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Biomedical subjects

G J van Ingen Schenau

Publications and source records attributed to G J van Ingen Schenau.

At least 19 recordsLinked to original sources
PubMed2000

Push-off mechanics in speed skating with conventional skates and klapskates.

PURPOSE: Personal and world records in speed skating improved tremendously after the introduction of the klapskate, which allows the foot to plantar flex at the end of the push-off while the full blade continues to glide on the ice. The purpose of this study was to gain insight into the differences in skating technique with conventional versus klapskates and to unveil the source of power enhancement using klapskates. METHODS: Ten elite speed skaters skated four 400-m laps at maximal effort with both conventional and klapskates. On the straight high-speed film, push-off force and EMG data were collected. An inverse dynamics analysis was performed in the moving reference plane through hip, knee, and ankle. RESULTS: Skating velocity increased 5% as a result of an increase in mean power output of 25 W when klapskates were used instead of conventional skates. The increase in mean power output was achieved through an 11-J increase in work per stroke and an increase in stroke frequency from 1.30 to 1.36 strokes x s(-1). The difference in work per stroke occurs during the final 50 ms of the push-off. This is the result of the ineffective way in which push-off forces are generated with conventional skates when the foot rotates about the long front end of the blade. No differences in muscle coordination were observed from EMG. CONCLUSION: A hinge under the ball of the foot enhances the effectiveness of plantar flexion during the final 50 ms of the push off with klapskates and increases work per stroke and mean power output.

Adult↗
PubMed1998

Activation patterns of mono- and bi-articular arm muscles as a function of force and movement direction of the wrist in humans.

1. In order to explain the task-dependent activation of muscles, we have investigated the hypothesis that mono- and bi-articular muscles have a different functional role in the control of multijoint movements. According to this hypothesis, bi-articular muscles are activated in a way to control the direction of external force. The mono-articular muscles are thought to be activated to contribute to joint torque mainly during shortening movements. 2. To investigate this hypothesis, surface electromyographic (EMG) recordings were obtained from several mono- and bi-articular arm muscles during voluntary slow movements of the wrist in a horizontal plane against an external force. The direction of force produced at the wrist and the direction of movement of the wrist were varied independently. 3. The results revealed distinct differences between the activation patterns of mono- and bi-articular muscles. The activation of the bi-articular muscles was not affected by movement direction, but appeared to vary exclusively with the direction of force. 4. The mono-articular muscles showed significantly more EMG activity for movements in a specific direction, which equalled the movement direction corresponding to the largest shortening velocity of the muscle. The EMG activity decreased gradually for movements in other directions. This direction-dependent activation appeared to be independent of the direction of the external force.

Arm↗
PubMed1997

Intermuscular co-ordination during fast contact control leg tasks in man.

From previous inverse dynamic analyses of human leg extensions, it was hypothesized that the underlying processes for the activation of mono- and biarticular muscles are different; the mono-articular muscles being activated when they shortened, whereas the biarticular muscles appeared responsible for the control of the external force direction. In the present study, experiments were performed on a dynamometer which was especially developed to test this hypothesis. Subjects had to exert different prescribed force vectors on a moving force-plate during leg extension, which they had intensively practised prior to the actual experiments. Of each trial, position, force and EMG activity were recorded. Net joint torques were calculated by the method of inverse dynamics and related to the EMG-patterns of the mono- and biarticular upper leg muscles to reveal whether the previously observed different roles in contact tasks might constitute a general principle in motor control. The results showed that although the action of the biarticular m. rectus femoris and hamstrings muscles was consistent in controlling the direction of the external force, the actions of the mono-articular muscles did not agree with their hypothesized role as simple work generators. The generalizability of a different control for mono- and biarticular muscles could thus not be confirmed for these tasks. They might rather reflect one out of more available strategies the CNS can use to control different contact control tasks.

Adult↗
PubMed1996

Mechanical output from individual muscles during explosive leg extensions: the role of biarticular muscles.

