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Muscle Activation Analysis of Flatfoot According to the Slope of a Treadmill
Abstract
[Purpose] The purpose of this study was to determine the difference between the flatfoot and normal foot on slopes using electromyography. [Subjects] This study was conducted on 30 adults having normal feet (N=15) and flatfeet (N=15) from who were 21 to 30 years old and no neurological history or gait problems. [Methods] A treadmill (AC5000M, SCIFIT, UK) was used to analyze kinematic features during walking, using slopes of -10, 0, and 10% and normal gait velocities. A surface electromyogram (TeleMyo 2400T, Noraxon Co., USA) was used to measure muscle activity changes. [Results] Muscle activity of the flatfoot was significantly different at most muscles, and muscle activity in the normal foot was significantly different in the vastus medialis, vastus lateralis, tibialis anterior, peroneus longus, medial gastrocnemius, and lateral gastrocnemius. Comparison of muscle activity between the flatfoot and normal foot showed significant differences in the tibialis anterior and abductor hallucis muscle. [Conclusion] In the gait of people with flatfoot while walking on slopes, muscle activation of the tibialis anterior is higher than for normal feet and muscle activation of the abductor hallucis muscle is relatively lower than for normal feet in the gait while walking on slopes. This is due to lack of the ability to absorb shock on the ground as a result of the weakned function of the medial longitudinal arch.
... However, there is no general consensus regarding the activity of some lower limb muscles including vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and medial gastrocnemius (MG) in pronated foot subjects. Some researchers have reported an increase in the activity of VL ( Chang et al., 2012) and VM ( Lee and Kim, 2014;Kim and Lee, 2013b) muscles, others reported reduced muscle activity in BF ( Chang et al., 2012) and MG ( Hunt and Smith, 2004;Chang et al., 2012) while some others found no difference in the activity of VL ( Lee and Kim, 2014;Lee, 2013a, 2013b;Lee et al., 2013;Kim and Lee, 2013a), VM ( Lee et al., 2013;Kim and Lee, 2013a), BF ( Lee and Kim, 2014;Lee, 2013a, 2013b) and MG ( Murley et al., 2009;Lee and Kim, 2014;Lee, 2013a, 2013b;Lee et al., 2013;Kim and Lee, 2013a). These conflicting results may arise from only regarding individual muscles, and not paying attention to their synergetic functions. ...
... However, there is no general consensus regarding the activity of some lower limb muscles including vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and medial gastrocnemius (MG) in pronated foot subjects. Some researchers have reported an increase in the activity of VL ( Chang et al., 2012) and VM ( Lee and Kim, 2014;Kim and Lee, 2013b) muscles, others reported reduced muscle activity in BF ( Chang et al., 2012) and MG ( Hunt and Smith, 2004;Chang et al., 2012) while some others found no difference in the activity of VL ( Lee and Kim, 2014;Lee, 2013a, 2013b;Lee et al., 2013;Kim and Lee, 2013a), VM ( Lee et al., 2013;Kim and Lee, 2013a), BF ( Lee and Kim, 2014;Lee, 2013a, 2013b) and MG ( Murley et al., 2009;Lee and Kim, 2014;Lee, 2013a, 2013b;Lee et al., 2013;Kim and Lee, 2013a). These conflicting results may arise from only regarding individual muscles, and not paying attention to their synergetic functions. ...
... However, there is no general consensus regarding the activity of some lower limb muscles including vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and medial gastrocnemius (MG) in pronated foot subjects. Some researchers have reported an increase in the activity of VL ( Chang et al., 2012) and VM ( Lee and Kim, 2014;Kim and Lee, 2013b) muscles, others reported reduced muscle activity in BF ( Chang et al., 2012) and MG ( Hunt and Smith, 2004;Chang et al., 2012) while some others found no difference in the activity of VL ( Lee and Kim, 2014;Lee, 2013a, 2013b;Lee et al., 2013;Kim and Lee, 2013a), VM ( Lee et al., 2013;Kim and Lee, 2013a), BF ( Lee and Kim, 2014;Lee, 2013a, 2013b) and MG ( Murley et al., 2009;Lee and Kim, 2014;Lee, 2013a, 2013b;Lee et al., 2013;Kim and Lee, 2013a). These conflicting results may arise from only regarding individual muscles, and not paying attention to their synergetic functions. ...
