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Biomedical subjects

A Stacoff

Publications and source records attributed to A Stacoff.

At least 19 recordsLinked to original sources
PubMed2000

Tibiocalcaneal kinematics of barefoot versus shod running.

Barefoot running kinematics has been described to vary considerably from shod running. However, previous investigations were typically based on externally mounted shoe and/or skin markers, which have been shown to overestimate skeletal movements. Thus, the purpose of this study was to compare calcaneal and tibial movements of barefoot versus shod running using skeletal markers. Intracortical bone pins with reflective marker triads were inserted under standard local anesthetic into the calcaneus and tibia of five healthy male subjects. The subjects ran barefoot, with a normal shoe, with three shoe soles and two orthotic modifications. The three-dimensional tibiocalcaneal rotations were determined using a joint coordinate system approach. Test variables were defined for eversion and tibial rotation. The results showed that the differences in bone movements between barefoot and shod running were small and unsystematic (mean effects being less than 2 degrees ) compared with the differences between the subjects (up to 10 degrees ). However, differences may occur during midstance when extreme shoe modifications (i.e. posterior orthosis) are used. It is concluded that calcaneal and tibial movement patterns do not differ substantially between barefoot and shod running, and that the effects of these interventions are subject specific. The result of this in vivo study contrasts with previous investigations using skin and shoe mounted markers and suggests that these discrepancies may be the result of the overestimation with externally mounted markers.

Adult↗
PubMed2000

Effects of foot orthoses on skeletal motion during running.

OBJECTIVE: To quantify the effects of medial foot orthoses on skeletal movements of the calcaneus and tibia during the stance phase in running. DESIGN: Kinematic effects of medial foot orthoses (anterior, posterior, no support) were tested using skeletal (and shoe) markers at the calcaneus and tibia. BACKGROUND: Previous studies using shoe and skin markers concluded that medially placed orthoses control/reduce foot eversion and tibial rotation. However, it is currently unknown if such orthoses also affect skeletal motion at the lower extremities. METHODS: Intracortical Hofman pins with reflective marker triads were inserted under standard local anesthetic into the calcaneus and tibia of five healthy male subjects. The three-dimensional tibiocalcaneal rotations were determined using a joint coordinate system approach. Eversion (skeletal and shoe) and tibial rotation were calculated to study the foot orthoses effects. RESULTS: Orthotic effects on eversion and tibial rotations were found to be small and unsystematic over all subjects. Differences between the subjects were significantly larger (p<0.01; up to 10 degrees ) than between the orthotic conditions (1-4 degrees ). Significant orthotic effects across subjects were found only for total internal tibial rotation; p<0.05). CONCLUSIONS: This in vivo study showed that medially placed foot orthoses did not change tibiocalcaneal movement patterns substantially during the stance phase of running. RELEVANCE: Orthoses may have only small kinematic effects on the calcaneus and tibia (measured with bone pins) as well as on the shoes (measured with shoe markers) during running of normal subjects. Present results showed that orthotic effects were subject specific and unsystematic across conditions. It is speculated that orthotic effects during the stance phase of running may be mechanical as well as proprioceptive.

Adult↗
PubMed2000

Movement coupling at the ankle during the stance phase of running.

The purpose of this study was to quantify movement coupling at the ankle during the stance phase of running using bone-mounted markers. Intracortical bone pins with reflective marker triads were inserted under standard local anaesthesia into the calcaneus and the tibia of five healthy male subjects. The three-dimensional rotations were determined using a joint coordinate system approach. Movement coupling was observed in all test subjects and occurred in phases with considerable individual differences. Between the shoe and the calcaneus coupling increased after midstance which suggested that the test shoes provided more coupling for inversion than for eversion. Movement coupling between calcaneus and tibia was higher in the first phase (from heel strike to midstance) compared with the second phase (from midstance to take-off). This finding is in contrast to previous in-vitro studies but may be explained by the higher vertical loads of the present in-vivo study. Thus, movement coupling measured at the bone level changed throughout the stance phase of running and was found to be far more complex than a simple mitered joint or universal joint model.

Adult↗
PubMed1997

[Sports medicine and rehabilitation. Surface and footwear].