The main result of this study is that biarticular leg muscles contribute significantly to the work done at joints, due to transfer of power during explosive leg extensions. In particular, a net power transfer was shown from hip to knee joint during jumping and sprinting. Seven elite athletes performed explosive one legged jump and spring push offs. Kinematics, ground reaction forces and electromyography (EMG) of leg muscles were recorded. The mechanical output of six individual muscle groups was estimated by using Hill-based muscle models. The EMG and kinematics served as input to these models. For jumping as well as for sprinting, the model estimated similar results for the relative work contribution done about a joint due to transfer of power by the biarticular muscles. Rectus femoris showed a power transfer from hip to knee joint, while in contrast hamstrings showed a power transfer from knee to hip joint. Regardless of these opposite directions of power transfer, a net transfer occurred from the hip to the knee joint. The relative work contribution of hamstrings done in hip extension was 7% in jumping and 11% in sprinting. For rectus femoris, the relative work contribution done in knee extension was 21% in jumping and 31% in sprinting. Power transferring actions by gastrocnemius from knee to ankle contributed 25% in jumping and 28% in sprinting to the work done in plantar flexion. These results support the hypothesis that the action of biarticular muscles contributes to a net transfer of power from proximal to distal joints during explosive leg extensions. This action of the biarticular muscles causes an efficient conversion of body segment rotations into the desired translation of the body centre of gravity.

Adult↗
PubMed1995

Stiffness control for lower leg muscles in directing external forces.

The role of lower leg muscles is investigated during contact control tasks, in which the external force, applied by the foot on the surface, has to be controlled. Force, position and muscle activation were recorded. All subjects showed a stereotyped activation pattern to accomplish the tasks. The torques about hip and knee changed by a reciprocal activation pattern of the upper leg muscles, whereas the ankle torque remained remarkably constant as a result of a strong co-activation of the ankle muscles.

Adult↗
PubMed1995

The control of mono-articular muscles in multijoint leg extensions in man.

1. Movements often require control of direction and a magnitude of force exerted externally on the environment. Bi-articular upper leg muscles appear to play a unique role in the regulation of the net torques about the hip and knee joints, necessary for the control of this external force. 2. The aim of this study was to test the hypothesis that the mono-articular muscles act as work generators in powerful dynamic leg extensions, which means that they should be activated primarily in the phases during which they can contribute to work, irrespective of the net joint torques required to control the external force. 3. Cycling movements of six trained subjects were analysed by means of inverse dynamics, yielding net joint torques as well as activity patterns and shortening velocities of four mono- and four bi-articular leg muscles. 4. The results show that the mono-articular muscles exert force only in the phase in which these muscles shorten, whereas this appears not to be the case for the bi-articular muscles. 5. Reciprocal patterns of activation of the rectus femoris and hamstring muscles appear to tune the distribution of net joint torques about the hip and knee joints, necessary to control the (changing) direction of the force on the pedal. 6. An analysis of running in man and additional related literature based on animal studies appears to provide further support for the hypothesis that mono- and bi-articular muscles have essentially different roles in these powerful multijoint leg extension tasks.

Bicycling↗
PubMed1995

The start in speed skating: from running to gliding.

The purpose of this study was to describe the push-off kinematics in speed skating using three-dimensional coordinates of elite male sprinters during the first part of a speed skating sprint. The velocity of the mass center of the skater's body VC, is decomposed into an "extension" velocity component VE, which is associated with the shortening and lengthening of the leg segment and a "rotational" velocity component Vr, which is the result of the rotation of the leg segment about the toe of the skate. It can be concluded that the mechanics of the first strokes of a sprint differ considerably from the mechanics of strokes later on. The first push-offs take place against fixed location on the ice. In these "running-like" push-offs the contribution of Vr in the forward direction is larger than the extension component Ve. Later on, the strokes are characterized by a gliding push-off in which Ve increases. In these gliding push-offs no direct relation exists between forward velocity of the skater and the extension in the joints. This allows skaters to obtain much higher velocities than can be obtained during running.

