Results of a referral-based weight management program targeted toward children aged 2 to 6 years with obesity or severe obesity.

BACKGROUND: Relatively little is known about weight management programs targeted toward young children with obesity. Using data from the Early Lifestyles Intervention program, we report outcomes from a referral-based, multi-disciplinary weight management program targeted toward children aged 2 to 6 years with obesity or severe obesity. METHODS: Data from 55 children (4.5 ± 1.3 years) medically referred to the ELI program were examined in this non-randomized investigation. At baseline, a nurse collected demographic, anthropometric and clinical measures from the study child, while parents/guardians completed questionnaires regarding their child's nutrition and activity behavior. Follow-up sessions were conducted to discuss healthy behavior strategies and collect anthropometrics from the study child. Body mass index (BMI) values were reported relative to the 95th BMI percentile (%BMIp95) and children were classified as obese (≥ 100% of 95th BMI percentile) or severely obese (≥ 120% of 95th BMI). Questionnaire data were analyzed to report group-level differences and to determine whether individual items predicted changes in %BMIp95 from baseline to follow-up. Regression models were used to examine the change in %BMIp95 by sex, ethnicity, and baseline body size. RESULTS: Certain behaviors were more frequent among non-Hispanic children compared to Hispanic children (demanding certain foods), whereas other behaviors were more frequent among children with severe obesity compared to children with obesity (requesting a second helping, getting own snack and sneaking food). Greater reductions in the study child's %BMIp95 were found among parents indicating their child requests a second helping, is a faster eater, or complains of being hungry. Among the combined sample, %BMIp95 significantly decreased from baseline to final follow-up. On average, the decrease in %BMIp95 did not differ by sex, ethnicity, or baseline body size. CONCLUSIONS: Modest improvements in body size were observed. Additional studies are needed to identify best practices for pediatric interventions seeking weight management.

Prospective bi-directional associations between sedentary time and physical activity with cognitive performance: a cohort study.

This prospective study determined whether: (1) objective physical activity (PA) and sedentary (SED) time at 9 years was associated with cognition at 15 years, (2) cognition at 9 years was associated with PA and SED at 15 years, and (3) the change in PA and SED from 9 to 15 years was associated with the change in cognition. Cognitive performance was assessed from picture vocabulary, verbal analogy, passage comprehension, and applied problem tasks. Regression models were used to explore each aim while adjusting for covariates. Among the combined sample, SED (min· day-1) at 9 years was unrelated with cognitive performance at 15 years, whereas participating in ≥ 60 min· day-1 of moderate-to-vigorous PA (MVPA) at 9 years predicted lower cognitive scores at 15 years. In the reverse direction, cognitive performance at 9 years was unrelated with SED and MVPA (min· day-1) at 15 years. Over 6 years, increased SED (min· day-1) predicted lower improvement to verbal analogy scores (B = -0.01, p = 0.028). In comparison, an increase (or relatively smaller decline) in MVPA (min· day-1) predicted greater improvement in applied problem scores (B = 0.06, p = 0.007). Contextual information regarding SED and MVPA behavior would help understand bi-directional associations of activity and cognition.

Sedentary Time, Physical Activity, and Executive Function in a Longitudinal Study of Youth.

BACKGROUND: This study examined associations between sedentary time, physical activity (PA), and executive function among youth participating in the Study of Early Child Care and Youth Development. METHODS: Sedentary time and PA (light, moderate, vigorous, and moderate-to-vigorous (MVPA)) were objectively assessed at 9 and 15 years, while executive function (inhibition, working memory, and fluid intelligence) were assessed at 15 years. Regression models were used to examine associations. RESULTS: Sedentary time at 9 years predicted fluid intelligence at 15 years (B = 0.031), whereas increased sedentary time from 9 to 15 years predicted higher inhibition (B = 0.003), working memory (B = 0.074), and fluid intelligence (B = 0.029). Relatively lower levels of working memory at 15 years were predicted from increased levels of light PA, moderate PA, and MVPA from 9 to 15 years (B = -0.075, -0.293, and -0.173, respectively). At 15 years, inhibition, working memory, and fluid intelligence were significantly associated with sedentary time (B = 0.003, 0.055, and 0.045, respectively). CONCLUSIONS: Childhood sedentary time and PA may affect executive function at 15 years; however, prospective studies are needed to examine the concurrent change in both sedentary time and PA with executive function.

School's out now what? Objective estimates of afterschool sedentary time and physical activity from childhood to adolescence.

