Plantar Flexion Movements Research Articles

The Mechanical Functionality of the EXO-L Ankle Brace

Background: A new type of ankle brace (EXO-L) has recently been introduced. It is designed to limit the motion of most sprains without limiting other motions and to overcome problems such as skin irritation associated with taping or poor fit in the sports shoe. Purpose: To evaluate the claimed functionality of the new ankle brace in limiting only the motion of combined inversion and plantar flexion. Study Design: Controlled laboratory study. Methods: In 12 patients who received and used the new ankle brace, the mobility of the joints was measured with a highly accurate and objective in vivo 3-dimensional computed tomography (3D CT) stress test. Primary outcomes were the ranges of motion as expressed by helical axis rotations without and with the ankle brace between the following extreme positions: dorsiflexion to plantar flexion, and combined eversion and dorsiflexion to combined inversion and plantar flexion. Rotations were acquired for both talocrural and subtalar joints. A paired Student t test was performed to test the significance of the differences between the 2 conditions (P ≤ .05). Results: The use of the ankle brace significantly restricted the rotation of motion from combined eversion and dorsiflexion to combined inversion and plantar flexion in both the talocrural (P = .004) and subtalar joints (P < .001). No significant differences were found in both joints for the motion from dorsiflexion to plantar flexion. Conclusion: The 3D CT stress test confirmed that under static and passive testing conditions, the new ankle brace limits the inversion–plantar flexion motion that is responsible for most ankle sprains without limiting plantar flexion or dorsiflexion. Clinical Relevance: This test demonstrated its use in the objective evaluation of braces.

Effects of implantable peroneal nerve stimulation on gait quality, energy expenditure, participation and user satisfaction in patients with post-stroke drop foot using an ankle-foot orthosis.

To investigate whether an implantable functional electrical stimulation (FES) system of the common peroneal nerve (ActiGait®) improves relevant aspects of gait in chronic stroke patients with a drop foot typically using an ankle-foot orthosis (AFO). Ten community-dwelling patients participated, of whom eight patients could be analysed. Gait quality (kinematic, kinetic, and spatiotemporal characteristics) during a 10-meter comfortable walk test, normalised net energy expenditure during a 6-minute walk test, participation (physical activity and stroke impact) and user satisfaction were tested before implantation and at various moments after FES-system activation up to 26 weeks. Walking with FES yielded increased maximum paretic ankle plantarflexion (FES: -0.12; AFO: -4.79°, p < 0.01), higher paretic peak ankle power (FES: 1.46; AFO: 0.98 W/kg, p < 0.05) and better step length symmetry (FES: 14.90; AFO: 21.45% , p < 0.05). User satisfaction was higher for FES, but was unrelated to objective gait improvements. Energy expenditure and participation did not change. Implantable FES improved the use of residual ankle plantarflexion motion, ankle power of the paretic leg and step length symmetry compared to using an AFO, however, not resulting in decreased energy expenditure or improved participation. User satisfaction was highest with FES, but this was not related to the observed gait improvements.

Comparison of screw fixation with elastic fixation methods in the treatment of syndesmosis injuries in ankle fractures

17 patients with ankle syndesmosic injury were treated with a 4.5mm single cortical screw fixation (passage of screw 4 cortices) and 15 patients were treated with single-level elastic fixation material. All patients were evaluated according to the AOFAS ankle and posterior foot scale at the third, sixth and twelfth months after the fixation. The ankle range of movement was recorded together with the healthy side. The Student's t test was used for statistical comparisons. No statistical significant difference was observed between the AOFAS scores (p>0.05). The range of dorsiflexion and plantar flexion motion of the elastic fixation group at the 6th and 12th months were significantly better compared to the screw fixation group (p<0.01).Elastic fixation is as functional as screw fixation in the treatment of ankle syndesmosis injuries. The unnecessary need of a second surgical intervention for removal of the fixation material is another advantageous aspect of this method of fixation.

Passive ankle movement increases cerebral blood oxygenation in the elderly: an experimental study.

