In speed skating, performance is related to the product of the amount of work per stroke and the stroke frequency. Work per stroke is dependent on the component of the push-off force in the direction perpendicular to the gliding direction of the skate. The push-off force at different velocities was measured in three trained speed skaters. The results showed that the peak push-off force and mean force do not change at different velocities, and that the stroke time was decreased at higher velocities. It can be concluded that these speed skaters regulate their velocity not by changing the push-off force but by changing their stroke time. The shape of push-off–time curves is dependent on push-off technique and differs during straight lane and curve skating.
Jos J. de Koning, Ruud W. de Boer, Gert de Groot and Gerrit Jan van Ingen Schenau
Jos J. de Koning, Gert de Groot and Gerrit Jan van Ingen Schenau
Mechanical characteristics of the sprint start in speed skating were measured during the 1988 Winter Olympic Games. From three-dimensional film analysis of the first 4 seconds of the male and female 500-m races, biomechanical variables were determined. The first strokes during the start appeared to be performed by a running-like technique. At a forward velocity of approximately 4 m/sec, the skaters are forced to change this technique to the typical gliding technique as used during speed skating at steady speed. In explaining the time differences on the first 100 meters of the 500-m speed skating race, the effectiveness of the push-off appears to be more important than the observed high power output levels.
Jos J. de Koning, Gert de Groot and Gerrit Jan van Ingen Schenau
The purpose of this study was to describe the intermuscular coordination and power production for the constrained asymmetrical movement during skating the curves. Seven elite male speed skaters took part in the experiments. The speed skaters were simultaneously filmed from frontal and sagittal views. EMGs were obtained telemetrically and push-off force was registered with special skates. Inverse dynamic analysis yielded power production data, which differed for left and right leg. Marked differences were also found in intermuscular coordination of each leg. The activation patterns of the muscles were influenced by the asymmetrical nature and the typical body position during the speed skating movement. External power output was determined by three methods. The mean joint power output for left and right leg showed similar values as the external power output calculated from air and ice friction. These values were lower than the values predicted with a geometrical model for skating the curves.
Gerrit Jan van Ingen Schenau, Ruud W. de Boer and Gert de Groot
The mechanics of speed skating, as many other endurance sports, can be described by an energy flow equation. With such an equation the influence of suit, local pressure, altitude, shielding, and body position on speed is predicted. Next to these model predictions, the peculiar properties of the skating technique are discussed and their practical implications for skating the straight parts and the curves are indicated.
Maarten F. Bobbert, Han Houdijk, Jos J. de Koning and Gert de Groot
To gain a better understanding of push-off mechanics in speed skating, forward simulations were performed with a model comprising four body segments and six muscles. We started with a simulated maximum height one-legged jump, obtained by optimization of muscle stimulation time histories. The simulated jump was very similar to one-legged jumps produced by a human, indicating that the model was realistic. We subsequently studied how performance was affected by introducing four conditions characteristic of speed skating: (a) We changed the initial position from that in jumping to that at the start of the push-off phase in skating. This change was accommodated by a delay in stimulation onset of the plantar flexors in the optimal solution. (b) The friction between foot and ground was reduced to zero. As a result, maximum jump height decreased by 1.2 cm and performance became more sensitive to errors in muscle stimulation. The reason is that without surface friction, the foot had to be prevented from slipping away, which constrained the solution space and reduced the tolerance to errors in stimulation. (c) We introduced the requirement to maintain the upper body in a more or less horizontal position. This change could be accommodated by a delay in stimulation onset of the hamstrings, which inevitably caused a reduction in maximum jump height by 11.6 cm. (d) We increased the effective foot length from 16.5 cm, representative of jumping, to 20.5 cm, representative of skating with klapskates. At the 20.5-cm foot length, rotation of the foot did not start during the buildup of plantar flexion moment as it did at smaller foot lengths, but was delayed until hip and knee extension moments decreased. This caused an unbalanced increase in segment angular velocities and muscle shortening velocities, leading to a decrease in muscle force and muscle work and a further decrease in maximum jump height by approximately 5 cm. Qualitatively, these findings help clarify why and how performance of speed skaters depends on the location of the hinge of their skate.
