Isokinetic knee extension and vertical jumping: are they related?

The aim of this study was to examine joint power generation during a concentric knee extension isokinetic test and a squat vertical jump. The isokinetic test joint power was calculated using four different methods. Five participants performed concentric knee extensions at 0.52, 1.57, 3.14 and 5.23 rad x s(-1) on a Lido isokinetic dynamometer. The squat vertical jump was performed on a Kistler force plate. Kinematic data from both tests were collected and analysed using an ELITE optoelectronic system. An inverse dynamics model was applied to measure knee joint moment in the vertical jump. Knee angular position data from the kinematic analysis in the isokinetic test were used to derive the actual knee angular velocity and acceleration, which, in turn, was used to correct the dynamometer moment for inertial effects. Power was measured as the product of angular velocity and moment at the knee joint in both tests. Significant differences (P < 0.05) were found between mean (+/- s) peak knee joint power in the two tests (squat vertical jump: 2255 +/- 434 W; isokinetic knee extension: 771 +/- 81 W). Correlation analysis revealed that there is no relationship between the peak knee joint power during the vertical jump and the slow velocity isokinetic tests. Higher isokinetic velocity tests show better relationships with the vertical jump but only if the correct method for joint power calculation is used in the isokinetic test. These findings suggest that there are important differences in muscle activation and knee joint power development that must be taken into consideration when isokinetic tests are used to predict jumping performance.     

Isokinetic trunk flexion–extension protocol to assess trunk muscle strength and endurance: Reliability,learning effect,and sex differences

PurposeThe purpose of this study was to examine the reliability and the learning effect of an isokinetic trunk flexion–extension protocol designed to simultaneously assess trunk muscle strength and endurance. In addition, the effect of the participants' sex on the reliability data was examined.MethodsFifty-seven healthy and physically active young men (n = 28) and women (n = 29) performed the isokinetic protocol 5 times, separated by a week between each of the first 4 sessions and by a month between the last 2 sessions. The protocol consisted of performing 4 trials of 15 maximum flexion–extension concentric exertions at 120°/s (range of trunk motion = 50°). The absolute and relative peak torque and total work were calculated to assess trunk flexion and extension strength. In addition, endurance ratio, modified endurance ratio, fatigue final ratio, recovery ratio, and modified recovery ratio variables were used for the assessment of trunk muscle endurance in both directions.ResultsRegarding the absolute reliability, no relevant changes were found between paired-comparison sessions for most strength and endurance variables, except for total work and relative total work variables in the flexion movement in both sexes. In addition, the typical error of the isokinetic variables was lower than 10% in both males and females, and minimum detectable changes ranged from 7% to 20%, with a tendency to be higher in females and in endurance variables. The strength variables showed high-to-excellent intraclass correlation coefficients (ICCs; >0.74); however, for the endurance variables only the endurance ratio and the modified endurance ratio obtained moderate-to-high ICC values (0.57 < ICC < 0.82). In addition, the analysis of the variance reported no significant differences between consecutive pairs of sessions for most variables in both sexes.ConclusionOverall, these findings provide clinicians, trainers, and researchers with a 10-min single-session protocol to perform a reliable muscle strength and endurance evaluation of trunk flexor and extensor muscles, all within the same protocol.     

Examining the intrinsic foot muscles’ capacity to modulate plantar flexor gearing and ankle joint contributions to propulsion in vertical jumping

BackgroundDuring human locomotion, a sufficiently stiff foot allows the ankle plantar flexors to generate large propulsive powers. Increasing foot stiffness (e.g., via a carbon plate) increases the ankle's external moment arm in relation to the internal moment arm (i.e., increasing gear ratio), reduces plantar flexor muscles’ shortening velocity, and enhances muscle force production. In contrast, when activation of the foot's intrinsic muscles is impaired, there is a reduction in foot and ankle work and metatarsophalangeal joint stiffness. We speculated that the reduced capacity to actively control metatarsophalangeal joint stiffness may impair the gearing function of the foot at the ankle.MethodsWe used a tibial nerve block to examine the direct effects of the intrinsic foot muscles on ankle joint kinetics, in vivo medial gastrocnemius’ musculotendinous dynamics, and ankle gear ratio on 14 participants during maximal vertical jumping.ResultsUnder the nerve block, the internal ankle plantar flexion moment decreased (p = 0.004) alongside a reduction in external moment arm length (p = 0.021) and ankle joint gear ratio (p = 0.049) when compared to the non-blocked condition. Although medial gastrocnemius muscle–tendon unit and fascicle velocity were not different between conditions, the Achilles tendon was shorter during propulsion in the nerve block condition (p < 0.001).ConclusionIn addition to their known role of regulating the energetic function of the foot, our data indicate that the intrinsic foot muscles also act to optimize ankle joint torque production and leverage during the propulsion phase of vertical jumping.     

