Bilateral knee osteoarthritis does not affect inter-joint coordination in older adults with gait deviations during obstacle-crossing

Effects of proprioceptive neuromuscular facilitation stretching in relieving pain and balancing knee loading during stepping over obstacles among older adults with knee osteoarthritis: A randomized controlled trial

OBJECTIVE

The purpose of this study was to investigate the effects of an 8-week proprioceptive neuromuscular facilitation (PNF) stretching in relieving pain and balancing knee loading during stepping over obstacles among older people with knee osteoarthritis, and further explore the improvements in gait patterns.

DESIGN

Thirty-two older adults (66~72 years) with KOA were recruited and randomly assigned into PNF or control groups. They received PNF stretching or health lecture series for 8 weeks. Final data analyses were conducted among 13 participants in the PNF and 14 in the control groups. At weeks 0 and 9, they were asked to step over an obstacle of 20% of their leg length. The pain scores and knee abduction moment (KAM) (primary outcomes) were analyzed by multivariate ANOVA, and the gait variables (secondary outcomes) were analyzed by two-way (group by pre-/post) ANOVAs with repeated measures.

RESULTS

Significant interactions were detected in the pain score, first and second peaks of KAM, and crossing velocity during stepping over obstacles, and significant between-group differences of these outcomes were detected at week 9.

CONCLUSION

An 8-week PNF stretching could relieve pain and balance loading between knee compartments, as well as increase crossing velocity during stepping over obstacles.

TRIAL REGISTRATION

Chinese Clinical Trial Registry: ChiCTR2100042278.

Quantifying lower extremity inter-segmental coordination variability during walking in people with multiple sclerosis with high and low fear of falling

BACKGROUND

Fear of falling (FOF) is associated with gait disturbances in people with multiple sclerosis (PwMS). However, previous studies mostly assessed FOF-related changes in gait patterns of PwMS using spatio-temporal gait parameters. Considering the complex nature of gait control, investigation of the higher order properties of the human movement system, particularly inter-segmental coordination variability may provide valuable information about underlying deficits in motor control patterns in PwMS with different levels of FOF. Therefore, the purpose of this study was to clarify the differences in lower extremity inter-segmental coordination variability between healthy controls and PwMS with high and low FOF.

METHODS

This cross-sectional study examined gait patterns of 40 PwMS and 20 age-and-sex-matched healthy controls during treadmill walking at a preferred walking speed for 3 min. The falls efficacy scale-international questionnaire was used to stratify PwMS into high and low FOF subgroups. Variability in coordinative relationships between shank-thigh and foot-shank segments was determined using deviation phase (DP), which is the average standard deviation calculated from all points of the ensemble continuous relative phase (CRP) curve during the stance and swing phases of gait.

RESULTS

DP values for shank-thigh (p = 0.005 and p < 0.001, respectively) and foot-shank inter-segmental relationships (p < 0.001) during the stance phase as well as for foot-shank inter-segmental relationships during the swing phase (p = 0.03) were significantly greater in PwMS with high FOF compared to those with low FOF and healthy controls. In addition, both groups of PwMS with high and low FOF indicated greater shank-thigh DP values compared to healthy controls during the swing phase (p < 0.001 and p = 0.002, respectively).

CONCLUSION

The findings suggest unsteadiness in neuromuscular organization during walking in PwMS with high FOF. Rehabilitative interventions targeting impairments in lower extremity inter-segmental coordination and FOF may be useful to improve walking and reduce risk of falls in PwMS with high FOF.