BackgroundAnkle exercise has been proven to be an effective intervention to increase venous velocity. However, the efficacy of ankle exercise for improving cerebral circulation has not been determined. We hypothesized that ankle exercise in the supine position would be able to increase oxyhemoglobin levels measured at the forehead.MethodsSeventeen community-dwelling elderly women participated in this study. We recorded blood pressure, heart rate (HR), and oxyhemoglobin (OxyHb) levels from the participants in the supine position. Participants repeated ankle plantar flexion and dorsiflexion movements for 1 min. Two types of exercise were used: active movement and passive movement. We used two-way analysis of variance to assess the differences in mean arterial blood pressure (MAP), HR, and OxyHb between different exercises (active and passive) and times (before and after exercise).ResultsThe HR and MAP increased during active exercise but not during passive exercise. On the other hand, the levels of OxyHb measured at the forehead were elevated during both active and passive exercises. This increase lasted at least 1 min after exercise. There was no significant difference between active and passive exercise with regard to OxyHb; however, a significant difference was observed between before and after exercise (p < 0.05, η2G = 0.153).ConclusionsThe physiological response of OxyHb to ankle exercise was different from that of the other cardiovascular functions. Both active and passive ankle exercises were able to increase cerebral blood oxygenation, whereas the other cardiovascular functions did not respond to passive exercise.

Comparison of the strength and range of motion of ankles' muscles in teenager boys with and without flatfoot

The purpose of the present survey is the comparison of the strength and range of motion of ankles' muscles in teenager boys with and without flatfoot. For this purpose, 50 subjects consisted of 25 students who had flexible flat foot, with a mean age, height and weight, 12 ± 0.87 years, 149.84 ± 9.71 cm, 45.92 ± 10.58 kg respectively, and 25 students without flatfoot with a mean age, height and weight, 11.92 ± 0.81 years, 150.88 ± 8.21 cm and 46.28 ± 9.34 kg respectively, participated in the research after medical examination by the physician. The comparison of the strength of ankle's muscles in D.F and P.F, and the ankles' range of motion in dorsiflexion and plantarflexion was evaluated in three conditions of without resistance, under pressure, and with resistance in both healthy and affected groups. Clear universal goniometer was used for measuring the range of motion. Lafayeette hand-held digital dynamometer was used for measuring the strength. All the data was evaluated through SPSS software version 20. Alpha 0.05 was regarded as the level of significance. Independent t-test was used for comparing the aforementioned variables in two groups. To compare the range of motion in D.F and P.F in three evaluating conditions for each of the motions one inter group variable of measurement condition (including 3 levels) and one intra group variable was used based on separated variance analysis. Multiple analysis of variance test and one-way analysis of variance (ANOVA) with Bonferroni correction was used. The present investigation showed that no significant difference was seen between the aforesaid hypotheses among two healthy and flat foot affected groups.

The effect of ankle Kinesio taping on range of motion and agility during exercise in university students

Objective: The purpose of this study was to examine the effects of ankle Kinesio taping on range of motion and agility during exercise in university students. Design: Cross-sectional study. Methods: Thirty subjects were randomly allocated to two groups: taping group (n=15) and non-taping group (n=15). All groups underwent the same exercise program including stretching for 30 minutes. The exercise program proceeded in the following order: five minutes of stretching, a 20-minutes exercise program, and additional five minutes of stretching. Of the eight exercise methods suggested by Purcell et al, seven were chosen (lateral shuffle, forward and backward running, agility ladder, figure-of-8, forward jogging while jumping over cones, wall jumps and zigzags); 90o cuts with lateral shuffle were omitted. The range of motion of ankle dorsiflexion and plantarflexion was measured using the goniometer. Agility was measured using the side hop test. Results: For ankle range of motion, the taping group showed significant differences in dorsiflexion and plantarflexion on both sides (p<0.05). The non-taping group showed significant differences only in left plantarflexion (p<0.05). There was a significant difference in dorsiflexion on both sides between the taping group and the non-taping group (p<0.05). All groups showed significant differences in agility on the left and right ankle (p<0.05). There was a significant difference in left ankles between the taping group and the non-taping group (p<0.05). Conclusions: Kinesio taping increased range of motion and agility during exercise in university students. Additional research on Kinesio taping for improving range of motion and agility is needed.

