Does an outdoor virtual environment projected in a head-mounted display affect balance in healthy young adults?

BACKGROUND: Virtual reality head-mounted display (VR-HMD) is increasingly used for balance evaluation and rehabilitation. However, more studies must be conducted on virtual environments (VE) effects. This study aimed to assess the impact of an outdoor VE projected in a high-quality VR-HMD and of the VR-HMD mass on postural stability, postural control and leaning. METHODS: This study involved ten healthy young men who performed five 30-s stabilometric trials. Four experimental conditions were randomly performed: eyes open (EO) or eyes closed (EC), with (VR) or without (No VR) VR-HMD. Postural stability (antero-posterior (AP) and medio-lateral (ML) ranges of the center of pressure (CoP), 90% confidence ellipse area), postural control (CoP velocity (global, AP and ML)) and standard deviation of the CoP mean position), and postural leaning (AP/ML CoP mean position) were assessed. The comparisons between EO VR and EO No VR were used to analyze the VE effects and comparisons between EC VR and EC No VR for the VR-HMD mass effects. RESULTS: Spatiotemporal parameters that characterised postural stability and postural control, except ML velocity (p > 0.05), were significantly influenced by the simulated VE with higher values in EO VR than EO No VR (p < 0.05), but not by the VR-HMD mass. The mean position of the CoP showed no significant differences between conditions. SIGNIFICANCE: Postural stability and postural control modification due to the VE used in this study revealed that this VE could be interesting for VR-HMD rehabilitation and assessment. VR-HMD is not a factor to be considered for stabilometric analysis.

A two-stage disto-proximal braking modality to interrupt gait initiation in healthy adults.

The purpose of this investigation was to determine the effect of unexpected gait termination in able-bodied participants during gait initiation on spatiotemporal and stance limb biomechanical parameters. Twenty-one healthy adults took part in this study and were divided into two groups based on the natural anterior or posterior incline of their trunk. Each participant performed 15 random trials of gait initiation: 10 trials with a Go signal and 5 with Go-&-Stop signals. Spatiotemporal parameters were assessed between the Go signal and the first heel contact. Ankle, knee, and hip joint moments were calculated in the sagittal plane. Free moment and impulse were also calculated for the stance limb. Spatiotemporal parameters were not influenced by the mean trunk inclination (p > 0.05), but participants with a forwardly-inclined trunk presented higher hip extension moments (p < 0.05). Unexpected stopping required smaller ankle and knee moments compared to the Go condition (p < 0.05). The hip extension moments appeared to be independent of gait initiation conditions (p > 0.05). The capacity of able-bodied people to interrupt their gait initiation relied on a two-stage disto-proximal braking modality involving explosive motor patterns at the ankle and hip joints. Such a pattern could be altered in vulnerable people, and further studies are needed to investigate this. This study determined a clinical method applicable as a functional protocol to assess and improve the postural control of people suffering from a lack of motor modulation during crucial transient tasks. Such tasks are essential in activities of daily living.

Machine Learning Identifies Chronic Low Back Pain Patients from an Instrumented Trunk Bending and Return Test.

Nowadays, the better assessment of low back pain (LBP) is an important challenge, as it is the leading musculoskeletal condition worldwide in terms of years of disability. The objective of this study was to evaluate the relevance of various machine learning (ML) algorithms and Sample Entropy (SampEn), which assesses the complexity of motion variability in identifying the condition of low back pain. Twenty chronic low-back pain (CLBP) patients and 20 healthy non-LBP participants performed 1-min repetitive bending (flexion) and return (extension) trunk movements. Analysis was performed using the time series recorded by three inertial sensors attached to the participants. It was found that SampEn was significantly lower in CLBP patients, indicating a loss of movement complexity due to LBP. Gaussian Naive Bayes ML proved to be the best of the various tested algorithms, achieving 79% accuracy in identifying CLBP patients. Angular velocity of flexion movement was the most discriminative feature in the ML analysis. This study demonstrated that: supervised ML and a complexity assessment of trunk movement variability are useful in the identification of CLBP condition, and that simple kinematic indicators are sensitive to this condition. Therefore, ML could be progressively adopted by clinicians in the assessment of CLBP patients.