Recovery of balance control in bilateral medial knee osteoarthritis after total knee arthroplasty during level walking

Older adults are at higher risk of falling following total knee arthroplasty (TKA). However, it remains unclear how long a full recovery of the balance control during gait post-TKA will take. The current study aimed to bridge this knowledge gap via long-term follow-up gait analyses. Twelve older adults with severe bilateral medial knee osteoarthritis (OA) before, 3 and 12 months after TKA, and twelve healthy controls were evaluated for their balance control during level walking, in terms of the inclination angle (IA) of the center of pressure to center of mass vector, and the rate of change of IA (RCIA). The patients before TKA showed significantly increased sagittal IA but decreased RCIA throughout the gait cycle (p < 0.04) compared to controls, suggesting a compromised balance control. Three months post-TKA, deviations in IA remained, although those in RCIA were improved to normal. One-year post-TKA, no significant differences were found in any of the IA- and RCIA-related variables between patient and Control groups. The results show that TKA surgery was effective in reducing the deviations in the center of mass-center of pressure control in patients with severe bilateral knee OA, and full recovery of balance control can be expected 1 year after surgery.

Effects of Tai-Chi Chuan Practice on Patterns and Stability of Lower Limb Inter-Joint Coordination During Obstructed Gait in the Elderly

Losing balance or tripping during obstacle-crossing is one of the most frequent causes of falls in the elderly. As a low speed, low impact exercise, Tai Chi Chuan (TCC) can be promising in helping the elderly develop strategies for improved balance, inter-joint coordination, and end-point control during obstacle-crossing. This study investigates the effects of TCC training on the patterns and variability of the lower-limb inter-joint coordination during obstacle-crossing in the elderly. Fifteen older TCC practitioners and 15 healthy controls crossed obstacles of three different heights, while sagittal angles (x) and angular velocities (x′) of the hips, knees and ankles were measured and their phase angles obtained. The continuous relative phases (CRP) of the hip-knee and knee-ankle coordination were also calculated. The standard deviations of the CRP curve points were averaged to obtain deviation phase (DP) values for the stance and swing phases. The TCC group was found to cross obstacles with increased leading and trailing toe-clearances with unaltered CRP values when the swing toe was above the obstacle. Long-term TCC training altered the patterns and magnitudes of the CRPs primarily over double-limb support and significantly reduced the variabilities of leading knee-ankle and trailing hip-knee and knee-ankle CRP curves over the crossing cycle, regardless of obstacle height. The current results suggest that long-term TCC practice was helpful for a crossing strategy with significantly increased foot-obstacle clearances and reduced variability of the way the motions of the lower limb joints are coordinated during obstacle-crossing. These benefits may be explained by the long-lasting effects of continuous practice of the slow movement patterns emphasizing between-limb transfer of body weight in TCC.

The impact of outdoor walking surfaces on lower-limb coordination and variability during gait in healthy adults

BACKGROUND

Inter-joint coordination and variability during gait provide insight into control and adaptability of the neuromuscular system. To date, coordination research has been restricted to laboratory settings, and it is unclear how these findings translate to real-world, outdoor walking environments.

RESEARCH QUESTION

Compared to flat walking, to what extent do outdoor surfaces impact lower-limb inter-joint coordination and variability during gait, in healthy adults?

METHODS

Data from inertial measurement units placed on the lower-back, thigh, and shank were extracted from thirty healthy young adults (15 females, 23.5 ± 4.2 years) during outdoor walking on flat (paved sidewalk); irregular (cobblestone, grass); sloped (slope-up, slope-down); and banked (banked-right, banked-left) surfaces. Sagittal joint angles for the right knee and hip were computed and partitioned by gait phase (stance and swing). Continuous Relative Phase analysis determined inter-joint coordination and variability for the knee-hip joint pair using Mean Absolute Relative Phase (MARP) and Deviation Phase (DP), respectively. One-way repeated measures ANOVAs tested surface effects. Post-hoc Bonferroni adjusted surface comparisons were assessed.

RESULTS

Significant knee-hip surface effects were seen during all gait phases for MARP (p < 0.001) and DP (p ≤ 0.001). Compared to flat walking, grass prompted more in-phase coordination (smaller MARP) during stance and swing phase (p ≤ 0.003). Slope-up caused more in-phase coordination during stance (p < 0.001), while slope-down caused more out-of-phase coordination during stance and swing (p ≤ 0.003), compared to the flat surface. Sloped surfaces prompted more variable (larger DP) knee-hip coordination (p ≤ 0.001), compared to flat walking during stance and swing phase.

