Measurement error in short-term power testing in young people

The aim of this study was to examine the consistency or reproducibility of measuring cycling peak power in children and adults. Twenty-seven pre-pubertal girls and boys and 27 female and male physical education students (age 9.8 +/- 0.5 and 24.4 +/- 4.3 years, respectively; mean +/- s) participated in the study. All participants performed five tests over 15 days and underwent a habituation session before the study. Each test included four sprints against four different braking forces. We found that braking forces of 7.5% of body weight in children and 10% of body weight in adults were too high for most of the participants to elicit maximal cycling power. Unlike the children, the physical education students improved their performance between session 1 and session 2 (1025 +/- 219 vs 1069 +/- 243 W; P < 0.001). Therefore, to obtain reproducible measures of cycling peak power, a habituation session including a complete test protocol (i.e. warm-up plus three sprints) is highly recommended. When the protocol included three sprints in children and at least two sprints in adults, measurement of cycling peak power was found to be highly reliable (test-retest coefficient of variation approximately 3%). Finally, to avoid performance fluctuations, especially over several consecutive evaluations (e.g. longitudinal studies), it is necessary to maintain high motivation in children.     

Indirect estimation of cable tension during gymnastic movements on rings

Knowledge of external forces acting on an athlete is often required to study performance and injury mechanisms, but direct measurements are difficult to obtain. While transducers in the rings cables typically measure external forces experienced by gymnasts performing static balances and swinging movements on rings, this solution is not always acceptable and an accurate technique that does not hinder the gymnasts’ performances is desirable. This study evaluates a video-based technique for estimating cable tension on the rings apparatus. Static loading of a rings frame coupled with a planar video analysis of the mandatory damped elastic devices (DEDs) provided a tension-deflection calibration curve. Three-dimensional video and cable tension data were obtained for two male gymnasts performing static balances and dynamic swinging movements. Cable tension was measured using a force link while a planar video analysis determined time histories of the DED deflections. Combined cable tension time histories were estimated fromrelative DED deflections coupled with the tension-deflection calibration curve and the orientation of the rings cables, and were compared to measured values to evaluate the proposed technique. For static balances the RMS difference between measured and estimated combined cable tension was 83 N. For dynamic swinging movements the maximum RMS difference was 189 N, equivalent to a 4% difference when expressed as a percentage of the peak value. The indirect video-based technique developed in this study accurately estimates combined cable tension throughout movements on rings and may be considered for studies where a remote measurement is required. There is potential for the technique to be extended to other sporting situations, where indirect accurate estimates of external forces acting on an athlete are needed.     

“Let’s make lots of money”: the determinants of performance in the recorded music sector

This research analyzes the performance of 467 record labels in eight European countries over a period of 13 years (2003–2015). The main goal is to explain a relative measure of profitability in terms of observed variables, although the nature of the dataset also allows us to include non-observed firm and country effects. To this end alternative models are estimated and three main research questions are tested, namely: (1) the effect of the dual structure of the recorded music market, in which a competitive segment and an oligopoly coexist; (2) the extent and source of the volatility of profits in record labels; and (3) the nonlinear impact of size on performance.     

Analysis of foot strike pattern,rearfoot dynamic and foot rotation over childhood. A cross-sectional study

The purpose of this study was to determine the foot strike patterns (FSP), rearfoot position at initial contact (RPic, i.e., No INV/EVE) and foot rotation in children in relation to age. A total of 932 children aged 3 to 16 years participated in this study. A sagittal and frontal-plane video was recorded using a high-speed camcorder to analyse these variables. There is a significant increase (p < 0.001) of rearfoot strike patterns (RFS) prevalence in relation to age; e.g. preschool children (3–6 years old) displayed an RFS prevalence 46.65% and the adolescent population(15–16 years old) an RFS prevalence 92.20%. The total RFS prevalence in all samples was 69.25%. There was a significant reduction (p < 0.001) of prevalence of RPic in relation to age groups; preschool children displayed a prevalence of RPic 60.37% and the adolescent population 10%. There was a significant reduction (p < 0.001) of prevalence of no foot rotation in relation to age groups; preschool children displayed a prevalence of no foot rotation 48.95% and the adolescent population 13.55%. In conclusion, FSP in children are influenced by age. It is noteworthy that the RFS prevalence of children is lower in comparison to the adult population.     