Sample Entropy as a Tool to Assess Lumbo-Pelvic Movements in a Clinical Test for Low-Back-Pain Patients.

Low back pain (LBP) obviously reduces the quality of life but is also the world's leading cause of years lived with disability. Alterations in motor response and changes in movement patterns are expected in LBP patients when compared to healthy people. Such changes in dynamics may be assessed by the nonlinear analysis of kinematical time series recorded from one patient's motion. Since sample entropy (SampEn) has emerged as a relevant index measuring the complexity of a given time series, we propose the development of a clinical test based on SampEn of a time series recorded by a wearable inertial measurement unit for repeated bending and returns (b and r) of the trunk. Twenty-three healthy participants were asked to perform, in random order, 50 repetitions of this movement by touching a stool and another 50 repetitions by touching a box on the floor. The angular amplitude of the b and r movement and the sample entropy of the three components of the angular velocity and acceleration were computed. We showed that the repetitive b and r "touch the stool" test could indeed be the basis of a clinical test for the evaluation of low-back-pain patients, with an optimal duration of 70 s, acceptable in daily clinical practice.

Is treadmill walking biomechanically comparable to overground walking? A systematic review.

BACKGROUND: The equivalency of treadmill and overground walking has been investigated in a large number of studies. However, no systematic review has been performed on this topic. RESEARCH QUESTION: The aim of this study was to compare the biomechanical, electromyographical and energy consumption outcomes of motorized treadmill and overground walking. METHODS: Five databases, ScienceDirect, SpringerLink, Web of Science, PubMed, and Scopus, were searched until January 13, 2021. Studies written in English comparing lower limb biomechanics, electromyography and energy consumption during treadmill and overground walking in healthy young adults (20-40 years) were included. RESULTS: Twenty-two studies (n = 409 participants) were included and evaluated via the Cochrane Collaboration's tool. These 22 studies showed that some kinematic (reduced pelvic ROM, maximum hip flexion angle for females, maximum knee flexion angle for males and cautious gait pattern), kinetic (sagittal plane joint moments: dorsiflexor moments, knee extensor moments and hip extensor moments and sagittal plane joint powers at the knee and hip joints, peak backwards, lateral and medial COP velocities and propulsive forces during late stance) and electromyographic (lower limbs muscles activities) outcome measures were significantly different for motorized treadmill and overground walking. SIGNIFICANCE: Spatiotemporal, kinematic, kinetic, electromyographic and energy consumption outcome measures were largely comparable for motorized treadmill and overground walking. However, the differences in kinematic, kinetic and electromyographic parameters should be taken into consideration by clinicians, trainers, and researchers when working on new protocols related to patient rehabilitation, fitness rooms or research as to be as close as possible to the outcome measures of overground walking. The protocol registration number is CRD42021236335 (PROSPERO International Prospective Register of Systematic Reviews).

Untreated adolescent idiopathic scoliotic girls display altered balance modalities during self-paced voluntary body sways compared to able-bodied girls.

