Decreased muscle strength relates to self-reported stooping, crouching, or kneeling difficulty in older adults

Abstract

Background: Bending down and kneeling are fundamental tasks of daily living, yet nearly a quarter of older adults report having difficulty performing or being unable to perform these movements. Older adults with stooping, crouching, or kneeling (SCK) difficulty have demonstrated an increased fall risk. Strength (force-generating capacity) measures may be useful for determining both SCK difficulty and fall risk.

Objective: The purposes of this study were: (1) to examine muscle strength differences in older adults with and without SCK difficulty and (2) to examine the relative contributions of trunk and leg muscle strength to SCK difficulty.

Design: This was a cross-sectional observational study.

Methods: Community-dwelling older adults (age [X+/-SD]=75.5+/-6.0 years) with SCK difficulty (n=27) or without SCK difficulty (n=21) were tested for leg and trunk strength and functional mobility. Isometric strength at the trunk, hip, knee, and ankle also was normalized by body weight and height.

Results: Compared with older adults with no SCK difficulty, those with SCK difficulty had significant decreases in normalized trunk extensor, knee extensor, and ankle dorsiflexor and plantar-flexor strength. In 2 separate multivariate analyses, raw ankle plantar-flexor strength (odds ratio [OR]=0.97, 95% confidence interval [CI]=0.95-0.99) and normalized knee extensor strength (OR=0.61, 95% CI=0.44-0.82) were significantly associated with SCK difficulty. Stooping, crouching, and kneeling difficulty also correlated with measures of functional balance and falls.

Limitations: Although muscle groups that were key to rising from SCK were examined, there are other muscle groups that may contribute to safe SCK performance.

Conclusions: Decreased muscle strength, particularly when normalized for body size, predicts SCK difficulty. These data emphasize the importance of strength measurement at multiple levels in predicting self-reported functional impairment.

Figure.

Mean normalized isometric peak torque (% body weight × body height) for all muscle groups tested in older adults with and without stooping, crouching, or kneeling (SCK) difficulty. Error bars show 1 standard deviation (* indicates P<.01). ADF=ankle dorsiflexors, APF=ankle plantar flexors, KE=knee extensors, HE=hip extensors, TE=trunk extensors.