[Show abstract][Hide abstract] ABSTRACT: It was hypothesized that differences in anthropometry, physical performance and motor coordination would be found between Belgian elite and sub-elite level female volleyball players using a retrospective analysis of test results gathered over a five-year period. The test sample in this study consisted of 21 young female volleyball players (15.3 ± 1.5 y) who were selected to train at the Flemish Top Sports Academy for Volleyball in 2008. All players (elite n = 13; sub-elite n = 8) were included in the same talent development program and the elite-level athletes were of a high to very high performance levels according European competition level in 2013. Five multivariate analyses of variance (MANOVA) were used. There was no significant effect of playing level on measures of anthropometry (F = 0.455, p = 0.718, ηp = 0.07), flexibility (F = 1.861, p = 0.188, ηp = 0.19), strength (F = 1.218, p = 0.355, ηp = 0.32); and speed and agility (F = 1.176, p = 0.350, ηp = 0.18). MANOVA revealed significant multivariate effects between playing levels for motor coordination (F=3.470, p = 0.036, ηp = 0.59). A Mann-Whitney U-test and a sequential discriminant analysis confirmed these results. Previous research revealed that stature and jump height are prerequisites for talent identification in female volleyball. In addition, the results show that motor coordination is an important factor in determining inclusion into the elite level in female volleyball.
Full-text · Article · Nov 2014 · The Journal of Strength and Conditioning Research
[Show abstract][Hide abstract] ABSTRACT: Abstract The aim of the present study was to evaluate the Flemish Sports Compass (FSC), a non-sport-specific generic testing battery. It was hypothesised that a set of 22 tests would have sufficient discriminant power to allocate athletes to their own sport based on a unique combination of test scores. First, discriminant analyses were applied to the 22 tests of anthropometry, physical fitness and motor coordination in 141 boys under age 18 (16.1 ± 0.8 years) and post age at peak height velocity (maturity offset = 2.674 ± 0.926) from Flemish Top Sport Academies for badminton, basketball, gymnastics, handball, judo, soccer, table tennis, triathlon and volleyball. Second, nine sequential discriminant analyses were used to assess the ability of a set of relevant performance characteristics classifying participants and non-participants for the respective sports. Discriminant analyses resulted in a 96.4% correct classification of all participants for the nine different sports. When focusing on relevant performance characteristics, 80.1% to 97.2% of the total test sample was classified correctly within their respective disciplines. The discriminating characteristics were briefly the following: flexibility in gymnastics, explosive lower-limb strength in badminton and volleyball, speed and agility in badminton, judo, soccer and volleyball, upper-body strength in badminton, basketball and gymnastics, cardiorespiratory endurance in triathletes, dribbling skills in handball, basketball and soccer and overhead-throwing skills in badminton and volleyball. The generic talent characteristics of the FSC enable the distinction of adolescent boys according to their particular sport. Implications for talent programmes are discussed.
Full-text · Article · Aug 2014 · European Journal of Sport Science
[Show abstract][Hide abstract] ABSTRACT: Background and Study Aim: The present study aims to discriminate young male taekwondo, judo, and karate athletes from two age groups. It is hypothesized that a generic test battery (i.e. consisting of non-sport specific items) can allocate athletes in their respective sports. It is also expected that due to training and experience, differences between sports would be larger in the oldest age group.
Material and Methods: Fifty-six highly trained taekwondo, judo, and karate athletes U13 (11.596 ± 0.578 years; n = 30) and U18 (16.097 ± 0.844 years; n = 26) completed five anthropometrical, six physical performance and three motor coordination tests. Discriminant analyses were used to investigate relevant performance measures while MANOVAs were conducted to elucidate the differences between taekwondo, judo and karate.
Results: The classification results for both discriminant analyses U13 and U18 showed a perfect classification (100%) of the athletes in their respective sports. U18 showed higher multivariate differences between the three martial arts i.e. for anthropometrical measures (F2.148, P =0.044, ES =0.36), physical performance characteristics (F2.216, P =0.033, ES =0.43) and motor coordination (F6.697, P <0.001, ES =0.49) when compared to their younger counterparts. Judo athletes had the highest scores for sit and reach, handgrip, counter movement jump and balance beam. While taekwondo athletes had the highest scores for sit-ups, sprint 5m and 30m and jumping sideways.
Conclusions: Generic talent characteristics allow for a successful discrimination between judo, taekwondo and karate athletes, while the differences between the martial arts profiles are more pronounced in older athletes.