OBJECTIVES: To describe the change in afterschool levels of sedentary time and physical activity from childhood to adolescence. DESIGN: Longitudinal. METHODS: 375 youth (50% boys) from the Study of Early Child Care and Youth Development (United States) provided accelerometer data at 9 (2000/01) and 15 yrs (2006/07). Average time spent in sedentary, light, moderate, vigorous, and moderate-to-vigorous physical activity (MVPA; minh(-1)) was reported across the afterschool period (15:00-22:00) and separately across whole days. Mean comparisons were conducted to report between- and within-group differences in afterschool data. Analysis of covariance was used to determine the effect of sex, ethnicity, and baseline body mass index (BMI) on the 6-yr change in afterschool sedentary time and MVPA before and after adjusting for covariates (baseline afterschool sedentary/MVPA time, change in non-afterschool sedentary/MVPA time, difference in afterschool wear time, and socioeconomic status). RESULTS: From 9 to 15 yrs, sedentary time increased and activity decreased during the afterschool period. After covariate adjustment, the decline in afterschool MVPA was significantly greater among girls, compared to boys (B coefficient (95%CI)=-0.94 (-1.47, -0.40)), and among overweight/obese youth, compared to youth with normal BMI values (B coefficient (95%CI)=-0.65 (-1.22, -0.08)). CONCLUSIONS: During the transition from childhood to adolescence, afterschool activity (minh(-1)) decreases while sedentary time increases. Programs are needed throughout this period that promote the maintenance of activity or encourage additional activity with age.

Reporting the reliability of accelerometer data with and without missing values.

OBJECTIVES: Participants with complete accelerometer data often represent a low proportion of the total sample and, in some cases, may be distinguishable from participants with incomplete data. Because traditional reliability methods characterize the consistency of complete data, little is known about reliability properties for an entire sample. This study employed Generalizability theory to report an index of reliability characterizing complete (7 days) and observable (1 to 7 days) accelerometer data. DESIGN: Cross-sectional. METHODS: Accelerometer data from the Study of Early Child Care and Youth Development were analyzed in this study. Missing value analyses were conducted to describe the pattern and mechanism of missing data. Generalizability coefficients were derived from variance components to report reliability parameters for complete data and also for the entire observable sample. Analyses were conducted separately by age (9, 11, 12, and 15 yrs) and daily wear time criteria (6, 8, 10, and 12 hrs). RESULTS: Participants with complete data were limited (<34%) and, most often, data were not considered to be missing completely at random. Across conditions, reliability coefficients for complete data were between 0.74 and 0.87. Relatively lower reliability properties were found across all observable data, ranging from 0.52 to 0.67. Sample variability increased with longer wear time criteria, but decreased with advanced age. CONCLUSIONS: A reliability coefficient that includes all participants, not just those with complete data, provides a global perspective of reliability that could be used to further understand group level associations between activity and health outcomes.

Evaluating the utility of the body adiposity index in adolescent boys and girls.

OBJECTIVES: This study examines the ability of the body adiposity index to estimate percent body fat in a mixed sample of adolescents. Additionally, the sensitivity of the body adiposity index to identify adolescents with increased health risk (i.e., high waist circumference) was determined and compared to other anthropometric indicators of health (skinfolds and body mass index). DESIGN: Cross-sectional. METHODS: Anthropometric data (height, weight, waist circumference, and skinfolds) were collected on 913 adolescents (50% boys; mean age: 15.1yrs). Percent body fat estimates were determined using skinfold equations and the body adiposity index, while body mass index was calculated using weight and height (wt/ht(2)). Age- and gender-specific thresholds for waist circumference, body fat, and body mass index were utilized to create categorical values. Correlation coefficients, t-tests, and kappa statistics were used to describe the relationship between anthropometric variables. RESULTS: Correlation coefficients revealed an association between percent body fat estimates from skinfolds and body adiposity index (boys 0.77; girls 0.67); however, the body adiposity index systematically overestimated percent body fat at lower levels of adiposity, primarily in boys. Higher mean percent body fat estimates were reported using the body adiposity index compared to skinfolds in boys (25.1% vs. 17.8%), while the opposite relationship was found in girls (body adiposity index 28.5% vs. skinfolds 29.6%). Among boys and girls, correlations to waist circumference and also sensitivity values were higher for body mass index compared to either skinfolds or body adiposity index. CONCLUSIONS: No clear advantage exists in using the body adiposity index to estimate percent body fat or to identify adolescents with increased health risk. The results support the continued use of the body mass index to identify adolescents with increased health risk.