Are gait characteristics and ground reaction forces related to energy cost of running in elite Kenyan runners?

The aim of this study was to determine whether gait cycle characteristics are associated with running economy in elite Kenyan runners. Fifteen elite Kenyan male runners completed two constant-speed running sets on a treadmill (12 km ·h^?1 and 20 km ·h^?1). VO₂ and respiratory exchange ratio values were measured to calculate steady-state oxygen and energy cost of running. Gait cycle characteristics and ground contact forces were measured at each speed. Oxygen cost of running at different velocities was 192.2 ± 14.7 ml· kg^?1· km^?1 at 12 km· h^?1 and 184.8 ± 9.9 ml· kg^?1· km^?1 at 20 km· h^?1, which corresponded to a caloric cost of running of 0.94 ± 0.07 kcal ·kg^?1·km^?1 and 0.93 ± 0.07 kcal· kg^?1· km^?1. We found no significant correlations between oxygen and energy cost of running and biomechanical variables and ground reaction forces at either 12 or 20 km· h^?1. However, ground contact times were ~10.0% shorter (very large effect) than in previously published literature in elite runners at similar speeds, alongside an 8.9% lower oxygen cost (very large effect). These results provide evidence to hypothesise that the short ground contact times may contribute to the exceptional running economy of Kenyan runners.     

Are parental concerns about children's inactivity warranted, and are they associated with a supportive home environment?

This paper explores parental concern about children's activity levels and whether parents who are concerned about their child's activity provide a supportive environment. A sample of 615 parents of 5-6-year-old children and 947 parents of 10-12-year-old children completed a questionnaire. Just over 50% of parents reported they were concerned their child was not getting enough activity. Children of concerned parents were less active than those whose parents were not concerned. These findings suggest that parents who are concerned about their child's physical activity levels provided a less supportive environment for physical activity than parents who are not concerned. The challenge for public health will be to harness parental concerns and translate them into action.     

Impact of an incremental running test on jumping kinematics in endurance runners: can jumping kinematic explain the post-activation potentiation phenomenon?

This study aimed to determine whether kinematic data during countermovement jump (CMJ) might explain post-activation potentiation (PAP) phenomenon after an exhausting running test. Thirty-three trained endurance runners performed the Léger Test; an incremental test which consists of continuous running between two lines 20 m apart. CMJ performance was determined before (pre-test) and immediately after the protocol (post-test). Sagittal plane, video of CMJs was recorded and kinematic data were obtained throughout 2-Dimensional analysis. In addition to the duration of eccentric and concentric phases of CMJ, hip, knee and ankle angles were measured at four key points during CMJ: the lowest position of the squat, take-off, landing, and at the lowest position after landing. Additionally, heart rate was monitored, and rate of perceived exertion was recorded at post-test. Analysis of variance revealed a significant improvement in CMJ (p = 0.002) at post-test. Cluster analysis grouped according to whether PAP was experienced (responders group: RG, n = 25) or not (non-responders group: NRG, n = 8) relative to CMJ change from rest to post-test. RG significantly improved (p < 0.001) the performance in CMJ, whereas NRG remained unchanged. Kinematic data did not show significant differences between RG and NRG. Thus, the data suggest that jumping kinematic does not provide the necessary information to explain PAP phenomenon after intensive running exercises in endurance athletes.     

Academic-Based and Aerobic-Only Movement Breaks: Are There Differential Effects on Physical Activity and Achievement?

