Muscle power deficiencies in fallers with lower-limb loss.

Background: Impaired muscle strength has been linked to increased fall risk in clinical populations (Hunter SW, et al. Risk factors for falls in people with a lower limb amputation: a systematic review. Amer Acad of Phys Med and Rehabil. 2017; 9(2):170-180). Limited studies have investigated muscle power output for individuals with lower-limb loss and high fall risk. This study aims to examine the effects of contraction speed on lower-extremity muscle power among 3 groups: control, nonfaller, and fallers with lower-limb loss.

Methods: Thirteen adults without lower-limb loss and 15 adults with lower-limb loss were recruited. Bilateral average power for hip, knee, and ankle was evaluated at 60°/s and 120°/s using a Biodex™ dynamometer. A mixed-model ANOVA was used to identify group and speed effects on muscle power.

Results: Sound limb hip extensor and flexor muscle power were significantly weaker in fallers compared with nonfallers (P = 0.048 and P = 0.43, respectively). Fallers were significantly weaker than control in sound limb hip extensor/flexor and affected knee extensor/flexor muscle groups, while nonfallers' sound hip muscle power was similar to the control. Significant speed effects were found in most muscle power values for control and nonfallers but only found in fallers' sound knee extensors.

Conclusions: Sound hip muscle weakness may contribute to a higher fall risk for individuals with lower-limb loss. Control and nonfallers with limb loss actively adjusted their muscle power output during higher velocity contractions, while fallers with limb loss could not adapt. Incorporating high-velocity power training may reduce fall risk in individuals with lower-limb loss.