Lower Limb Loading Research Articles

Anterior cruciate ligament rupture is associated with abnormal and asymmetrical lower limb loading during walking.

Anterior Cruciate Ligament (ACL) deficiency may result in abnormal lower limb loading with increased foot pronation. This study evaluated spatiotemporal parameters and plantar pressure distribution during walking in participants with and without an ACL rupture. Cross-sectional. Plantar pressure was measured in 42 unilateral ACL deficient (ACLD) participants and 32 healthy controls while walking barefoot. Spatiotemporal parameters, pressure distribution and center of pressure (CoP) during foot roll off were determined. Differences in spatiotemporal parameters and pressure distribution were analyzed using a Linear Mixed Model. CoP position was analyzed with one-way ANOVA. ACLD participants had a longer contact time and earlier forefoot contact compared to controls. The ACLD side showed a shorter contact time and a faster roll off toward the forefoot compared to the ACL intact side. Compared to controls, ACLD participants had increased pressure under the medioproximal side of the midfoot. Within ACLD participants, the ACLD side had decreased pressure under the heel and increased pressure under the forefoot. Foot pronation was not different between groups or within ACLD participants. CoP of the ACLD participants was significantly more toward the toes during initial contact and toward the heel during foot flat. Changes in lower limb loading during barefoot walking in ACLD participants are due to changes in roll off pattern, most likely in order to reduce anterior shear forces on the knee. Dynamic plantar pressure measurements may assist in evaluating and guiding interventions aimed at normalizing lower limb and knee biomechanics in ACL deficiency.

Asymmetrical Lower Extremity Loading Early After Anterior Cruciate Ligament Reconstruction Is a Significant Predictor of Asymmetrical Loading at the Time of Return to Sport.

The aim of this study was to examine whether asymmetrical lower limb loading early after anterior cruciate ligament reconstruction (1 mo) can predict asymmetrical lower limb loading at the time of return to sport (6 mos) and whether other early predictors as knee joint range of motion or maximal isometric strength affect this relationship. Ground reaction forces were measured during a sit-to-stand task 1 mo after anterior cruciate ligament reconstruction and a vertical countermovement jump 6 mos after anterior cruciate ligament reconstruction in 58 athletes. Other early postoperative measurements were knee joint range of motion (2 wks, 1 mo, and 2 mos after surgery) and maximal isometric strength of the knee extensor and flexor muscles (2 mos after surgery). Linear regression models were developed using side-to-side limb symmetry index (LSI) of countermovement jump as the dependent variable. LSI of sit-to-stand task 1 mo after surgery was a significant independent predictor of LSI of countermovement jump 6 mos after surgery. After accounting for deficits in knee joint range of motion and LSI of maximal isometric strength (ΔR² = 0.35, P < 0.01), LSI of sit-to-stand task predicted LSI of countermovement jump (ΔR² = 0.14 P < 0.01). Asymmetrical lower extremity loading 1 mo after anterior cruciate ligament reconstruction is an early predictor of asymmetrical lower extremity loading 6 mos after surgery.

Lower Limb Loading during Gait in Patients Long Period after Total Hip Arthroplasty Revision.

The aim of the study was to assess lower limb loading during walking after unilateral total hip arthroplasty (THA) revision. Twenty-three THA revision subjects (12 men, 11 women) were divided into three groups according to time since surgery as 1 to 6 years, 6 to 11 years, and over 11 years. Two force plates were used to measure the ground reaction force during the stance phase. On the operated limb, compared to nonoperated limb, we found lower first vertical peak in the group of 1 to 6 years after revision and lower propulsion peak in the group of 6 to 11 years since revision. In the group of 11 years since THA revision, no significant difference was found. With advancing years after surgery, the stance phase duration got reduced and propulsion peak increased in the operated limb; minimal vertical force decreased and the time of minimal vertical force increased in the nonoperated limb. The study findings suggest the tendency to a more gradual and safer weight acceptance on the operated limb during the first years after THA revision, followed by limitation of foot propulsion. Despite this fact, lower limb loading can be considered as symmetrical across the whole measured period.