[Show abstract][Hide abstract] ABSTRACT: Subjects (N = 14) were instructed to walk at comfortable walking speed and to start sprinting on an external (visual) stimulus. This is a burst transition. To accelerate maximally, different strategies can be used. The choice for a strategy was hypothesized to be (a) dependent of the body's dynamical status, which is in its turn dependent on the signal timing within the gait cycle; and (b) influenced by the performance and efficacy of the different strategies. Three-dimensional kinematics and ground reaction forces were used to discriminate between strategies and to calculate work (Wtotal). Distance laser data yielded performance measures and the work related to the forward acceleration (Wobjective). Efficacy was calculated as the ratio of Wobjective to Wtotal. Subjects mainly used 2 strategies among others depending on the timing of the stimulus: (a) subjects placed their body center of mass (BCOM) in front of their center of pressure (COP) by tilting the trunk forward and flexing the knee, resulting in a sudden forward acceleration but a relatively fair efficacy; (b) subjects placed their COP behind their BCOM by placing the foot of the swing leg backward. This led to a high performance with high efficacy and was therefore the most ecologically relevant.
No preview · Article · Apr 2014 · Journal of Motor Behavior
[Show abstract][Hide abstract] ABSTRACT: The ability to perform fast cutting manoeuvres is essential in soccer and requires sufficient traction between shoe and surface. Artificial turf (AT) surfaces are widely used in soccer and among others turf moisture and shoe studs can influence traction. The aim of this study was to quantify the influence of moisture (DRY and WET AT), for three realistic shoe stud characteristics sets [Turf Field (TF), Artificial Grass (AG) and Firm Ground (FG)], on cutting performance, executed traction and perception of the players. Twelve experienced soccer players performed 10 × 5 m shuttle run tests. Ground reaction forces of the open stance phase of the 180° turns were measured and required traction was calculated. Players' perception was also measured. A two-way 2×3 analysis of variance (ANOVA) Repeated Measures with Bonferroni correction was conducted. On dry AT no performance differences between the three tested shoe stud characteristics sets could be measured. On wet AT the AG and FG designs performed evenly well but when wearing the TF shoe, equipped with 74 short studs, significant surface x shoe interaction effects indicated decreased performance and traction on the wet surface. The experienced players perceived shoe x surface evoked differences in performance and traction very well.
No preview · Article · Apr 2014 · Footwear Science
[Show abstract][Hide abstract] ABSTRACT: The purpose of the present study is to describe the biomechanics of spontaneous walk-to-run transitions (WRTs) in humans. After minimal instructions, 17 physical active subjects performed WRTs on an instrumented runway enabling measurement of speed, acceleration, spatiotemporal variables, ground reaction forces and 3D kinematics. The present study describes (1) the mechanical energy fluctuations of the body centre-of-mass (BCOM) as a reflection of the whole body dynamics and (2) the joint kinematics and kinetics. Consistent with previous research, the spatiotemporal variables show a sudden switch from walking to running in one transition step. During this step there is a sudden increase in forward speed, the so-called speed jump (0.42 m/s). At total body level, this is reflected in a sudden increase in energy of the BCOM (0.83 ± 0.14 J/kg) and an abrupt change from an out-of-phase to an in-phase organization of the kinetic and potential energy fluctuations. During the transition step a larger net propulsive impulse compared to the preceding and following steps is observed due to a decrease in the braking impulse. It is suggested that the altered landing configuration (prepared during the last 40% of the preceding swing) places the body in an optimal configuration to minimize this braking impulse. We hypothesize this configuration also evokes a reflex allowing a more powerful push off, which generates enough power to complete the transition and launch the first flight phase. This powerful push-off is also reflected in the vertical ground reaction force which suddenly changes to a running pattern.