Acceleration↗
PubMed1994

Longitudinal development of young talented speed skaters: physiological and anthropometric aspects.

A longitudinal analysis of a group of speed skaters was done to identify the performance-determining factors for a successful speed skating career. This paper presents both the physiological and anthropometric results of this longitudinal study. Twenty-four athletes from the Dutch National Junior Speed Skating Team were followed from age 16-17 yr to age 20-21 yr. During the development from junior to senior speed skater, a number of anthropometric and physiological variables changed. There were no differences between successful and unsuccessful speed skaters from an anthropometric perspective; consequently, it was not possible to distinguish successful from unsuccessful athletes on anthropometric grounds. The longitudinal data showed that at a younger age the successful speed skaters had similar oxygen consumption, mechanical efficiency, and power output values compared with the unsuccessful speed skaters. Later in the study, successful speed skaters distinguished themselves by the ability to produce higher power output values. There were no anthropometric or physiological relationships found in this study on which performance at the age of 20-21 yr could be predicted with measurements at a junior age.

Adolescent↗
PubMed1994

Optimisation of sprinting performance in running, cycling and speed skating.

Sprinting performances rely strongly on a fast acceleration at the start of a sprint and on the capacity to maintain a high velocity in the phase following the start. Simulations based on a model developed in which the generation of metabolic power is related to the mechanical destinations of power showed that for short-lasting sprinting events, the best pacing strategy is an all out effort, even if this strategy causes a strong reduction of the velocity at the end of the race. Even pacing strategies should only be used in exercises lasting longer than 80 to 100 seconds. Sprint runners, speed skaters and cyclists need a large rate of breakdown of energy rich phosphates in the first 4 to 5 seconds of the race (mechanical equivalent > 20 W/kg) in order to accelerate their body, and a power output of more than 10 W/kg in the phase following the start to maintain a high velocity. Maximal speed in running is mainly limited by the necessity to rotate the legs forwards and backwards relative to the hip joint. The acceleration phase, however, relies on powerful extensions of all leg joints. Through a comparison of the hindlimb design of highly specialised animal sprinters (as can be found among predators) and of long distance animal runners (as found among hoofed animals), it is illustrated that these 2 phases of a sprint rely on conflicting requirements: improvement of maximal speed would require lower moments of inertia of the legs whereas a faster acceleration would require the involvement of more muscle mass (not only of the hip and knee extensors but also of the plantar flexors). Maximal speed in cycling and speed skating is not limited by the necessity to move leg segments but rather on air friction and rolling or ice friction. Since the drag coefficients found for speed skaters and cyclists (about 0.8) are considerably higher than those of more streamlined bodies, much progress can still be expected from the reduction of air friction. Speed skaters and especially cyclists show much smaller accelerations during the start than do sprint runners. Skaters might try to improve their very first push off by developing a start technique that allows a much more horizontally directed propulsive force. The small propulsive force at the onset of a cycling sprint is due to the gearing system.(ABSTRACT TRUNCATED AT 400 WORDS)

Acceleration↗
PubMed1993

The influence of the biarticularity of the gastrocnemius muscle on vertical-jumping achievement.

Hypotheses concerning the influence of changes in the design of the human musculoskeletal system on performance cannot be tested experimentally. Computer modelling and simulation provide a research methodology that does allow manipulation of the system's design. In the present study this methodology was used to test a recently formulated hypothesis concerning the role of the biarticularity of the gastrocnemius muscle (GAS) in vertical jumping [Bobbert and van Ingen Schenau, J. Biomechanics 21, 249-262 (1988)]. This was done by comparing maximal jump heights for a model equipped with biarticular GAS with a model equipped with a monoarticular GAS. It was found that jump height decreased by 10 mm when GAS was changed into a monoarticular muscle. Thus, the hypothesis formulated by Bobbert was substantiated, although quantitatively the effect is small. Our result differs from that of Pandy and Zajac [J. Biomechanics 24, 1-10 (1991)], who performed similar model calculations. It is shown that the results described by these authors can be explained from the moment-arm-joint-angle relation of GAS at the knee in their model.