The Influence of Feedback on Competence,Motivation, Vitality,and Performance in a Throwing Task

Purpose: The purpose of this work is focused on the study of the effect that feedback has on competence valuation, perceived competence, autonomous motivation, vitality, and performance in a throwing task. Method: Thirty-five college students (26 men and 9 women), without previous experience in the task, participated in this study. The students were randomly assigned to three experimental conditions (positive, negative, and lack of feedback). Results: The results of this study point out that only those who received positive feedback before the handball throwing task, in contrast to those who received negative feedback or did not receive any feedback, showed increased levels of competence valuation (p < .05, Cliff’s delta effect size = ?.30), perceived competence (p < .001, Cliff’s delta effect size = ?.77), and autonomous motivation (p < .05, Cliff’s delta effect size = ?.48). This group also presented higher levels of perceived competence (p < .001, Cliff’s delta effect size = ?.84) and subjective vitality (p < .001, Cliff’s delta effect size = ?.80) than the group who received negative feedback after the throwing task. Those who received positive feedback also showed a higher throwing speed at the end of task than those who received negative feedback (p < 0.001, Cliff’s delta effect size = ?.71) or than those who did not receive any feedback (p < .05, Cliff’s delta effect size = ?.56). Conclusions: Competence valuation, perceived competence, autonomous motivation, subjective vitality, and throwing speed were favorably influenced by positive feedback. These results have important implications for the training style applied by coaches.     

Acute intraocular pressure responses to high-intensity interval-training protocols in men and women

We aimed (1) to test the acute impact of two high-intensity interval-training (HIIT) protocols differing in the level of effort on intraocular pressure (IOP) responses, and (2) to elucidate whether the IOP responses differ between men and women. Twenty-four physically active collegiate (12 men and 12 women) performed three protocols: low-fatigue HIIT (eight 30-m sprints with 60-s of rest), high-fatigue HIIT (eight 30-m sprints with 30-s of rest), and control (walking). IOP was taken at baseline, after sprints and recovery by rebound tonometry. Our data revealed an acute IOP reduction during both HIIT protocols compared to the control condition (effect size [ES]:0.81–1.65). The differences between both HIIT protocols were generally negligible (ES<0.30), however, the reduction of IOP was moderately higher for the low-fatigue HIIT protocol after the 7th (ES: 0.67) and 8th (ES: 0.74) sprints. Women showed a more prominent lowering effect on IOP during the control condition (ES: 0.42–1.02), and during the two first sprints of both HIIT protocols (ES: 0.54–1.03). These findings highlight that a time-efficient HIIT protocol may acutely reduce IOP levels, while low-fatigue HIIT protocol could be recommended since it induced a higher reduction on IOP than the high-fatigue HIIT protocol.     

Cardiorespiratory fitness and arm bone mineral health in young males with spinal cord injury: the mediator role of lean mass

Spinal cord injury (SCI) derives in loss of bone mineral content (BMC) and bone mineral density (BMD). However, physical activity is an important determinant in bone mass acquisition, which is partially mediated through the lean mass (LM). The aim was to examine the effect of cardiorespiratory fitness (CRF) on BMD and BMC arms of adult males with SCI and able-bodied controls using the arm LM as a mediator variable. Thirty able-bodied men and thirty men with SCI participated. BMC and BMD were analysed by DXA, and indirect calorimetry was used to calculate VO_2peak during a progressive arm-cranking test. When groups were divided by the amount of LM, the subgroup with highest LM had significantly higher arm BMC compared to the lowest LM subgroup (p ≤ 0.05) in both SCI and able-bodied groups. Moreover, same differences were found when confidence intervals were analysed. Only in the SCI group, arm LM mediated the relationship between bone mass and CRF at 30.9%, as indicated by the Sobel test (z = 2.17 and z = 2.04 for BMC and BMD, respectively). In conclusion, LM mediates the indirect association between CRF and bone health, specifically in the arms. This finding highlights the importance of having an adequate CRF for the maintenance of good bone health in SCI men.