The present study demonstrates that MAI is characterised by impairments of ankle-joint control in close-to-injury situations. This could make these individuals more prone to recurrent ankle sprains, and suggests the need for additional mechanical support such as braces or even surgery. In addition, the study highlights the fact that dynamic experimental test conditions in the acting participant are needed to further unravel the mystery of chronic ankle instability.
IntroductionOsteoarthritis of the knee affects millions of people. Elastic knee sleeves aim at relieving symptoms. While symptomatic improvements have been demonstrated as a consequence of elastic knee sleeves, evidence for biomechanical alterations only exists for the sagittal plane. We therefore asked what effect an elastic knee sleeve would have on frontal plane gait biomechanics.Methods18 subjects (8 women, 10 men) with osteoarthritis of the medial tibiofemoral joint walked over ground with and without an elastic knee sleeve. Kinematics and forces were recorded and joint moments were calculated using an inverse dynamics approach. Conditions with sleeve and without sleeve were compared with paired t-Tests.ResultsWith the sleeve, knee adduction angle at ground contact was reduced by 1.9±2.1° (P = 0.006). Peak knee adduction was reduced by 1.5±1.6° (P = 0.004). The first peak knee adduction moment and positive knee adduction impulse were decreased by 10.1% (0.74±0.9 Nm•kg-1; P = 0.002) and 12.9% (0.28±0.3 Nm•s•kg-1; P < 0.004), respectively.ConclusionOur study provides evidence that wearing an elastic knee sleeve during walking can reduce knee adduction angles, moments and impulse in subjects with knee osteoarthritis. As a higher knee adduction moment has previously been identified as a risk factor for disease progression in patients with medial knee osteoarthritis, we speculate that wearing a knee sleeve may be beneficial for this specific subgroup.
The new system allows reactive jumps that are rather comparable to natural jumps. Therefore, the new SJS seems to be an adequate system in order to examine the SSC under controlled and almost natural conditions.
The classical stretch shortening cycle (SSC) describes sagittal joint flexion-extensions in motions like running or hopping. However, lateral movements are integral components of team sports and are associated with frontal plane joint displacements. The purpose of this study is to identify neuromuscular and kinematical mechanisms determining motor control and performance of reactive laterally conducted SSCs. Lateral jumps were performed from four distances in order to investigate the influence of lateral stretch loads on the lower extremity. Electromyographic (EMG) data of nine lower extremity muscles were collected. Foot, ankle, knee, and hip kinematics were recorded by 3-D motion analysis. High stretch loads were characterized by a greater foot exorotation during the initial phase of contact. In the sagittal plane knee and hip joint, displacements increased, whereas in the frontal plane only the hip joint displacement was significantly raised. In particular, frontal peak joint moments increased with stretch load. Thigh muscles' mean pre-activity amplitude was enhanced. It was possible to detect stretch reflexes in the thigh muscles, whereas in particular the short-latency reflex (SLR) was stretch load-dependently modulated. The results of the present study suggest that the foot exorotation seems to play a decisive role in the movement control of lateral jumps. The association between exorotation and increased sagittal joint displacements may be seen as a compensation strategy to shift load from the frontal to the sagittal plane. Lateral load compensation seems to strongly depend on upper leg's kinematic and neuromuscular adjustments, rather than on the ankle joint complex.
The aim of this study was to determine possible influences, including data processing and sport-specific demands, on the validity of acceleration measures by an inertial measurement unit (IMU) in indoor environments. IMU outputs were compared to a three-dimensional (3D) motion analysis (MA) system and processed with two sensor fusion algorithms (Kalman filter, KF; Complementary filter, CF) at temporal resolutions of 100, 10, and 5 Hz. Athletes performed six team sport-specific movements whilst wearing a single IMU. Mean and peak acceleration magnitudes were analyzed. Over all trials (n = 1093), KF data overestimated MA resultant acceleration by 0.42 ± 0.31 m∙s−2 for mean and 4.18 ± 3.68 m∙s−2 for peak values, while CF processing showed errors of up to 0.57 ± 0.41 m∙s−2 and −2.31 ± 2.25 m∙s−2, respectively. Resampling to 5 Hz decreased the absolute error by about 14% for mean and 56% for peak values. Still, higher acceleration magnitudes led to a large increase in error. These results indicate that IMUs can be used for assessing accelerations in indoor team sports with acceptable means. Application of a CF and resampling to 5 Hz is recommended. High-acceleration magnitudes impair validity to a large degree and should be interpreted with caution.
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