Load on the human body can be influenced by shoes and surfaces which is important both in sports and rehabilitation. The loading which can primarily be influenced are impact situations and friction as well as the stability of the foot. This stability is of main interest in the prevention of pain and injury. However, a certain amount of loading is necessary to improve strength and structure of biological materials. In the past, the development of shoe and surface materials has hardly been perceived under this aspect, but may be increasingly important in the future.

Athletic Injuries↗
PubMed1996

Lateral stability in sideward cutting movements.

Sideward cutting movements occur frequently in sports activities, such as basketball, soccer, and tennis. These activities show a high incidence of injuries to the lateral aspect of the ankle. Consequently, the lateral stability of sport shoes seems important. The purpose of this study was to show the effect of different shoe sole properties (hardness, thickness, torsional stiffness) and designs on the lateral stability during sideward cutting movements. A film analysis was conducted including 12 subjects performing a cutting movement barefoot and with five different pairs of shoes each filmed in the frontal plane. A standard film analysis was conducted; for the statistical analysis, various parameters such as the range of motion in inversion and the angular velocity of the rearfoot were used. The results showed a large difference between the barefoot and shod conditions with respect to the lateral stability. Two shoes performed significantly better (P < 0.05) than the others with a decreased inversion movement and less slipping inside the shoe. The two shoes differed mainly in the shoe sole design (hollow inner core) and the upper (high-cut). It is concluded that lateral stability may be improved by altering the properties and design of the shoe sole as well as the upper.

Adult↗
PubMed1994

Influence of hip and knee joint angles on excitation of knee extensor muscles.

The purpose of this study was to test if (and how) maximal excitation of the knee extensor muscles rectus femoris (RF), vastus lateralis (VL) and vastus medialis (VM) is influenced by knee and/or hip joint angles. Excitation was quantified using surface electromyography. Isometric knee extensions were performed at systematically varying knee and hip joint configurations using a strength testing machine. The results indicate that excitation of the one-joint knee extensor muscles (VL and VM) depends systematically on hip joint angles. In particular, excitation levels are higher at hip joint angles of 90 degrees (sitting) and 180 degrees (lying) compared to intermediate hip joint angles (112 degrees, 135 degrees, 157 degrees). Furthermore, it was found that excitation of all knee extensor muscles tested is higher near full knee extension (170 degrees) compared to an intermediate knee joint angle (130 degrees). Since knee extensor moments are much smaller at knee joint angles of 170 degrees compared to those at 130 degrees, it is speculated that the high excitation observed near full knee extension constitutes a neurophysiological compensation mechanism for the reduced force production ability of the muscles at this joint configuration.

Adult↗
PubMed1993

[Control of the rear foot in lateral movements in sports].

The goals of this investigation were to establish the frequency distribution of different movements in various ball sports (1) and to test the influence of altered shoe sole constructions on the stability in lateral breaking movements (2). Firstly, a video analysis was carried out to establish the frequency distribution of different movements in sporting activities such as volleyball, basketball, team handball and football (soccer). It is shown that a selected number of lateral cutting movements can represent more than half of all movements observed in one of the sporting activities. For part 2 an investigation with three systematically varied shoes was undertaken. The results show that with altered shoe sole constructions (torsion and change of shape of the shoe-sole) the supination movement with shoes comes close to the barefoot values. In respect of abduction/adduction of the foot the systematic changes of the shoe soles had no measurable influence.

Adult↗
PubMed1993

[Cushioning versus stability].

Cushioning and stability are still key words for functionally constructed sport shoes. The goal of this investigation is to present and discuss the possibilities and limits of these shoe properties. Here, stability is not regarded as rigidity (like in a ski boot), but as a "dynamic stability" in the sense of functionality which supports the foot under load in such a manner that no unphysiological movements are provoked. Cushioning (in physics terminology: "damping") is defined to reduce and eliminate (kinetic) energy. When considering the impact peak in running, this peak can be reduced by using hard shoe soles with large heel flares. However, by doing that, large levers are introduced which produce an increased distance to decelerate the touchdown. This is basically the opposite of dynamic stability. Current shoe sole materials (homogeneous/isotropic) improve the "cushioning" but enhance the instability. New ways of shoe construction using more sophisticated anisotropic materials may lead out of this dichotomy.