Modelling and Analysis of Alternative “Tile to Tile” Attachment Mechanism Designs, for a Modular Plastic Tile Sports Surface Using FEA

A sports surface that encourages elastic deformation during contact in combined anterior-posterior and medial-lateral directions through a process of horizontal deformation and displacement, may result in reduced foot and lower limb loading. Research concluded that a modular plastic tile surface which permits a limited amount of horizontal displacement via the tile connections has the potential to attenuate more braking force in comparison to a typical homogenous sports surface and therefore reduce the risk of tissue overloading and potential injury. A system whereby a modular plastic tile surface could encourage a limited amount of multi-lateral horizontal displacement via the tile attachment mechanisms was therefore developed.During rapid changes in direction or while landing on a sports surface, forces are transmitted from the athlete into the sports floor. Energy is preserved in the surface as the floor deforms, with a component of this energy being dissipated as a result of the dampening characteristics of the materials used to construct the sports surface. The sports tile development process therefore required the realisation of a retaining clip system to hold the tiles in firm engagement. Each tile also had to be able to be easily pulled apart for disassembly purposes. The tiles used in the surface had to be able to move independently from each other, in order for the surface to be able to dissipate energy. A design method was therefore adopted which saw the development of a number of alternative attachment approaches which were analysed via the Finite Element Analysis (FEA) method.A design solution was developed through a combination of iterative design and finite element simulation, with the final solution encouraging horizontal elastic deformation during athlete to surface contact, as a result of horizontal displacement. The “tile to tile” interface is the most critical aspect of the new modular tile surface that has been developed, as this feature in addition to its unique octagonal and square tessellated tile configuration, combine to allow multi-lateral horizontal displacement in the surface, and therefore the potential to reduce horizontal braking forces.

Design and Development Process for a novel Technology Capable of Providing a New Breaking Force Attenuating Sports Surface

Lower limb loading rate is a major contributor to athletic injury because it represents the stress being absorbed by an athlete's lower limbs that makes them vulnerable to stress fractures, as well as knee and ankle joint injuries. This research therefore sought to identify a means by which lower limb loading rates could be reduced and therefore the risk of overloading injury reduced. A sports surface that encourages elastic deformation during contact in both the horizontal anterior-posterior direction and the horizontal medial-lateral direction through a process of horizontal deformation and displacement may result in reduced foot and limb loading. This surface should maximise horizontal energy attenuation in order to reduce the risk of injury while at the same time provide satisfactory energy return to avoid player fatigue.Effective product research and development methods centre on the ways in which the activities can be effectively planned, controlled and implemented. The process can be regarded as a sequence of activities and decisions which progress a problem solving process from the initial identification of the problem, through to a final implementable design solution. The process of design is fundamentally an iterative method, which comprises the articulation of the problem which is to be solved, collecting and codifying pertinent information, the divergent exploration of potential problem solutions, convergence towards a favourable solution, and finally, the detailed implementation and optimisation of the design solution.The creative process followed, has resulted in the design of a novel, and commercially improved modular plastic tile sports surface system. This has been realised through the development of an innovative, sustainable, shock attenuating tile and connector geometry, which aims to reduce braking forces on the sports surface to acceptable levels, and thus reduce the risk of athlete injury. This research is significant as currently no sports surface exists which specifically targets horizontal force reduction, as a means to reduce injury rates.

Does providing real-time augmented feedback affect the performance of repeated lower limb loading to exhaustion?

IntroductionThis study aimed to determine whether real-time augmented feedback influenced performance of single-leg hopping to volitional exhaustion. MethodsTwenty-seven healthy, male participants performed single-leg hopping (2.2Hz) with (visual and tactile feedback for a target hop height) or without feedback on a force plate. Repeated measures ANOVA were used to determine differences in vertical stiffness (k), duration of flight (tf) and loading (tl) and vertical height displacement during flight (zf) and loading (zl). A Friedman 2-way ANOVA was performed to compare the percentage of trials between conditions that were maintained at 2.2Hz±5%. Correlations were performed to determine if the effects were similar when providing tactile or visual feedback synchronously with the audible cue. ResultsAugmented feedback resulted in maintenance of the tf, zf and zl between the start and end of the trials compared to hopping with no feedback (p<0.01). With or without feedback there was no change in tl and k from start to end. Without feedback, 21 of 27 participants maintained >70% of total hops at 2.2±5% Hz and this was significantly lower (p=0.01) with tactile (13/27) and visual (15/27) feedback. There was a strong correlation between tactile and visual feedback for duration of hopping cycle (Spearman's r=0.74, p≤0.01). ConclusionFeedback was detrimental to being able to maintain hopping cadence in some participants while other participants were able to achieve the cadence and target hop height. This indicates variability in the ability to use real-time augmented feedback effectively.