SIGNIFICANCE

Compared to flat walking, changes in knee-hip coordination and variability were greatest on slope-up/slope-down surfaces. This could reflect greater changes in lower-limb kinematics on sloped surfaces and/or a neuromuscular response to the demands of a more challenging task.

Best-Compromise Control Strategy Between Mechanical Energy Expenditure and Foot Clearance for Obstacle-Crossing in Older Adults: Effects of Tai-Chi Chuan Practice

Background: Obstacle-crossing increases the risk of falls in older people. This study aimed to identify the effects of long-term Tai-Chi Chuan (TCC) practice on the control strategies for obstacle-crossing in older people.

Methods: A multi-objective optimal control technique with measured gait data was used to identify the control strategies adopted by 15 long-term TCC practitioners and 15 healthy controls when crossing obstacles of different heights, in terms of the best-compromise weighting sets for the conflicting objectives of minimizing energy expenditure and maximizing the toe-obstacle and heel-obstacle clearances.

Results and Conclusions: The long-term TCC older practitioners adopted a best-compromise control strategy similar to those adopted by young adults, with greater weightings on the minimization of the mechanical energy expenditure and smaller weightings on foot-clearance as compared to non-TCC controls (TCC: 0.72, 0.14, 0.14; Control: 0.55, 0.225, 0.225). This strategy enabled the long-term TCC older practitioners to cross obstacles with significantly greater leading-toe clearances but with relatively less mechanical energy expenditure. With the current approach, further simulations of obstacle-crossing mechanics with a given weighting set will be useful for answering clinically relevant what-if questions, such as what abilities would be needed if the non-TCC older people were to cross obstacles using the crossing strategy of the TCC people.

Compromised balance control in older people with bilateral medial knee osteoarthritis during level walking

About half of the elderly population has knee osteoarthritis (OA), showing altered gait patterns with increased fall risk. The current study aimed to identify the effects of severe bilateral medial knee osteoarthritis on gait balance control, in terms of the inclination angle (IA) of the center of pressure to center of mass vector, and the rate of change of IA (RCIA). Fifteen older adults with severe bilateral medial knee OA and 15 healthy controls walked at their preferred walking speed while the kinematic and forceplate data were measured to calculate IA, RCIA and temporal-spatial parameters. The OA group showed compromised gait balance control, due to a decreased average and range of sagittal RCIA over double-limb support (DLS, p < 0.002) and single-limb support (SLS, p < 0.002), as well as an increased sagittal IA (DLS, p < 0.005). Significantly decreased frontal RCIA averages during DLS, heel-strike and toe-off, and decreased RCIA ranges during SLS and swing (p < 0.027) were also observed. Reducing RCIA during DLS appeared to help reduce the loading rate and pain at the knees, and reduced RCIA at the subsequent SLS. The results indicated an increased risk of loss of balance in the OA group, and may warrant regular monitoring for reduced RCIA during gait to determine fall risk.

Effects of knee osteoarthritis severity on inter-joint coordination and gait variability as measured by hip-knee cyclograms

Inter-joint coordination and gait variability in knee osteoarthritis (KOA) has not been well investigated. Hip-knee cyclograms can visualize the relationship between the hip and knee joint simultaneously. The aim of this study was to elucidate differences in inter-joint coordination and gait variability with respect to KOA severity using hip-knee cyclograms. Fifty participants with KOA (early KOA, n = 20; advanced KOA, n = 30) and 26 participants (≥ 50 years) without KOA were recruited. We analyzed inter-joint coordination by hip-knee cyclogram parameters including range of motion (RoM), center of mass (CoM), perimeter, and area. Gait variability was assessed by the coefficient of variance (CV) of hip-knee cyclogram parameters. Knee RoM was significantly reduced and total perimeter tended to be decreased with KOA progression. KOA patients (both early and advanced) had reduced stance phase perimeter, swing phase area, and total area than controls. Reduced knee CoM and swing phase perimeter were observed only in advanced KOA. Both KOA groups had a greater CV for CoM, knee RoM, perimeter (stance phase, swing phase and total) and swing phase area than the controls. Increased CV of hip RoM was only observed in advanced KOA. These results demonstrate that hip-knee cyclograms can provide insights into KOA patient gait.

