Relative Strength at the Hip, Knee, and Ankle Is Lower Among Younger and Older Females Who Are Obese

Abstract

Background and Purpose:The mobility of individuals who are obese can be limited compared with their healthy weight counterparts. Lower limb strength has been associated with mobility, and reduced strength may contribute to mobility limitation among individuals who are obese. However, our understanding of the effects of obesity on lower limb strength is limited. The purpose of this study was to investigate the effects of obesity and age on extension and flexion strength at the hip, knee, and ankle.Methods:Using a cross-sectional design, 10 younger (18-30 years) healthy weight (body mass index = 18-24.9 kg/m2), 10 younger obese (body mass index >30 kg/m2), 10 older (65-80 years) healthy weight, and 10 older obese female participants performed isokinetic maximum voluntary contractions in ankle plantar flexion (PF), ankle dorsiflexion (DF), knee extension (KE), knee flexion (KF), hip extension (HE), and hip flexion (HF).Results and Discussion:Absolute strength among obese participants was 29% higher in DF (P = .002), 27% higher in KE (P = .004), and 23% higher in HF (P = .001), compared with healthy weight participants. Strength relative to body mass among obese participants was 31% lower in PF (P < .001), 14% lower in DF (P = .042), 16% lower in KE (P = .015), 27% lower in KF (P < .001), 29% lower in HE (P < .001), and 19% lower in HF (P = .001).Conclusions:Obese females exhibited lower relative strength at the ankle and hip, similar to the lower relative strength exhibited at the knee. Obese females also exhibited higher absolute strength, but only for 3 of 6 lower limb exertions investigated. This lack of uniformity across the 6 exertions is likely due to the still unclear underlying biomechanical mechanism responsible for these strength differences, which may also be influenced by aging. The effects of obesity on lower limb strength were also generally consistent between the 2 age groups investigated.

Effect of aging on the association between ankle muscle strength and the control of bipedal stance

“…Comparison of young and older adults demonstrated that there is a significant effect of age on ankle muscle strength. Our results support the existing literature [33–34]. Significant differences in muscle strength had been found between the young (mean age 23 years) and older (mean age 77 years) participants in all ankle muscle groups, with older participants being weaker than the young participants by approximately 30% [34].…”

Kinematics Adaptation and Inter-Limb Symmetry during Gait in Obese Adults

“…At last, we observe that another factor involved in the ROM reduction at knee joint might be due to the excess fat on the thigh and shank, which mechanically encumbers intersegmental rotation and counteracts the antigravity action exerted by the knee flexors [ 48 ]. As for the ankle joint, the deficits in plantar- and dorsiflexion might be due to a reduced strength of the ankle muscles, which were already reported by previous studies [ 49 ]. In this context, it is noteworthy that such effect could be reduced through suitable physical and rehabilitative intervention [ 50 , 51 ].…”

Effect of Obesity on Knee and Ankle Biomechanics during Walking

“…As for the ankle joint, kinematic data revealed a reduced plantarflexion position during terminal stance, which lead to a reduction in ankle ROM. This result may be directly related to a possible weakness of plantarflexor muscles in obese subjects [23] and probably associated with reduced physical activity typical of obese individuals [24], other than the previously quoted excessive amount of fat tissue. These abnormal ankle kinematics together with muscle weakness relate to the ankle moment and power.…”