Immediate Effects of Talocrural and Subtalar Joint Mobilization on Balance in the Elderly

The aim of the present study was to evaluate the immediate effects of therapeutic mobilization of the talocrural and subtalar joints on ankle mobility and postural control in elderly subjects. Nineteen subjects (83.1 ± 6 years, 159 ± 1 cm; 56.1 ± 9.7 kg - mean ± standard deviation) participated in this study. The centre of pressure (COP) displacements along the anterior-posterior and medial-lateral axes was recorded in static and dynamic conditions on a force platform before and after therapeutic mobilization of the feet and ankles without blinding the subjects. In static conditions, the sway area is reduced contrarily to dynamic conditions where the sway area is increased. In the two experimental sessions, subjects showed comparable COP displacements and the total length of the oscillations. Results demonstrated a significant improvement immediately after mobilization for ankle range of motion in dorsal flexion (right +4.7°; left +3.2°) and plantar flexion (right 5.2°; left +4.2°). These results suggested that postural control is improved in static conditions and decreased in dynamic conditions. Therapeutic mobilization of feet and ankles in the elderly provides an immediate improvement in joint range of movement in dorsal and plantar flexion.

Characterization of kinesiological patterns of the frontal kick, mae-geri, in karate experts and non-karate practitioners

Presently, coaches and researchers need to have a better comprehension of the kinesiological parameters that should be an important tool to support teaching methodologies and to improve skills performance in sports. The aim of this study was to (i) identify the kinematic and neuromuscular control patterns of the front kick (&lt;em&gt;mae-geri&lt;/em&gt;) to a fixed target performed by 14 experienced karate practitioners, and (ii) compare it with the execution of 16 participants without any karate experience, allowing the use of those references in the analysis of the training and learning process. Results showed that the kinematic and neuromuscular activity during the kick performance occurs within 600 ms. Muscle activity and kinematic analysis demonstrated a sequence of activation bracing a proximal-to-distal direction, with the muscles presenting two distinct periods of activity (1, 2), where the karateka group has a greater intensity of activation – root mean square (RMS) and electromyography (EMG) peak – in the first period on &lt;em&gt;Rectus Femoris&lt;/em&gt; (RF1) and &lt;em&gt;Vastus Lateralis&lt;/em&gt; (VL1) and a lower duration of co-contraction in both periods on &lt;em&gt;Rectus Femoris&lt;/em&gt;-&lt;em&gt;Biceps Femoris&lt;/em&gt; and &lt;em&gt;Vastus Lateralis&lt;/em&gt;-&lt;em&gt;Biceps Femoris&lt;/em&gt; (RF-BF; VL-BF). In the skill performance, the hip flexion, the knee extension and the ankle plantar flexion movements were executed with smaller difference in the range of action (ROA) in the karateka group, reflecting different positions of the segments. In conclusion, it was observed a general kinesiological pattern, which was similar in karateka and non-karateka practitioners. However, in the karateka group, the training induces a specialization in the muscle activity reflected in EMG and kinematic data, which leads to a better ballistic performance in the execution of the &lt;em&gt;mae-geri&lt;/em&gt; kick, associated with a maximum speed of the distal segments, reached closer to the impact moment, possibly representing more power in the contact.

Relative sensitivity of depth discrimination for ankle inversion and plantar flexion movements.

25 participants (20 women, 5 men) were tested for sensitivity in discrimination between sets of six movements centered on 8 degrees, 11 degrees, and 14 degrees, and separated by 0.3 degrees. Both inversion and plantar flexion movements were tested. Discrimination of the extent of inversion movement was observed to decline linearly with increasing depth; however, for plantar flexion, the discrimination function for movement extent was found to be non-linear. The relatively better discrimination of plantar flexion movements than inversion movements at around 11 degrees from horizontal is interpreted as an effect arising from differential amounts of practice through use, because this position is associated with the plantar flexion movement made in normal walking. The fact that plantar flexion movements are discriminated better than inversion at one region but not others argues against accounts of superior proprioceptive sensitivity for plantar flexion compared to inversion that are based on general properties of plantar flexion such as the number of muscle fibres on stretch.

Relationship of EMG/SMG features and muscle strength level: an exploratory study on tibialis anterior muscles during plantar-flexion among hemiplegia patients.