INTRODUCTION: This study investigated self-paced voluntary oscillations of scoliotic and non-scoliotic girls. Temporal variables and frequency coherence were calculated for the overall, low and high frequency bandwidths of the center of pressure excursions and free-moment to identify which variables best describe sway balance modalities in both groups. METHODS: Twenty-three girls with adolescent idiopathic moderate scoliosis (spinal curves to the right) formed the scoliotic group and 19 matched able-bodied girls formed the non-scoliotic group. Each girl performed self-paced voluntary medio-lateral and antero-posterior sways while standing on a force platform. Center of pressure displacements, out of plane deviation and free-moment were measured and their frequency content calculated. The magnitude of the coherence was calculated for each signal pairs for three frequency ranges. RESULTS: In both sway conditions, the center of pressure excursion parameters were on average 28% higher for the scoliotic group. Factor analysis revealed that balance modalities were essentially based on frequency coherence pair interactions whereas temporal parameters play a secondary role. However, these balance modalities were altered in the scoliotic group. They relied essentially on 2 additional principal components and 3 additional variables reflecting a fine tuning of the control mechanism to maintain dynamic balance. INTERPRETATION: Scoliotic girls appear to be performing a wide ellipsoidal trajectory when performing whole body oscillations. Superfluous variables could be related to the difficulty in preserving balance during body sway tasks and could parasitize the scoliotic dynamic control balance modalities. Self-paced voluntary sways could be an appropriate complementary balance test for untreated scoliotic girls.

Standing posture and balance modalities in unilateral transfemoral and transtibial amputees.

INTRODUCTION: Lower limb amputation impairs postural performance that could be characterized by biomechanical parameters. This study is to investigate postural performance of persons with transfemoral and transtibial amputation compared to controls without amputation. METHODS: Eight transtibial, nine transfemoral and twelve able-bodied males participated in this study. Lower limb joints, pelvis and trunk angles were obtained from an optoelectronic motion analysis system to evaluate body posture parameters. The mean, range and speed of the center of pressure (CoP) in both antero-posterior and medio-lateral axes as well as the ellipse area covered by 90% of CoP and free moment were calculated using a single force-plate. RESULTS AND DISCUSSION: Differences in body posture were only noted between the non-amputee and the transtibial groups. Transtibial amputees leaned more forwardly their trunk by 3.5° compared to able-bodied (p = 0.028). The mean CoP position in transfemoral amputees was closer to the non-amputated side than transtibial amputees (p = 0.034) and as compared to the dominant side in non-amputees (p = 0.042). Factor analysis revealed three postural performance modalities. Non-amputees postural performance was characterized solely by body posture parameters. Transfemoral amputees exclusively favored a modality associated with standing balance parameters, whereas transtibial amputees exhibited a mixed modality comprising a combination of postural and balance parameters. CONCLUSION: These findings support that the level of amputation is characterized by postural performance modalities different from non-amputees. Clinicians could apply this knowledge as part of their routine rehabilitation program to enhance postural and standing balance assessments in unilateral transfemoral and transtibial amputees.

Contribution of Achilles tendon mechanical properties to torque steadiness in persons with transfemoral amputation.

BACKGROUND: How Achilles tendon mechanics and plantar flexion strength and torque steadiness are altered in the intact leg of persons with trauma-related amputation is unknown. Understanding Achilles tendon mechanics following amputation will further inform rehabilitation approaches to enhance posture, balance, and force control. OBJECTIVE: Conduct a pilot study to quantify plantar flexion maximal voluntary contraction torque, torque steadiness, and Achilles tendon mechanics in persons with unilateral trauma-related transfemoral amputation and controls without amputation. STUDY DESIGN: Cross-sectional study. METHODS: Isometric plantar flexion maximal voluntary contractions were performed with the intact leg of ten males with transfemoral amputation (48 ± 14 years) and the dominant leg of age-matched male controls without amputation. Torque steadiness was calculated as the coefficient of variation in torque over 6 s during submaximal tracking tasks (5%, 10%, 25%, 50%, and 75% maximal voluntary contraction). Achilles tendon elongation and cross-sectional area were recorded with ultrasound to calculate strain, stress, and stiffness. RESULTS: Maximal voluntary contraction and torque steadiness did not differ between persons with amputation (90.6 ± 31.6 N m, 3.7 ± 2.0%) and controls (95.8 ± 26.8 N m, 2.9 ± 1.2%; p > 0.05). Tendon stiffness (21.1 ± 18.2 N/mm) and strain (5.2 ± 1.3%) did not differ between groups (p > 0.05). Tendon cross-sectional area was 10% greater in persons with amputation leading to 29% lower stress (p = 0.021). Maximal voluntary contraction was a predictor of a lower coefficient of variation in torque (R2 = 0.11, p < 0.05). CONCLUSION: Persons with trauma-related transfemoral amputation do not differ in plantar flexion maximal voluntary contraction and torque steadiness of the intact leg compared with controls without amputation. Larger tendon cross-sectional area reduces stress and enables distribution of force across a greater area.

