What is dynapenia?

Abstract

Dynapenia (pronounced dahy-nuh-pē-nē-a, Greek translation for poverty of strength, power, or force) is the age-associated loss of muscle strength that is not caused by neurologic or muscular diseases. Dynapenia predisposes older adults to an increased risk for functional limitations and mortality. For the past several decades, the literature has largely focused on muscle size as the primary cause of dynapenia; however, recent findings have clearly demonstrated that muscle size plays a relatively minor role. Conversely, subclinical deficits in the structure and function of the nervous system and/or impairments in the intrinsic force-generating properties of skeletal muscle are potential antecedents to dynapenia. This review highlights in the contributors to dynapenia and the etiology and risk factors that predispose individuals to dynapenia. In addition, we address the role of nutrition in the muscular and neurologic systems for the preservation of muscle strength throughout the life span.

Fig. 1

Relative risk of poor physical performance, functional limitation, or physical disability in older adults with dynapenia (low muscle strength). The counterfactuals are older adults with normal muscle strength or mass. Studies investigating multiple outcomes or expressing findings by sex are repeated. The author of each study is followed by whether the relative risk was estimated in men, women, or men and women and preceded by whether the outcome was a self-reported physical function/disability (^*) or an observed physical performance (ˆ). Figure modified from Manini and Clark. CI, confidence interval; M, men; W, women.

Fig. 2

The age-related loss of muscle strength is weakly associated with the loss of muscle mass. These figures were adapted from published data obtained from the Health ABC Study to examine the relation between changes in knee extensor strength and quadriceps femoris cross-sectional area muscle (measured by computed tomography) in a 5-y longitudinal study of older adults [15]. These data represent the annualized rate of loss over a 5-y period in older adults who lost body weight (left; n = 309 men) and gained body weight (right; n = 143 men). Note that 1) muscle strength is lost at a substantially faster rate than muscle mass and 2) gaining muscle mass does not prevent the aging-related loss of muscle strength (right). Adapted from data presented by Delmonico et al. [15], with the created figure being approved by the corresponding author (M. J. Delmonico).

Fig. 3

Conceptual model of how nervous and muscle system impairments lead to dynapenia.