Resistance training with slow speed of movement is better for hypertrophy and muscle strength gains than fast speed of movement.

Repetition speed is an important variable during resistance training. However, the effects of different speeds on the muscular strength and hypertrophy in isotonic resistance training are not clear. The study compared fast speed with slow speed of isotonic resistance training on muscular strength and hypertrophy in well-trained adults. Twelve healthy adults were randomly assigned into two groups: fast speed (FS) and low speed (SS). Muscle hypertrophy was measured by an ultrasound examination of the cross-sectional area of the brachial biceps muscle. Muscular strength was verified by 1 RM test. To check the possible differences in strength and hypertrophy between pre and post training and between groups there were compared by two-way ANOVA for repeated measurements and the effect size (ES) was calculated. Improvement in the cross-sectional area (P=0.019) and muscular strength (P=0.021) in the SS group between pre and post training was verified. The SS group had bigger effect sizes than FS group for hypertrophy and strength from pre to post training. SS training was more effective to improve hypertrophy and muscle strength in well-trained adults. KEY WORDS: strength training, isotonic contraction, muscle strengt