Ankle Joint↗
PubMed1993

The global design of the hindlimb in quadrupeds.

In the hindlimb of quadrupeds three major segments can be distinguished which can rotate with respect to each other in the hip, knee and ankle joints. Movements in a sagittal plane appear to be controlled by three sets of antagonistic mono-articular muscle groups (one set per joint) and two sets of antagonistic bi-articular muscles. This design allows co-activations of mono-articular agonists and their bi-articular antagonists. These co-contractions occur for example in ballistic tasks such as jumping where the transfer of angular acceleration in the joints into the translational acceleration of the hip decreases as a function of joint extension. Well-trained humans appear to solve this problem by a distinct proximodistal sequence in the timing of the joint extensions and a transport of energy via bi-articular muscles. This can also be observed in a number of animals. A second example has to do with the necessity for a certain distribution of net moments in the joints which is required to control the direction and magnitude of the external force on the ground. The control of these moments can to a large extent be judged as a requirement which is independent of the joint displacements required in the same task. Many walking, running or pulling tasks, for example, require knee extension combined with a net knee flexing moment. Co-activation of mono-articular agonists and their bi-articular antagonists appear to solve these problems in an effective and efficient way.

Animals↗
PubMed1993

Function of mono- and biarticular muscles in running.

In this study the function of leg muscles during stretch-shortening cycles in fast running (6 m.s-1) was investigated. For a single stance phase, kinematics, ground reaction forces, and EMG were recorded. First, rough estimates of muscle force, obtained by shifting the EMG curves +90 ms, were correlated with origin-to-insertion velocity (VOI). Second, active state and internal muscle behavior were estimated by using a muscle model that was applied for soleus and gastrocnemius. High correlations were found between estimates of muscle force and VOI time curves for mono-articular hip, knee, and ankle extensor muscles. The correlation coefficients for biarticular muscles were low. The model results showed that active state of gastrocnemius was high during increase of origin-to-insertion length (LOI), whereas active state of soleus was low during the start of increase of LOI and rose to a plateau at the time lengthening ended and shortening started. It seems that the difference in stimulation between gastrocnemius and soleus is a compromise between minimizing energy dissipation and using the stretch-shortening cycle optimally. Furthermore, it was found that the net plantar flexion moment during running reached a value of 302 Nm, which was 158% and 127% higher than the peak values reached in maximal jump and sprint push-offs, respectively. It was argued that the higher mechanical output in running than in jumping could be ascribed to the utilization of the stretch-shortening cycle in running. The higher values in running compared with sprinting, however, may lie in a difference in muscle stimulation.

Adult↗
PubMed1992

Supramaximal cycle tests do not detect seasonal progression in performance in groups of elite speed skaters.

Seven female and eight male elite junior skaters performed cycle ergometer tests at four different times during the 1987/1988 season. The tests consisted of a Wingate-type 30-s sprint test and a 2.5-min supramaximal test. The subjects were tested in February, May and September 1987 and in January 1988. Maximal oxygen consumption was measured during the 2.5-min test. With the exception of the maximal oxygen consumption of the women in May which was about 6% lower than in the other three tests, no seasonal changes in the test results could be observed--this, in spite of a distinct increase in training volume (from 10 to more than 20 h.week-1) and training intensity in the course of the season. When the test data were compared to those of elite senior skaters, it appeared that the junior skaters showed the same values for mean power output during the sprint test [14.2 (SD 0.4) W.kg-1 for the men and 12.6 (SD 0.5) W.kg-1 for the women] and maximal oxygen consumption [63.1 (SD 2.8) ml.kg-1.min-1 for the men and 55.3 (SD 3.5) ml.kg-1.min-1 for the women, respectively] as found for senior skaters. It seemed, therefore, that the effects of training in these skaters had already levelled off in the period before they participated in this investigation. In contrast to previous studies, no relationship could be shown between the test results and skating performance. This was most likely due to the homogenous character of the groups (mean standard deviations in power and oxygen consumption were only 5%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Intermuscular coordination in a sprint push-off.

