Changes of functional status and volume of triceps brachii measured by magnetic resonance imaging after maximal resistance training.

To evaluate the effect of 6‐week self‐perceived maximal resistance training on muscle volume utilizing magnetic resonance imaging and maximal, average, and endurance strength of the elbow extensors and to assess the relationship between muscle strength and volume before and after the training. Materials and Methods This was a prospective blinded study. A total of 15 healthy untrained men, aged 22.5 ± 3.7 years (mean ± SD), were engaged in elbow extensor training using isoacceleration dynamometry for 6 weeks with a frequency of five sessions per week (five sets of 10 maximal voluntary contractions, 1‐minute rest period between each set). Prior to and after the training, cross‐sectional magnetic resonance images of the upper arm were obtained and muscle volumes were calculated using the truncated cone formula. Results Average, maximal, and endurance strength of the upper arm extensors increased significantly by 43%, 15%, and 56%, respectively. The volume of triceps brachii increased in both arms (P < 0.05): right from 456.9 ± 113.8 cm3 to 475.8 ± 100.9 cm3 and left from 444.3 ± 121.9 cm3 to 468.4 ± 110.4 cm3, or 5%. Maximal and average strength correlated significantly with muscle volume before and after the training. Conclusion A specific 6‐week resistance training protocol resulted in muscle strength improvement, together with increase in triceps brachii muscle volume, as demonstrated by volumetric imaging. J. Magn. Reson. Imaging 2009;29:671–676. © 2009 Wiley‐Liss, Inc.