Gerda Strutzenberger

Effect of brace design on patients with ACL-ruptures.

Different designs of functional knee braces for ACL-injury rehabilitation exist. In addition to the mechanical stabilization provided by rigid shell braces, sleeve braces also address proprioceptive mechanisms, but little is known if this leads to benefits for ACL-deficient subjects. Therefore the aim of this study was to investigate the effect of 2 different functional brace designs (shell and sleeve brace) on functional achievements in ACL-deficient patients. 28 subjects with ACL-ruptured knees performed tests for knee joint laxity, joint position sense, static and dynamic balance and isometric and dynamic lower limb extension strength in non-braced, sleeve braced and shell braced condition. The results showed a significant decrease in knee joint laxity for sleeve (33%; p<0.001) and rigid shell bracing (14%, p=0.039). The sleeve brace revealed a significant increase in dynamic balance after perturbation (20%; p=0.024) and a significant increase in dynamic lower limb peak rate of force development (17%; p=0.015) compared to the non-braced condition. The effects might be caused by the flexible area of support and the incorporated mechanisms to address proprioceptive aspects. Braces might not be needed in simple daily life tasks, but could provide beneficial support in more dynamic settings when patients return to sporting activities after an ACL-injury.

Effects of age, sex and activity level on counter-movement jump performance in children and adolescents

Abstract The aim of this study was to investigate counter-movement jump performance and its reliability in children and adolescents with respect to age, sex and activity level. We tested 1835 children and adolescents aged between 4 and 17 years. All participants performed three counter-movement jumps on a force platform with arms akimbo. The participants were divided into six age groups and subdivided by sex within each group, to analyse age and sex effects. Subsequently, jumping performance of active and sedentary participants was compared. Jump height was calculated and the highest jump out of three was used for the calculations of peak force and peak rate of force development. Variability of all parameters was quantified using the coefficient of variation over all jumps. Jump height increased significantly with increasing age while peak rate of force development decreased. Peak force was similar for all age groups. Jump height was significantly higher in male participants and peak force and peak rate of force development was significantly lower in male participants. Variability of jump height and peak force decreased significantly with increasing age leading to reliable data above the age of 10 years. Peak rate of force development showed a high variability and, therefore, should be interpreted with caution. This could be useful information for coaches as they need to know from which age onwards the counter-movement jump is applicable in performance diagnostics and which parameters are sensible for interpretation. Finally, the present study provides data to be used as normative references.

Sprint start kinetics of amputee and non-amputee sprinters

The purpose of this study was to explore the relationship between the forces applied to the starting blocks and the start performances (SPs) of amputee sprinters (ASs) and non-amputee sprinters (NASs). SPs of 154 male and female NASs (100-m personal records [PRs], 9.58–14.00 s) and 7 male ASs (3 unilateral above knee, 3 unilateral below knee, 1 bilateral below knee; 100 m PRs, 11.70–12.70 s) with running specific prostheses (RSPs) were analysed during full-effort sprint starts using instrumented starting blocks that measured the applied forces in 3D. Using the NAS dataset and a combination of factor analysis and multiple regression techniques, we explored the relationship between force characteristics and SP (quantified by normalized average horizontal block power). Start kinetics were subsequently compared between ASs and NASs who were matched based on their absolute 100 m PR and their 100 m PR relative to the world record in their starting class. In NASs, 86% of the variance in SP was shared with five latent factors on which measured parameters related to force application to the rear and front blocks and the respective push-off directions in the sagittal plane of motion were loaded. Mediolateral force application had little influence on SP. The SP of ASs was significantly reduced compared to that of NASs matched on the basis of relative 100-m PR (−33.8%; d = 2.11, p < 0.001), while a non-significant performance reduction was observed when absolute 100-m PRs were used (−17.7%; d = 0.79, p = 0.09). These results are at least partially explained by the fact that force application to the rear block was clearly impaired in the affected legs of ASs.

Effect of chainring ovality on joint power during cycling at different workloads and cadences.