Frequency coherence analysis of postural balance in able-bodied and in non-treated adolescent idiopathic scoliotic girls.

BACKGROUND: This study test if the frequency coherence calculated for the overall, low and high frequency bandwidths of the center of pressure excursions and free-moment calculated during standing balance are similar between scoliotic and non-scoliotic girls and if the coherence values within each frequency band are comparable for a given group of girls. METHODS: Twenty-nine girls with adolescent idiopathic scoliosis formed the scoliotic group and 22 able-bodied girls formed the non-scoliotic group. Each girl maintained a quiet upright stance on a force plate. Three trials were performed at a sampling frequency of 64 Hz for 64 s. Mean anterio-posterior, medio-lateral center of pressure positions and free-moment were measured and their frequency content calculated. The magnitude of the coherence was calculated for each signal pairs for three frequency ranges. RESULTS: The magnitude of the medio-lateral center of pressure/free-moment coherence in the low and high frequency bands was significantly different between the groups. Within each group, the magnitude of the medio-lateral center of pressure/free-moment coherence was significantly higher than the other two coherence pairs at low frequencies (P < 0.001). Factor analysis revealed that able-bodied girls exhibited a mixed standing balance modality consisting of posture (center of pressure) and proprioceptive information (free-moment). Scoliotic girls adopted an adaptive modality mostly based on proprioception information to maintain their standing balance. INTERPRETATION: Scoliotic girls systematically depend on the free-moment to modulate their antero-posterior center of pressure displacements. These results suggest a postural reeducation program aimed at improving proprioception while repositioning the mean center of pressure by postural corrections.

Does Unilateral Lower Limb Amputation Influence Ankle Joint Torque in the Intact Leg?

OBJECTIVE: To investigate ankle torque and steadiness in the intact leg of transtibial and transfemoral unilateral amputees. DESIGN: Comparative study. SETTING: Medical rehabilitation centers. PARTICIPANTS: Fifteen persons with a unilateral transfemoral amputation, 8 persons with a transtibial amputation, and 14 able-bodied male participants volunteered to participate in this study (N=37). INTERVENTIONS: Not applicable. MAIN OUTCOMES MEASURES: Maximal isometric torque performed during ankle plantarflexion and dorsiflexion in the intact limb of amputees and in the dominant limb of able-bodied persons. The coefficient of variation (CV) of the plantarflexion torque was calculated over 5 seconds during a submaximal isometric contraction (15%) in order to assess torque steadiness. Furthermore, electromyographic activity (the root mean square amplitude) of the gastrocnemius medialis and tibialis anterior muscles was analyzed. RESULTS: Plantarflexion maximal torque was significantly higher for the able-bodied group (115±39 Nm) than for the group with a transfemoral amputation (77±34 Nm) (P<.01), and did not differ between able-bodied group and the group with a transtibial amputation (97±26 Nm) (P=.25). Furthermore, the transfemoral amputee group was 29% less steady than the able-bodied group (P=.01). However, there were no significant differences in torque steadiness between the able-bodied group and transtibial amputee group (P=.26) or between transtibial and transfemoral amputee groups (P=.27). The amputation had no significant effect between groups on dorsiflexion maximal torque (P=.10), gastrocnemius medialis electromyography (EMG) (P=.85), tibialis anterior coactivation (P=.95), and coactivation ratio (P=.75). CONCLUSION: The present study suggests that as the level of amputation progresses from below the knee to above the knee, the effect on the intact ankle is progressively more negative.