Reliability and validity of the Mywellness Key physical activity monitor.

BACKGROUND: This study evaluated the reliability and criterion validity of the Mywellness Key accelerometer (MWK) using treadmill protocols and indirect calorimetry. METHODS: Twenty-five participants completed two four-stage 20-minute treadmill protocols while wearing two MWK accelerometers. Reliability was assessed using raw counts. Validity was assessed by comparing the estimated VO(2) calculated from the MWK with values from respiratory gas exchange. RESULTS: Good overall and point estimates of reliability were found for the MWK (all intraclass correlations > 0.93). Generalizability theory coefficients showed lower values for running speed (0.70) versus walking speed (all > 0.84), with the majority of the overall percentage of variability derived from the participant (68%-88% of the total 100%). Acceptable validity was found overall (Pearson's r = 0.895-0.902, P < 0.0001), with an overall mean absolute error of 16.22% and a coefficient of variance of 16.92%. Bland-Altman plots showed an overestimation of energy expenditure during the running speed, but total kilocalories were underestimated during the protocol by approximately 10%. CONCLUSION: Good validity was found during light and moderate walking, while running was slightly overestimated. The MWK may be useful for clinicians and researchers interested in promotion or assessment of physical activity.

Longitudinal change in active and sedentary behavior during the after-school hour.

BACKGROUND: Relatively little is known regarding after-school behavior. This study examined after-school active and sedentary behaviors among youth participating in the Study of Early Child Care and Youth Development. METHODS: An interview guided time-use approach was used to obtain detailed longitudinal information about after-school (3-6 PM) behavior of a mixed gender cohort (n = 886) at ages 9 and 11 yrs. Responses obtained in 15-min intervals were coded into 29 exclusive behaviors and separated into 3 main categories [moderate and vigorous-intensity physical activity (MVPA), light-intensity physical activity, and sedentary]. Sedentary category was further divided into screen and nonscreen categories. A mixed ANOVA design was used to examine gender and age-related differences in MVPA, light-intensity physical activity, sedentary, screen, and nonscreen. RESULTS: MVPA was higher among boys compared with girls (P < .001) and decreased from 9 to 11 yrs (P < .001). Overall, total sedentary time was comparable between boys and girls despite a difference in reported screen time (boys > girls; P < .001) and nonscreen time (boys < girls; P < .001). Total sedentary time increased from 9 to 11 yrs (P < .001). CONCLUSION: Engagement in after-school behavior appears to change during preadolescence. Additional research is needed to understand factors associated with the selection of active and sedentary behavior over time.

Patterns of noncompliance in adolescent field-based accelerometer research.

BACKGROUND: The primary purpose of this study was to investigate patterns of noncompliance in an adolescent field based accelerometer study. A further purpose was to investigate the effect of a cost efficient strategy (SMS reminder message) on the compliance of adolescents METHOD: The research carried out in 2010 involved 117 second level students (12.41 ± .53 yrs) from 4 schools in a rural Irish town. The Actigraph accelerometer data were processed over 7 days to determine compliance level. RESULTS: Students were more likely to remove their monitor in the evening period than at any other time, however if students removed their monitor after school it remained unworn for a significantly longer duration than in any other time period. Students who received a SMS message were significantly more likely (P = .008) to wear their monitor in the morning than those that did not. CONCLUSIONS: Sending an SMS message each morning is effective for improving the number of students wearing monitors to school. The after school period is a critical period for nonwear time and should be targeted in future studies wishing to improve compliance.

Blood lactate and hormonal responses to prototype flywheel ergometer workouts.

The purpose of the study was to compare blood lactate and hormonal responses with flywheel ergometer (FERG) leg presses for preliminary assessment of workouts best suited for future in-flight resistance exercise. Comprised of 10 repetition sets, the workouts entailed 3 sets of concentric and eccentric (CE3) actions, or concentric-only actions done for 3 (CO3) or 6 (CO6) sets. Methods employed included assessment of blood lactate concentrations ([BLa-]) before and 5 minutes postexercise. Venous blood was also collected before and at 1 and 30 minutes postexercise to assess growth hormone, testosterone, cortisol concentrations ([GH], [T], [C]) and [T/C] ratios. [BLa-] were compared with 2 (time) x 3 (workout) analysis of variance. Hormones were assessed with 2 (gender) x 3 (time) x 3 (workout) analysis of covariances. Results showed [BLa-] had a time effect. Growth hormone concentration showed gender x workout, gender x time, and workout x time interactions, whereas [T] had a 3-way interaction. [C] had gender, time, and workout effects. [T/C] yielded a gender x time interaction. It was concluded that, because CO6 and CE3 yielded similar anabolic hormonal data but the latter had a lower [C] 30 minutes postexercise, CE3 served as the best workout. Although the FERG was originally designed for microgravity, the effort put forth by current subjects was like that for workouts aimed at greater athletic performance and conditioning. Practical applications suggest that eccentric actions should be used for FERG workouts geared toward muscle mass and strength improvement.

