This study developed and validated a vector magnitude (VM) two-regression model (2RM) for use with an ankle-worn ActiGraph accelerometer. For model development, 181 youth (mean ± SD; age, 12.0 ± 1.5 yr) completed 30 min of supine rest and 2-7 structured activities. For cross-validation, 42 youth (age, 12.6 ± 0.8 yr) completed approximately 2 hr of unstructured physical activity (PA). PA data were collected using an ActiGraph accelerometer, (non-dominant ankle) and the VM was expressed as counts/5-s. Measured energy expenditure (Cosmed K4b) was converted to youth METs (MET; activity VO divided by resting VO). A coefficient of variation (CV) was calculated for each activity to distinguish continuous walking/running from intermittent activity. The ankle VM sedentary behavior threshold was ≤10 counts/5-s, and a CV≤15 counts/5-s was used to identify walking/running. The ankle VM2RM was within 0.42 MET of measured MET during the unstructured PA (P > 0.05). The ankle VM2RM was within 5.7 min of measured time spent in sedentary, LPA, MPA, and VPA (P > 0.05). Compared to the K4b, the ankle VM2RM provided similar estimates to measured values during unstructured play and provides a feasible wear location for future studies.

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METHODS: Fifty-seven males and females (mean±SD; age=66.5±7.09 yrs; height=165.2±10.6 cm; body mass=74.5±14.6 kg) volunteered to participate in this study. Participants underwent a total body dual-energy x-ray absorptiometry (DXA) scan for segmental and total body bone mineral content (BMC) and bone mineral density (BMD). Participants were block randomized into one of three groups: elastic band resistance training (EBRT; n=24), dumbbell resistance training (DBRT; n=21), or control (CON; n=12). EBRT and DBRT were asked to visit the laboratory twice weekly over 6-weeks while CON maintained their daily routine. Three-day dietary recalls were collected to ensure dietary maintenance throughout the intervention period. Data were analyzed using a two-way (time x treatment) repeated measures ANOVA and an alpha pre-determined at 0.05. RESULTS: Results indicated there was no two-way interaction for total body BMC (p=0.164) nor was there a main effect for time (p=0.39) or group (p=0.40). Likewise, total body BMD indicated no 2-way interaction (p=0.79) and no main effect for time (p=0.753). However, there was a main effect for group where collapsed across time, DBRT had a higher BMD than CON (p=0.05), but no other differences were observed. CONCLUSIONS: These data suggest that either the load provided throughout the training from DBRT and EBRT to stimulate change in bone over 6-weeks was insufficient or the duration was not long enough. Most previous research supports the latter as bone remodeling occurs in a throughout 4-8 month periods. Other factors that may impact the outcome of the stimuli include exogenous pharmacological treatment for bone loss and dietary factors.

Physical activity is a critical component of a healthy lifestyle for adults and children alike. This chapter addresses the importance of physical activity for health, and the synergistic influences of the family on both child and parent physical activity levels. Furthermore, this chapter provides examples of family-focused interventions, implications for counseling, and emerging research questions in the field.Evidence suggests that physical inactivity is one of the 10 leading causes of death globally, and will contribute to approximately 334,000 deaths each year in the United States. Regular physical activity participation has been shown to lower the risk of early death, coronary heart disease, stroke, type 2 diabetes, colon and breast cancers, and weight gain (U.S. Department of Health and Human Services, 2008). Further, participation in physical activity may positively influence mental and emotional health outcomes including depression, anxiety, stress, and various cognitive impairments. From a family-level perspective, physical activity participation has also been suggested to have a positive influence on a number of family outcomes such as family cohesion and bonding (Kitzman-Ulrich et al., 2010).Given the importance of activity for health, the U.S. Department of Health and Human Services has established public health recommendations for physical activity for both children and adults (U.S. Department of Health and Human Services, 2008).