Finite Element Analysis Of Large Deformation Of Articular Cartilage In Upper Ankle Joint Of Occupant In Military Vehicles During Explosion

AbstractThe paper presents the analysis of the load of lower limbs of occupants in the armoured military vehicle, which has been destroyed by detonation of the Improvised Explosive Device (IED) charge under the vehicle. A simplified model of the human lower limb focused on upper ankle joint was developed in order to determine the reaction forces in joints and load in particular segments during the blast load. The model of upper ankle joint, include a tibia and an ankle bone with corresponding articular cartilage, has been developed. An analysis of the stress distribution under the influence of forces applied at different angles to the biomechanical axis of a limb has been performed. We analyzed the case of the lower limb of a sitting man leaning his feet on the floor. It has been shown that during a foot pronation induced by a knee outward deviation, the axial load on the foot causes significantly greater tension in the tibia. At the same time it has been shown that within the medial malleolus, tensile stresses occur on the surface of the bone which may lead to fracture of the medial malleolus. It is a common case of injuries caused by loads on foot of passengers in armored vehicles during a mine or IED load under the vehicle. It was shown that the outward deviation of the knee increases the risk of the foot injury within the ankle joint.

Content Validity Index and Intra- and Inter-Rater Reliability of a New Muscle Strength/Endurance Test Battery for Swedish Soldiers.

The objective of this study was to examine the content validity of commonly used muscle performance tests in military personnel and to investigate the reliability of a proposed test battery. For the content validity investigation, thirty selected tests were those described in the literature and/or commonly used in the Nordic and North Atlantic Treaty Organization (NATO) countries. Nine selected experts rated, on a four-point Likert scale, the relevance of these tests in relation to five different work tasks: lifting, carrying equipment on the body or in the hands, climbing, and digging. Thereafter, a content validity index (CVI) was calculated for each work task. The result showed excellent CVI (≥0.78) for sixteen tests, which comprised of one or more of the military work tasks. Three of the tests; the functional lower-limb loading test (the Ranger test), dead-lift with kettlebells, and back extension, showed excellent content validity for four of the work tasks. For the development of a new muscle strength/endurance test battery, these three tests were further supplemented with two other tests, namely, the chins and side-bridge test. The inter-rater reliability was high (intraclass correlation coefficient, ICC2,1 0.99) for all five tests. The intra-rater reliability was good to high (ICC3,1 0.82–0.96) with an acceptable standard error of mean (SEM), except for the side-bridge test (SEM%>15). Thus, the final suggested test battery for a valid and reliable evaluation of soldiers’ muscle performance comprised the following four tests; the Ranger test, dead-lift with kettlebells, chins, and back extension test. The criterion-related validity of the test battery should be further evaluated for soldiers exposed to varying physical workload.

The epidemiology of symptomatic midfoot osteoarthritis in community-dwelling older adults: cross-sectional findings from the Clinical Assessment Study of the Foot.

IntroductionThe foot is largely overlooked in calls for better characterisation of clinical phenotypes in osteoarthritis (OA). Yet the midfoot complex in particular has the potential to provide important insights into OA pathogenesis given its central role in lower limb load transmission and alignment. Its recent inclusion in radiographic atlases has paved the way for international studies. In this UK study, we provide the first comprehensive account of the descriptive epidemiology of symptomatic midfoot OA.MethodsParticipants aged ≥50 years registered with four general practices were recruited via a mailed health survey (n = 5109 responders) and research clinic (n = 560 responders). Symptomatic midfoot OA was defined as midfoot pain in the last 4 weeks, combined with radiographic OA in one or more joints (1st and 2nd cuneometatarsal, navicular first cuneiform and talonavicular joints) graded from weight-bearing dorso-plantar and lateral radiographs using a validated atlas. Prevalence estimates, overall and stratified by age, gender, and socio-economic class, were derived using multiple imputation and weighted logistic regression. Associations between symptomatic midfoot OA and current body mass index, previous injury, history of high-heeled footwear, nodal interphalangeal joint OA and patterns of comorbidity were estimated using binary logistic regression. Healthcare use was summarised.ResultsSymptomatic midfoot OA was present in 12.0 % (95 % CI: 10.9, 13.2) of the population aged over 50 years. Higher occurrence was observed in females, adults aged over 75 years, and those in intermediate/routine occupational classes. Obesity, previous foot/ankle injury, and pain in other weight-loaded joints, but not high-heeled footwear or nodal interphalangeal joint OA, were associated with increased risk of symptomatic midfoot OA. Persons with symptomatic midfoot OA were also more likely to report multiple non-musculoskeletal comorbidities, including diabetes. In the previous 12 months, the proportions consulting a general practitioner, physiotherapist or podiatrist/chiropodist about foot pain were 46.2 %, 18.5 % and 47.9 % respectively. A total of 64.7 % had used oral analgesia in the past month for foot pain (36.1 % paracetamol, 31.9 % mild/moderate opioids, 27.7 % NSAIDs).ConclusionsOur study confirms that symptomatic OA frequently affects the midfoot. The patterns of associations are interpreted as being largely consistent with the role of mechanical factors in its pathogenesis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-015-0693-3) contains supplementary material, which is available to authorized users.