This study was designed to investigate the patterns of intermuscular coordination during a sprinting event. In previous research it was found that despite the indeterminacy problem of movement control, movements like vertical jumping, speed skating and cycling are performed in a stereotyped manner. It was hypothesized that this might be due to constraints associated with the transformation of joint rotations into the desired translation. The objective of the present study was to determine the extent to which the intermuscular coordination patterns during other movements also are performed in a stereotyped manner and, if that is true, whether this can be understood on the basis of such constraints. Seven elite sprint runners were instructed to execute an explosive sprinting dash. Ground reaction forces and cinematographic data were recorded for the second stance phase of the sprint. Simultaneously, electromyographic activity of nine leg muscles was recorded telemetrically. Linked-segment modeling was used to obtain net joint moments and net joint powers. Different athletes appeared to perform the sprint in a stereotyped manner. The muscle coordination pattern is characterized by a proximo to distal sequence in timing of the monoarticular muscles. When compared to the sequential pattern found in jumping, the biarticular hamstrings and rectus femoris muscles behave differently; in the sprint a more pronounced reciprocal activity between these muscles exists. The resulting movement pattern is characterized by a sequence of upper leg extension and plantar flexion. The observed sequence in timing of muscle activation patterns is aimed at solving the problems associated with the earlier identified geometrical and anatomical constraint. However, the coordination pattern cannot be fully understood on the basis of these constraints. A specific constraint is identified with respect to the direction of the ground reaction force, which explains the pronounced reciprocal activity of the biarticular hamstring and rectus femoris muscles. The intermuscular coordination pattern in the sprint can be seen as a compromise between the specific requirement of the sprint and the advantageous effect of a proximo to distal sequence as found previously for jumping.

Adult↗
PubMed1992

SPACAR: a software subroutine package for simulation of the behavior of biomechanical systems.

Direct dynamics computer simulation is gaining importance as a research tool in the biomechanical study of complex human movements. Therefore, the need for general-purpose software packages with which the equations of motion can be derived automatically and solved numerically is growing. In this paper such a method is described: SPACAR. The method is compared to well-known commercially available software packages. On the basis of the results obtained on a test problem simulated with both SPACAR and DADS, it is concluded that both methods are accurate; DADS is much faster. The user-friendliness of SPACAR is less than that of DADS. However, SPACAR has two major advantages. First is the basic deformability of all elements, which allows handling of all kinds of problems within a unified framework; second is the full availability of the source code, which allows the experienced user to broaden the scope of possibilities to any extent.

Biomechanical Phenomena↗
PubMed1992

Ice friction during speed skating.

During speed skating, the external power output delivered by the athlete is predominantly used to overcome the air and ice frictional forces. Special skates were developed and used to measure the ice frictional forces during actual speed skating. The mean coefficients of friction for the straights and curves were, respectively, 0.0046 and 0.0059. The minimum value of the coefficient of ice friction was measured at an ice surface temperature of about -7 degrees C. It was found that the coefficient of friction increases with increasing speed. In the literature, it is suggested that the relatively low friction in skating results from a thin film of liquid water on the ice surface. Theories about the presence of water between the rubbing surfaces are focused on the formation of water by pressure-melting, melting due to frictional heating and on the 'liquid-like' properties of the ice surface. From our measurements and calculations, it is concluded that the liquid-like surface properties of ice seem to be a reasonable explanation for the low friction during speed skating.

Biomechanical Phenomena↗