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Brigit De Wit and Dirk De Clercq

This study investigates the timing differences between subtalar and knee joint movement of 9 male subjects while running barefoot and shod at three velocities. An alternative approach is used by dividing the pronation curve into 3 phases. Consequently, the timing of the maximum pronation phase was evaluated, not just the event of the maximum pronation value. Statistical differences were tested using the General Linear Method and paired t tests (p £.05), The extension of the knee starts both barefoot and shod significantly earlier than the resupination phase. Individual analysis shows that a larger time discrepancy between knee extension and the end of pronation mainly depends on the presence of bimodal pronation curves. The relative time differences significantly diminish with increased running velocity. Results suggest that by using this alternative approach, more detailed and useful information is available to describe the lime relationship between flexion-extension of the knee and pro-supination.

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Brigit De Wit, Dirk De Clercq and Matthieu Lenoir

The purpose of this study was to investigate the influence of midsole hardness on both impact forces and rearfoot motion. Seven trained male long-distance runners were assessed with a Kistler force plate and with high-speed video, while running at 4.5 ± 0.1 m · s"1 with soft and hard shoe soles (EVA; soft shore Asker C40; hard shore Asker C65). The results showed smaller initial vertical impact peaks, occurring with a higher loading rate, and a significantly larger and faster initial eversion when subjects ran with hard shoes. Support is given to the concept that a more pronounced initial eversion offers an additional deceleration mechanism (Stacoff, Denoth, Kaelin, & Stuessi, 1988) also increasing the eccentric loading of the inverting muscles. On the other hand, during midstance soft shoe soles were found to produce a larger maximum eversion and pronation, also imposing an increased load on the same muscles. So, a good running shoe should be focused on a balance between reducing impact forces and reducing overpronation.

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Greet Cardon, Stefanie Verstraete, Dirk De Clercq and Ilse De Bourdeaudhuij

The main goal of the current study was to compare physical activity levels during swimming and nonswimming elementary physical education classes. We conducted a preliminary study and found that the System for Observing Fitness Instruction Time (SOFIT) could be used to register physical activity engagement levels in swimming classes. Thirty-nine classes, involving 8- to 12-year olds, participated in one swimming and one nonswimming physical education class. Classes were videotaped and physical activity levels for 234 students were quantified using SOFIT. Students engaged in more moderate-to-vigorous physical activity during swimming classes than during nonswimming classes. As a consequence, we advocate the inclusion of swimming lessons in physical education. Because the average engagement in moderate-to-vigorous physical activity was lower than the recommended 50% in 41% of swimming classes and in 77% of the nonswimming classes, however, comprehensive efforts are needed to increase physical activity levels during both types of elementary physical education classes.

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Veerle Segers, Peter Aerts, Matthieu Lenoir and Dirk De Clercq

The purpose of this study was to examine the kinetics of the walk-to-run transition (WRT) and run-to-walk transition (RWT), when accelerating or decelerating across transition speed (a = 0.17 m·s−2). Nine women performed gait transitions on a 50-m-long walkway. Vertical ground reaction forces (GRFs) and the center of pressure (COP) were examined in the range from 3 steps before to 3 steps after transition in order to identify the possible occurrence of a transition process, in order to facilitate the actual realization of transition. The actual transition is realized in one step, during WRT and RWT. This transition step was characterized by an outlying vertical GRF and COP trajectory (deviating from walking and running). Despite this clear discontinuity, a transitional adaptation period (process) appeared in both transitions. In the WRT, transition was prepared and kinetic adaptations were found in the last step before transition. The RWT was pre- and “post”-pared and only completed during the first walking step after transition. Thus, the WRT and RWT are two distinct phenomena, with different kinetics.

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Jorge Cottyn, Dirk de Clercq, Geert Crombez and Matthieu Lenoir

Preparatory heart rate deceleration occurs in tasks with an external focus of attention and is often assumed to facilitate balance performance. However, its effects upon sport-related complex balance movements have not been studied. Heart rate patterns during the preparation period of an acrobatic element (flic-flac) on the balance beam were studied in 14 female gymnasts (M age 13.2 years). A significant heart rate deceleration was found in attempts with a fall in the consecutive acrobatic element, but not in attempts without a fall. These data suggest that preparatory heart rate deceleration may be detrimental to the performance of complex movements on the balance beam.

