Differential Effect of Obesity on Muscular Strength in Adults with Cerebral Palsy

Abstract

Cerebral palsy (CP) is a non-progressive and permanent neurological disorder that is characterized by muscular deterioration and atrophy. The major clinical problem with CP is early development of cardiovascular disease with increased rates of mortality. Due to the inevitability of motor dysfunction adults with CP can develop health risk factors such as obesity at a higher rate compared to the general population. Limited information is available to identify levels of obesity and its relation to muscular function in adults with CP. PURPOSE: To determine whether severity of obesity may affect muscular function and strength in adults with CP. METHODS: We studied total of sixteen adults with and without CP. Muscular strength (i.e., torque, work, and power) during knee extension and flexion was measured at 90, 150, and 210 °/sec in the lower extremity using Humac Norm Isokinetic Dynamometer. Maximal isometric forearm muscular strength was measured using a handgrip dynamometer. Body mass index (BMI), waist to hip ratio, and whole-body scan from Dual Energy X-Ray Absorptiometry were used to identify the levels of obesity. RESULTS: Compared to control, individuals with CP had similar BMI (26.8±3.0 CP vs. 22.9±1.0 control kg/m2; P>0.05), % body fat (35.2±4.5 CP vs. 28.4±3.7 control %; P>0.05), and % leg fat (40.7±4.3 CP vs. 30.5±4.1 control %; P>0.05). However, waist to hip ratio was significantly greater in CP (0.90±0.02 CP vs. 0.80±0.02 control; P<0.05); muscular strength was significantly lower in CP compared to control (e.g., knee extensor peak torque at 90°/sec; 25.9±8.1 CP vs. 72.5±12.2 control ft-lb; P<0.05). There was no relationship between BMI and extensor/flexor peak torque in both groups; however, there was a linear relationship between waist to hip ratio and extensor/flexor peak torque only in CP group (R2=0.34). A strong inverse relationship between % leg fat and extensor/flexor peak torque was observed in both groups (R2=0.79). CONCLUSION: These findings suggest that central obesity rather than BMI appeared to influence muscular strength in CP adults. In addition, less fat in the legs rather than the total body may contribute for higher leg muscular strength in adults with CP. Supported by Central RSCA and Undergraduate Research Grant, SJSU