Relative Strength at the Hip, Knee, and Ankle Is Lower Among Younger and Older Females Who Are Obese.
Hoda Koushyar, Maury A Nussbaum, Kevin P Davy and 1 others
PMID 27007990WHAT IT FOUND
Obese women had lower strength relative to their body weight at the ankle, knee, and hip compared to healthy weight women.
Absolute strength was higher only for three movements. This suggests mobility support training should target the hip and ankle, not just the knee.
Key findings
01Relative strength was significantly lower in obese participants across all six tested movements at the ankle, knee, and hip.
02Absolute strength was higher in obese participants for only three of the six movements: dorsiflexion, knee extension, and hip flexion.
03There was no significant interaction between age and obesity, meaning the effect of obesity on strength was consistent across younger and older adults.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The study was cross-sectional, so it cannot prove that obesity causes the strength differences; other factors like motivation or muscle mass distribution may play a role. The sample size was small, with only 10 participants in each group, which may have limited the ability to detect smaller effects. The plantar flexion testing setup allowed for some knee extension effort to influence the results, despite instructions to isolate the ankle. Only sagittal plane movements were tested, so the findings do not apply to side-to-side or rotational strength. The study included only women, so the results may not generalize to men.
Declared interests
The paper does not report any funding sources or conflicts of interest.
The easy way to misread this
Do not assume that higher absolute strength in obese patients means they have adequate functional capacity. While absolute strength was higher in some movements, relative strength was lower in all movements tested. A patient can lift more force in absolute terms but still struggle with mobility tasks because they have more body mass to move.