Ski-geometric parameters do not differ between ACL injury mechanisms in recreational alpine skiing

Purpose It is not known so far if ski-equipment-related factors differ between the ACL injury mechanisms, potentially influencing the circumstances and causes of falling, finally resulting in ACL injury. More specifically focusing on the injury mechanisms will provide a deeper understanding of injury causation. The aim of the study was to evaluate whether ACL injury mechanisms in recreational alpine skiing differ with regard to ski-geometric parameters, self-reported circumstances and causes of accident and injury severity. Methods Among a cohort of 392 ACL-injured (57.9% females) skiers, age, sex, height, weight, skill level, risk-taking behavior, circumstances and causes of accident, and ACL injury severity were collected by questionnaire. Additionally, patients had to recall their type of fall (ACL injury mechanism) by classifying forward and backward falls with and without body rotation. Ski length, side cut radius and widths of the tip, waist and tail were directly notated from the ski. Results The forward fall with body rotation was the most common reported ACL injury mechanism (63%). A riskier behavior was associated with forward falls without body rotation. Ski-geometric parameters did not significantly influence the type of ACL injury mechanism. Regarding accident characteristics, catching an edge of the ski was more frequent (p < 0.001) the cause for forward falls (75% and 67%) when compared to the backward falls (46 and 15%) and executing a turn was the most frequent action in all falls (39–68%). A complete rupture of the ACL (66–70%) was more commonly reported than a partial tear (30–34%) among all four non-contact ACL injury mechanisms (n.s.). Conclusion In contrast to risk-taking behavior and accident characteristics, ski-geometric parameters and injury severity do not significantly differ between ACL injury mechanisms in recreational skiing. Thus, an individual skiing style seems to have more impact on ACL injury mechanisms than ski equipment. Future studies should evaluate potential effects of ski geometry on the incidence of ACL injury. Level of evidence III.

EFFECTS OF WRIST GUARD AND ELBOW ARREST STRATEGY ON IMPACT FORCE IN FORWARD FALLS

Wrist guards are widely used for preventing distal radius fracture during in-line skating and snowboard-related activities. However, more than half of people wearing wrist guards nonetheless sustain a fracture of the wrist in forward falls. Accordingly, this study evaluates the effects of three factors, namely the wrist guard design, the fall height and the arrest strategy, on the impact force during a forward fall onto a single outstretched hand. Fifteen physically healthy male participants volunteered for the biomechanical investigation. None of the participants had a previous history of upper extremity injuries or disorders. A 1000[Formula: see text]Hz AMTI force plate was used to measure the ground reaction force (GRF) in forward falls performed using a self-built release system onto a single hand. The GRF and impact time were analyzed in terms of three factors, namely (1) the wrist guard design, including bare hand (BH), conventional wrist guard (WG), wrist guard pad on palm (WG+), and WG+ with no lower splint (WG[Formula: see text]; (2) the elbow arrest strategy, including elbow extended and elbow flexed; and (3) the fall height, including 4[Formula: see text]cm and 8[Formula: see text]cm. The impact force and loading rate significantly increased with an increasing fall height. However, the elbow flexed strategy attenuated the GRF peak force and delayed the point of peak impact force. The GRF in the WG, WG+ and WG− conditions was significantly lower than that in the BH condition. Overall, a lower fall height, a wrist guard with a compliant pad (WG+ or WG[Formula: see text], and an elbow flexed strategy reduced the impact force, delayed the peak impact force, and reduced the loading rate in forward falls.

Age-related differences in stair descent balance control: Are women more prone to falls than men?