Determination of optimal shoe fitting for children tennis players: Effects of inner-shoe volume and upper stiffness.

The purpose of this study was to determine the optimal inner-shoe volume for children tennis players. Sixteen participants, aged from 8 to 12 years old assessed comfort of 6 shoes, which were a combination of 3 lasts (thin, medium and wide) and 2 upper constructions (flexible and stiff), while a sock equipped with textile sensors was measuring the pressure applied on their foot. The thin last was based on the proportion of an adult last. The widest shoes produced the lowest pressure on the 1st and 5th metatarsal heads, the medial midfoot and the medial and lateral heel (p < 0.05), whilst they were perceived the most comfortable for the 3rd and 5th metatarsal heads, the 5th metatarsal base and the medial and lateral heel (p < 0.05). These outcomes indicated that footwear manufacturers should design wider shoes for children than for adults.

Effect of the phase of force production on corticomuscular coherence with agonist and antagonist muscles.

During isometric contractions, the net joint torque stability is modulated with the force production phases, i.e., increasing (IFP), holding (HFP), and decreasing force (DFP) phases. It was hypothesized that this modulation results from an altered cortical control of agonist and antagonist muscle activations. Eleven healthy participants performed 50 submaximal isometric ankle plantar flexion contractions. The force production phase effect (IFP, HFP and DFP) was assessed on the net joint torque stability, agonist and antagonist muscles activations, cortical activation, and corticomuscular coherence (CMC) with agonist and antagonist muscles. In comparison to HFP, the net joint torque stability, the agonist muscles activation and the CMC with agonist muscles were lower during IFP and even more during DFP. Antagonist muscle activations, cortical activations and CMC with antagonist muscles were higher during HFP than during IFP only. Increased CMC with agonist and antagonist muscles appeared to enhance the fine motor control. At a cortical level, agonist and antagonist muscle activations seemed to be controlled independently according to their muscle function and the phase of force production. Results revealed that CMC was an adequate measure to investigate the cortical regulation of agonist and antagonist muscle activations. This may have potential applications for patients with altered muscle activations.

Effect of natural sagittal trunk lean on standing balance in untreated scoliotic girls.

BACKGROUND: Generally, scoliotic girls have a tendency to lean further back than a comparable group of non-scoliotic girls. To date, no study has addressed how standing balance in untreated scoliotic girls is affected by a natural backwardly or forwardly inclined trunk. METHODS: 27 able-bodied young girls and 27 young girls with a right thoracic curve were classified as leaning forward or backward according to the median of their trunk sagittal inclination. Participants stood upright barefoot. Trunk and pelvis orientations were calculated from 8 bony landmarks. Upright standing balance was assessed by 9 parameters calculated from the excursion of the center of pressure and the free moment. FINDINGS: In the anterior-posterior direction, backward scoliotic girls had a greater center of pressure range (P=0.036) and speed (P=0.015) by 10.4mm and 2.8mm/s respectively than the forward scoliotic group. Compared to their matching non-scoliotic group, the backward scoliotic girls stood more on their heels by 14.6mm (P=0.017) and display greater center of pressure speed by 2.5mm/s (P=0.028). Medio-lateral center of pressure range (P=0.018) and speed (P=0.008) were statistically higher by 8.7mm and 3.6mm/s for the backward group. Only the free moment RMS was significantly larger (P=0.045) for the backward scoliotic group when compared to the forwardly inclined scoliotic group. INTERPRETATION: Only those with a backward lean displayed statistically significant differences from both forward scoliotic girls and non-scoliotic girls. Untreated scoliotic girls with an exaggerated back extension could profit more from postural rehabilitation to improve their standing balance.

Shoe drop reduction influences the lower limb biomechanics of children tennis players during an open stance forehand: A longitudinal study.

