Dominic Gehring

Gender and fatigue have influence on knee joint control strategies during landing

BACKGROUND Gender and fatigue are thought to affect the anterior cruciate ligament injury risk. In spite of much effort, the influence of these factors on knee joint biomechanics is still under discussion. The purpose of this study was to investigate kinematics, kinetics, and active muscle control strategies of the knee joint across gender in fatigue conditions during a landing task. METHODS Thirteen females and thirteen males performed two-legged landings before and after a closed kinetic chain exercise protocol. Knee joint kinematics and vertical ground reaction forces were assessed as well as electromyography of the quadriceps, hamstring, and gastrocnemius muscles. FINDINGS Females landed with increased knee flexion velocities (P<0.001) and knee joint abduction angles (P<0.01). Compared to males, females also showed different muscle activation patterns such as a delayed activation of the lateral hamstring (P<0.05) and the m. vastus lateralis (P<0.05) during the preparatory phase of the landing. Fatigue led to a reduced pre-activation of the medial and lateral hamstrings (P<0.05 and P<0.001) and the gastrocnemius muscle (P<0.05) both in males and females. INTERPRETATION The gender differences in knee flexion velocity, abduction angle, and muscle activation suggest that females and males possess different neuromuscular strategies to control the knee joint during dynamic landing movements. These differences as well as decreased hamstring and gastrocnemius muscle activity, due to fatigue, provide evidence for different knee joint control in females as well as in fatigued conditions.

How to sprain your ankle - a biomechanical case report of an inversion trauma.

In order to develop preventive measures against lateral ankle sprains, it is essential to have a detailed understanding of the injury mechanism. Under laboratory experimental conditions the examination of the joint load has to be restricted with clear margins of safety. However, in the present case one athlete sprained his ankle while performing a run-and-cut movement during a biomechanical research experiment. 3D kinematics, kinetics, and muscle activity of the lower limb were recorded and compared to 16 previously performed trials. Motion patterns of global pelvis orientation, hip flexion, and knee flexion in the sprain trail deviated from the reference trials already early in the preparatory phase before ground contact. During ground contact, the ankle was rapidly plantar flexed (up to 1240°/s), inverted (up to 1290°/s) and internally rotated (up to 580°/s) reaching its maximum displacement within the first 150 ms after heel strike. Rapid neuromuscular activation bursts of the m. tibialis anterior and the m. peroneus longus started 40-45 ms after ground contact and overshot the activation profile of the reference trials with peak activation at 62 ms and 74 ms respectively. Therefore, it may be suggested that neuromuscular reflexes played an important role in joint control during the critical phase of excessive ankle displacement. The results of this case report clearly indicate that (a) upper leg mechanics, (b) pre-landing adjustments, and (c) neuromuscular contribution have to be considered in the mechanism of lateral ankle sprains.

Load-dependent movement regulation of lateral stretch shortening cycle jumps.

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.

A new sledge jump system that allows almost natural reactive jumps

AIM Sledge jump systems (SJS) are often employed to examine the underlying mechanical and neuromuscular mechanisms of the stretch-shortening cycle (SSC) as they allow the systematic variation of impact velocity and energy. However, in existing SJS the jumps are not very comparable to natural jumps because of the long contact times (∼200%), which prevent the storage of kinetic energy. The aim of the present study was to evaluate if an ultra-light sledge, built in a way that joint movement is barely restricted, allows jumps that are comparable to natural jumps. METHODS Ground reaction forces, kinematic and electromyographic (EMG) data of 21 healthy subjects were compared between normal hoppings (NH) on the ground and hoppings in a custom-built SJS (sledge hoppings, SH). RESULTS Normalized to NH, the ground contact times for the SH were prolonged (+22%), while the peak forces (-21%) and the preactivity of the soleus and gastrocnemius medialis muscles were reduced (-20% and -22%, respectively). No significant changes were observed for the iEMG of the short latency response of those muscles (+1% and +8%) and the ranges of motion in the ankle, knee and hip joint (differences of 1, 1 and 2 degrees). The reduced peak forces were associated with a reduced leg stiffness (-21%). CONCLUSION 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.

Mechanical instability destabilises the ankle joint directly in the ankle-sprain mechanism

Background Despite massive research efforts, it remains unclear how mechanical ankle instability (MAI) and functional ankle instability (FAI) affect joint control in the situation of ankle sprain. Thus, the purpose of this study was to evaluate whether individuals with MAI have deficits in stabilising their ankle joint in a close-to-injury situation compared with those with FAI and healthy controls. Methods Ankle-joint control was assessed by means of three-dimensional motion analysis and electromyography in participants with FAI and MAI (n=19), in participants with pure FAI (n=9) and in healthy controls (n=18). Close-to-injury situations were simulated during standing, walking and jumping by means of a custom-made tilt platform. Results Individuals with FAI and MAI displayed significantly greater maximum ankle inversion angles (+5°) and inversion velocities (+50°/s) in the walking and jumping conditions compared to those with pure FAI and controls. Furthermore, individuals in the FAI and MAI group showed a significantly decreased pre-activation of the peroneus longus muscle during jumping compared to those with FAI. No differences between groups were found for plantar flexion and internal rotation, or for muscle activities following tilting of the platform. Conclusions 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.

