Verification of Maximal Oxygen Uptake in Obese and Nonobese Children.

Purpose: The purpose of this study was to examine whether a supramaximal constant load verification test at 105% of the highest work rate would yield a higher V[Combining Dot Above]O2max when compared with an incremental test in 10 - 12 year old nonobese and obese children. Methods: Nine non-obese (BMI percentile: 57.5 +/- 23.2) and nine obese (BMI percentile: 97.9 +/- 1.4) children completed a two-test protocol that included an incremental test followed 15 minutes later by a supramaximal constant-load verification test. Results: The V[Combining Dot Above]O2max achieved in verification testing (Nonobese: 1.71 +/- 0.31 and Obese: 1.94 +/- 0.47 L/min) was significantly higher than that achieved during the incremental test (Nonobese: 1.57 +/- 0.27 and Obese: 1.84 +/- 0.48 L/min; P

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Accuracy and Reliability of Assessing Lateral Compartmental Leg Composition Using DXA.

Purpose: Investigate the accuracy and reliability of a novel dual X-ray absorptiometry (DXA) scanning method in the frontal plane for total, fat, and lean mass quantification of the anterior and posterior upper leg compartments. Methods: Twenty-one (11 female; X[Combining Overline]age=20.3+/-1.3 yrs) college athletes were assessed for total and regional body composition using DXA. Segmentation of anterior/posterior thigh compartments was measured with participants lying on their right and left sides and the scanned leg elevated with two foam pads. Custom regions of interest (ROIs) were created manually with enCoreTM software for each scan using bony landmarks to quantify lean, fat, and total masses. Paired t-tests assessed this novel positioning method's accuracy against standard positioning. Intra-class correlations (ICCs) and coefficients of variation (CV) examined inter- and intra-rater reliability for lateral scan measures of total, fat, and lean masses from manually created ROIs. Results: All mean differences (+/-SD) between frontal and lateral DXA scans of right (R) and left (L) leg total mass (R: 8.42+/-195.57 g; L: 19.47+/-131.80 g), fat mass (R: 61.26+/-215.66 g; L: -5.89+/-239.97 g), and lean mass (R: -103.00+/-302.54 g; L: -27.58+/-288.14 g) were non-significant (p-value range: 0.15 to 0.91). ICCs were high for all composition measures between- and within-raters, ranging from 0.983 to 0.999 and 0.954 to 0.999, respectively, with low variation across measures (all CVs:

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Exercise Attenuates High-Fat Diet-Induced Disease Progression in 3xTg-AD Mice.

Purpose: Little is known regarding the therapeutic role of exercise against the risk of a high-fat diet (HFD) for Alzheimer's disease (AD) and AD-like cognitive deficits. This study aimed to investigate the therapeutic effect of treadmill running against HFD-induced progression in AD neuropathology and cognitive impairments in the triple transgenic-AD (3xTg-AD) mice. Methods: The 3xTg-AD mice were assigned to a chow diet (control, n=10), a high-fat diet (HFD, n=10), or a high-fat diet combined with exercise (HFD+EX, n=10) group. Mice in the HFD were fed with a 60% fat diet for 20 weeks. The HFD+EX mice were additionally subjected to treadmill running. Results: Compared to the control mice, the HFD mice had impaired brain insulin signaling, exacerbated AD neuropathology, defects in synaptic stability/plasticity, and apoptotic neuronal cell death in conjunction with exacerbated cognitive deficits in the affected brain regions, which were all significantly alleviated in the HFD+EX mice. Conclusion: The current findings suggest that treadmill running protects against AD-like disease progression and cognitive deficits caused by a HFD in the 3xTg-AD mice. (C) 2016 American College of Sports Medicine

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Physical Activity: Absolute Intensity vs. Relative-to-Fitness-Level Volumes.

Purpose: To investigate in a real-life setting how moderate and vigorous intensity physical activity (PA) volumes differ according to absolute intensity recommendation and relative to individual fitness level by sex, age, and body mass index (BMI). Methods: 23 224 Finnish employees (10 201 men, 13 023 women; ages 18-65 years; BMI 18.5-40.0 kg/m2) participated in heart rate recording for 2+ days. We used heart rate and its variability, respiration rate, and on/off response information from R-R interval data calibrated by participant characteristics to objectively determine daily PA volume, as follows: daily minutes of absolute moderate (3-=6 METs) PA; and minutes relative to individual aerobic fitness for moderate (40-=60%) PA. Results: According to absolute intensity categorization, the volume of both moderate and vigorous PA was higher in men compared to women (P

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A Murine Model of Robotic Training to Evaluate Skeletal Muscle Recovery after Injury.