Compared to traditional tennis shoes, using 0-drop shoes was shown to induce an immediate switch from rear- to forefoot strike pattern to perform an open stance tennis forehand for 30% of children tennis players. The purpose of the study was to examine the long-term effects of a gradual reduction in the shoe drop on the biomechanics of children tennis players performing open stance forehands. Thirty children tennis players participated in 2 laboratory biomechanical test sessions (intermediate: +4 months and final: +8 months) after an inclusion visit where they were randomly assigned to control (CON) or experimental (EXP) group. CON received 12-mm-drop shoes twice, whereas EXP received 8 mm then 4-mm-drop shoes. Strike index indicated that all CON were rearfoot strikers in intermediate and final test sessions. All EXP were rearfoot strikers in intermediate test session, but half the group switched towards a forefoot strike pattern in final test session. This switch resulted in a decreased loading rate of the ground reaction force (-73%, p = .005) but increased peak ankle plantarflexors moment (+47%, p = .050) and peak ankle power absorption (+107%, p = .005) for these participants compared with CON. Biomechanical changes associated with the long-term use of partial minimalist shoes suggest a reduction in heel compressive forces but an increase in Achilles tendon tensile forces.

Ultrasonographic quantification of architectural response in tibialis anterior to neuromuscular electrical stimulation.

While muscle contraction in voluntary efforts has been widely investigated, little is known about contraction during neuromuscular electrical stimulation (NMES). The aim of this study was to quantify in vivo muscle architecture of agonist and antagonist muscles at the ankle joint during NMES. Muscle fascicle lengths and pennation angles of the tibialis anterior (TA) and lateral gastrocnemius muscles were assessed via ultrasonography in 8 healthy young males. Measures were obtained during maximal NMES and torque-matched voluntary dorsiflexion contractions. In the TA, NMES induced a shorter fascicle length (67.2±8.1mmvs 74.6±11.4mm; p=0.04) and a greater pennation angle (11.0±2.4° vs 9.3±2.5°; p=0.03) compared with voluntary torque-matched dorsiflexion contractions. Architectural responses in the antagonist lateral gastrocnemius muscle did not significantly differ from rest or between voluntary and electrically induced contractions (p>0.05). Contraction of the antagonist muscle was not a contributing factor to a greater fascicle shortening and increased pennation angle in the TA during NMES. TA architectural response during NMES likely arose from the contribution of muscle synergists during voluntary contractions coupled with a potentially localized contractile activity under the stimulation electrodes during NMES induced contractions.

The influence of shoe aging on children running biomechanics.

Athletic children are prone to overuse injuries, especially at the heel and knee. Since footwear is an extrinsic factor of lower limb injury risk, the aim of this study was to assess the influence of shoe aging on children running biomechanics. Fourteen children active in sports participated in a laboratory biomechanical evaluation. A new pair of shoes was provided to each participant at an inclusion visit. Four months later, the participants performed a running task and their kinematics and kinetics were assessed both with their used shoes and with a new pair of shoes identical to the first. Furthermore, mechanical cushioning properties of shoes were evaluated before and after in-vivo aging. After 4months of use, the sole stiffness increased by 16% and the energy loss capacity decreased by 18% (p<0.001). No ankle or knee kinematic adjustment was found at foot strike in used shoes but changes were observed later during stance. Running with used shoes produced a higher loading rate of the vertical ground reaction force (+23%, p=0.016), suggesting higher compressive forces under the heel and placing children at risk to experience impact-related injuries. Nevertheless, the decreased peak ankle and knee power absorption in used shoes (-11%, p=0.010 and -12%, p=0.029, respectively) suggests a lower ankle and knee joints loading during the absorption phase that may be beneficial regarding stretch-related injuries.

The influence of shoe drop on the kinematics and kinetics of children tennis players.

