Abstract
Backgrounddespite evidence of an obesity-related disability, there is a lack of objective muscle functional data in overweight subjects. Only few studies provide instrumental strength measurements in non-syndromal obesity, whereas no data about Prader-Willi syndrome (PWS) are reported. The aim of our study was to characterize the lower limb muscle function of patients affected by PWS as compared to non-syndromal obesity and normal-weight subjects.MethodsWe enrolled 20 obese (O) females (age: 29.1 ± 6.5 years; BMI: 38.1 ± 3.1), 6 PWS females (age: 27.2 ± 4.9 years; BMI: 45.8 ± 4.4) and 14 healthy normal-weight (H) females (age: 30.1 ± 4.7 years; BMI: 21 ± 1.6). Isokinetic strength during knee flexion and extension in both lower limbs at the fixed angular velocities of 60°/s, 180°/s, 240°/s was measured with a Cybex Norm dynamometer.Resultsthe H, O and PWS populations appear to be clearly stratified with regard to muscle strength.: PWS showed the lowest absolute peak torque (PT) for knee flexor and extensor muscles as compared to O (-55%) and H (-47%) (P = 0.00001). O showed significantly higher strength values than H as regard to knee extension only (P = 0.0014). When strength data were normalised by body weight, PWS showed a 50% and a 70% reduction in PT as compared to O and H, respectively. Knee flexors strength values were on average half of those reported for extension in all of the three populations.Conclusionthe novel aspect of our study is the determination of objective measures of muscle strength in PWS and the comparison with O and H patients. The objective characterization of muscle function performed in this study provides baseline and outcome measures that may quantify specific strength deficits amendable with tailored rehabilitation programs and monitor effectiveness of treatments.
Highlights
Obesity has a profound relationship with disability and, at severe levels, is itself disabling in terms of mobility and exercise capacity
Post hoc analysis showed that peak torque (PT) was lower in Prader-Willi syndrome (PWS) compared to both O and H (p < 0.001) at all speeds, and in H compared to O (p < 0.001)
PT at 180°/s was higher than 240°/s for H and O (p < 0.001) and PWS (p = 0.013)
Summary
Obesity has a profound relationship with disability and, at severe levels, is itself disabling in terms of mobility and exercise capacity. As the prevalence of obesity is increasing at an alarming rate worldwide, obesity-related disabilities will eventually become a serious threat to national health systems, specially if, in regard to children and adolescents, they occur in early life and continue for a longer life span. Despite this evidence, supported by more than 100 papers published in the last two years with the key-words "obesity and disability", the physiopathological determinants of the obesity-related disability have been scarcely investigated. PWS is characterized by severe neonatal hypotonia, feeding problems and a failure to thrive This is followed by hyperphagia and weight gain between the ages of 1 and 6, leading most PWS subjects to develop morbid obesity. The progressive effects of obesity on joints, small feet, hypotonia and the other orthopaedic problems produce further gait deviations [2]
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