Purpose: In vivo studies have suggested that motor exercise can improve muscle regeneration after injury. Nevertheless, pre-clinical investigations still lack reliable tools to monitor motor performance over time and to deliver optimal training protocols to maximize force recovery. Here, we evaluated the utility of a murine robotic platform to (i) detect early impairment and longitudinal recovery after acute skeletal muscle injury and (ii) administer varying intensity training protocols to enhance forelimb motor performance. Methods: A custom-designed robotic platform was used to train mice to perform a forelimb retraction task. Following an acute injury to bilateral biceps brachii muscles, animals performed a daily training protocol in the platform at high (HL) or low (LL) loading levels over the course of three weeks. Control animals were not trained (NT). Motor performance was assessed by quantifying force, time, sub-movement count, and number of movement attempts to accomplish the task. Myofiber number and cross-sectional area at the injury site were quantified histologically. Results: Two days after injury, significant differences in the time, sub-movement count, number of movement attempts and exerted force were observed in all mice, as compared to baseline values. Interestingly, recovery time of muscle force production differed significantly between intervention groups, with HL group showing a significantly accelerated recovery. Three weeks after injury, all groups showed motor performance comparable to baseline values. Accordingly, there were no differences in the number of myofibers or average cross-sectional area among groups after 3 weeks. Conclusion: Our findings demonstrate the utility of our custom designed robotic device for quantitative assessment of skeletal muscle function in pre-clinical murine studies. Moreover, we demonstrate that this device may be used to apply varying levels of resistance longitudinally as a means manipulate physiological muscle responses. (C) 2016 American College of Sports Medicine

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Impact of Acute Dietary Manipulations on DXA and BIA Body Composition Estimates.

Purpose: To examine the effects of acute pre-assessment diets on body composition estimates obtained by dual-energy x-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA). Methods: In a counterbalanced design, 48 males and females were provided with two one-day diets: high-carbohydrate diet (9 g CHO/kg) and very low-carbohydrate diet (1 to 1.5 g CHO/kg). For each condition, body composition was assessed in the morning after an overnight fast, in the afternoon after feeding, and the following morning after a second overnight fast. Results: Acute food ingestion, regardless of macronutrient content, altered DXA and BIA body composition estimates, and both sexes responded similarly. DXA total and regional lean soft tissue estimates increased up to 1.7% and 3% on average in response to feeding, with individual increases of over 4.5% and 9%. DXA total and trunk fat mass estimates decreased by up to 3% on average. All DXA-derived measures of body composition returned to baseline values after the second overnight fast. Impedance measured by BIA decreased by 4.4% in response to feeding, leading to a 2% increase in total body water and fat-free mass, with individual increases up to 4.5%. BIA fat mass estimates decreased 1.4 to 2.4%, with individual decreases of up to 10%. Unlike DXA, most BIA-derived estimates did not return to baseline values after a second overnight fast. Conclusion: Acute food and fluid intake can artificially influence body composition estimates, regardless of macronutrient content. An overnight fast is likely sufficient pre-assessment dietary control for DXA and possibly sufficient for BIA. (C) 2016 American College of Sports Medicine

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Activity Levels over Four Years in a Cohort of Urban-Dwelling Adolescent Females.

Purpose: Evidence suggests that female adolescents and those living in urban environments may have lower physical activity (PA) levels compared to their peers. Yet, few studies report PA for urban adolescent females and there is no consensus regarding potential causes for low PA in this subgroup. We examined PA levels, in a large, diverse cohort of 14-17 year old urban-dwelling females and assessed the impact of socio-economic, personal, and neighborhood/environmental factors on PA. Methods: One week of time-stamped step count data was collected on 926 girls from the Pittsburgh Girls Study (PGS) at four annual visits. Valid recordings (worn at least 10 hours on 3+ days) were examined and compared to normalized step count values from a U.S. population-representative sample. Relationships between important covariates and average steps/day were examined with regression models. Results: Adjusted mean (stdev) step counts/day at baseline were 5,614 (2,434) after controlling for important covariates with less than 6% of girls achieving at least 10,000 steps/day. PGS girls accrued ~45% of their steps during school hours. Age specific, median step counts/day for study participants were similar to the 25th percentile of U.S. population normalized values and did not significantly change over follow-up. Non-Hispanic African American race/ethnicity was associated with higher average step counts/day; obesity and a recent childbirth were associated with lower average step counts/day. Conclusions: Step counts in this cohort of urban adolescent girls were considerably lower than expected for U.S. adolescent females. Targeted efforts to improve PA levels in urban youth should consider the importance of school-based activity while increasing PA opportunities outside of school. (C) 2016 American College of Sports Medicine

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