Browse

Purpose: To investigate the indirect measurement of 1-repetition-maximum (1RM) free-weight half-squat in high-level sprinters using the load–velocity relationship. Methods: Half-squat load and velocity data from 11 elite sprinters were collected in 2 separate testing sessions. Approximately 24 hours prior to the first testing session, sprinters completed a fatiguing high-intensity training session consisting of running intervals, staircase exercises, and body-weight exercises. Prior to the second testing session, sprinters had rested at least 48 hours. Two different prediction models (multiple-point method, 2-point method) were used to estimate 1RM based on the load and either mean or peak concentric velocity data of submaximal lifts (40%–90% 1RM). The criterion validity of all methods was examined through intraclass correlation coefficients, coefficient of variation (CV%), Bland–Altman plots, and the SEM. Results: None of the estimations were significantly different from the actual 1RM. The multiple-point method showed higher intraclass correlation coefficients (.91 to .97), with CVs from 3.6% to 11.7% and SEMs from 5.4% to 10.6%. The 2-point method showed slightly lower intraclass correlation coefficients (.76 to .95), with CVs 1.4% to 17.5% and SEMs from 9.8% to 26.1%. Bland–Altman plots revealed a mean random bias in estimation of 1RM for both methods (mean and peak velocity) ranging from 1.06 to 13.79 kg. Conclusion: Velocity-based methods can be used to roughly estimate 1RM in elite sprinters in the rested and fatigued conditions. However, all methods showed variations that limit their applicability for accurate load prescription for individual athletes.

Deficits in movement patterns during cutting while running might place soccer players at risk of injury. The objective was to compare joint angles and intersegment coordination between sexes and ages during an unanticipated side-step cutting task in soccer players. This cross-sectional study recruited 11 male (four adolescents and seven adults) and 10 female (six adolescents and four adults) soccer players. Three-dimensional motion capture was used to measure lower-extremity joint and segment angles as participants performed an unanticipated cutting task. Hierarchical linear models examined relationships between joint angle characteristics with age and sex. Continuous relative phase was used to quantify intersegment coordination amplitude and variability. These values were compared between age and sex groups using analysis of covariance. Adult males had greater hip flexion angle excursions than adolescent males, while adult females had smaller excursions than adolescent females (p = .011). Females had smaller changes in hip flexion angles (p = .045), greater hip adduction angles (p = .043), and greater ankle eversion angles (p = .009) than males. Adolescents had greater hip internal rotation (p = .044) and knee flexion (p = .033) angles than adults, but smaller changes in knee flexion angles at precontact compared with stance/foot off (p < .001). For intersegment coordination, females were more out-of-phase than males in the foot/shank segment in the sagittal plane. There were no differences in intersegment coordination variability between groups. Differences in joint motion during an unanticipated cutting task were present between age groups and sexes. Injury prevention programs or training programs may be able target specific deficits to lower injury risk and improve performance.

Background: Laboratory assessment of maximal oxygen uptake ( ${\dot{\mathrm{V}}\mathrm{O}}_2\text{max}$ ) is physically and mentally draining for the athlete and requires expensive laboratory equipment. Indirect measurement of ${\dot{\mathrm{V}}\mathrm{O}}_2\text{max}$ could provide a practical alternative to laboratory testing. Purpose: To examine the relationship between the maximal power output (MPO) in an individualized 7 × 2-minute incremental test (INCR-test) and ${\dot{\mathrm{V}}\mathrm{O}}_2\text{max}$ and to develop a regression equation to predict ${\dot{\mathrm{V}}\mathrm{O}}_2\text{max}$ from MPO in female rowers. Methods: Twenty female club and Olympic rowers (development group) performed the INCR-test on a Concept2 rowing ergometer to determine ${\dot{\mathrm{V}}\mathrm{O}}_2\text{max}$ and MPO. A linear regression analysis was used to develop a prediction of ${\dot{\mathrm{V}}\mathrm{O}}_2\text{max}$ from MPO. Cross-validation analysis of the prediction equation was performed using an independent sample of 10 female rowers (validation group). Results: A high correlation coefficient (r = .94) was found between MPO and ${\dot{\mathrm{V}}\mathrm{O}}_2\text{max}$ . The following prediction equation was developed: ${\dot{\mathrm{V}}\mathrm{O}}_2\text{max}$ (mL·min⁻¹) = 9.58 × MPO (W) + 958. No difference was found between the mean predicted ${\dot{\mathrm{V}}\mathrm{O}}_2\text{max}$ in the INCR-test (3480 mL·min⁻¹) and the measured ${\dot{\mathrm{V}}\mathrm{O}}_2\text{max}$ (3530 mL·min⁻¹). The standard error of estimate was 162 mL·min⁻¹, and the percentage standard error of estimate was 4.6%. The prediction model only including MPO, determined during the INCR-test, explained 89% of the variability in ${\dot{\mathrm{V}}\mathrm{O}}_2\text{max}$ . Conclusion: The INCR-test is a practical and accessible alternative to laboratory testing of ${\dot{\mathrm{V}}\mathrm{O}}_2\text{max}$ .

