Bone characteristics and physical fitness in children and adolescents with visual impairment.

Background: Lower habitual physical activity in adolescents with visual impairment (VI) have detrimental effect on their general health such as bone quality and physical fitness. The aim of this study was to demonstrate the bone quality in children with VI and to analyze the correlations of their bone characteristics with anthropometric and physical fitness tests.

Methods: The participants (N.=38) were adolescents (14.85±2.79 yrs) with low vision (N.=18) or blindness (N.=20). Dual-energy X-ray absorptiometry (DEXA) was used to measure bone mineral density (BMD), bone mineral content (BMC) of the total body and L1-L4 of the lumbar spinal region. After anthropometry physical fitness was examined by laboratory test (V̇O2peak) and field tests (strength and running).

Results: Height, weight, Body Mass Index (BMI), V̇O2peak were similar in the two groups. Blind boys showed significant higher handgrip strength. Estimated V̇O2peak (from 20-m shuttle running test) was significantly lower in blind children (43.84±4.42 mL/kg/min) than in children with low vision (35.08±5.23 mL/kg/min; P<0.001). BMD and BMC did not differ in subgroups, Z-score of total body BMD was significantly lower in blind children. Means of Z-score in L1-L4 lumbal spinal region were negative values and similar in blind and low vision adolescents' subgroups. A linear regression model in the collective group revealed significant associations of BMD (r2=0.538; P=0.0001) and BMC (r2=0.698; P=0.048) with BMI and handgrip strength test.

Conclusions: Adolescents with VI have generally decreased bone health and physical fitness level. BMI and handgrip strength are predictors of total body BMD and BMC; suggesting that these measures may be adequate to estimate bone health.