Effect of Exercise on Bone Status and Body Composition in Japanese Students

Physical activity cut-offs and risk factors for preventing child obesity in Japan

BACKGROUND

There is no official recommendations for physical activity level or steps for preventing and improving child obesity in Japan.

METHODS

Three hundred and two Japanese children aged 9-12 years were recruited wore 3-D speed sensors. Subjects were divided into two groups using the criteria for child obesity in Japan. Body composition was measured on bioelectrical impedance analysis. Physical fitness test was done to evaluate physical strength. Twenty-four hour total steps, energy expenditure, and metabolic equivalents (MET) from Monday to Sunday were consecutively measured. The cut-offs for steps and physical activity level for preventing child obesity were evaluated on receiver operating characteristic curves. Daily life-related risk factors for child obesity were assessed on logistic regression analysis.

RESULTS

In both sexes, body volume; bodyweight, body mass index, fat mass, and percentage body fat in the obese group was significantly higher than in the normal group, but age and height were not different (P < 0.001). Aerobic power, running speed, and explosive strength in the obese group were inferior to those in the normal group (P < 0.001). More than 40 min of 4 MET exercise, defined as moderate-vigorous exercise, and 11,000 steps per day are essential to prevent child obesity. Additionally, >2 h TV viewing per day is a significant risk factor for child obesity (OR, 3.43; 95%CI: 1.27-9.31).

CONCLUSION

Cut-offs for physical activity and potential risk factors for child obesity have been identified. Recommendations for changes to daily lifestyle for school-aged Japanese children are given.

Work- and travel-related physical activity and alcohol consumption: relationship with bone mineral density and calcaneal quantitative ultrasonometry

A number of healthy workers rarely exercise because of a lack of time or resources. Physical activity related to work and everyday travel may be more feasible, but evidence of its beneficial effect on bone health is scarce. We assessed if this form of physical activity was associated with higher bone mineral density (BMD) and stiffness index (SI) when adjusted for recreational physical activity, age, body mass index, smoking, alcohol consumption, education, and serum level of 25-hydroxyvitamin D. Healthy workers, aged 25-54 yr, of the Electricity Generating Authority of Thailand were surveyed. The outcomes were BMD (lumbar spine, femoral neck, and total hip) and calcaneal SI. Physical activity was estimated using the global physical activity questionnaire and considered active when >600 metabolic equivalent tasks (min). Of 2268 subjects, 74% were men. Active male subjects had significantly higher BMD at the femoral neck and total hip (p<0.005). However, the association was not significant with male lumbar spine BMD, male SI, or any bone parameters in women (p>0.05). In men, work and travel physical activity seems beneficial to male bone health; hence, it should be encouraged. Furthermore, smoking appeared harmful while moderate alcohol consumption was beneficial.

Impact of Walking and Running on the Heel bone: the Adventist Health Study-2

Aims

Physical activity is well recognized for its bone health benefit. We examined the benefit of walk/run/jog on bone health using broadband ultrasound attenuation (BUA) of the calcaneus.

Methodology

Caucasian and African American males (n=593) and females (n=1,106) had their calcaneal BUA measured two years later after enrollment into the AHS-2. The association between calcaneal BUA (dB/Mhz) and the distance of walk/run/ jog level per week (miles) was assessed using multiple linear regression.

Results

In a multivariable model adjusted for important covariates, BUA was positively associated with BMI (P < .001), total calcium intake (P =0.31), total protein intake (P =0.38) and inversely associated with age (P < .001) and smoking (P < .05). Compared to women who did not walk/ run/ jog, women walking 10 or more miles per week had an increase in BUA by 4.08 (dB/Mhz) (P _trend=0.03). Similarly, compared to men who did not walk/ run/ jog, men walking 10 or more miles per week had an increase in BUA by 5.97 (dB/Mhz) (P _trend=0.01).

Conclusions

We concluded that BUA is positively associated with walk/ run/jog after accounting for age, BMI, smoking status, calcium intake, protein intake and estrogen usage.