Purpose: This study investigated the academic achievement and physical activity differences between types of activity breaks implemented in elementary school classrooms. This study evaluated whether there was a difference between the impact of purely aerobic-based movement breaks and the impact of academic-based breaks on children’s academic achievement outcomes. Method: Participants included 460 children in 3rd grade through 5th grade at 4 elementary schools. There were 176 children in the schools that engaged in academic-based breaks and 284 in the schools that engaged in aerobic-only breaks. Schools were randomly assigned at the school level to implement either aerobic movement breaks with academic content infused within the breaks (“academic-based breaks”) or aerobic-only movement breaks without the addition of academic material (“aerobic-only breaks”) for approximately 10 min of activity per day. Math and reading achievement as well as children’s step counts were measured before and after the intervention. A mixed-effects (multilevel-growth) model, in which the repeated measures of individuals nested within a classroom are analyzed, was used to answer all posited research questions. Results: Small to moderate effect sizes (ES) indicating gains in reading achievement (ES = .13) and steps (ES = .33) were found for classrooms that used aerobic-only movement breaks compared with those that used academic-based breaks. Conclusions: The type of movement breaks that are implemented in classrooms may have differential outcomes for children’s achievement and activity levels. Results from the present study indicate that children who were given aerobic-only movement breaks had slightly larger gains in reading achievement and physical activity levels than children who were given academic-based breaks.     

Measurement Research: Where Have We Been and Where Are We Going?

First, where we have been regarding measurement research will be discussed since the type, quality, and quantity of measurement research conducted in the past influences the type of measurement research which is presently conducted. Second, where we are now regarding measurement research will be discussed since the type of measurement research presently being conducted will influence the type of research which will be conducted in the future. Certainly the present status of, trends in, and needed measurement research should be identified to guide measurement researchers in deciding what measurement research to conduct. Third, where we are going regarding to measurement research will be discussed.     

Are the Measurements of Attention Allocation and Perceived Exertion Trustworthy?

Two studies examined the trustworthiness of commonly used measurement scales for ratings of perceived exertion (RPE) and state attentional focus (SAF) during exercise. In Study 1, participants (N = 24, 14 female) performed a treadmill graded-exercise test. The order of scale presentation during the task was manipulated (i.e., RPE followed by SAF or vice versa). In Study 2 the same order manipulation was used while participants (N = 70, 36 female) performed a stepping task for three consecutive trials. Additionally, time intervals between scale presentations were manipulated (i.e., 30 sec, 60 sec, or 90 sec) and counterbalanced between trials. Non-significant order effects of RPE and SAF emerged in both studies; however, a more frequent presentation of the two scales (30 sec and 60 sec) yielded higher RPE scores and increased associative attentional focus than a less frequent presentation (90 sec). The authors recommend minimizing measurement interruptions during the measurement process.     

Does whole body vibration training affect knee kinematics and neuromuscular control in healthy people?

Abstract

This study aimed to investigate the effect of whole body vibration (WBV) training on the knee kinematics and neuromuscular control after single-legged drop landings. Surface electromyographic (EMG) activity of the rectus femoris and hamstring muscles and knee and ankle accelerometry signals were acquired from 42 healthy volunteers. Participants performed three pre-test landings and after a recovery period of three minutes, they completed one set of six bouts of WBV each of one minute duration (30 Hz – 4 mm), followed by a single-leg drop landing. After the WBV intervention no significant changes were observed in the kinematic outcomes measured, although the time to stabilise the lower-limb was significantly lower after the vibration training (F(8,41) = 6.55; P < 0.01). EMG analysis showed no significant differences in the amplitude of rectus femoris or hamstring muscles after WBV training, however, significant differences in EMG frequency of the rectus femoris were found before (F(8,41) = 7.595; P < 0.01) and after toe-down (F(8,41) = 4.440; P < 0.001). Finally, no significant changes were observed in knee or ankle acceleration after WBV. Results suggest that WBV can help to acutely enhance knee neuromuscular control, which may have clinical significance and help in the design of rehabilitation programmes.     