Task-specific initial impact phase adjustments in lateral jumps and lateral landings.

Load-dependant adjustments in lateral jumps are thought to rely on foot placement and on upper leg’s kinematic and neuromuscular adaptations. The aim of this study was to elucidate task-specific adjustments during the initial impact phase under varying stretch-loads by the comparison of lateral jumps and lateral landings. Ten subjects performed lateral jumps and landings from four distances. Electromyographic (EMG) data of five lower extremity muscles were measured, whilst lower extremity kinematics and kinetics were analysed by 3D motion analysis. Lateral jumps were characterized by increased impact forces, higher lower extremity joint moments with exception of the initial knee abduction moment, greater sagittal knee and hip joint displacements, and a further exorotated foot placement. In lateral landings frontal ankle and hip joint displacements were greater. Thigh muscle and m. tibialis anterior (TA) pre-activity as well as initial post-impact EMG were higher in lateral jumps than in lateral landings, whilst during the reflex-induced phase thigh and shank muscle EMG, except for TA, were enhanced in lateral jumps. From these findings it can be concluded that task specificity in lateral jumps in contrast to lateral landings impedes a stretch-load adequate modulation of initial impact forces which particularly affects ankle joint loading. Foot placement seems to play a decisive role for limiting lateral ankle and medial knee joint loading. Therefore, in sports containing high-impact frontal plane movements a special emphasis in training routines should be paid to foot placement strategy in those movements. Such training interventions might contribute to injury prevention in lateral movements.

Anticipatory postural adjustments during cutting manoeuvres in football and their consequences for knee injury risk

Abstract Anticipatory postural adjustments (APAs), i.e. preparatory positioning of the head, the trunk and the foot, are essential to initiate cutting manoeuvres during football games. The aim of the present study was to determine how APA strategies during cutting manoeuvres are influenced by a reduction of the time available to prepare the movement. Thirteen football players performed different cutting tasks, with directions of cutting either known prior to the task or indicated by a light signal occurring 850, 600 or 500 ms before ground contact. With less time available to prepare the cutting manoeuvre, the head was less orientated towards the cutting direction (P = 0.033) and the trunk was even more rotated in the opposite direction (P = 0.002), while the foot placement was not significantly influenced. Moreover, the induced higher lateral trunk flexion correlated with the increased knee abduction moment (r = 0.41; P = 0.009). Increasing lateral trunk flexion is the main strategy used to successfully perform a cutting manoeuvre when less time is available to prepare the movement. However, higher lateral trunk flexion was associated with an increased knee abduction moment and therefore an increased knee injury risk. Reducing lateral trunk flexion during cutting manoeuvres should be part of training programs seeking the optimisation of APAs.

Knee and hip joint biomechanics are gender-specific in runners with high running mileage.

Female runners are reported to be more prone to develop specific knee joint injuries than males. It has been suggested that increased frontal plane joint loading might be related to the incidence of these knee injuries in running. The purpose of this study was to evaluate if frontal plane knee and hip joint kinematics and kinetics are gender-specific in runners with high mileage. 3D-kinematics and kinetics were recorded from 16 female and 16 male runners at a speed of 3 m/s, 4 m/s, and 5 m/s. Frontal plane joint angles and joint moments were ascertained and compared between genders among speed conditions. Across all speed conditions, females showed increased hip adduction and reduced knee adduction angles compared to males (p < 0.003). The initial peak in the hip adduction moment was enhanced in females (p = 0.003). Additionally, the hip adduction impulse showed a trend towards an increase in females at slow running speed (p = 0.07). Hip and knee frontal plane joint kinematics are gender-specific. In addition, there are indications that frontal plane joint loading is increased in female runners. Future research should focus on the relationship of these observations regarding overuse running injuries.

Immediate Effects of an Elastic Knee Sleeve on Frontal Plane Gait Biomechanics in Knee Osteoarthritis

Introduction Osteoarthritis 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. Methods 18 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. Results With 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. Conclusion Our 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.

Jump performance and augmented feedback: Immediate benefits and long-term training effects

Drop jumps and their adaptations to training have been extensively investigated. However, the influence of augmented feedback (aF) on stretch-shortening cycle (SSC) was not scrutinized so far despite the well-known positive effects of aF on motor performance and motor learning. The aim of the present study was therefore to investigate the effects of aF by evaluating immediate within-session effects and long-term adaptations. 34 participants were assigned to three groups that trained drop jumps with different relative frequencies of aF about their jump height: 100%, 50%, or 0%. A significant within-session effect of aF on jump height was observed before and also after the training period (pre: +4.6%; post: +2.6%). In the long-term (comparing pre- to post-measurement), the 100% group showed the greatest increase in jump height (+14%), followed by the 50% (+10%) and the 0% group (+6%). The importance of aF on drop jumps is therefore twofold: (i) to immediately increase jump performance and (ii) to improve long-term training efficacy. In contrast to the proposition of the guidance hypothesis, high frequency of aF seems to be beneficial when maximizing SSC-performance. As jump height cannot be quantified without objective technical measures it is recommended to include them into daily training.