Computer Simulation↗
PubMed1993

[Biomechanical and orthopedic problems of tennis and indoor sports shoe].

In contrast to running, a large number of indoor sports show a variety of body and foot movements with fast changes of direction. These "stop-and-go" movements (including jumps and rotations) produce loads at the joints of the foot, knee and hip in an order of magnitude often underestimated. The goal of this investigation was to provide an overview over various indoor sports movements and to draw conclusions with respect to sport shoe constructions. Reconsideration of the functionality of the foot led to shoe constructions which allow the shoe to rotate about its longitudinal axis (torsion), a movement with which the forefoot can again "reach" for the ground in landing situations. However, the problem of the rear foot stability and cushioning at a rear foot touch down is not yet solved. Therefore it must be postulated that shoes for indoor sports and tennis should be provided with an increased lateral stability at the rear foot.

Athletic Injuries↗
PubMed1993

[External stabilizers for the foot].

The stability in the lateral direction is particularly important in indoor sports as well as tennis, where the frequency of injury at the lateral aspect of the ankle is considerably high (according to various sources between 20-30%). The goal of the present work was to discuss the reasons of instability at the ankle and the effect of external stabilizers. In a number of investigations the stability was measured via film analysis during sports activities in barefoot and shoe conditions. It was concluded that stability and blocking of a movement cannot be regarded as equal. The latter restricts necessary movements of the foot at the ankle and may also provoke large internal forces elsewhere. Negative in respect to stability are stiff and thick shoe soles, positive are: the torsional ability of the sole, softness of the shoe sole edge, the link between the shaft and the sole, shaft height, taping and bracing.

Ankle Injuries↗
PubMed1992

Heel movement within a court shoe.

Lateral movements of the leg and foot were filmed from behind to evaluate court shoes. Inversion/eversion may be an indicator of potential injuries, but estimates of actual inversion/eversion have typically been measured as the angular displacement of marker pairs on the lower leg and on the shoe. The purpose of this study was to measure the shoe movement versus the heel movement inside the shoe in order to determine the appropriateness of using shoe markers to represent the heel position. Two windows were cut into the heel counter of the shoe to show the heel position in addition to shoe position. The subjects were filmed from behind during a lateral side-stepping movement. The difference between the shoe and heel position was [corrected] statistically significant. The average maximum change in heel inversion inside the shoe was 13.3 +/- 3.8 degrees, compared with 30.7 +/- 6.2 degrees for the shoe. In addition, the maximum change in heel inversion in a barefoot movement was 10.1 +/- 3.1 degrees. The results suggest that for a lateral movement shoe markers do not accurately represent the position of the heel, and heel movement inside a shoe is similar to a barefoot movement. Skin markers on the heel as observed through windows in the shoe give a better indication of the actual position of the calcaneus than do markers placed directly on the shoe.

Adult↗
PubMed1992

[Biomechanical considerations of the load on the ankle joint].

The biomechanical approach to the characteristics of load on the ankle joint and the surrounding structures allows a better understanding of the cause and effect of externally acting forces in human movement (walking, running, jumping). This detailed understanding of the mechanics involved (not only in the functional anatomical sense) makes preventive measures possible that can reduce the risk of distortion at the ankle. With the same mechanical models, clinically applicable methods allow biomechanically monitored rehabilitation. The case studies reported here illustrate that therapeutic success can be measured objectively, leading to improvement in therapy and in the ability to make decisions in the clinical environment.

Achilles Tendon↗
PubMed1992

The movement of the heel within a running shoe.

Most running shoe investigations have used the same standard procedure for the evaluation of the shoes: the runners are filmed from behind and a film analysis is carried out digitizing markers at the heel counter of the shoe and on the lower leg. The angular displacement of these markers relative to the horizontal or the vertical is assumed to be an indicator for various sports injuries. The goal of this investigation was to measure the movement of the heel counter as well as the movement of the heel inside the shoe. First, the influence of the size of different heel counter windows was controlled and found negligible for the test conditions of this study. Second, 15 subjects performed the following procedure: running (a) barefoot, (b) with shoes with windows, and (c) without windows. Overall, the heel was found to move similarly but not identically to the heel counter. The maximum change of pronation was (a) 13.7 +/- 3.7 degrees, barefoot; (b) 14.1 +/- 3.8 degrees for the shoe with windows and 12.1 +/- 3.7 degrees for the heel inside these shoes; and 14.9 +/- 4.2 degrees for the shoes with no windows. To achieve a general impression of a shoe in the sense of a qualitative description, the previous method without heel counter windows still seems adequate. However, for a detailed analysis of quantitative nature, it is important to use the method with heel counter windows.

