Maximal strength and power characteristics in isometric and dynamic actions of the upper and lower extremities in middle-aged and older men

Muscle cross-sectional area of the quadriceps femoris (CSA(QF)), maximal is ometric strength (handgrip test and unilateral knee extension/flexion), the shape of isometric force-time curves, and power-load curves during concent ric and stretch-shortening cycle (SSC) actions with loads ranging from 15 t o 70% of one repetition maximum half-squat (1RM(HS)) and bench-press (1RM(B P)) were examined in 26 middle-aged men in the 40-year-old (M40) (mean age 42, range 35-46) and 21 elderly men in the 65-year-old age group (M65) (mea n age 65, range 60-74). Maximal bilateral concentric (1RM(HS) and 1RM(BP)), unilateral knee extension (isometric; MIFKE and concentric; 1 RMKE) streng th and muscle CSA in M65 were lower (P < 0.001) than in M40. The individual values of the CSA(QF) correlated with the individual values of maximal con centric 1RM(HS), 1RM(KE) and MIFKE in M65, while the corresponding correlat ions were tower in M40. The maximal MIFKE value per CSA of 4.54 +/- 0.7 N m cm(-2) in M40 was greater (P < 0.05-0.01) than that of 4.02 +/- 0.7 N m cm (-2) recorded in M65, The maximal rate of force development of the knee ext ensors and flexors in M65 was lower (P < 0.01-0.001) and the heights in squ at and counter-movement jumps as much as 27-29% lower (P < 0.001) than thos e recorded in M40. M65 showed lower (P < 0.001) concentric power values for both upper and lower extremity performances than those recorded for M40. M aximal power output was maximized at the 30-45% loads for the upper extremi ty and at the 60-70% loads for the lower extremity extensors in both age gr oups. Muscle activation of the antagonists was significantly higher (P < 0. 01-0.001) during the isometric and dynamic knee extension actions in M65 th an in M40. The present results support a general concept that parallel decl ines in muscle mass and maximal strength take place with increasing age, al though loss of strength may vary in both lower and upper extremity muscles in relation to the type of action and that ageing may also lead to a decrea se in voluntary neural drive to the muscles. Explosive strength and power s eem to decrease with increasing age even more than maximal isometric streng th in both actions but power was maximized at the 30-45% loads for the uppe r and at the 60-70% loads for the lower extremity action in both age groups . High antagonist muscle activity may limit the full movement efficiency de pending on the type of muscle action, testing conditions and the velocity a nd/or the rime duration of the action, especially in the elderly.