Coordination of lower limbs in patients with knee osteoarthritis during walking

BACKGROUND

The movement coordination in patients with knee osteoarthritis may be impaired and the identification of the deficits in lower limb inter-segmental coordination is crucial to understand the effect of knee osteoarthritis on knee function.

RESEARCH QUESTION

This study utilizes continuous relative phase to investigate the pattern and variability of lower limb inter-segmental coordination in patients with knee osteoarthritis and in healthy subjects during walking, and to evaluate inter-segmental coordination alterations in patients.

METHODS

Gait was measured by a three-dimensional motion capture system for 44 patients with late-stage knee osteoarthritis and 22 healthy subjects. Segmental kinematic parameters, continuous relative phase and its variability were calculated. Independent samples t-tests were used to detect differences between patients and healthy subjects.

RESULTS

Thigh-shank continuous relative phase of patients is significantly decreased by 16.04° and 16.18° during late stance and swing phase as compared with healthy subjects (P < 0.05). Shank-foot continuous relative phase of patients is significantly decreased by 6.89° during early stance and significantly increased by 5.49° and 6.39° during late stance and swing phase (P < 0.05). Patients also exhibit increased variability of thigh-shank continuous relative phase during late stance and swing phase by 1.90° and 1.65° respectively, and increased variability of shank-foot continuous relative phase during early stance and swing phase by 0.83° and 0.88° respectively as compared to healthy subjects (P < 0.05).

SIGNIFICANCE

Patients with knee osteoarthritis exhibit altered coordination patterns and increased coordination variability of thigh-shank and shank-foot. Knee dysfunction results in altered lower limbs coordination and unstable motor control during walking. Investigation of inter-segmental coordination could therefore provide insights into changes in neuromuscular control of gait in patients with knee osteoarthritis.

Lower Limb Inter-Joint Coordination of Unilateral Transfemoral Amputees: Implications for Adaptation Control

The gait of transfemoral amputees can be made smoother by adjusting the inter-joint coordination of both lower limbs. In this study, we compared the inter-joint coordination of the amputated and non-amputated limbs of unilateral amputees to able-bodied controls. Eight amputees and eight able-bodied control participants were recruited. Walking speed, stance–swing time ratio, joint angle, joint angular velocity, and inter-joint coordination parameters—including continuous relative phase (CRP) and decomposition index (DI)—of the lower-limb joint pairs in stance and swing phases were investigated. Similarity of the CRP between groups was evaluated using cross-correlation measures and root-mean-square, and the variability of the CRP was examined by deviation phase (DP). There were significant differences between the amputated limbs and controls in CRP of hip–knee and knee–ankle in stance and swing, DP of knee–ankle and hip–ankle in stance, and DI of hip–knee in swing. For the non-amputated limbs, there were significant differences in CRP and DP of knee–ankle, and DI of hip–knee in swing compared to controls. The amputees utilized unique inter-joint coordination patterns for both limbs—particularly the hip joint—to compensate for the support-capability impairment due to limb salvage and ensure foot placement accuracy.

Leg-amplitude differentiation guided by haptic and visual feedback to detect alterations in motor flexibility due to Total Knee Replacement