Adult↗
PubMed1991

[Load and stress of musculature. Some considerations from the mechanical viewpoint].

Injuries in the musculature belong to the most frequent injuries in sports. However, the various explanations regarding the reasons which lead to these problems differ considerably. In this work the muscle is simplified from a mechanical point of view and then explanations are derived in respect to possible origins of muscle injuries. The terms stress and distribution of stress are important in material science to describe the strength of a material. The same is true for the human body, for a muscle fibre or for an entire muscle. Due to its anatomical construction, the distribution of stress in the muscle is very inhomogeneous. It can be very large, even if the acting load is quite small. The most critical movements which lead to muscle injuries are fast, passive elongations of a muscle. The larger the rate of this elongation, the higher the risk of injury. These theoretical conclusions can also be supported by observations in everyday life. For example, muscle pain after exercise occurs almost exclusively after excentric loading.

Athletic Injuries↗
PubMed1991

The effects of shoes on the torsion and rearfoot motion in running.

Excessive pronation is accepted as a good indicator for various running injuries. The least amount of pronation takes place when running barefoot. The latest investigations show that this is connected to a large torsional movement between forefoot and rearfoot which can be influenced by the shoe sole construction. The shoes which are in use among runners in track and field are basically of two types, running shoes (in general torsionally stiff) and spikes (torsionally flexible). The possibly varying effect of these shoes on the shoe/foot motion in running is not known. The purpose of this investigation was therefore to show whether the pronation angle and the torsion angle differ when running barefoot, with spikes, and with running shoes (forefoot touchdown, N = 9 left and right). A film analysis provided the angular movements of the lower leg, rearfoot, and forefoot as well as pronation and torsion in the frontal plane. The results show that at touchdown the torsional movements with both shoe types are quite different from those of running barefoot. With shoes, the torsion angle is reduced back to zero--with running shoes more than with spikes--and the pronation angle is increased beyond the barefoot values (P less than 0.01). In order to reduce the risk of injury, both shoe types should be improved--the running shoes with respect to torsion and the spikes with respect to pronation.

Achilles Tendon↗
PubMed1988

[Running injuries and running shoe construction: demonstration of possible correlations].

Previous investigations about the running shoe design demonstrated a relationship between the geometry of the shoe sole, the ground reaction forces and the foot movements during impact. Thus, the question arised in which way this relationship would influence the internal forces. The purpose of this investigation was to model the impact situation and to simulate different sole geometries in order to calculate the internal forces and the pronation velocity. The results show that the geometry has a small effect upon the joint forces, but a very high effect on the pronation velocity. As a consequence, the joint forces changed only by 10% or less, but the load of the structures which are stressed by pronation is increased up to 200%. Thus, the control of the initial pronation is much more important in current running shoe design than the shock-absorption.

Ankle Injuries↗
PubMed1982

[Sports show support inlays. A biomechanical comparison of three different types of arch support (author's transl)].

The effect of three different types of support inlays for sports shoes was investigated in the basis of measurements made on 37 athletes who use such shoes in their daily training. The date were obtained from force measurements (repulsion force on the ground) and with the aid of films. The investigation showed that there was no difference in the average values of the three types of support (loose inlay, glued-in inlay and support permanently attached to the shoe). All the supports reduced medial bending at the ankle joint. None of them caused a reduction medial bending at the ankle joint. None of them caused a reduction of repulsion forces when the foot came into contact with the support. In propulsion, all the supports caused an increase in the lateral outturn of the foot. The scatter range in the measurements obtained with the loose inlay was greater; a connection was found between this and the possibility of the foot slipping in the shoe.

Biomechanical Phenomena↗