[Show abstract][Hide abstract] ABSTRACT: Literature shows that running on an accelerated motorized treadmill is mechanically different from accelerated running overground. Overground, the subject has to enlarge the net anterior-posterior force impulse proportional to acceleration in order to overcome linear whole body inertia, whereas on a treadmill, this force impulse remains zero, regardless of belt acceleration. Therefore, it can be expected that changes in kinematics and joint kinetics of the human body also are proportional to acceleration overground, whereas no changes according to belt acceleration are expected on a treadmill. This study documents kinematics and joint kinetics of accelerated running overground and running on an accelerated motorized treadmill belt for 10 young healthy subjects. When accelerating overground, ground reaction forces are characterized by less braking and more propulsion, generating a more forward-oriented ground reaction force vector and a more forwardly inclined body compared with steady-state running. This change in body orientation as such is partly responsible for the changed force direction. Besides this, more pronounced hip and knee flexion at initial contact, a larger hip extension velocity, smaller knee flexion velocity and smaller initial plantarflexion velocity are associated with less braking. A larger knee extension and plantarflexion velocity result in larger propulsion. Altogether, during stance, joint moments are not significantly influenced by acceleration overground. Therefore, we suggest that the overall behaviour of the musculoskeletal system (in terms of kinematics and joint moments) during acceleration at a certain speed remains essentially identical to steady-state running at the same speed, yet acting in a different orientation. However, because acceleration implies extra mechanical work to increase the running speed, muscular effort done (in terms of power output) must be larger. This is confirmed by larger joint power generation at the level of the hip and lower power absorption at the knee as the result of subtle differences in joint velocity. On a treadmill, ground reaction forces are not influenced by acceleration and, compared with overground, virtually no kinesiological adaptations to an accelerating belt are observed. Consequently, adaptations to acceleration during running differ from treadmill to overground and should be studied in the condition of interest.
Full-text · Article · Apr 2013 · Journal of The Royal Society Interface
[Show abstract][Hide abstract] ABSTRACT: Unilateral skipping or bipedal galloping is one of the gait types humans are able to perform. In contrast to many animals, where gallop is the preferred gait at higher speeds, human bipedal gallop only occurs spontaneously in very specific conditions (e.g. fast down-hill locomotion). This study examines the lower limb mechanics and explores the possible reasons why humans do not spontaneously opt for gallop for steady state locomotion on level ground. In 12 subjects, who were required to run and gallop overground at their preferred speed, kinematic and kinetic data were collected and mechanical work at the main lower limb joints (hip, knee, ankle) was calculated. In a separate treadmill experiment, metabolic costs were measured. Analysis revealed that the principal differences between running and galloping are located at the hip. The asymmetrical configuration of gallop involves distinct hip actions and foot placing, giving galloping legs different functions compared with running legs: the trailing leg decelerates the body in vertical direction but propels it forward while the leading leg acts in the opposite way. Although both legs conserve mechanical energy by interchanging external mechanical energy with potential elastic energy, the specific orientation of the legs causes more energy dissipation and generation compared with running. This makes gallop metabolically more expensive and involves high muscular stress at the hips which may be the reasons why humans do not use gallop for steady state locomotion.
No preview · Article · Dec 2012 · Journal of Experimental Biology
[Show abstract][Hide abstract] ABSTRACT: Unsteady state gait involving net accelerations has been studied overground and on a treadmill. Yet it has never been tested if and to what extent both set-ups are mechanically equal. This study documents the differences in ground reaction forces for accelerated running on an instrumented runway and running on an accelerating treadmill by building a theoretical framework which is experimentally put to the test. It is demonstrated that, in contrast to overground, no mean fore-after force impulse should be generated to follow an accelerating treadmill due to the absence of linear whole body acceleration. Accordingly, the adaptations in the braking phase (less braking) and propulsive phase (more propulsion) to accelerate overground are not present to follow an accelerating treadmill. It can be concluded that running on an accelerating treadmill is mechanically different from accelerated running overground.
[Show abstract][Hide abstract] ABSTRACT: We describe a multi-segmented foot model comprising lower leg, rearfoot, midfoot, lateral forefoot, medial forefoot, and hallux for routine use in a clinical setting. The Ghent Foot Model describes the kinematic patterns of functional units of the foot, especially the midfoot, to investigate patient populations where midfoot deformation or dysfunction is an important feature, for example, rheumatoid arthritis patients. Data were obtained from surface markers by a 6 camera motion capture system at 500 Hz. Ten healthy subjects walked barefoot along a 12 m walkway at self-selected speed. Joint angles (rearfoot to shank, midfoot to rearfoot, lateral and medial forefoot to midfoot, and hallux to medial forefoot) in the sagittal, frontal, and transverse plane are reported according to anatomically based reference frames. These angles were calculated and reported during the foot rollover phases in stance, detected by synchronized plantar pressure measurements. Repeated measurements of each subject revealed low intra-subject variability, varying between 0.7° and 2.3° for the minimum values, between 0.5° and 2.1° for the maximum values, and between 0.8° and 5.8° for the ROM. The described movement patterns were repeatable and consistent with biomechanical and clinical knowledge. As such, the Ghent Foot model permits intersegment, in vivo motion measurement of the foot, which is crucial for both clinical and research applications.
