Neuromuscular adaptations during intensive strength training in middle-aged and elderly males and females.

Effects of progressive heavy resistance strength training combined with explosive types of exercises for 12 weeks on electromyographic activity (EMG), muscle cross-sectional area of the quadriceps femoris (QF), isometric maximal force and force-time curve of the leg extensor muscles were investigated in 9 middle-aged males and 9 females in the 50-year age group (M50; range 44-57), (F50; range 43-54), and in 10 elderly males and 11 females in the 70-year age group (M70; range 64-73), (F70; range 66-73). Great gradual increases took place in maximal force during the 12-week training period both in M50 (from 2834 +/- 452 N to 3941 +/- 772 N; p < 0.001) and in F50 (from 2627 +/- 725 N to 3488 +/- 1017 N; p < 0.001) as well as in M70 (from 2591 +/- 736 N to 3075 +/- 845 N; p < 0.01) and in F70 (from 1816 +/- 427 N to 2483 +/- 408 N; p < 0.001). Significant (p < 0.05-0.001) increases occurred also in the maximum integrated EMGs of the trained muscles in all groups primarily during the first 8 weeks of the training. Significant (p < 0.05-0.001) enlargements took place during the 12-week training period in the CSA of the QF muscle in all groups. Significant (p < 0.05-0.001) shifts occurred in all groups in the shape of the absolute force-time curves and the maximal rate of force production increased (p < 0.05-0.001) during the training as well. The present findings suggest that progressive heavy strength training combined with explosive types of exercises may lead to considerable increases not only in maximal strength but also in explosive force production characteristics of the trained muscles accompanied by adaptations in the nervous system as well as by muscular hypertrophy not only in middle-aged but in elderly males and females as well.