scholarly journals Asymmetries in Ground Reaction Forces During Turns by Elite Slalom Alpine Skiers Are Not Related to Asymmetries in Muscular Strength

2021 ◽  
Vol 12 ◽  
Author(s):  
Jan Ogrin ◽  
Nejc Šarabon ◽  
Mads Kjær Madsen ◽  
Uwe Kersting ◽  
Hans-Christer Holmberg ◽  
...  
Keyword(s):  
Muscular Strength ◽  
Satellite System ◽  
The Body ◽  
Ground Reaction Forces ◽  
Alpine Skiing ◽  
Reaction Forces ◽  
Left And Right ◽  
Alpine Skiers ◽  
Global Navigation Satellite ◽  
Right Turns

The ground reaction forces (GRF) associated with competitive alpine skiing, which are relatively large, might be asymmetric during left and right turns due to asymmetries in the strength of the legs and torso and the present investigation was designed to evaluate this possibility. While skiing a symmetrical, 20-gate slalom course, the asymmetries of 9 elite alpine skiers were calculated on the basis of measurements provided by inertial motion units (IMU), a Global Navigation Satellite System and pressure insoles. In addition, specialized dynamometers were utilized to assess potential asymmetry in the strength of their legs and torso in the laboratory. In total, seven variables related to GRF were assessed on-snow and eight related to strength of the legs and torso in the laboratory. The asymmetries in these parameters between left and right turns on snow were expressed in terms of the symmetry (SI) and Jaccard indices (JI), while the asymmetries between the left and right sides of the body in the case of the laboratory measurements were expressed as the SIs. The three hypotheses to be tested were examined using multivariable regression models. Our findings resulted in rejection of all three hypotheses: The asymmetries in total GRF (H1), as well as in the GRF acting on the inside and outside legs (H2) and on the rear- and forefeet GRF (H3) during left and right turns were not associated with asymmetries in parameters related to muscular strength. Nevertheless, this group of elite slalom skiers exhibited significant asymmetry between their right and left legs with respect to MVC during ankle flexion (0.53 ± 0.06 versus 0.60 ± 0.07 Nm/kg, respectively) and hip extension (2.68 ± 0.39 versus 2.17 ± 0.26 Nm/kg), as well as with respect to the GRFs on the inside leg while skiing (66.8 ± 7.39 versus 76.0 ± 10.0 %BW). As indicated by the JI values, there were also large asymmetries related to GRF as measured by pressure insoles (range: 42.7–56.0%). In conclusion, inter-limb asymmetries in GRFs during elite alpine skiing are not related to corresponding asymmetries in muscular strength. Although our elite athletes exhibited relatively small inter-limb asymmetries in strength, their asymmetries in GRF on-snow were relatively large.

scholarly journals Asymmetries in the Technique and Ground Reaction Forces of Elite Alpine Skiers Influence Their Slalom Performance

2020 ◽  
Vol 10 (20) ◽  
pp. 7288
Author(s):  
Matej Supej ◽  
Jan Ogrin ◽  
Nejc Šarabon ◽  
Hans-Christer Holmberg
Keyword(s):  
Three Dimensional ◽  
Ground Reaction Forces ◽  
Performance Variables ◽  
Reaction Forces ◽  
Multivariable Regression ◽  
Turn Radius ◽  
Alpine Skiers ◽  
Global Navigation Satellite ◽  
Hip Flexion ◽  
Multivariable Regression Models

Background: Although many of the movements of skiers are asymmetric, little is presently known about how such asymmetry influences performance. Here, our aim was to examine whether asymmetries in technique and the ground reaction forces associated with left and right turns influence the asymmetries in the performance of elite slalom skiers. Methods: As nine elite skiers completed a 20-gate slalom course, their three-dimensional full-body kinematics and ground reaction forces (GRF) were monitored with a global navigation satellite and inertial motion capture systems, in combination with pressure insoles. For multivariable regression models, 26 predictor skiing techniques and GRF variables and 8 predicted skiing performance variables were assessed, all of them determining asymmetries in terms of symmetry and Jaccard indices. Results: Asymmetries in instantaneous and sectional performance were found to have the largest predictor coefficients associated with asymmetries in shank angle and hip flexion of the outside leg. Asymmetry for turn radius had the largest predictor coefficients associated with asymmetries in shank angle and GRF on the entire outside foot. Conclusions: Although slalom skiers were found to move their bodies in a quite symmetrical fashion, asymmetry in their skiing technique and GRF influenced variables related to asymmetries in performance.