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Greet Cardon, Ilse De Bourdeaudhuij, Dirk De Clercq, Renaat Philippaerts, Stefanie Verstraete and Elisatbeth Geldhof

The present study investigates whether physical fitness, physical activity, and determinants of physical activity are associated with reports of back and neck pain in children. A total of 749 children (mean age: 9.7 years ± 0.7) were evaluated, using a standardized physical fitness test (Eurofit), a physical activity questionnaire, and a pain prevalence questionnaire. Results indicate that physical fitness levels are not associated with back pain reports, but pain reports are lower in girls reporting higher frequencies of moderate physical activity and better estimates for attitude toward physical activity. Therefore, in girls, increased levels of physical activity might contribute to better back health.

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Pieter Tijtgat, Jos Vanrenterghem, Simon J. Bennett, Dirk De Clercq, Geert J.P. Savelsbergh and Matthieu Lenoir

The purpose of this study was to investigate postural adjustments in one-handed ball catching. Specifically, the functional role of anticipatory postural adjustments (APA) during the initial arm raising and subsequent postural adjustments (SPA) for equilibrium control and ball-hand impact were scrutinized. Full-body kinematics and kinetics allowed an analysis of the mechanical consequences of raising up the arm and preparing for ball-hand impact. APA for catching were suggested to be for segment stabilization. SPA had a functional role for equilibrium control by an inverted pendulum mechanism but were also involved in preparing for the impact of the ball on the hand, which was illustrated by an increased postural response at the end of the movement. These results were compared with raising up the arm in a well-studied reaction-time task, for which an additional counter rotation equilibrium mechanism was observed. Together, our findings demonstrate that postural adjustments should be investigated in relation to their specific functional task constraints, rather than generalizing the functional role of these postural adjustments over different tasks.

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Margot Callewaert, Jan Boone, Bert Celie, Dirk De Clercq and Jan G. Bourgois

The aim of this work was to gain more insight into the cardiorespiratory and muscular (m. vastus lateralis) responses to simulated upwind sailing exercise in 10 high-level male and female Optimist sailors (10.8–14.4 years old). Hiking strap load (HSL) and cardiorespiratory variables were measured while exercising on a specially developed Optimist sailing ergometer. Electromyography (EMG) was used to determine mean power frequency (MPF) and root mean square (RMS). Near-infrared spectroscopy was used to measure deoxygenated Hemoglobin and Myoglobin concentration (deoxy[Hb+Mb]) and re-oxygenation. Results indicated that HSL and integrated EMG of the vastus lateralis muscle changed in accordance with the hiking intensity. Cardiorespiratory response demonstrated an initial significant increase and subsequently steady state in oxygen uptake (VO2), ventilation (VE), and heart rate (HR) up to circa 40% VO2peak, 30% VEpeak and 70% HRpeak respectively. At muscle level, results showed that highly trained Optimist sailors manage to stabilize the muscular demand and fatigue development during upwind sailing (after an initial increase). However, approaching the end of the hiking exercise, the MPF decrease, RMS increase, and deoxy[Hb+Mb] increase possibly indicate the onset of muscle fatigue.

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Stefanie J.M. Verstraete, Greet M. Cardon, Dirk L.R. De Clercq and Ilse M.M. De Bourdeaudhuij

The study aim was to evaluate the effectiveness of a 2-year health-related physical education intervention in a pretest-posttest design. Sixteen elementary schools (764 pupils, mean age: 11.2 ± 0.7) participated in the study. Schools were randomly assigned to the intervention condition (n = 8) and the control condition (n = 8). Making use of direct observation data gathered according to SOFIT (System for Observing Fitness Instruction Time), the moderate-to-vigorous physical activity engagement during physical education classes was significantly higher in the intervention condition than in the control condition. Children’s moderate-to-vigorous physical activity engagement during physical education lessons increased with 14% in the intervention condition (from 42 to 56%). No significant effects were found on the accelerometer data. The health-related physical education intervention was found to be promising in promoting physical activity during physical education classes.

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Frederik J.A. Deconinck, Dirk De Clercq, Geert J.P. Savelsbergh, Rudy Van Coster, Ann Oostra, Griet Dewitte and Matthieu Lenoir

One-handed catching behavior was studied in nine 6- to 8-year-old boys with Developmental Coordination Disorder (DCD) and nine matched typically developing boys. The participants performed a catching task under two conditions. In the first condition, one ball speed was used while three ball speeds were randomly presented in the second condition. Boys with DCD showed a significantly smaller maximal hand aperture and a lower maximal closing velocity in both the first and the second condition; however, the temporal structure of the catch as well as the adaptations to the varying ball speeds did not differ between groups. This leads to the suggestion that the motor problems of boys with DCD in one-handed catching are not primarily due to debilitated visuo-perceptual or planning processes but are more likely caused by problems at the execution level.