Anatomic landmarks facilitate predictable partial lower limb loading during aquatic weight bearing.

Anatomic landmarks facilitate predictable partial lower limb loading during aquatic weight bearing.

The effect of perceived LLD on lower limb load characteristics during early postoperative static standing in patients who underwent THA

Background: Many patients complain about Perceived LegLengthDiscrepancy (P-LLD) followingTHA, regardless of the degree of actual LLD evaluated by X-ray (XP-LLD). Purpose: To clarify the effect of P-LLD on lower limb load characteristics during early postoperative static standing following THA. Methods:The subjects of this studywere 15 unilateral hip osteoarthritis patients who underwent THA. The subjects’ P-LLD, lower limb load characteristics in a static standing position (operated side lower limb load ratio, pelvic inclination angle, trunk inclination angle, pelvis/trunk inclination angle, operated side hip adduction ROM, and operated side hip adduction moment), and patient characteristics (Operated side hip extension ROM, operated side hip abduction torque, pain, and satisfaction) were measured on day 7, 14, and 21 post-operation (POD7, 14, 21). Patients who felt a LLD of 0.5 cm or more were considered as having P-LLD. Subjects with an actual LLD of 0.5 cm or more were considered as having XP-LLD. In statistical analysis, subjects were divided into three groups on each measurement day: subjects with both XP-LLD and P-LLD (Group A), subjects with no XP-LLD but with P-LLD (Group B), and subjects with no XP-LLD and no P-LLD (Group C) and compared with each item. Results:Significant differenceswere observed in operated side lower limb load ratio and operated side hip adduction moment on POD7.Namely, the operated side lower limb load ratio was significantly lower in Group B compared to Group C, and the operated side hip adduction moment was lower in Groups A and B compared to Group C. The operated side hip adduction ROM was also more limited in Groups A and B compared to Group C, although the difference was not statistically significant (p= 0.082). A significant difference was observed in operated side hip adductionmoment on POD14 – the operated side hip adduction moment was lower in Groups A and B compared to Group C. The operated side lower limb load ratio was also lower in Groups A and B compared to Group C, although the difference was not statistically significant (p= 0.074). Significant differences were observed in pain and satisfaction on POD 21 – Group B had significantly stronger pain and lower levels of satisfaction than Group C. Conclusion(s): Subjects with P-LLD on POD7 find it difficult to create an adduction moment with load on the abducted operated side hip, and their adduction moment is also reduced as a result of the lower operated side lower limb load. Although there were improvements with respect to load on the abducted operated side hip on POD14, groups with P-LLD had reduced adduction moment as a result of their continued low operated side lower limb load. From results of POD21, sustained postoperative pain has an effect on the persistence of P-LLD, and the persistence of P-LLD also affects satisfaction during the early postoperative period. Implications: It was suggested that increasing the amount of load on the abducted operated side hip during static standing in the early postoperative period to promote creation of an adduction moment on the operated side hip can improve P-LLD.