Stair descent is one of the most common forms of daily locomotion and concurrently one of the most challenging and hazardous daily activities performed by older adults. Thus, sufficient attention should be devoted to this locomotion and to the factors that affect it. This study investigates gender and age-related differences in balance control during and after stair descent on a foam mat. Forty-seven older adults (70% women) and 38 young adults (58% women) performed a descent from one step onto a foam mat. Anteroposterior (AP) and mediolateral (ML) centre of pressure velocity (CoP) and standard deviation of the CoP sway were investigated during stair descent and restabilization. A two-way analysis of variance (ANOVA) revealed the main effects of age for the first 5 s of restabilization. Older women exhibited significantly higher values of CoP sway and velocity in both directions compared to the younger individuals (CoP SDAP5, 55%; CoP SDML5, 30%; CoP VAP5, 106%; CoP VML5, 75%). Men achieved significantly higher values of CoP sway and velocity only in the AP direction compared to their younger counterparts (CoP SDAP5, 50% and CoP VAP5, 79%). These findings suggest that with advancing age, men are at higher risk of forward falls, whereas women are at higher risk of forward and sideways falls.

IMMEDIATE EFFECT OF DIFFERENT FOREFOOT WEDGES ON STANDING STABILITY IN YOUNG ADULTS

The aim of this study was to investigate the immediate effect of wearing the functional insoles with different slopes of forefoot wedges on postural stability in young adults during quiet stance. In this study, the functional insole was composed of a forefoot wedge and a medial arch support. Twelve healthy young adults (six males and six females) participated. Each subject wore sneakers with and without functional insole and stood as still as possible on a force plate with feet together, arms by side and head facing ahead for 60[Formula: see text]s, while eyes open and eyes closed, respectively. The functional insole was applied in the random sequence of no insole, wearing insole with a medial arch and a four-degree forefoot wedge, as well as wearing insole with a medial arch and an eight-degree forefoot wedge. The sway areas as well as the maximal excursions of the center of pressure (COP) in anterior–posterior (AP) and medial–lateral (ML) directions were used to evaluate the static postural stability. During stance with feet together and eyes closed, the sway area and maximal excursion of the COP in the AP direction were significantly decreased when wearing an eight-degree forefoot wedge functional insole. Since the reduced displacements of the COP indicated better postural control, it was suggested that the functional insole with an eight-degree forefoot wedge and a medial arch support might be beneficial to improve the postural stability in patients with impaired balance control, especially for whom having high risk of forward falls.

Reliability of Impact Forces, Hip Angles and Velocities during Simulated Forward Falls Using a Novel Propelled Upper Limb Fall ARrest Impact System (PULARIS)

Previous forward fall simulation methods have provided good kinematic and kinetic data, but are limited in that they have started the falls from a stationary position and have primarily simulated uni-directional motion. Therefore, a novel Propelled Upper Limb fall ARest Impact System (PULARIS) was designed to address these issues during assessments of a variety of fall scenarios. The purpose of this study was to present PULARIS and evaluate its ability to impact the upper extremities of participants with repeatable velocities, hand forces and hip angles in postures and with vertical and horizontal motion consistent with forward fall arrest. PULARIS consists of four steel tubing crossbars in a scissor-like arrangement that ride on metal trolleys within c-channel tracks in the ceiling. Participants are suspended beneath PULARIS by the legs and torso in a prone position and propelled horizontally via a motor and chain drive until they are quick released, and then impact floor-mounted force platforms with both hands. PULARIS velocity, hip angles and velocities and impact hand forces of ten participants (five male, five female) were collected during three fall types (straight-arm, self-selected and bent-arm) and two fall heights (0.05 m and 0.10 m) to assess the reliability of the impact conditions provided by the system. PULARIS and participant hip velocities were found to be quite repeatable (mean ICC = 0.81) with small between trial errors (mean = 0.03 m/s). The ratio of horizontal to vertical hip velocity components (∼0.75) agreed well with previously reported data (0.70-0.80). Peak vertical hand impact forces were also found to be relatively consistent between trials with a mean ICC of 0.73 and mean between trial error of 13.4 N. Up to 83% of the horizontal hand impact forces displayed good to excellent reliability (ICC > 0.6) with small between trial differences. Finally, the ICCs for between trial hip angles were all classified as good to excellent. Overall, PULARIS is a reliable method and is appropriate for studying the response of the distal upper extremity to impact loading during non-stationary, multi-directional movements indicative of a forward fall. This system performed well at different fall heights, and allows for a variety of upper and lower extremity, and hip postures to be tested successfully in different landing scenarios consistent with elderly and sport-related falls.