scholarly journals Ground Reaction Forces during Vertical Hops Are Correlated with the Number of Supervised Physiotherapy Visits after Achilles Tendon Surgery

2021 ◽  
Vol 10 (22) ◽  
pp. 5299
Author(s):  
Łukasz Sikorski ◽  
Andrzej Czamara
Keyword(s):  
Achilles Tendon ◽  
Study Groups ◽  
The Body ◽  
Ground Reaction Forces ◽  
Group I ◽  
Tendon Surgery ◽  
Reaction Forces ◽  
Number Of Visits ◽  
Group Ii ◽  
The Right

The objective of this study was to assess the effectiveness of, and the correlation between, an average of 42 supervised physiotherapy (SVPh) visits for the vertical ground reaction forces component (vGRF) using ankle hops during two- and one-legged vertical hops (TLH and OLH, respectively), six months after the surgical suturing of the Achilles tendon using the open method (SSATOM) via Keesler’s technique. Hypothesis: Six months of supervised physiotherapy with a higher number of visits (SPHNVs) was positively correlated with higher vGRF values during TLH and OLH. Group I comprised male patients (n = 23) after SSATOM (SVPh x = 42 visits), and Group II comprised males (n = 23) without Achilles tendon injuries. In the study groups, vGRF was measured during TLH and OLH in the landing phase using two force plates. The vGRF was normalized to the body mass. The limb symmetry index (LSI) of vGRF values was calculated. The ranges of motion of the foot and circumferences of the ankle joint and shin were measured. Then, 10 m unassisted walking, the Thompson test, and pain were assessed. A parametric test for dependent and independent samples, ANOVA and Tukey’s test for between-group comparisons, and linear Pearson’s correlation coefficient calculations were performed. Group I revealed significantly lower vGRF values during TLH and OLH for the operated limb and LSI values compared with the right and left legs in Group II (p ≤ 0.001). A larger number of visits correlates with higher vGRF values for the operated limb during TLH (r = 0.503; p = 0.014) and OLH (r = 0.505; p = 0.014). An average of 42 SVPh visits in 6 months was insufficient to obtain similar values of relative vGRF and their LSI during TLH and OLH, but the hypothesis was confirmed that SPHNVs correlate with higher relative vGRF values during TLH and OLH in the landing phase.

Twisting and Bending: The Functional Role of Salamander Lateral Hypaxial Musculature During Locomotion

2001 ◽  
Vol 204 (11) ◽  
pp. 1979-1989 ◽  
Author(s):  
Wallace O. Bennett ◽  
Rachel S. Simons ◽  
Elizabeth L. Brainerd
Keyword(s):  
High Intensity ◽  
High Speed ◽  
The Body ◽  
Transversus Abdominis ◽  
Fine Motor ◽  
Emg Activity ◽  
Ground Reaction Forces ◽  
Terrestrial Locomotion ◽  
Reaction Forces ◽  
Hypaxial Muscle

SUMMARY The function of the lateral hypaxial muscles during locomotion in tetrapods is controversial. Currently, there are two hypotheses of lateral hypaxial muscle function. The first, supported by electromyographic (EMG) data from a lizard (Iguana iguana) and a salamander (Dicamptodon ensatus), suggests that hypaxial muscles function to bend the body during swimming and to resist long-axis torsion during walking. The second, supported by EMG data from lizards during relatively high-speed locomotion, suggests that these muscles function primarily to bend the body during locomotion, not to resist torsional forces. To determine whether the results from D. ensatus hold for another salamander, we recorded lateral hypaxial muscle EMGs synchronized with body and limb kinematics in the tiger salamander Ambystoma tigrinum. In agreement with results from aquatic locomotion in D. ensatus, all four layers of lateral hypaxial musculature were found to show synchronous EMG activity during swimming in A. tigrinum. Our findings for terrestrial locomotion also agree with previous results from D. ensatus and support the torsion resistance hypothesis for terrestrial locomotion. We observed asynchronous EMG bursts of relatively high intensity in the lateral and medial pairs of hypaxial muscles during walking in tiger salamanders (we call these ‘α-bursts’). We infer from this pattern that the more lateral two layers of oblique hypaxial musculature, Mm. obliquus externus superficialis (OES) and obliquus externus profundus (OEP), are active on the side towards which the trunk is bending, while the more medial two layers, Mm. obliquus internus (OI) and transversus abdominis (TA), are active on the opposite side. This result is consistent with the hypothesis proposed for D. ensatus that the OES and OEP generate torsional moments to counteract ground reaction forces generated by forelimb support, while the OI and TA generate torsional moments to counteract ground reaction forces from hindlimb support. However, unlike the EMG pattern reported for D. ensatus, a second, lower-intensity burst of EMG activity (‘β-burst’) was sometimes recorded from the lateral hypaxial muscles in A. tigrinum. As seen in other muscle systems, these β-bursts of hypaxial muscle coactivation may function to provide fine motor control during locomotion. The presence of asynchronous, relatively high-intensity α-bursts indicates that the lateral hypaxial muscles generate torsional moments during terrestrial locomotion, but it is possible that the balance of forces from both α- and β-bursts may allow the lateral hypaxial muscles to contribute to lateral bending of the body as well.