BackgroundImprovement in muscle strength is an important aim for the rehabilitation of hemiplegia patients. Presently, the rehabilitation prescription depends on the evaluation results of muscle strength, which are routinely estimated by experienced physicians and therefore not finely quantitative. Widely-used quantification methods for disability, such as Barthel Index (BI) and motor component of Functional Independent Measure (M-FIM), yet have limitations in their application, since both of them differentiated disability better in lower than higher disability, and they are subjective and recorded in wide scales. In this paper, to explore finely quantitative measures for evaluation of muscle strength level (MSL), we start with the study on quantified electromyography (EMG) and sonomyography (SMG) features of tibialis anterior (TA) muscles among hemiplegia patients.Methods12 hemiplegia subjects volunteered to perform several sets of plantar-flexion movements in the study, and their EMG signals and SMG signals were recorded on TA independently to avoid interference. EMG data were filtered and then the root-mean-square (RMS) was computed. SMG signals, specifically speaking, the muscle thickness of TA, were manually measured by two experienced operators using ultrasonography. Reproducibility of the SMG assessment on TA between operators was evaluated by non-parametric test (independent sample T test). Possible relationship between muscle thickness changes (TC) of TA and muscle strength level of hemiplegia patients was estimated.ResultsMean of EMG RMS between subjects is found linearly correlated with MSL (R2 = 0.903). And mean of TA muscle TC amplitudes is also linearly correlated with MSL among dysfunctional legs (R2 = 0.949). Moreover, rectified TC amplitudes (dysfunctional leg/ healthy leg, DLHL) and rectified EMG signals (DLHL) are found in linear correlation with MSL, with R2 = 0.756 and R2 = 0.676 respectively. Meanwhile, the preliminary results demonstrate that patients’ peak values of TC are generally proportional to their personal EMG peak values in 12 dysfunctional legs and 12 healthy legs (R2 = 0.521).ConclusionsIt’s concluded that SMG could be a promising option to quantitatively estimate MSL for hemiplegia patients during rehabilitation besides EMG. However, after this exploratory study, they should be further investigated on a larger number of subjects.

Decrease in Talocrural Joint Mobility is Related to Alteration of the Arterial Blood Flow Velocity in the Lower Limb in Diabetic Women.

[Purpose] The purpose of this study was to correlate the talocrural range of motion (ROM) and blood flow velocity in the lower limb arteries of diabetic women. [Subjects and Methods] Thirty women were divided into a control group (G1), consisting of 15 sedentary right-handed subjects (41.27 ± 7.24 years old) who had no history of blood system disorder, and a diabetes group (G2), consisting of 15 sedentary right-handed subjects (57.87 ± 6.20 years old) who had type 2 diabetes mellitus. Talocrural ROM was measured by using goniometry for dorsiflexion and plantar flexion movements. In addition, blood flow velocity of the dorsalis pedis, posterior tibial, and popliteal arteries was also assessed. [Results] No significant differences were found between the groups by comparing talocrural ROM and arterial blood velocity. However, a significant association was found in G2 only between the following variables: plantar flexion and blood flow velocity of the dorsalis pedis artery (rs = 0.57), plantar flexion and blood flow velocity of the popliteal artery (rs = 0.50), and dorsiflexion and blood flow velocity of the posterior tibial artery (rs = 0.57). [Conclusion] The decrease in talocrural ROM is related to a decrease in the arterial blood flow velocity in diabetic women.

S1110302 空気圧アクチュエータを用いて3自由度の動作を実現する足首関節用リハビリ装置の開発([S111-03]第20回卒業研究コンテスト(3),機素潤滑設計部門)

With aging society, the number of bedridden people is increasing. Contracture in the joint of bedridden person occurs and physical therapists try to prevent contracture by rehabilitation. However, patients cannot receive enough rehabilitation due to a physical therapist shortage. This study aims at development of an automatic rehabilitation system for the range of motion exercise in the ankle joint. The system is configured with light weight and flexible pneumatic actuators. Dorsiflexion, plantar flexion, eversion, inversion, abduction and adduction motions are confirmed by the system. Basic experiments for clarifying the characteristics of these units were conducted. Subjects of this experiment are nine persons with a normal of men and women from 19 years old to 38 years old. About dorsiflexion, adduction and abduction, It was achieved a necessary angle at the ankle joints excursion training, but was insufficient about planter flexion, inversion and eversion.