Following total knee replacement (TKR), patients often persist in maladaptive motor behavior which they developed before surgery to cope with symptoms of osteoarthritis. An important challenge in physical therapy is to detect, recognize and change such undesired movement behavior. The goal of this study was to measure the differences in clinical status of patients pre-TKR and post-TKR and to investigate if differences in clinical status were accompanied by differences in the patients'' motor flexibility. Eleven TKR participants were measured twice: pre-TKR and post-TKR (twenty weeks after TKR). In order to infer maladaptation, the pre-TKR and post-TKR measurements of the patient group were separately compared to one measurement in a control group of fourteen healthy individuals. Clinical status was measured with the Visual Analogue Scale (VAS) for pain and knee stiffness and the Knee Injury and Osteoarthritis Outcome Score (KOOS). Furthermore, Lower-limb motor flexibility was assessed by means of a treadmill walking task and a leg-amplitude differentiation task (LAD-task) supported by haptic or visual feedback. Motor flexibility was measured by coordination variability (standard deviation (SD) of relative phase between the legs) and temporal variability (sample entropy) of both leg movements. In the TKR-group, the VAS-pain and VAS- stiffness and the subscales of the KOOS significantly decreased after TKR. In treadmill walking, lower-limb motor flexibility did not significantly change after TKR. Between-leg coordination variability was significantly lower post-TKR compared to controls. In the LAD-task, a significant decrease of between-leg coordination variability between pre-TKR and post-TKR was accompanied by a significant increase in temporal variability. Post-TKR-values of lower-limb flexibility approached the values of the control group. The results demonstrate that a clinically relevant change in clinical status, twenty weeks after TKR, is not accompanied by alterations in lower-limb motor flexibility during treadmill walking but is accompanied by changes in motor flexibility towards the level of healthy controls during a LAD-task with visual and haptic feedback. Challenging patients with non-preferred movements such as amplitude differentiation may be a promising tool in clinical assessment of motor flexibility following TKR.

Inter-joint coordination during obstacle crossing in people with diabetic neuropathy

Sensori-motor deficit due to diabetic peripheral neuropathy (DPN) alters the quality of obstacle-crossing which may increase the risk of falling. The aim of this study was to compare inter-joint coordination (IJC) during obstacle-crossing between people with DPN and healthy controls. Fifteen DPN and 15 healthy people crossed over obstacles with heights of 10% and 20% of the subject's leg length. The mean absolute relative phase (MARP) and deviation phase (DP) of both leading and trailing limbs were used to calculate the phase dynamic and variability of IJC. Furthermore, correlation between Berg Balance Scale (BBS), Fall Efficacy Scale (FES-I), Timed Up and Go (TUG) and MARP, DP were assessed in DPN group. There was no significant interaction between group and obstacle height on measured variables. However, Group had significant main effect on DP of hip-knee in leading limb (p < 0.05). Additionally, the main effects of the obstacle's height were significant on MARP of hip-knee of trailing limb (p < 0.01) and knee-ankle in leading limb (p < 0.05). FES-I was significantly correlated to hip-knee and knee-ankle MARPs of leading limb for crossing over 20% and knee-ankle MARP for crossing over 10% height obstacle (r = 0.68, 0.69, 0.59, respectively, p < 0.05). This score was also significantly correlated with hip-knee DP of both trailing and leading limbs when crossing 10% obstacle (r = 0.59, 0.57, respectively, p < 0.05). In conclusion, IJC during obstacle-crossing was less variable and more out-of-phase, as a result of DPN and obstacle height, respectively. Moreover, when crossing over lower obstacles, fear of falling is related to IJC dynamics and variability of more proximal segment, especially in the leading limb.

Effects of personal and task constraints on limb coordination during walking: A systematic review and meta-analysis

BACKGROUND

In human behaviour, emergence of movement patterns is shaped by different, interacting constraints and consequently, individuals with motor disorders usually display distinctive lower limb coordination modes.

OBJECTIVES

To review existing evidence on the effects of motor disorders and different task constraints on emergent coordination patterns during walking, and to examine the clinical significance of task constraints on gait coordination in people with motor disorders.

METHODS

The search included CINHAL Plus, MEDLINE, HSNAE, SPORTDiscus, Scopus, Pubmed and AMED. We included studies that compared intra-limb and inter-limb coordination during gait between individuals with a motor disorder and able-bodied individuals, and under different task constraints. Two reviewers independently examined the quality of studies by using the Newcastle Ottawa Scale-cohort study.

FINDINGS

From the search results, we identified 1416 articles that studied gait patterns and further analysis resulted in 33 articles for systematic review and 18 articles for meta-analysis-1, and 10 articles for meta-analysis-2. In total, the gait patterns of 539 patients and 358 able-bodied participants were analysed in the sampled studies. Results of the meta-analysis for group comparisons revealed a low effect size for group differences (ES = -0.24), and a moderate effect size for task interventions (ES = -0.53), on limb coordination during gait.