Background: There is currently a nationwide effort to bring parks and green spaces within a 10-minute walk of the home. We examined the association between park area within 1 km of a child’s residence and self-reported park-specific physical activity (PA) along with accelerometer-derived moderate to vigorous physical activity (MVPA). Methods: A subsample of K through eighth-grade youth (n = 493) from the Healthy Communities Study reported whether they engaged in park-specific PA during the last 24 hours and wore an accelerometer for up to 7 days. Park area was defined as the percentage of park land in a 1 km Euclidean buffer around the participant’s residence, categorized into quintiles. Analysis consisted of logistic and linear regression modeling with interaction effects that controlled for clustering within communities. Results: Regression models estimated greater park-specific PA for participants in the fourth and fifth quintiles of park land. Age, sex, race ethnicity, and family income were unrelated to park-specific PA. Accelerometer analysis indicated that total MVPA was unrelated to park area. Older children (β = −8.73, P < .001) and girls (β = −13.44, P < .001) engaged in less MVPA. Seasonality significantly predicted both park-specific PA and total MVPA. Conclusion: Increasing park area is likely to improve youth PA patterns, lending support for the 10-minute walk initiative.

Background: Prescription medication usage has been used as a predictor of disease prevalence and overall health status. Evidence suggests an inverse relationship exists between polypharmacy, which is the use of 5 or more medications, and physical activity participation. However, there is limited evidence examining the relationship between sedentary time and polypharmacy in adults. The aim of this study was to examine the associations between sedentary time and polypharmacy in a large nationally representative sample of US adults. Methods: Study sample (N = 2879) included nonpregnant adult (≥20 y old) participants from the 2017–2018 National Health and Nutrition Examination Survey. Self-reported minutes per day of sedentary time were converted to hours per day. The dependent variable was polypharmacy (≥5 medications). Results: Analysis revealed that for every hour of sedentary time, there was 4% greater odds of polypharmacy (odds ratio, 1.04; 95% confidence interval, 1.00–1.07, P = .04) after adjusting for age, race/ethnicity, education, waist circumference, and the interaction term between race/ethnicity and education. Conclusion: Our findings suggest increased sedentary time is associated with an increased risk of polypharmacy among a large nationally representative sample of US adults.

Purpose: To determine whether competitive performance, as defined by International Biathlon Union (IBU) and International Ski Federation (FIS) points in biathlon and cross-country (XC) skiing, respectively, can be projected using a combination of anthropometric and physiological metrics. Shooting accuracy was also included in the biathlon models. Methods: Data were analyzed using multivariate methods from 45 (23 female and 22 male) biathletes and 202 (86 female and 116 male) XC skiers who were all members of senior national teams, national development teams, or ski-university or high school invite-only programs (age range: 16–36 y). Anthropometric and physiological characteristics were assessed via dual-energy X-ray absorptiometry and incremental roller-ski treadmill tests, respectively. Shooting accuracy was assessed via an outdoor standardized testing protocol. Results: Valid projective models were identified for female biathletes’ IBU points (R ² = .80/Q ² = .65) and female XC skiers’ FIS distance (R ² = .81/Q ² = .74) and sprint (R ² = .81/Q ² = .70) points. No valid models were identified for the men. The most important variables for the projection of IBU points were shooting accuracy, speeds at blood lactate concentrations of 4 and 2 mmol·L⁻¹, peak aerobic power, and lean mass. The most important variables for the projection of FIS distance and sprint points were speeds at blood lactate concentrations of 4 and 2 mmol·L⁻¹ and peak aerobic power. Conclusions: This study highlights the relative importance of specific anthropometric, physiological, and shooting-accuracy metrics in female biathletes and XC skiers. The data can help to identify the specific metrics that should be targeted when monitoring athletes’ progression and designing training plans.

Background: Parents play an important role in shaping youth’s lifestyle behaviors. This study aimed to investigate physical activity parenting practices (PAPP) for Chinese early adolescents and compare reporting discrepancies between parents and adolescent boys and girls. Methods: Fifty-five adolescent–parent dyads participated in 16 paired focus group interviews, and an additional 122 dyads completed questionnaire surveys with open-ended questions. Participants were recruited from 3 public middle schools in Suzhou, China. Qualitative data were analyzed inductively using an open-coding scheme. Frequencies of codes were compared by parent–child role and adolescent gender using chi-square tests. Results: Eighteen types of PAPP were identified and grouped into 6 categories: goals/control, structure, parental physical activity participation, communication, support, and discipline. These PAPP were viewed as promotive, preventive, or ineffective. Participants had mixed opinions on the effects of 11 PAPP and identified parental, adolescent, and environmental barriers for parents to promote youth physical activity. Compared with parents, adolescents were more likely to value the effects of setting expectation, scheduling, and coparticipation as well as dislike pressuring, restriction, and punishment. Girls were more likely to favor coparticipation and were more sensitive about negative communication than boys. Parents paid more attention to environmental barriers, whereas adolescents, especially girls, focused more on personal issues. Conclusions: Future studies need to address both positive and negative PAPP as well as perception discrepancies by child–parent role and adolescent gender to generate more evidence to promote parents as favorable socialization agents of youth physical activity.