Comparing Self-Selected Speed Walking of the Elderly With Self-Selected Slow, Moderate, and Fast Speed Walking of Young Adults

ObjectiveTo find the characteristics of elderly gait, we compared the elderly walking at a moderate speed with the young adult walking at a slow, moderate, and fast speed.Methods3D gait analysis was performed on 15 elderly and 15 young adults. Temporo-spatial, kinematic, and kinetic parameters were obtained. Self-selected moderate speed of the elderly walking was compared with self-selected varying speed of the young adults walking.ResultsThe elderly walked at slower speeds and had shorter step length, but showed similar cadences compared to the young adults. These results remained identical even after the normalization with height. The kinematic and the kinetic graph patterns did not show specific differences between the elderly and the young subjects. Ankle plantarflexion (APF) motion was prominently decreased in the elderly subjects. Hip flexion (HF) motion remained within similar range for the young adults'. HF moment and power were similar with the young adults', but APF power and hip extension power were decreased in the elderly subjects'.ConclusionA decreased APF motion and power were thought to be specific findings in the elderly walking. The preservation of HF motion and power could be considered a compensation mechanism or a modified neuromuscular pattern in the elderly. The characteristics of the elderly walking should be taken into account when planning rehabilitation strategies of elderly gait training and for future studies on the elderly population.

Ankle Arthroplasty and Ankle Arthrodesis

This study compared patients with isolated end-stage ankle osteoarthritis, after undergoing either total ankle arthroplasty or arthrodesis, using gait analysis and patient-reported outcome measures to elucidate differences between the two treatment options, as compared with a healthy control group. Gait analyses were performed on patients with isolated ankle arthritis more than one year after undergoing either total ankle arthroplasty or arthrodesis during a ten-year period. Validated outcome questionnaire data were obtained. Seventeen patients undergoing total ankle arthroplasty, seventeen patients undergoing arthrodesis, and ten matched control subjects were included for comparison. Patients who had undergone arthroplasty, when compared with patients who had undergone arthrodesis, demonstrated greater postoperative total sagittal plane motion (18.1° versus 13.7°; p < 0.05), dorsiflexion (11.9° versus 6.8°; p < 0.05), and range of tibial tilt (23.1° versus 19.1°; p < 0.05). Plantar flexion motion was not equivalent to normal in either group. Ankle moments and power in both treatment groups remained significantly lower compared with the control group (p < 0.05 between each treatment group and the control group for both variables). Gait patterns in both treatment groups were not completely normalized. Improvements in patient-reported Ankle Osteoarthritis Scale and Short Form-36 scores were similar for both treatment groups. The gait patterns of patients following three-component, mobile-bearing total ankle arthroplasty more closely resembled normal gait when compared with the gait patterns of patients following arthrodesis. Dorsal motion in the sagittal plane was primarily responsible for the differences. Improvement in self-reported clinical outcome scores was similar for both groups. Further investigation is needed to determine why patients who have undergone total ankle arthroplasty do not use the plantar flexion motion in the terminal-stance phase and to explain the limited increase in power generation at toe-off after arthroplasty. Results obtained from this study may be used for future modifications of ankle prostheses and may add to clinicians' ability to inform patients of predicted functional outcomes prior to the treatment of end-stage ankle osteoarthritis.

Oxygen cost during walking in children with arthrogryposis

plantarflexion stiffness. This decrease in stiffness, however, could not be confirmed during gait by increased plantarflexion motion during the first ankle rocker (initial contact to foot flat) contact; plantarflexionmotion during the first ankle rocker was found to be unchanged. However, the significantly less maximum ankle power absorption with the SSO versus the SO indicates less energy storage during dorsiflexion in the SSO carbon spring than in the SO. This may also have influenced the significantly lower ankle plantarflexion moment with the SSO versus the SO. All children in the study

Gait characteristics of multiple sclerosis patients in the absence of clinical disability