Han Houdijk, Jos J. de Koning, Maarten F. Bobbert and Gert de Groot
In speed skating, the conventional skate has been replaced by the klapskate, in which the shoe can rotate around a hinge between shoe and blade. It has been hypothesized that the improved performance with klapskates vs. conventional skates can be attributed to the difference in the anterior/posterior position of the foot’s center of rotation relative to the ice. This study investigated the effect of the position of the foot’s center of rotation on push-off mechanics in speed skating. Eight elite speed skaters skated four 2000-m trials on instrumented klapskates at a fixed velocity. In each trial the hinge was placed at a different position between the 5th metatarso-phalangeal joint and the tip of the toes. 3-D kinematics and pushoff forces were measured to analyze push-off kinematics and kinetics. Shifting the hinge from the most posterior to the more anterior positions resulted in a delayed onset of foot rotation and longer duration of push-off. This delay coincided with an increase in angular displacement and peak angular velocity of the knee and hip joint, an increase in the flexing knee joint moment at the end of the push-off, and a reduction in work generated at the knee joint. Total work per stroke was similar for the various hinge positions. Besides the similar work per stroke, the observed effects are in accordance with the differences between klapskating and conventional skating. It was concluded that the position of the foot’s center of rotation affects the timing of foot rotation, and therefore the balanced pattern of segmental rotations. Although it could not be proven in this study, it was shown that this constraint could affect work per stroke and might explain the difference between klapskates and conventional skates.
Ruud W. de Boer, Paul Schermerhorn, Jan Gademan, Gert de Groot and Gerrit Jan van Ingen Schenau
In speed skating, the amount of work per stroke is dependent on the component of the push-off force in the direction perpendicular to the gliding direction of the skate. One stroke consists of a gliding phase and a push-off phase in which the knee is explosively extended. Film and video analysis showed that the better skaters show a higher power production and no differences in stroke frequency. Differences in performance are related to differences in push-off mechanics. The faster skaters reach a higher angular velocity at the knee; the time during which the knee is extended is shorter. At the start of the push-off, the velocity of the body center of gravity in the horizontal direction is higher due to a passive falling movement in the frontal plane. It is concluded that the better skaters show a better timing that results in a more explosive and effective directed push-off.
Gert-Jan de Bruijn, Ruben de Groot, Bas van den Putte and Ryan Rhodes
The present study explored the influence of the Big Five dimensions extroversion and conscientiousness on action control regarding both moderate and vigorous physical activity within the framework of the theory of planned behavior (TPB). Prospective data were available from 186 respondents, who completed measures of intention, cognitive and affective attitude, subjective norm, perceived behavioral control, extroversion, conscientiousness, and physical activity at T1. Four weeks later, physical activity was assessed again. Respondents were grouped into four profiles: nonintenders, successful nonintenders, unsuccessful intenders, and successful intenders. Logistic regression analyses revealed that successful enactment in moderate physical activity was associated with extroversion, subjective norm, and affective attitude, whereas successful enactment in vigorous physical activity was associated with conscientiousness. Findings illustrate the differential role played by personality dimensions and TPB concepts in the explanation of moderate and vigorous physical activity action control.
Auke A. Post, Gert de Groot, Andreas Daffertshofer and Peter J. Beek
In mechanical studies of pumping a playground swing, two methods of energy insertion have been identified: parametric pumping and driven oscillation. While parametric pumping involves the systematic raising and lowering of the swinger’s center of mass (CM) along the swing’s radial axis (rope), driven oscillation may be conceived as rotation of the CM around a pivot point at a fixed distance to the point of suspension. We examined the relative contributions of those two methods of energy insertion by inviting 18 participants to pump a swing from standstill and by measuring and analyzing the swing-swinger system (defined by eight markers) in the sagittal plane. Overall, driven oscillation was found to play a major role and parametric pumping a subordinate role, although the relative contribution of driven oscillation decreased as swinging amplitude increased, whereas that of parametric pumping increased slightly. Principal component analysis revealed that the coordination pattern of the swing-swinger system was largely determined (up to 95%) by the swing’s motion, while correlation analysis revealed that (within the remaining 5% of variance) trunk and leg rotations were strongly coupled.
Ruud W. de Boer, Gertjan J.C. Ettema, Hans van Gorkum, Gert de Groot and Gerrit Jan van Ingen Schenau
Characteristics of stroke mechanics of elite and trained speed skaters were measured during the skating of curves. Film and video analysis from the 5000-meter races at the Dutch National Championships yielded biomechanical variables that were correlated to performance. There are fundamental differences in push-off mechanics between skating the straight parts and skating the curves. The left stroke shows a more powerful push-off in the curve, caused by a greater push off angle compared to the right leg. The high speed and power output of the better skaters is a result of a high amount of work per stroke, caused by a short and effective directed push-off. These results strongly support the previous finding that skaters of different performance levels can be distinguished by differences in amount of work per stroke and not by differences in stroke frequency.