Applying generalizability theory to estimate habitual activity levels.

PURPOSE: Relative and absolute decisions in physical activity research are commonly based on a single assessment period that may not represent habitual activity behavior. This study used the generalizability theory to 1) quantify multiple sources of measurement error and 2) estimate the number of days and seasons needed to characterize long-term levels of activity. METHODS: Between 2005 and 2006, youth participating in an intervention program were asked to wear a pedometer across seven consecutive days during three separate months (September, January, and May). Total variance in activity was partitioned and quantified according to differences among participants, inconsistency across days, relative differences among seasons, and the interactions among variables. Two coefficients (generalizability and phi) were calculated from multiple decision studies using a random and mixed design to determine the study protocol needed to achieve a reliability of 0.80 for relative and absolute decisions, respectively. Data were analyzed in 2009. RESULTS: Complete data were available for 42 boys and 38 girls. Residual variance accounted for the largest source of measurement error (55.64%), whereas smaller amounts were attributed to the participant (18.74%), season (6.59%), and day (2.67%) terms. Using a random design, both coefficients failed to reach an acceptable level of reliability using a single season. In contrast, using a mixed design, an acceptable level of reliability could be reached using 7-8 d from a single, fixed season. CONCLUSIONS: This study demonstrates the potential for using the generalizability theory to make decisions regarding the rank order of activity among individuals (relative decision) and compliance rates for physical activity recommendations (absolute decision).

Maturity-related differences in physical activity among 10- to 12-year-old girls.

Besides environmental and psycho-social factors explaining the variation in physical activity levels during adolescence, some evidence suggests that biological processes are involved in regulating habitual daily physical activity and energy expenditure. The purpose of this study was to examine the influence of biological maturity status on physical activity. Chronological age, standing height, sitting height, and body mass were measured cross-sectionally in 268 girls, aged 9.5 to 11.5 years. Biological maturity groups (Early, Average, Late) were created according to estimated age at peak-height-velocity (estAPHV). Habitual physical activity was determined with a pedometer (Yamax Digiwalker SW-200) over a 7-day period. Differences in steps/day across maturity groups were examined by ANCOVA, controlling separately for time the pedometer was worn, leg length, and body mass. Mean pedometer steps/day was 10,822 +/- 2,639. As expected, body size varied by maturity status (e.g., early > average > late). Significant maturity group differences were found with early maturing girls showing lower activity levels compared to average or late maturers. These differences remained after controlling for time the pedometer was worn and leg length; however, the differences were no longer significant when controlling for body mass. The results suggest that biological maturity status influences physical activity levels in girls between 10 and 12 years of age but the relationship is not independent of body mass. Further research is needed to establish the complex inter-relationships among adiposity, biological maturation, and energy expenditure during puberty.

Maturity-related variation in moderate-to-vigorous physical activity among 9-14 year olds.

BACKGROUND: This study compared physical activity levels among early, average, and late maturing boys and girls. METHODS: Physical activity was assessed with an Actigraph accelerometer in 161 (76 boys, 85 girls) 9 to 14 year olds over 7 consecutive days. Anthropometric variables were measured and the maturity offset (ie, years from peak height velocity) was predicted. Biological maturity groups (early, average, and late) were created based on the mean estimated age at peak height velocity for boys and girls separately. RESULTS: Levels of moderate-to-vigorous physical activity (MVPA) were similar between early, average, and late maturing boys and girls after adjusting for differences in chronological age. Levels of MVPA progressively declined across chronological age in boys and girls (P < .001) and gender differences existed at 10-, 12-, and 13-years, with boys having higher levels than girls (P < .05). When aligned according to biological age, gender-related differences in MVPA did not exist. CONCLUSIONS: Within this sample of 9 to 14 year old boys and girls, there were no significant differences in MVPA among early, average, and late maturing individuals.