Purpose: Motor deficits in lower extremities and gait abnormalities are a major feature of the multiple sclerosis (MS) patients. Patients with minimal clinical disability have subtle gait changes. The aim of this study was to analyze the gait characteristics of MS patients in the absence of clinical disability. Method: A case–control study was carried out with 12 MS patients and 12 matched healthy controls. The subjects underwent a clinical neurological evaluation to determine their disability level (EDSS ≤ 1.5). Then, the subjects were referred for completion self-report questionnaires (gait, perceived balance confidence, physical activity and fatigue), gait clinical trials, and 3D kinematic analysis. Results: MS patients showed more impairment of perceived fatigue, perceived of walking impact and perceived balance confidence, despite having no disability. Gait characteristics showed no differences when they were determined by clinical observation. The 3D kinematic analysis of gait showed slight but significant changes in ankle movement. Conclusion: MS patients with no clinical disability have discrete changes in gait that can be evidenced by perceived impact on walking and kinematic evaluation, mainly of ankle movement. Moreover, there is a decrease in perceived balance confidence and an increase in perceived fatigue, which are correlated despite having different origins.Implications for RehabilitationMultiple sclerosis patients showed changes in gait pattern even with no clinical disability.The reduction of plantar flexion movement at toe off may be the first compensatory strategy on early phases of disease.Fatigue, higher walking impact, and less balance confidence are early symptoms of Multiple Sclerosis.

Direct Quantitative Assessment of the Peripheral Artery Collateral Circulation in Patients Undergoing Angiography

Despite the fact that numerous studies have pursued the strategy of improving collateral function in patients with peripheral artery disease, there is currently no method available to quantify collateral arterial function of the lower limb. Pressure-derived collateral flow index (CFIp, calculated as (occlusive pressure-central venous pressure)/(aortic pressure-central venous pressure); pressure values in mm Hg) of the left superficial femoral artery was obtained in patients undergoing elective coronary angiography using a combined pressure/Doppler wire (n=30). Distal occlusive pressure and toe oxygen saturation (Sao2) were measured for 5 minutes under resting conditions, followed by an exercise protocol (repetitive plantar-flexion movements in supine position; n=28). In all patients, balloon occlusion of the superficial femoral artery over 5 minutes was painless under resting conditions. CFIp increased during the first 3 minutes from 0.451±0.168 to 0.551±0.172 (P=0.0003), whereas Sao2 decreased from 98±2% to 93±7% (P=0.004). Maximal changes of Sao2 were inversely related to maximal CFIp (r(2)=0.33, P=0.003). During exercise, CFIp declined within 1 minute from 0.560±0.178 to 0.393±0.168 (P<0.0001) and reached its minimum after 2 minutes of exercise (0.347±0.176), whereas Sao2 declined to a minimum of 86±6% (P=0.002). Twenty-five patients (89%) experienced pain or cramps/tired muscles, whereas 3 (11%) remained symptom-free for an occlusion time of 10 minutes. CFIp values were positively related to the pain-free time span (r(2)=0.50, P=0.002). Quantitatively assessed collateral arterial function at rest determined in the nonstenotic superficial femoral artery is sufficient to prevent ischemic symptoms during a total occlusion of 5 minutes. During exercise, there is a decline in CFIp that indicates a supply-demand mismatch via collaterals or, alternatively, a steal phenomenon. CLINICAL TRIAL REGISTRATION-URL: http://www.clinicaltrials.gov. UNIQUE IDENTIFIER: NCT01742455.

Ankle morphology amplifies calcaneus movement relative to triceps surae muscle shortening

