The specific contributions of force and velocity to muscle power in older adults

Abstract

The purpose of this study is to examine the relative importance of the force-based and velocity-based measures of muscle performance to explain inter-individual differences in power production capability and functional task performance. Participants included seventy-nine men and women: middle-aged healthy adults (MH: 40–55 years), older healthy adults (OH: 70–85 years), and older adults with mobility limitations (OML: 70–85 years). Muscle power at 180°/s, isometric maximal torque, and maximal contraction velocity at 40% 1RM were measured during unilateral leg extension. The Short Physical Performance Battery (SPPB) was used to differentiate between healthy and mobility limited older adults. Functional task performance was assessed using multiple chair rise and stair climb tests. Leg extensor force (torque), but not maximal contraction velocity, was significantly associated with muscle power in MH. Both torque and velocity were significantly associated with muscle power in OH. Maximal velocity, but not torque, was associated with power in OML. Maximal velocity demonstrated an association with multiple chair rise time and stair climb time in OML, but not MH or OH. It is concluded that movement velocity is an increasingly important determinant of maximal power output with advancing age. Furthermore, movement velocity is also a critical component of functional task performance with aging and may contribute to functional deficits. These findings help to explain why the rate-dependent variable power has emerged as a critical component of both assessment and rehabilitation of muscular performance and physical function in older adults.

Older men are more fatigable than young when matched for maximal power and knee extension angular velocity is unconstrained

“…Thus, the older men performed the isotonic fatigue task at a slower relative velocity, yet exhibited greater fatigability (i.e., performed fewer contractions) than the young. Despite the importance of contractile velocity per se for dynamic contractions (Dalton et al 2012;Pojednic et al 2012;Bean et al 2013;Thompson et al 2014), it is clear that by accounting for the different age-related inherent capabilities of the neuromuscular system (equating for maximal power) that factors other than only velocity are involved in the greater fatigability of older men compared with young.…”

“…The age-related loss of torque-generating capacity combined with slower contractile velocities results in a greater relative loss of power production than the percentage loss in either factor separately (Power et al 2013). Maximal power production is achieved by an optimal combination of both submaximal torque and angular velocity and has emerged as a key component in quantifying physical function in older adults (Pojednic et al 2012;Bean et al 2013). However, decrements in contractile velocity rather than torque may be the more important contributing factor accounting for reductions in maximal power in older individuals (Dalton et al 2010b;Dalton et al 2012;Pojednic et al 2012;Thompson et al 2014).…”

“…Maximal power production is achieved by an optimal combination of both submaximal torque and angular velocity and has emerged as a key component in quantifying physical function in older adults (Pojednic et al 2012;Bean et al 2013). However, decrements in contractile velocity rather than torque may be the more important contributing factor accounting for reductions in maximal power in older individuals (Dalton et al 2010b;Dalton et al 2012;Pojednic et al 2012;Thompson et al 2014). Thus, as a result of their slower contracting muscles, older adults may rely more on the torque component to generate maximal power than their younger counterparts (Dalton et al 2014).…”

Muscle Mechanography: A Novel Method to Measure Muscle Function in Older Adults

“…Muscle force is one of the primary regulators of bone mass and an important determinant of bone and joint health in older adults. Muscle force is strongly correlated with bone strength, bone size, total bone area, and femoral neck bone mineral density (Hardcastle et al, 2014;Pojednic et al, 2012;Rantalainen et al, 2009;Runge & Hunter, 2006). Muscle velocity (or movement velocity) is the rate of motion (speed) in a specific direction.…”

“…Muscle force and velocity are significant determinates of power production and functional task performance in older adults (Pojednic et al, 2012). Muscle power is defined as the ability to generate as much force as possible and as quickly as possible.…”