‘How do you feel? What is your heart doing?’ … ‘It’s jumping’: the body and health in Early Years Education

Policy agendas for early childhood education in the UK as in many countries elsewhere are driven by expectations that play will impact positively on a child’s educational attainment, health and well-being. This paper focuses on health knowledge, social class and cultural reproduction within early year education in England, looking specifically at how health discourse is framed by Early Years Foundation Stage (EYFS) policy imperatives and subsequently by practitioners as they re-contextualise health knowledge through play across three socially and culturally different early years education (EYE) settings within England. Across the three settings, 15 practitioners and 80 children, aged 3–4 years old, participated in the research. Drawing on the theoretical work of Basil Bernstein particularly his concepts, ‘pedagogic device’ and ‘classification’ (c) and ‘framing’ (f), the paper documents how health is designed, defined, constructed and experienced through play pedagogy within each of these EYE settings. The analyses illustrate how the different organisational and curriculum structures, pedagogical interactions and transactions of each setting cultivate distinctive relationships to health knowledge. These relationships, in turn, play their part in the reproduction of social class and cultural inequalities, despite the best intentions of EYE policy to address these matters.     

Do accelerometers mounted on the back provide a good estimate of impact loads in jumping and landing tasks?

Artistic gymnasts are frequently exposed to both low- and high-magnitude loads through impacts with the apparatus. These impact loads are thought to be associated with the high injury rates observed in gymnastics. Due to the variable apparatus and surfaces in gymnastics, impact loads during training are difficult to quantify. This study aimed to use triaxial accelerometers mounted on the back to assess impact loading during jumping and landing tasks. Twelve participants were fitted with an accelerometer on their upper and lower back, before performing a continuous hopping task, as well as drop landings and rebound jumps from various heights (37.5, 57.5, and 77.5 cm) onto a force platform. Peak resultant acceleration (PRA) was low-pass filtered with four cut-off frequencies (8, 15, 20, and 50 Hz). Filtering of PRA with the 20 Hz cut-off frequency showed the highest correlations between ground reaction force (GRF) and PRA. PRA recorded at the upper back, filtered with a 20 Hz cut-off frequency, appears to provide a good estimate of impact loading for continuous hopping and rebound jumps, but less so for drop landings since correlations between GRF and PRA were only significant when landing from 57.5 cm.     

Return to competitive football after major knee surgery: more questions than answers?

Abstract

Despite significant advances in the diagnostics and treatment of knee injuries over the last decade, several challenges related to the subject “return to sport” remain largely unknown. For example, how should “return to sport” be defined precisely? What is the optimal timing and progression to enable a return to sport? Which criteria should be used during this process? What type of training is indicated? Which measurements can support the decision-making process? How do we optimally prepare athletes for competition without risking re-injury?

This paper critically addresses these questions, and proposes a return to play model to prepare football players to compete after major knee surgery (anterior cruciate ligament reconstruction, cartilage repair). The goal is to re-integrate the player gradually into the game, taking into account his individual characteristics. Several evidence-based and empirical criteria are needed to plan and monitor the efficient return to competitive football. Injury-prevention education should be part of this process to maximise the chance of a durable career and decrease the risk of re-injury.

However, because of the paucity of research on “return to sport”, further research is more than warranted.     

A kinematic comparison of the overhand throw and tennis serve in tennis players: How similar are they really?

Tennis coaches often use the fundamental throwing skill as a training tool to develop the service action. However, recent skill acquisition literature questions the efficacy of non-specific training drills for developing complex sporting movements. Thus, this study examined the mechanical analogy of the throw and the tennis serve at three different levels of development. A 500 Hz, 22-camera VICON MX motion capture system recorded 28 elite female tennis players (prepubescent (n = 10), pubescent (n = 10), adult (n = 8)) as they performed flat serves and overhand throws. Two-way ANOVAs with repeated measures and partial correlations (controlling for group) assessed the strength and nature of the mechanical associations between the tasks. Preparatory mechanics were similar between the two tasks, while during propulsion, peak trunk twist and elbow extension velocities were significantly higher in the throw, yet the peak shoulder internal rotation and wrist flexion angular velocities were significantly greater in the serve. Furthermore, all of these peak angular velocities occurred significantly earlier in the serve. Ultimately, although the throw may help to prime transverse trunk kinematics in the serve, mechanics in the two skills appear less similar than many coaches seem to believe. Practitioners should, therefore, be aware that the throw appears less useful for priming the specific arm kinematics and temporal phasing that typifies the tennis serve.     