INTERPRETATION

Findings demonstrated that motor disorders can be considered as an individual constraint, significantly altering gait patterns. These findings suggest that gait should be interpreted as functional adaptation to changing personal constraints, rather than as an abnormality. Results imply that designing gait interventions, through modifying locomotion tasks, can facilitate the emergent re-organisation of inter-limb coordination patterns during rehabilitation.

The collision forces and lower-extremity inter-joint coordination during running

The purpose of this study was to compare the lower extremity inter-joint coordination of different collision forces runners during running braking phase. A dynamical system approach was used to analyse the inter-joint coordination parameters. Data were collected with six infra-red cameras and two force plates. According to the impact peak of the vertical ground reaction force, twenty habitually rearfoot-strike runners were categorised into three groups: high collision forces runners (HF group, n = 8), medium collision forces runners (MF group, n = 5), and low collision forces runners (LF group, n = 7). There were no significant differences among the three groups in the ankle and knee joint angle upon landing and in the running velocity (p > 0.05). The HF group produced significantly smaller deviation phase (DP) of the hip flexion/extension-knee flexion/extension during the braking phase compared with the MF and LF groups (p < 0.05). The DP of the hip flexion/extension-knee flexion/extension during the braking phase correlated negatively with the collision force (p < 0.05). The disparities regarding the flexibility of lower extremity inter-joint coordination were found in high collision forces runners. The efforts of the inter-joint coordination and the risk of running injuries need to be clarified further.

Comparison of the trunk-pelvis and lower extremities sagittal plane inter-segmental coordination and variability during walking in persons with and without chronic low back pain

Inter-segmental coordination can be influenced by chronic low back pain (CLBP). The sagittal plane lower extremities inter-segmental coordination pattern and variability, in conjunction with the pelvis and trunk, were assessed in subjects with and without non-specific CLBP during free-speed walking. Kinematic data were collected from 10 non-specific CLBP and 10 non-CLBP control volunteers while the subjects were walking at their preferred speed. Sagittal plane time-normalized segmental angles and velocities were used to calculate continuous relative phase for each data point. Mean absolute relative phase (MARP) and deviation phase (DP) were derived to quantify the trunk-pelvis and bilateral pelvis-thigh, thigh-shank and shank-foot coordination pattern and variability over the stance and swing phases of gait. Mann-Whitney U test was employed to compare the means of DP and MARP values between two groups (same side comparison). Statistical analysis revealed more in-phase/less variable trunk-pelvis coordination in the CLBP group (P<0.05). CLBP group demonstrated less variable right or left pelvis-thigh coordination pattern (P<0.05). Moreover, the left thigh-shank and left shank-foot MARP values in the CLBP group, were more in-phase than left MARP values in the non-CLBP control group during the swing phase (P<0.05). In conclusion, the sagittal plane lower extremities, pelvis and trunk coordination pattern and variability could be generally affected by CLBP during walking. These changes can be possible compensatory strategies of the motor control system which can be considered in the CLBP subjects.

Modifications of gait as predictors of natural osteoarthritis progression in STR/Ort mice

Objective

Osteoarthritis (OA) is a common chronic disease for which disease-modifying therapies are not currently available. Studies to seek new targets for slowing the progress of OA rely on mouse models, but these do not allow for longitudinal monitoring of disease development. This study was undertaken to determine whether gait can be used to measure disease severity in the STR/Ort mouse model of spontaneous OA and whether gait changes are related to OA joint pain.

Methods

Gait was monitored using a treadmill-based video system. Correlations between OA severity and gait at 3 treadmill speeds were assessed in STR/Ort mice. Gait and pain behaviors of STR/Ort mice and control CBA mice were analyzed longitudinally, with monthly assessments.