Rotating horizontal ground reaction forces to the body path of progression

2007 ◽  
Vol 40 (15) ◽  
pp. 3527-3532 ◽  
Author(s):  
Brian C. Glaister ◽  
Michael S. Orendurff ◽  
Jason A. Schoen ◽  
Glenn K. Klute
Keyword(s):  
The Body ◽  
Ground Reaction Forces ◽  
Reaction Forces

Acceleration and balance in trotting dogs

1999 ◽  
Vol 202 (24) ◽  
pp. 3565-3573 ◽  
Author(s):  
D.V. Lee ◽  
J.E. Bertram ◽  
R.J. Todhunter
Keyword(s):  
Body Weight ◽  
Steady State ◽  
The Body ◽  
Ground Reaction Forces ◽  
Pitching Moment ◽  
Acceleration And Deceleration ◽  
Reaction Forces ◽  
Force Time

During quadrupedal trotting, diagonal pairs of limbs are set down in unison and exert forces on the ground simultaneously. Ground-reaction forces on individual limbs of trotting dogs were measured separately using a series of four force platforms. Vertical and fore-aft impulses were determined for each limb from the force/time recordings. When mean fore-aft acceleration of the body was zero in a given trotting step (steady state), the fraction of vertical impulse on the forelimb was equal to the fraction of body weight supported by the forelimbs during standing (approximately 60 %). When dogs accelerated or decelerated during a trotting step, the vertical impulse was redistributed to the hindlimb or forelimb, respectively. This redistribution of the vertical impulse is due to a moment exerted about the pitch axis of the body by fore-aft accelerating and decelerating forces. Vertical forces exerted by the forelimb and hindlimb resist this pitching moment, providing stability during fore-aft acceleration and deceleration.

scholarly journals The Effect of Different Global Navigation Satellite System Methods on Positioning Accuracy in Elite Alpine Skiing

Sensors ◽  
2014 ◽  
Vol 14 (10) ◽  
pp. 18433-18453 ◽  
Author(s):  
Matthias Gilgien ◽  
Jörg Spörri ◽  
Philippe Limpach ◽  
Alain Geiger ◽  
Erich Müller
Keyword(s):  
Global Navigation Satellite System ◽  
Satellite System ◽  
Navigation Satellite ◽  
Alpine Skiing ◽  
Positioning Accuracy ◽  
Global Navigation ◽  
Global Navigation Satellite

Motion planning and implementation for the self-recovery of an overturned multi-legged robot

Robotica ◽  
2015 ◽  
Vol 35 (5) ◽  
pp. 1107-1120 ◽  
Author(s):  
Saijin Peng ◽  
Xilun Ding ◽  
Fan Yang ◽  
Kun Xu
Keyword(s):  
Motion Planning ◽  
The Body ◽  
The Self ◽  
Legged Robots ◽  
Ground Reaction Forces ◽  
Robot Design ◽  
Legged Robot ◽  
Reaction Forces ◽  
Recovery Approach ◽  
And Control

SUMMARYThis paper first presents a method of motion planning and implementation for the self-recovery of an overturned six-legged robot. Previous studies aimed at the static and dynamic stabilization of robots for preventing them from overturning. However, no one can guarantee that an overturn accident will not occur during various applications of robots. Therefore, the problems involving overturning should be considered and solved during robot design and control. The design inspirations of multi-legged robots come from nature, especially insects and mammals. In addition, the self-recovery approach of an insect could also be imitated by robots. In this paper, such a self-recovery mechanism is reported. The inertial forces of the dangling legs are used to bias some legs to touch the ground, and the ground reaction forces exerted on the feet of landing legs are achieved to support and push the body to enable recovery without additional help. By employing the mechanism, a self-recovery approach named SSR (Sidewise-Self-Recovery) is presented and applied to multi-legged robots. Experiments of NOROS are performed to validate the effectiveness of the self-recovery motions. The results show that the SSR is a suitable method for multi-legged robots and that the hemisphere shell of robots can help them to perform self-recovery.

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