Non-circular chainrings theoretically enhance cycling performance by increasing effective chainring diameter and varying crank velocity, but research has failed to consistently reproduce the benefits in cycling trials. The aim of this study was (1) to investigate the effect of different chainring shapes on sagittal knee joint moment and sagittal lower limb joint powers and (2) to investigate whether alterations are affected by cadence and workload. Fourteen elite cyclists cycled in six conditions (70, 90 and 110 rpm, each at 180 and 300 W), for 2 min each, using three chainrings of different ovalities (1.0–1.215). Kinematic data and pedal forces were collected. For most conditions, only the chainring with the highest ovality (1.215) was characterised by smaller sagittal knee joint moments, smaller relative sagittal knee joint power contribution and larger relative sagittal hip joint power contribution, which suggests a change from maximising efficiency to maximising power production. Effect sizes increased with higher cadences, but not with higher workload. This study has application for athletes, clinicians and sports equipment industry as a non-circular chainring can change joint-specific power generation and decrease knee joint moment, but certain ovality seems to be necessary to provoke this effect.

Lower limb joint work and joint work contribution during downhill and uphill walking at different inclinations

Work performance and individual joint contribution to total work are important information for creating training protocols, but were not assessed so far for sloped walking. Therefore, the purpose of this study was to analyze lower limb joint work and joint contribution of the hip, knee and ankle to total lower limb work during sloped walking in a healthy population. Eighteen male participants (27.0±4.7yrs, 1.80±0.05m, 74.5±8.2kg) walked on an instrumented ramp at inclination angles of 0°, ±6°, ±12° and ±18° at 1.1m/s. Kinematic and kinetic data were captured using a motion-capture system (Vicon) and two force plates (AMTI). Joint power curves, joint work (positive, negative, absolute) and each joints contribution to total lower limb work were analyzed throughout the stance phase using an ANOVA with repeated measures. With increasing inclination positive joint work increased for the ankle and hip joint and in total during uphill walking. Negative joint work increased for each joint and in total work during downhill walking. Absolute work was increased during both uphill (all joints) and downhill (ankle & knee) walking. Knee joint contribution to total negative and absolute work increased during downhill walking while hip and ankle contributions decreased. This study identified, that, when switching from level to a 6° and from 6° to a 12° inclination the gain of individual joint work is more pronounced compared to switching from 12° to an 18° inclination. The results might be used for training recommendations and specific training intervention with respect to sloped walking.

Biomechanical and metabolic effects of a leaf spring structured midsole in heel–toe running

Purpose: The purpose of this study was to investigate effects of a novel leaf spring midsole construction on biomechanical variables affecting running economy. The midsole construction is designed to exploit the directionality of the ground reaction force to shift the shoe anteriorly during the stance phase in running. Methods: Nine male long-distance runners ran 5 min on a treadmill (3 m s−1) with two types of shoes: a leaf spring structured midsole shoe and a standard reference shoe with a standard ethylene vinyl acetate foam midsole. Runner and shoe kinematics were analysed using a three-dimensional motion capture system, and oxygen cost was measured by an open circuit breath-by-breath spirometer. Group differences for all variables were tested using paired t-tests (p < 0.05). Results: The leaf spring structured midsole shoe significantly increased the anterior shift of the foot by 8 ± 4 mm (p = 0.001) during stance leading to an increased stride length (1%; p = 0.044), while oxygen cost (2%; p = 0.031) and stride rate (1%; p = 0.039) were significantly reduced compared to the reference shoe. Conclusion: It is concluded that the leaf spring structured midsole contributes to a more economic running style in heel–toe running at moderate running speeds.

Static and dynamic evaluation of a pedal system for measuring three-dimensional forces in cycling

The purpose of this study was to determine the accuracy of a newly developed pedal system (JA:Ped3) for measuring three-dimensional pedal forces in laboratory conditions in cycling. Three-dimensional force measurements were obtained using 12 strain gauges in each pedal, and the pedal angle was measured with a rotary potentiometer mounted on the pedal axle. The pedal forces were validated in a static condition by comparing a range of known forces and in dynamic conditions using the JA:Ped3 with the data collected simultaneously by two commercially available systems, SRM Powermeter and PowerForce. An incremental cycling test was performed with seven elite cyclists. In the static measurements, JA:Ped3 showed an average deviation of <2% and the maximum absolute error did not exceed 4.2 N. In the dynamic measurements, JA:Ped3-calculated pedal torque and power output yielded similar values to the corresponding data from the SRM Powermeter and showed an average deviation of <3%. Using the JA:Ped3 in a laboratory setting for testing, elite cyclists revealed plausible results. The pedal is lightweight and data transmission could be implemented to offer a device for laboratory and field measurements. This pedal would be specifically helpful for cyclists, coaches, therapists and scientists.