Full-text · Article · Apr 2012 · Journal of Orthopaedic Research
[Show abstract][Hide abstract] ABSTRACT: Morphology and kinematic parameters were recorded for 31 children between 15 and 36 months to investigate the relation between morphology and the walking pattern. A full 3D gait analysis using a VICON motion system was performed to gather kinematic data. Next, the differences in kinematic parameters between four morphological classes were assigned with a multiple analysis of variance, with a correction for walking experience. Also stepwise linear regressions were performed, to examine the relation between detailed morphological measurements and kinematic parameters. The regression models showed relationships between kinematic parameters of the ankle, hip, thorax and morphology. All results indicated that the upper body played an important role in the coordination of the walking pattern, especially in the frontal plane.
[Show abstract][Hide abstract] ABSTRACT: Pedobarographic images reflect the dynamic interaction between the plantar foot and supporting surfaces during gait and postural activities. Since intra-foot and inter-subject contact geometry are grossly similar, images may be spatially registered and directly compared. Previously arbitrary subjects have been selected as registration templates, but this can conceivably introduce anatomical bias. The purposes of this study were: (i) to compute an unbiased pedobarographic template from a large sample of healthy young adult subjects, and (ii) to demonstrate how the resulting template may be used for practical clinical and scientific analyses. Images were obtained from N=104 subjects and were registered (10,712 pairs) using (i) an optimal linear scaling technique and (ii) a nonlinear, locally affine, globally smooth technique. The nonlinear technique was found to offer biomechanically non-trivial advantages over the linear technique, most likely due to non-proportional inter-subject geometry. Specifically, the nonlinear template was able to detect morphological signals in a hallux valgus sample with greater sensitivity than the linear template. Validity of the approach was confirmed by independently assessing left and right feet, through a statistical comparison of local maximal pressures, and also through examination of random subject subsets. The current template, representative of an average healthy foot, could be a valuable resource for automated clinical and scientific analyses of foot morphology and function.
[Show abstract][Hide abstract] ABSTRACT: Previous research has suggested that perceptual-motor difficulties may account for obese children's lower motor competence; however, specific evidence is currently lacking. Therefore, this study examined the effect of altered visual conditions on spatiotemporal and kinematic gait parameters in obese versus normal-weight children. Thirty-two obese and normal-weight children (11.2±1.5 years) walked barefoot on an instrumented walkway at constant self-selected speed during LIGHT and DARK conditions. Three-dimensional motion analysis was performed to calculate spatiotemporal parameters, as well as sagittal trunk segment and lower extremity joint angles at heel-strike and toe-off. Self-selected speed did not significantly differ between groups. In the DARK condition, all participants walked at a significantly slower speed, decreased stride length, and increased stride width. Without normal vision, obese children had a more pronounced increase in relative double support time compared to the normal-weight group, resulting in a significantly greater percentage of the gait cycle spent in stance. Walking in the DARK, both groups showed greater forward tilt of the trunk and restricted hip movement. All participants had increased knee flexion at heel-strike, as well as decreased knee extension and ankle plantarflexion at toe-off in the DARK condition. The removal of normal vision affected obese children's temporal gait pattern to a larger extent than that of normal-weight peers. Results suggest an increased dependency on vision in obese children to control locomotion. Next to the mechanical problem of moving excess mass, a different coupling between perception and action appears to be governing obese children's motor coordination and control.
[Show abstract][Hide abstract] ABSTRACT: Determination of the walk-to-run transition (WRT) speed is a crucial aspect of gait transition research, which has been conducted on treadmill as well as overground. Overground WRT-speeds were reported to be higher than on treadmill. Part of this difference could be related to the lower acceleration magnitudes on treadmill. In this study, spontaneous WRT overground was compared to WRT at a comparable acceleration on treadmill. In addition, calculation procedures correcting for movement in the lab reference frame on treadmill were implemented. As such, this study was, in contrast to previous treadmill studies, able to detect a speed jump. This speed jump was until now a typical feature of overground WRT and contributed to the higher transition speed. By incorporating horizontal movements of the COM, a speed jump was also detected on treadmill. Yet, treadmill WRT-speed (2.61 ms(-1)) remained lower than overground (2.85 ms(-1)). Nevertheless, this difference was much smaller than assumed in the literature. The remaining difference could be explained by a larger speed jump (treadmill: 0.40 ms(-1); overground: 0.51 ms(-1)), and a higher speed at the start of the transition step overground (treadmill: 2.21 ms(-1); overground: 2.34 ms(-1)). In conclusion, even when controlling for effects of acceleration and movement in the lab reference frame a treadmill influence on WRT was visible.