Over one-third of adults in the United States are obese. One of the many problems associated with obesity is impaired mobility. This impaired mobility is likely related to lower extremity strength, though most prior studies investigating the effects of obesity on lower extremity strength have only investigated the knee.
PURPOSE: The purpose of this study was to perform a more comprehensive investigation of the effects of obesity on lower extremity strengths.
METHODS: Forty adult females completed the study, including 10 young (18-30 years) healthy-weight (BMI = 18-24.9 kg/m2), 10 young obese (BMI >30 kg/m2), 10 older (65-80 years) healthy-weight, and 10 older obese participants. Strengths were measured using a Biodex System 3 dynamometer, during concentric maximum isokinetic contractions in hip extension (HE) and flexion (HF) at 60 deg/sec, knee extension (KE) and flexion (KF) at 75 deg/sec, and ankle plantar flexion (PF) and dorsiflexion (DF) at 60 deg/sec. Peak moment during each test was obtained as “absolute” strength, whereas “relative” strength was derived as absolute strength divided by body mass.
RESULTS: The effects of obesity were generally consistent between age groups, with only absolute hip flexion strength exhibiting a significant (p=0.05) obesity x age interaction. Mean absolute strength among obese participants was 5% higher in plantar flexion (p=0.56), 28% higher in dorsiflexion (p<0.01), 28% higher in knee extension (p<0.01), 10% higher in knee flexion (p=0.15), 5% higher in hip extension (p=0.59), 31% higher in hip flexion among young participants (p<0.01), and 10% higher in hip flexion among older participants (p=0.25). Relative strength among obese participants was 31% lower in plantar flexion (p=0.02), 16% lower in dorsiflexion (p<0.01), 17% lower in knee extension (p=0.01), 29% lower in knee flexion (p<0.01), 31% lower in hip extension (p<0.01), and 21% lower in hip flexion (p<0.01).
CONCLUSIONS: The reason obese females exhibited statistically significantly higher absolute strength in only three of six tests was unclear. However, obese females exhibited lower relative strength in all six tests. Determining which strength measurements are most closely related to mobility may inform future exercise interventions for obese individuals.