Effects of resistance training in older women with knee osteoarthritis and total knee arthroplasty

OBJECTIVES:This study sought to analyze the effects of resistance training on functional performance, lower-limb loading distribution and balance in older women with total knee arthroplasty (TKA) and osteoarthritis (OA) in the contralateral knee. In addition, this older knee OA and TKA group (OKG) was compared to older (OG) and young women (YG) without musculoskeletal diseases who underwent the same resistance training program.METHODS:Twenty-three women divided into OKG (N = 7), OG (N = 8) and YG (N = 8) had their functional performance, lower-limb loading distribution and balance compared before and after 13 weeks of a twice-weekly progressive resistance training program.RESULTS:At baseline, the OKG showed lower functional performance and unilateral balance, and impaired lower-limb loading distribution compared to the OG and the YG (p<0.05). After resistance training, the OKG showed improvements in functional performance (∼13% in sit-to-stand and rising from the floor, ∼16% in stair-climbing and ∼23% in 6-minute walking (6 MW)), unilateral balance (∼72% and ∼78% in TKA and OA leg, respectively) and lower-limb loading distribution, which were greater than those observed in the OG and the YG. The OKG showed post-training 6 MW performance similar to that of the OG at baseline. Sit-to-stand performance and unilateral stand balance were further restored to post-training levels of the OG and to baseline levels of the YG.CONCLUSIONS:Resistance training partially restored functional, balance and lower-limb loading deficits in older women with TKA and OA in the contralateral knee. These results suggest that resistance training may be an important tool to counteract mobility impairments commonly found in this population.

Effects of Nordic walking and walking on spatiotemporal gait parameters and ground reaction force.

[Purpose] The purpose of this study was to investigate the effects of Nordic walking and walking on spatiotemporal gait parameters and ground reaction force. [Subjects] The subjects of this study were 30 young adult males, who were divided into a Nordic walking group of 15 subjects and a walking group of 15 subjects. [Methods] To analyze the spatiotemporal parameters and ground reaction force during walking in the two groups, the six-camera Vicon MX motion analysis system was used. The subjects were asked to walk 12 meters using the more comfortable walking method for them between Nordic walking and walking. After they walked 12 meters more than 10 times, their most natural walking patterns were chosen three times and analyzed. To determine the pole for Nordic walking, each subject’s height was multiplied by 0.68. We then measured the spatiotemporal gait parameters and ground reaction force. [Results] Compared with the walking group, the Nordic walking group showed an increase in cadence, stride length, and step length, and a decrease in stride time, step time, and vertical ground reaction force. [Conclusion] The results of this study indicate that Nordic walking increases the stride and can be considered as helping patients with diseases affecting their gait. This demonstrates that Nordic walking is more effective in improving functional capabilities by promoting effective energy use and reducing the lower limb load, because the weight of the upper and lower limbs is dispersed during Nordic walking.

Augmented feedback and the dual-task paradigm during repeated submaximal lower limb loading

Augmented feedback and the dual-task paradigm during repeated submaximal lower limb loading

Using accelerometry to quantify deceleration during a high-intensity soccer turning manoeuvre

The mechanics of cutting movements have been investigated extensively, but few studies have considered the rapid deceleration phase prior to turning which has been linked to muscle damage. This study used accelerometry to examine the influence of turning intensity on the last three steps of a severe turn.Ten soccer players performed 135° “V” cuts at five different intensities. Resultant decelerations were recorded from a trunk-mounted tri-axial accelerometer. Lower limb kinematics and ground reaction forces (GRF) from the pivot foot-ground contact (FGC) were also monitored.Average peak trunk decelerations were larger at the two preceding steps (4.37 ± 0.12 g and 4.58 ± 0.11 g) compared to the PIVOT step (4.10 ± 0.09 g). Larger peak joint flexion angular velocities were observed at PRE step (ankle: 367 ± 192 deg.s−1; knee 493 ± 252 deg.s−1) compared to PIVOT step (ankle 255 ± 183 deg.s−1; knee 377 ± 229 deg.s−1). Turn intensity did not influence peak GRF at PIVOT step.This study highlights the importance of steps prior to turning and their high-frequency loading characteristics. It is suggested that investigations of lower limb loading during turning should include this deceleration phase and not focus solely on pivot FGC.

Disuse deterioration of human skeletal muscle challenged by resistive exercise superimposed with vibration: evidence from structural and proteomic analysis.