Does an inverted pendulum model accurately represent the gait of individuals with unilateral transfemoral amputation while walking over level ground

Background: An inverted pendulum model represents the mechanical function of able-bodied individuals walking accurately, with centre of mass height and forward velocity data plotting as sinusoidal curves, 180° out of phase. Objectives: This study investigated whether the inverted pendulum model represented level gait in individuals with a unilateral transfemoral amputation. Study Design: Controlled trial. Methods: Kinematic and kinetic data from 10 individuals with unilateral transfemoral amputation and 15 able-bodied participants were recorded during level walking. Results: During level walking, the inverted pendulum model described able-bodied gait well throughout the gait cycle, with median relative time shifts between centre of mass height and velocity maxima and minima between 1.2% and 1.8% of gait cycle. In the group with unilateral transfemoral amputation, the relative time shift was significantly increased during the prosthetic-limb initial double-limb support phase by 6.3%. Conclusion: The gait of individuals with unilateral transfemoral amputation shows deviation from a synchronous inverted pendulum model during prosthetic-limb stance. The reported divergence may help explain such individuals’ increased metabolic cost of gait. Temporal divergence of inverted pendulum behaviour could potentially be utilised as a tool to assess the efficacy of prosthetic device prescription. Clinical relevance The size of the relative time shifts between centre of mass height and velocity maxima and minima could potentially be used as a tool to quantify the efficacy of innovative prosthetic device design features aimed at reducing the metabolic cost of walking and improving gait efficiency in individuals with amputation.

Joint moments during downhill and uphill walking of a person with transfemoral amputation with a hydraulic articulating and a rigid prosthetic ankle—a case study

Introduction Functional characteristics of prosthetic ankle design may facilitate sloped walking for individuals with transfemoral (TF) amputation. The aim of the current case study was to analyze the effects of a rigid versus a hydraulically articulating ankle component on the biological joint moments of an individual with TF amputation during downhill, uphill, and level walking. Materials and Methods The gait of one individual with unilateral TF amputation, using the same prosthetic foot with rigid and hydraulic ankle components, was analyzed and compared with a control group of 18 able-bodied participants. Kinematic and kinetic data were recorded at self-selected walking speed on a sloped ramp with inclinations of −12°, −4° (downhill), 0° (level), +4°, and +12° (uphill). Results The slope influenced lower-limb joint moments similarly in both the able-bodied participants and the participant with unilateral TF amputation. The effect of altering ankle movement through exchanging prosthetic ankle componentry was most acutely seen at the hip joint of the residual limb. The use of a hydraulic ankle joint component resulted in decreased mean hip joint extension and flexion moments of up to 92% and 48%, respectively, in the residual limb when compared with the use of the rigid ankle joint component. Conclusions During sloped walking, the use of a hydraulically articulating versus rigid ankle joint component reduced the joint moments observed at the hip joint of the residual limb in an individual with unilateral TF amputation. This indicates a benefit for persons with TF amputation as the increased ankle function reduces the moment producing requirements of the hip joint, which may result in decreased energy consumption and subsequently a more efficient gait.

Technique selection in young female gymnasts: elbow and wrist joint loading during the cartwheel and round-off

Abstract Biophysical loading of the elbow and wrist is a potential reason for chronic lesions in gymnastics and present a real concern for coaches, scientist and clinicians. Previous research has identified injury risk factors during round-off (RO) skills in elite female gymnasts. The aim of this study was to investigate key elbow and wrist joint injury risk factors during different techniques of fundamental cartwheel (CW) and RO skills performed by young female artistic gymnasts. Seventeen active young female gymnasts performed 30 successful trials of both CW and RO from a hurdle step with three different hand positions (parallel (10), T-shape (10) and reverse (10)). Synchronised kinematic (240 Hz) and kinetic (1200 Hz) data were collected for each trial. One-way repeated measures ANOVA and effect size (ES) were used for statistical analysis. The results showed statistically significant differences (P < .05) and large ES (>0.8) among hand positions for peak vertical ground reaction force (VGRF), peak elbow compression force, peak wrist compression force, elbow internal adduction moment and wrist dorsiflexion angle. In conclusion, the parallel and reverse techniques increase peak VGRF, elbow and wrist compression forces, and elbow internal adduction moment. These differences indicate that the parallel and reverse techniques may increase the potential of elbow and wrist injuries in young gymnasts compared with the T-shape technique; this is of particular importance with the high frequency of the performance of these fundamental skills.