This study investigated the immediate effects of reducing the shoe drop (i.e. the difference between the heel and the forefoot height) on the kinematics and kinetics of the lower extremities of children tennis players performing a tennis-specific movement. Thirteen children tennis players performed a series of simulated open stance forehands wearing 3 pairs of shoes differing only in the drop: 0 (D0), 6 (D6) and the control condition of 12 mm (D12). Two embedded forceplates and a motion capture system were used to analyse the ground reaction forces and ankle and knee joint angles and moments of the leading lower limb. In D6 compared with D12, the peak impact force was reduced by 24% (p = .004) and the ankle was less dorsiflexed at foot strike (p = .037). In D0 compared with D12, the peak impact force was reduced by 17% (p = .049), the ankle was less dorsiflexed at foot strike (p = .045) and the knee was more flexed at foot strike (p = .007). In addition, 4 out of 13 participants (31%) presented a forefoot strike pattern for some of the trials in D0. No difference was observed across shoe conditions for the peak knee extensor moment (p = .658) or the peak ankle plantarflexor moment (p = .071). The results provide preliminary data supporting the hypothesis that for children tennis players, using a 6-mm lower shoe drop might reduce heel impact forces and thus limit potentially impact-related injuries.

Differential impact of visual feedback on plantar- and dorsi-flexion maximal torque output.

The effect of visual feedback on enhancing isometric maximal voluntary contractions (MVC) was evaluated. Twelve adults performed plantar-flexion and dorsi-flexion MVCs in 3 conditions (no visual feedback, visual feedback, and visual feedback with target). There was no significant effect of visual conditions on dorsi-flexion MVC but there was an effect on plantar-flexion. Irrespective of whether a target was evident, visual feedback increased plantar-flexion MVC by ∼15%. This study highlights the importance of optimal feedback to enhance MVC.

A new approach of the Star Excursion Balance Test to assess dynamic postural control in people complaining from chronic ankle instability.

The purpose of this study was to quantitatively and qualitatively assess dynamic balance with accuracy in individuals with chronic ankle instability (CAI). To this aim, a motion capture system was used while participants performed the Star Excursion Balance Test (SEBT). Reached distances for the 8 points of the star were automatically computed, thereby excluding any dependence to the experimenter. In addition, new relevant variables were also computed, such as absolute time needed to reach each distance, lower limb ranges of motion during unipodal stance, as well as absolute error of pointing. Velocity of the center of pressure and range of variation of ground reaction forces have also been assessed during the unipodal phase of the SEBT thanks to force plates. CAI group exhibited smaller reached distances and greater absolute error of pointing than the control group (p<0.05). Moreover, the ranges of motion of lower limbs joints, the velocity of the center of pressure and the range of variation of the ground reaction forces were all significantly smaller in the CAI group (p<0.05). These reduced quantitative and qualitative performances highlighted a lower dynamic postural control. The limited body movements and accelerations during the unipodal stance in the CAI group could highlight a protective strategy. The present findings could help clinicians to better understand the motor strategies used by CAI patients during dynamic balance and may guide the rehabilitation process.

A reliable measure of footwear upper comfort enabled by an innovative sock equipped with textile pressure sensors.

Footwear comfort is essential and pressure distribution on the foot was shown as a relevant objective measurement to assess it. However, asperities on the foot sides, especially the metatarsals and the instep, make its evaluation difficult with available equipment. Thus, a sock equipped with textile pressure sensors was designed. Results from the mechanical tests showed a high linearity of the sensor response under incremental loadings and allowed to determine the regression equation to convert voltage values into pressure measurements. The sensor response was also highly repeatable and the creep under constant loading was low. Pressure measurements on human feet associated with a perception questionnaire exhibited that significant relationships existed between pressure and comfort perceived on the first, the third and the fifth metatarsals and top of the instep. Practitioner Summary: A sock equipped with textile sensors was validated for measuring the pressure on the foot top, medial and lateral sides to evaluate footwear comfort. This device may be relevant to help individuals with low sensitivity, such as children, elderly or neuropathic, to choose the shoes that fit the best.