In the present bed rest (BR) study, 23 volunteers were randomized into 3 subgroups: 60 d BR control (Ctr); BR with resistive exercise (RE; lower-limb load); and resistive vibration exercise (RVE; RE with superimposed vibration). The aim was to analyze by confocal and electron microscopy the effects of vibration on myofibril and filament integrity in soleus (Sol) and vastus lateralis (VL) muscle; differential proteomics of contractile, cytoskeletal, and costameric proteins (TN-C, ROCK1, and FAK); and expression of PGC1α and atrophy-related master genes MuRF1 and MuRF2. RVE (but not RE) preserved myofiber size and phenotype in Sol and VL by overexpressing MYBPC1 (42%, P ≤ 0.01), WDR1 (39%, P ≤ 0.01), sarcosin (84%, P ≤ 0.01), and CKM (20%, P ≤ 0.01) and prevented myofibrillar ultrastructural damage as detectable by MuRF1 expression. In Sol, cytoskeletal and contractile proteins were normalized by RVE, and TN-C increased (59%, P ≤ 0.01); the latter also with RE (108%, P ≤ 0.01). In VL, the outcomes of both RVE (acting on sarcosin and desmin) and RE (by way of troponinT-slow and MYL2) were similar. RVE appears to be a highly efficient countermeasure protocol against muscle atrophy and ultrastructural and molecular dysregulation induced by chronic disuse.

Distal Forelimb Kinematics During the Extended Trot of Dressage Horses Ridden on Two Different Arena Surfaces

IntroductionSuspensory apparatus injuries are common in dressage horses. Studies demonstrate that surface type affects hoof forces and distal limb kinematics of equine athletes. Because synthetic race surfaces have lower stiffness and limb loads than dirt surfaces, it was hypothesized that dressage horses have less fetlock hyperextension on a synthetic surface than a dirt surface.MethodsTwo‐dimensional, high‐speed videos (250 Hz, 2 ppcm) of 6 dressage horses (ages 8–13; 5 males, 1 female) during extended trot on dirt and synthetic surfaces (6 trials (strides) per horse per surface) were digitized (low‐pass Butterworth filter, 15 Hz). Fetlock and solar hoof angles determined from skin and hoof markers were compared between surfaces using a mixed model ANCOVA that accounted for horse velocity (saddle billet marker) and repeated horse measures. Surface mechanical behaviors were characterized using a track testing device. Maximum force, time to maximum force, maximum displacement, resting rebound, maximum vertical rebound, average stiffness, and maximum load rate were compared between surfaces and time of day (morning, afternoon) using a general linear model ANOVA.ResultsMaximum and toe off fetlock angles were greater on the synthetic surface compared to dirt (Δ = 2°, P = 0.070). Mean maximum fetlock angle on the synthetic surface was 260°. The maximum load rate of the synthetic surface was 5 times greater than the dirt surface (P = 0.0086).ConclusionsSynthetic surfaces were designed to reduce injuries in equine athletes. Because suspensory apparatus elongation is largely dependent on fetlock extension, it is possible that suspensory apparatus strain is greater on synthetic surfaces. Thus, surface design may require more refinement to promote injury prevention based on horse discipline and gait.Ethical Animal ResearchThe University of California, Davis Institutional Animal Care and Use Committee reviewed and approved the protocols used in the study. Owner informed consent was obtained for all study horses. Sources of funding: Merial (A Sanofi Company) in association with the Student Training in Advanced Research (STAR) program, School of Veterinary Medicine, University of California, Davis and the Endowed Research Funds of School of Veterinary Medicine, University of California, Davis. Competing interests: none.

The impact of foot position on sit-to-stand stability and lower limb loading in hemiplegic stroke patients