The biological basis of physical activity in children: revisited.

In his seminal paper, Rowland clearly outlined the rationale, evidence, and implications for the biological control of physical activity. Ten years later, there has been some progress in this area related to childhood physical activity with perhaps the greatest progress being made in the areas of genetics and the neuroendocrinology of physical activity. It is clear that heredity contributes to the physical activity (and inactivity) phenotype and candidate genes are now being identified. Furthermore, animal models indicate that maternal exposure to various environmental factors may alter offspring physical activity. Although the mechanisms of this maternal-fetal interaction are unknown, it may involve the development programming of anatomical structures or biophysical pathways involved in energy homeostasis. In this regard, it is also clear that key brain structures and biomolecules involved in motivation, reward, and/or energy balance are also critical to understanding the biological basis of physical activity. Given the potential links between the neuro-endocrine and body composition changes during puberty and the decline in physical activity during this period, future multidisciplinary research in the human child and postnatal animal should be encouraged to provide a better understanding of the biological basis of physical activity during early life. Finally, there are also clear links between between the neuro-endocrine and body composition changes during puberty and the decline in physical activity with psycho-social factors. Thus, there should also be emphasis on understanding the "biocultural" development of the child and its influence on the physical activity phenotype.

Day-to-day variability in voluntary wheel running among genetically differentiated lines of mice that vary in activity level.

This study examined the day-to-day variability in voluntary wheel-running behavior among three genetically distinct lines of young male and female mice. Daily wheel revolutions were recorded at an age of 6-8 weeks in 10 males and 10 females from each of 3 lines: selectively bred line for high wheel running (Line 8), selectively bred for high wheel-running activity and fixed for a Mendelian recessive allele that reduces hind-limb muscle mass by 50% (Line 3), non-selected control (Line 2). There were significant mean differences in revolutions/day among weeks (P = 0.003), but the effect size was small (10%). Significant main effects for wheel running were also revealed for sex and line (P < 0.001). The grand mean +/- SD for the coefficient of variation (CV) of intra-individual wheel running was 23.0 +/- 10.8%. Although a significant main effect for the CV was found for week, the effect size was low (7%) (age 6 weeks, 23.4 +/- 10.9%; age 7 weeks, 25.1 +/- 13.2%; age 8 weeks, 20.1 +/- 7.8%). The overall mean CV was similar between females (21.4 +/- 9.8%) and males (24.4 +/- 12.0%) and among lines (Line 2, 23.4 +/- 9.8%; Line 3, 20.4 +/- 7.6%; and Line 8, 25.0 +/- 14.4%). These findings are consistent with our previous work in young humans and lend further support for the hypothesis that biological mechanisms influence daily levels of physical activity.

Combined influence of physical activity and screen time recommendations on childhood overweight.

OBJECTIVES: To examine the combined influence of physical activity and screen time (television and video games) on the odds of being overweight and to evaluate the utility of current public policy recommendations. STUDY DESIGN: Physical activity was assessed by a pedometer and screen time was assessed by survey in a sample of 709 children age 7 to 12 years. The percentage of subjects meeting current physical activity and screen time recommendations was calculated. Cross-tabulated physical activity-screen time groups were formed depending on whether or not the children were meeting current recommendations. Logistic regression was used to examine the influence of physical activity and screen time on the odds of being overweight. RESULTS: Children meeting physical activity and screen time recommendations were the least likely to be overweight. Approximately 10% of the boys and 20% of the girls meeting both recommendations were overweight, compared with 35% to 40% of those who did not meet either recommendation. Screen time and physical activity appeared to be equivalent risk factors for boys, even though physical activity in girls was more strongly associated with body mass index. CONCLUSIONS: Children not meeting the physical activity or screen time recommendations were 3 to 4 times more likely to be overweight than those complying with both recommendations.

Albuterol and exercise effects on ankle extensor strength during 40 days of unloading.