What Are the Contributory and Compensatory Relationships Between Physical Education and Physical Activity in Children?

Limited data are available on the contributory and compensatory relationships between physical education and physical activity in children. Four hundred eighty-five (280 girls) children in first through sixth grades wore sealed pedometers during waking hours, including normally scheduled physical education lessons. The least, moderately, and most active children accumulated approximately 1,700, 1,100, and 2,500 more steps/day, respectively, on school days with physical education. No compensatory increases in physical activity were found on school days that did not offer physical education. The implications of the contributory relationship are highlighted by the evidence that 50% of the least active children were at risk for overweight or overweight and that no compensatory increases in physical activity were found on school days when physical education classes were not scheduled.     

Do they make a difference? Professional team sports clubs’ effects on migration and local growth: Evidence from Denmark

It is a common argument in Denmark that municipal involvement in professional team sports can be justified on the grounds of local impact. The use of public funds to directly or indirectly subsidise local professional team sports clubs (PTSCs) is often seen as warranted due to the PTSCs’ positive effects on local economic growth or (inbound) municipal migration. However, can PTSCs be associated with tangible effects at all? This question has never been answered properly in a European context. Based on data covering the 2008–2013 period, and using spatial panel regression models, this article examines this issue in relation to three dominant professional sports in Denmark: football (soccer), handball and ice hockey. The study finds effects for only one of the sports examined, with Danish handball clubs exercising a marginal effect on average income. Ice hockey’s effect is negative and football remains insignificant in all models deployed. Concerning migration, negative effects are found in relation to female handball clubs. These findings are consistent with previous research and have implications for local sport policies and managers. Municipal politicians, public authorities or sport managers should no longer rationalise the use of public funds for local PTSCs on the assumption of (tangible) economic effects or population growth, as it appears to be an inefficient use of public money. If policy makers want to increase municipal income or inbound migration, they should engage themselves in developing more appropriate strategies.     

Emotions and aesthetics: an inevitable trade-off?

Sport is a producer of both emotional and aesthetic experiences. But how do these relate? Does a spectator’s emotional engagement in sport enhance or hinder it as an aesthetic experience? And does the aesthetic perception of sport enhance or hinder the emotional experiences? These questions will be addressed with particular reference to the distinction that can be drawn between partisan and purist watchers of sport, and making use of thinking in contemporary aesthetics and philosophy of emotion. There are some reasons to think that emotion and aesthetics pull in opposite directions, in both sport and wider life. Does a purist miss out on the essence of sport if they adopt a detached aesthetic attitude? If that were the case, it would suggest that the sports spectator might have to choose between the two: experiencing one or the other but not both at the same time. Emotions and aesthetics would be a trade-off but I argue for some significant exceptions to this conclusion.     

The great leap backward: changes in the jumping performance of Australian children aged 11−12-years between 1985 and 2015

Previous data have indicated relative stability over time of paediatric jumping performance, but few data exist since the early 2000s. This study quantified the 30-year secular changes in jumping performance of Australian children aged 11?12-years using data from the Australian Schools Health and Fitness Survey (1985, n = 1967) and Growing Up in Australia’s Child Health CheckPoint (2015, n = 1765). Both cohorts measured jumping performance (standing long jump distance), anthropometric and demographic data. Secular changes in jumping performance means and quantiles were examined using multivariable linear and quantile regression. Between 1985 and 2015, jumping performance declined by 16.4 cm or by 11.2% (standardised change 0.66 SD, 95%CI 0.60 to 0.73). Adjustment for body mass reduced the effect by 32%, although the decline remained (absolute change – 11.1 cm, 95%CI ?12.5 to ?9.7; percent change 7.7%, 95%CI 6.7 to 8.6; standardised change 0.51 SD, 95%CI 0.44 to 0.57). This decline was evident across all quantiles. The jumping performance of Australian children aged 11?12-years has declined between 1985 and 2015, with body mass changes accounting for only part of the decline. Efforts should continue to promote paediatric muscular fitness, reduce adiposity, and aim to reverse this decline in jumping performance.