Results

The best speed to identify paw area changes associated with OA severity in STR/Ort mice was found to be 17 cm · seconds⁻¹. Paw area was modified with age in CBA and STR/Ort mice, but this began earlier in STR/Ort mice and correlated with the onset of OA at 20 weeks of age. In addition, task noncompliance appeared at 20 weeks. Surprisingly, STR/Ort mice did not show any signs of pain with OA development, even when treated with the opioid antagonist naloxone, but did exhibit normal pain behaviors in response to complete Freund's adjuvant–induced arthritis.

Conclusion

The present results identify an animal model in which OA severity and OA pain can be studied in isolation from one another. The findings suggest that paw area and treadmill noncompliance may be useful tools to longitudinally monitor nonpainful OA development in STR/Ort mice. This will help in providing a noninvasive means of assessing new therapies to slow the progression of OA.

Characterization of lower-limbs inter-segment coordination during the take-off extension in ski jumping

Take-off, the most important phase in ski jumping, has been primarily studied in terms of spatio-temporal parameters; little is known about its motor control aspects. This study aims to assess the inter-segment coordination of the shank-thigh and thigh-sacrum pairs using the continuous relative phase (CRP). In total 87 jumps were recorded from 33 athletes with an inertial sensor-based system. The CRP curves indicated that the thighs lead the shanks during the first part of take-off extension and that the shanks rotated faster at the take-off extension end. The thighs and sacrum first rotated synchronously, with the sacrum then taking lead, with finally the thighs rotating faster. Five characteristic features were extracted from the CRP and their relationship with jump length was tested. Three features of the shank-thigh pair and one of the thigh-sacrum pair reported a significant association with jump length. It was observed that athletes who achieved longer jumps had their thighs leading their shanks during a longer time, with these athletes also having a more symmetric movement between thighs and sacrum. This study shows that inter-segment coordination during the take-off extension is related to performance and further studies are necessary to contrast its importance with other ski jumping aspects.

Best-compromise between mechanical energy expenditure and foot clearance predicts leading limb motion during obstacle-crossing

This study aimed to identify the control strategy of obstacle-crossing of different heights with a multi-objective optimal control technique. Twelve young healthy adults walked and crossed obstacles of three different heights while their kinematic and ground reaction force data were measured simultaneously. Obstacle-crossing was formulated as an optimal control problem with two conflicting objectives: minimization of mechanical energy expenditure and maximization of foot-obstacle clearance. The results supported the hypothesis that experimentally measured ankle trajectories and joint angles of the swing limb and the joint moments of the stance limb could be predicted by the best compromise between these objectives, which was also independent of obstacle height. This control strategy was fundamentally different from that for unobstructed gait, and appeared to be pre-programmed into the nervous system. The results will serve as baseline data and the current technique be used for identifying changes in obstacle-crossing control strategies in people at higher risk of falling.

Biomechanics of human movement and its clinical applications

All life forms on earth, including humans, are constantly subjected to the universal force of gravitation, and thus to forces from within and surrounding the body. Through the study of the interaction of these forces and their effects, the form, function and motion of our bodies can be examined and the resulting knowledge applied to promote quality of life. Under gravity and other loads, and controlled by the nervous system, human movement is achieved through a complex and highly coordinated mechanical interaction between bones, muscles, ligaments and joints within the musculoskeletal system. Any injury to, or lesion in, any of the individual elements of the musculoskeletal system will change the mechanical interaction and cause degradation, instability or disability of movement. On the other hand, proper modification, manipulation and control of the mechanical environment can help prevent injury, correct abnormality, and speed healing and rehabilitation. Therefore, understanding the biomechanics and loading of each element during movement using motion analysis is helpful for studying disease etiology, making decisions about treatment, and evaluating treatment effects. In this article, the history and methodology of human movement biomechanics, and the theoretical and experimental methods developed for the study of human movement, are reviewed. Examples of motion analysis of various patient groups, prostheses and orthoses, and sports and exercises, are used to demonstrate the use of biomechanical and stereophotogrammetry-based human motion analysis studies to address clinical issues. It is suggested that further study of the biomechanics of human movement and its clinical applications will benefit from the integration of existing engineering techniques and the continuing development of new technology.