INTRODUCTION: In-flight ankle extensor (AEXT) strength losses are an impediment to long-term space travel. The current study examines if albuterol helps resistance exercise (RE) abate AEXT strength loss incurred over a 40-d unloading period. METHODS: All subjects (21 men, M; 15 women, W) performed unilateral limb suspension (ULLS) and exercised on a flywheel ergometer (FERG) with their otherwise unloaded AEXT. With a double-blind randomization assignment, subjects either received placebo (PLA, lactose) or albuterol (ALB, 16 mg x d(-1)) via four daily capsule doses with no crossover. FERG calf press workouts done 3 d x wk(-1) provided concentric and eccentric total work (CTW, ETW) and average power (CAP, EAP) measures. Workout data from the 40-d period were averaged and partitioned into four consecutive 10-d periods. Data were compared with a 2 (gender) x 2 (treatment) x 4 (time) MANCOVA, with day 0 AEXT strength measurements and a drug/body mass ratio as covariates. RESULTS: CTW and ETW days 11-20, 21-30, and 31-40, as well as CAP and EAP days 11-20 and 21-30 showed the following significant results: ALB-W > ALB-M, PLA-M > PLA-W. CAP and EAP days 31-40 showed the following significant results: ALB-W, ALB-M, PLA-M > PLA-W. DISCUSSION: The combined RE-albuterol treatment most likely evoked unloaded AEXT strength gains in women due to heightened myofibril sensitivity for Ca+2. Despite a drug/body mass covariate, gender-related differences should be interpreted with caution. Future work should compare absolute and relative beta2 agonist dosages on gender-related muscle mass and strength changes.

Evaluation of youth pedometer-determined physical activity guidelines using receiver operator characteristic curves.

OBJECTIVE: Evidence-based pedometer guidelines have not been sufficiently validated in youth. The purpose of this paper was to evaluate the utility of current pedometer-determined physical activity guidelines for youth. METHODS: Participants (n=812, mean age 9.7 years) were from two Midwestern communities during Fall 2005. Participants completed 7 days of pedometer monitoring using a Digiwalker 200-SW. ROC analyses were utilized to assess the utility of the cutpoints in reference to weight status. The percentage of subjects meeting physical activity recommendations (steps/day) was determined using two published recommendations. RESULTS: The mean (SD) steps/day for boys, girls, and sexes combined were 12,709 (3,384), 10,834 (2562), and 11,665 (3028), respectively. Depending on the recommendation, approximately 55-75% of children did not meet the recommended number of steps/day. Sensitivity was high and specificity was low for both current guidelines evaluated. The ROC analysis indicated that lowering the steps/day cutpoint for boys and girls may increase accuracy. CONCLUSIONS: This study demonstrates that a large percentage of children from two Midwestern communities do not meet current pedometer-based physical activity recommendations. Because the percentage of children categorized as active or inactive depends on the criteria that are employed, it is recommended that researchers select cutpoints based on the preferred context of application.

The effect of floor slope on sub-maximal lifting capacity and technique.

Inclined surfaces, where both the lifter and load are on the slope, may be encountered in a jobsite situation. The purpose of this study was to determine if facing up or down a sloped surface (10 degrees and 20 degrees ) would affect maximal acceptable weights of lift (MAWL) using a 10 min psychophysical approach with symmetric freestyle technique at 4 lifts/min. Seventeen healthy men and 18 women determined floor to knuckle height MAWL while facing uphill, downhill, and on a level surface. Motion capture was also performed to examine sagittal plane joint angles and foot placement relative to a milk crate. Slope did not alter MAWL (p>0.05) with the men lifting more than the women in every condition (p<0.001) (25 kg vs. 15 kg, respectively). Foot placement relative to the box was altered by slope such that both horizontal position behind and vertical position below the box increased as slope changed from the downhill to uphill conditions (both p<0.001). Forward torso lean as well as hip, knee, and ankle (plantar) flexion generally decreased as slope changed from the downhill to uphill conditions (all p<0.001). Torso and knee motion appeared to be protected compared to the other joints, changing the least. Though trends were the same in both sexes, interactions did exist in vertical foot position and hip angle (both p0.001). In conclusion, the body is highly adaptive to floor slope, maintaining MAWL at least in the short term. However, while slight technique differences exist between men and women, care should be taken by all when facing uphill due to the tendency to stand further from the load horizontally and when facing downhill due to increased torso lean.

Maturity-related differences in physical activity among 13- to 14-year-old adolescents.

The age-related decline in physical activity during adolescence is well documented; however, little is known about differences in physical activity among early, average, and late maturing adolescents. The purpose of this study was to examine the relationship between maturity status and physical activity among 167 adolescents who were 13-14 years old. The maturity offset was derived and biological maturity groups were created. Habitual physical activity was determined with a pedometer over a 7-day period. No significant maturity-group differences were found for physical activity. The results of this study did not demonstrate significant differences in physical activity as determined by a pedometer among early, average, and late maturing 13- to 14-year-olds.