The present study investigated the mechanical role of the dorsoventral curvature of the Achilles tendon in the conversion of the shortening of the plantarflexor muscles into ankle joint rotation. Dynamic, sagittal-plane magnetic resonance spin-tagged images of the ankle joint were acquired in six healthy subjects during both passive and active plantarflexion movements driven by a magnetic resonance compatible servomotor-controlled foot-pedal device. Several points on these images were tracked to determine the 1) path and deformation of the Achilles tendon, 2) ankle's center of rotation, and 3) tendon moment arms. The degree of mechanical amplification of joint movement was calculated as the ratio of the displacements of the calcaneus and myotendinous junction. In plantarflexion, significant deflection of the Achilles tendon was evident in both the passive (165.7 ± 7.4°; 180° representing a straight tendon) and active trials (166.9 ± 8.8°). This bend in the dorsoventral direction acts to move the Achilles tendon closer to the ankle's center of rotation, resulting in an ∼5% reduction of moment arm length. Over the entire range of movement, the overall displacement of the calcaneus exceeded the displacement of the myotendinous junction by ∼37%, with the mechanical gains being smaller in dorsi- and larger in plantarflexed joint positions. This is the first study to assess noninvasively and in vivo using MRI the curvature of the Achilles tendon during both passive and active plantarflexion movements. The dorsoventral tendon curvature amplifies the shortening of the plantarflexor muscles, resulting in a greater displacement of the tendon's insertion into the calcaneus compared with its origin.

Investigation of the biomechanical behaviour of hindfoot ligaments

The aim of this work is to provide a computational tool for the mechanical characterization of the hindfoot ligaments. The investigation is performed by a coupled numerical and experimental approach. For this purpose, a numerical model that represents the complex structural configuration of the hindfoot and the typical features of the mechanical behaviour of the ligament tissue is developed. The geometrical analysis of the anatomical site is performed starting from the processing of computed tomography and magnetic resonance images. Accounting for morphometric measurements, the virtual solid model provides an averaged configuration of the hindfoot structure. In order to specify the mechanical behaviour of the ligament tissue, a fibre-reinforced visco-hyperelastic model is adopted. The formulation accounts for the anisotropic configuration, geometric non-linearity, non-linear elasticity and time-dependent phenomena. Numerical analyses are performed to evaluate the biological tissues and structure mechanics with regard to physiological boundary conditions, accounting for dorsiflexion and plantarflexion movements. In order to evaluate the reliability of the numerical model developed, the experimental data are compared with the numerical results. The numerical results are in agreement with the range of values obtained by experimental test confirming the accuracy of the procedure adopted.

Neuromuscular determinants of maximum walking speed in well-functioning older adults

Maximum walking speed may offer an advantage over usual walking speed for clinical assessment of age-related declines in mobility function that are due to neuromuscular impairment. The objective of this study was to determine the extent to which maximum walking speed is affected by neuromuscular function of the lower extremities in older adults. We recruited two groups of healthy, well functioning older adults who differed primarily on maximum walking speed. We hypothesized that individuals with slower maximum walking speed would exhibit reduced lower extremity muscle size and impaired plantarflexion force production and neuromuscular activation during a rapid contraction of the triceps surae muscle group (soleus (SO) and gastrocnemius (MG)).All participants were required to have usual 10-meter walking speed of >1.0m/s. If the difference between usual and maximum 10m walking speed was <0.6m/s, the individual was assigned to the “Slower” group (n=8). If the difference between usual and maximum 10-meter walking speed was >0.6m/s, the individual was assigned to the “Faster” group (n=12). Peak rate of force development (RFD) and rate of neuromuscular activation (rate of EMG rise) of the triceps surae muscle group were assessed during a rapid plantarflexion movement. Muscle cross sectional area of the right triceps surae, quadriceps and hamstrings muscle groups was determined by magnetic resonance imaging.Across participants, the difference between usual and maximal walking speed was predominantly dictated by maximum walking speed (r=.85). We therefore report maximum walking speed (1.76 and 2.17m/s in Slower and Faster, p<.001) rather than the difference between usual and maximal. Plantarflexion RFD was 38% lower (p=.002) in Slower compared to Faster. MG rate of EMG rise was 34% lower (p=.01) in Slower than Faster, but SO rate of EMG rise did not differ between groups (p=.73). Contrary to our hypothesis, muscle CSA was not lower in Slower than Faster for the muscle groups tested, which included triceps surae (p=.44), quadriceps (p=.76) and hamstrings (p=.98). MG rate of EMG rise was positively associated with RFD and maximum 10m walking speed, but not the usual 10m walking speed.These findings support the conclusion that maximum walking speed is limited by impaired neuromuscular force and activation of the triceps surae muscle group. Future research should further evaluate the utility of maximum walking speed for use in clinical assessment to detect and monitor age-related functional decline.