Objective To explore the effects of different foot positions on lower limb loading and the sit- to-stand stability of hemiplegic stroke patients. Methods Thirty-six hemiplegic stroke patients were recruited as the experimental group and 36 healthy elderly as the control group. Both groups of subjects completed sit-to-stand movements with 3 different foot positions： （ 1 ） both feet （BF） placed at 10° of ankle dorsiflexion; （2） the paretic foot placed posterior （PFP） for hemiparetic subjects or the undominant foot placed posterior （UDFP） for healthy subjects; （3） the non-paretic foot placed posterior （NPFP） for hemiparetic subjects or the dominant foot placed posterior （DFP） for healthy subjects. The time required to rise from sitting, the average load difference （ALD） be- tween the left and right feet and sway of the center of gravity in the mediolateral direction （COGX） were measured. Results Comparing BF with PFP positioning, the time to rise was not significantly different but the loads on the two legs, the ALD and the COGX in were all significantly different. Comparing NPFP with PFP positioning, all the indexes were significantly different, and the time to rise was significantly different from the BF positioning. For the control group, all the indexes significantly different in the BP and PFP positions, and the time to rise was signifi- cantly different from that required with the UDFP placement. In all 3 foot positions, all of the experimental group＇ s indices differed significantly from those of the control group. In both groups there was a strong positive correlation between the average ALD and COGX values in all three foot positions. Conclusions Foot placement influences lower limb loading and stability in rising from sitting for hemiplegic stroke survivors. The greater the symmetry of lower limb loading, the better the postural stability. Key words: Stroke ; Hemiplegia; Sit-to-stand ; Posture ; Lower limb loading

Design and Test of a Custom Instrumented Leg Press for Injury and Recovery Intervention

There is an increasing desire and emphasis to integrate assessment tools into the everyday training environment of athletes. These tools are intended to fine-tune athlete development, enhance performance and aid in the development of individualised programmes for athletes. The areas of workload monitoring, skill development and injury assessment are expected to benefit from such tools. This paper describes the development of an instrumented leg press and its application to testing leg dominance with a cohort of athletes. The developed instrumented leg press is a 45° reclining sled-type leg press with dual force plates, a displacement sensor and a CCD camera. A custom software client was developed using C#. The software client enabled near-real-time display of forces beneath each limb together with displacement of the quad track roller system and video feedback of the exercise. In recording mode, the collection of athlete particulars is prompted at the start of the exercise, and pre-set thresholds are used subsequently to separate the data into epochs from each exercise repetition. The leg press was evaluated in a controlled study of a cohort of physically active adults who performed a series of leg press exercises. The leg press exercises were undertaken at a set cadence with nominal applied loads of 50%, 100% and 150% of body weight without feedback. A significant asymmetry in loading of the limbs was observed in healthy adults during both the eccentric and concentric phases of the leg press exercise (P < .05). Mean forces were significantly higher beneath the non-dominant limb (4–10%) and during the concentric phase of the muscle action (5%). Given that symmetrical loading is often emphasized during strength training and remains a common goal in sports rehabilitation, these findings highlight the clinical potential for this instrumented leg press system to monitor symmetry in lower-limb loading during progressive strength training and sports rehabilitation protocols.

Forefoot Strikers Exhibit Lower Running-Induced Knee Loading than Rearfoot Strikers

Knee pain and Achilles tendinopathies are the most common complaints among runners. The differences in the running mechanics may play an important role in the pathogenesis of lower limb overuse injuries. However, the effect of a runner's foot strike pattern on the ankle and especially on the knee loading is poorly understood. The purpose of this study was to examine whether runners using a forefoot strike pattern exhibit a different lower limb loading profile than runners who use rearfoot strike pattern. Nineteen female athletes with a natural forefoot strike (FFS) pattern and pair-matched women with rearfoot strike (RFS) pattern (n = 19) underwent 3-D running analysis at 4 m·s⁻¹. Joint angles and moments, patellofemoral contact force and stresses, and Achilles tendon forces were analyzed and compared between groups. FFS demonstrated lower patellofemoral contact force and stress compared with heel strikers (4.3 ± 1.2 vs 5.1 ± 1.1 body weight, P = 0.029, and 11.1 ± 2.9 vs 13.0 ± 2.8 MPa, P = 0.04). In addition, knee frontal plane moment was lower in the FFS compared with heel strikers (1.49 ± 0.51 vs 1.97 ± 0.66 N·m·kg⁻¹, P =0.015). At the ankle level, FFS showed higher plantarflexor moment (3.12 ± 0.40 vs 2.54 ± 0.37 N·m·kg⁻¹; P = 0.001) and Achilles tendon force (6.3 ± 0.8 vs 5.1 ± 1.3 body weight; P = 0.002) compared with RFS. To our knowledge, this is the first study that shows differences in patellofemoral loading and knee frontal plane moment between FFS and RFS. FFS exhibit both lower patellofemoral stress and knee frontal plane moment than RFS, which may reduce the risk of running-related knee injuries. On the other hand, parallel increase in ankle plantarflexor and Achilles tendon loading may increase risk for ankle and foot injuries.