The Influence of Aging on Muscle Strength and Muscle Fiber Characteristics With Special Reference to Eccentric Strength

Abstract

It is well established that aging seriously reduces isometric and concentric muscle strength due to atrophy, deterioration of mechanical properties, and motor unit loss. However, there is limited information on the impact of aging on eccentric strength despite the fact that such forces play an equally important role during daily activities. The purpose of this study was to examine the influence of aging on three expressions of muscle strength (isometric, concentric, and eccentric) in relation to muscle fiber characteristics, with special emphasis on eccentric force. Sedentary but healthy men (age range 18-80 years, n = 60) and women (20-74 years, n = 30) were tested for maximal effort isometric, concentric, and eccentric (1.05, 2.09, 3.14 rads.s-1) quadriceps strength, body composition, and muscle fiber characteristics of the vastus lateralis (men only). There was a significant (p < .05) approximately 30 N per decade decline in isometric and concentric forces, but only 9 N per decade reduction in eccentric strength. There was a significant reduction in Type II muscle fiber area with aging (p < .05). Isometric, eccentric, and concentric force correlated r = .33, r = .32 (p < .05), and r = .12 (p > .05) with Type II muscle fiber area, respectively. The correlation between age and fat-free mass/force ratio ranged from r = .39 to .43 in men and r = .27 to .50 in women. The data suggest a relative preservation of eccentric strength with aging in men and women that seems to be independent of muscle mass or muscle fiber type or size.

Preservation of eccentric strength in older adults: Evidence, mechanisms and implications for training and rehabilitation

“…Numerous cross-sectional comparative studies have provided evidence of the relative maintenance of eccentric torque (Horstmann et al, 1999;Hortobagyi et al, 1995;Klass et al, 2005;Porter et al, 1997;Porter et al, 1995;Poulin et al, 1992;Pousson et al, 2001;Vandervoort et al, 1990) and strength (Phillips et al, 1998) in healthy older adults in spite of overall reductions in muscle contractile capacity. For the purposes of this review, muscle torque is defined as the rotatory effect of a force (force x moment arm) assessed with an isokinetic device, while strength is simply the magnitude of force that a muscle can produce (Enoka, 2002).…”

“…A detailed description of the studies that support the evidence of the preservation of eccentric strength, including participants' characteristics, muscle groups tested, methods of normalization and magnitude of strength deficits is outlined in table 1. In short, these studies compare muscle torque (Horstmann et al, 1999;Hortobagyi et al, 1995;Klass et al, 2005;Porter et al, 1997;Porter et al, 1995;Poulin et al, 1992;Pousson et al, 2001;Vandervoort et al, 1990) or strength (Phillips et al, 1998) values between groups of young and older individuals to determine whether age-related deficits in strength are consistent across different types of muscle contractions.…”

“…The relative maintenance of eccentric strength with aging is consistently reported across different muscle groups (table 1), independent of muscle structural characteristics. For example, Hortobagyi et al (1995) found that eccentric torque of knee extensors was relatively maintained in a group of older adults, although the correlations of either concentric or eccentric torque with muscle mass and fiber type and size were similar. Furthermore, while the majority of studies (Hortobagyi et al, 1995;Poulin et al, 1992) report a greater degree of preservation with higher contraction velocities, consistent with the low influence of velocity of contraction on force production during eccentric contractions (Katz, 1939), the maintenance of eccentric torque is reported across a wide range of velocities (from 30°s −1 to 300°s −1 ).…”

“…In contrast, dynamic muscle contractions can be divided into concentric contractions, involving the shortening of the muscle, and eccentric contractions, consisting of the active lengthening of the muscle by external forces. While it is well accepted that there is a progressive decline in muscle strength with aging, recent studies report a relative preservation of the capacity to produce eccentric torque (Horstmann et al, 1999;Hortobagyi et al, 1995;Klass et al, 2005;Porter et al, 1997;Porter et al, 1995;Poulin et al, 1992;Pousson et al, 2001;Vandervoort et al, 1990) and strength (Phillips et al, 1998), in older adults. In other words, when the age-related reduction of contractile capacity is considered in terms of different types of muscle contractions, the degree to which concentric and isometric strength is reduced is more pronounced than eccentric strength ( fig.…”

Eccentric contraction-induced injury to type I, IIa, and IIa/IIx muscle fibers of elderly adults

“…The latter includes fiber loss and atrophy (Larsson et al 1979;Sato et al 1984;Lexell et al 1988), impairments in the excitation-contraction process (Delbono et al 1995;Wang et al 2002), and perturbations to actomyosin cross-bridge function (Larsson et al 1997; Thompson and Brown 1999;Lowe et al 2001;Frontera et al 2000;Hook et al 2001;Krivickas et al 2001). These factors are specific to the mode of muscle contraction, impacting force during isometric and shortening contractions but having much less effect on force during lengthening or eccentric, muscular activity (Porter et al 1997;Poulin et al 1992;Phillips et al 1991;Ochala et al 2006;Hortobagyi et al 1995).…”