22 ± 3 y with previous weight training experience trained using only free weights or only machines for eight weeks. Hormone concentrations were assessed via saliva samples pre and post workout at the beginning, mid-way, and end of the study. Muscle thickness, lean tissue mass, and strength were measured at the beginning and the end of the study.

Elbow flexor thickness increased significantly by 3.9% and a 5.1% in the free weight group and machine group, respectively (p<0.01), with no difference between groups. Knee extensor thickness increased significantly by 4.6% and a 4.9% in the free weight group and machine group, respectively (p<0.01), with no difference between groups. No significant changes occurred in the lean tissue mass during the eight week training period. The group x time interaction for machine bench press strength was close to significance (p=0.054) with the machine training group experiencing a greater increase in strength compared to the free weight training group (13.9% vs. 8.6%). Free weight bench press, free weight squat, and Smith machine squat strength increased significantly in both groups (11-19%; p<0.01) with no difference between groups. The males in the free-weight group had a 21.7%

increase in testosterone from before to after acute training sessions (p<0.01); however, the acute increase in testosterone to cortisol ratio in males training with free weights did not differ from males

training on machines.

Results from this study indicate that training with free weights or machines result in similar increases in muscle mass and strength, and testosterone to cortisol ratio. Males training with free weights may benefit from a greater acute increase in testosterone levels during individual training

sessions.

Chilibeck, Phil

Farthing, Jon; Arnold, Bart; Rodgers, Carol

http://hdl.handle.net/10388/etd-12172008-121030

strength training

hormones

hypertrophy

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