Background:
Pronated foot is one of the most important factors that may lead to musculoskeletal injuries of the lower extremities. It is known that in a pronated foot, excessive mechanical loads are applied to the lower limb structures, which result in the altered foot biomechanics, including vertical ground reaction forces (VGRFs) and rate of loading (ROL). Therefore, the aim of this study was to determine the changes in foot kinetic parameters in the pronated compared to the normal foot structures.
Methods:
In this cross-sectional study, 15 individuals (mean age of 23.27 ± 3.28 years) with asymptomatic pronated feet and 15 normal subjects (mean age of 23.40 ± 3.11 years) were recruited from both genders by using a simple non-random sampling method. VGRF, ROL, and the resultant vector of time to stabilization (RVTTS) were evaluated during the forward jump landing task by using a force plate.
Results:
The findings showed that the following parameters were significantly higher in the group of pronated feet than in the normal subjects: VGRF (3.30 ± 0.17 vs. 2.81 ± 0.15, p = .042), ROL (0.10 ± 0.01 vs. 0.07 ± 0.006, p = .020), and RVTTS (2592.80 ± 141.24 vs. 2114.00 ± 154.77, p = .030).
Conclusion:
All the measured foot kinetic parameters were higher in the pronated foot subjects than in the normal participants. An impaired movement control and greater forces imposed on the foot region of the pronated foot, compared to the normal foot individuals, were discovered indicating the former group's possible increase of susceptibility to various musculoskeletal injuries.
... However, there is no general consensus regarding the activity of some lower limb muscles including vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and medial gastrocnemius (MG) in pronated foot subjects. Some researchers have reported an increase in the activity of VL (Chang et al., 2012) and VM Kim, 2014, Kim andLee, 2013b) muscles, others reported reduced muscle activity in BF (Chang et al., 2012) and MG (Hunt andSmith, 2004, Chang et al., 2012) while some others found no difference in the activity of VL (Lee and Kim, 2014, Kim and Lee, 2013b, Lee et al., 2013, Kim and Lee, 2013a, VM (Lee et al., 2013, Kim andLee, 2013a) (Lee and Kim, 2014, Kim and Lee, 2013b, Kim and Lee, 2013a and MG (Murley et al., 2009, Lee and Kim, 2014, Kim and Lee, 2013b, Lee et al., 2013, Kim and Lee, 2013a. These conflicting results may arise from only regarding individual muscles and not paying attention to their synergetic functions. ...
... However, there is no general consensus regarding the activity of some lower limb muscles including vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and medial gastrocnemius (MG) in pronated foot subjects. Some researchers have reported an increase in the activity of VL (Chang et al., 2012) and VM Kim, 2014, Kim andLee, 2013b) muscles, others reported reduced muscle activity in BF (Chang et al., 2012) and MG (Hunt andSmith, 2004, Chang et al., 2012) while some others found no difference in the activity of VL (Lee and Kim, 2014, Kim and Lee, 2013b, Lee et al., 2013, Kim and Lee, 2013a, VM (Lee et al., 2013, Kim andLee, 2013a) (Lee and Kim, 2014, Kim and Lee, 2013b, Kim and Lee, 2013a and MG (Murley et al., 2009, Lee and Kim, 2014, Kim and Lee, 2013b, Lee et al., 2013, Kim and Lee, 2013a. These conflicting results may arise from only regarding individual muscles and not paying attention to their synergetic functions. ...
... However, there is no general consensus regarding the activity of some lower limb muscles including vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and medial gastrocnemius (MG) in pronated foot subjects. Some researchers have reported an increase in the activity of VL (Chang et al., 2012) and VM Kim, 2014, Kim andLee, 2013b) muscles, others reported reduced muscle activity in BF (Chang et al., 2012) and MG (Hunt andSmith, 2004, Chang et al., 2012) while some others found no difference in the activity of VL (Lee and Kim, 2014, Kim and Lee, 2013b, Lee et al., 2013, Kim and Lee, 2013a, VM (Lee et al., 2013, Kim andLee, 2013a) (Lee and Kim, 2014, Kim and Lee, 2013b, Kim and Lee, 2013a and MG (Murley et al., 2009, Lee and Kim, 2014, Kim and Lee, 2013b, Lee et al., 2013, Kim and Lee, 2013a. These conflicting results may arise from only regarding individual muscles and not paying attention to their synergetic functions. ...
Background:
Pronated of the foot is one of the important factors contributing to musculoskeletal problems affecting the lower extremities. It is known that in a pronated foot, excessive mechanical load is applied to the lower limb structures which may result in altered biomechanics and muscle activation patterns. The aim of this study was to determine changes in the muscle activation pattern of the lower extremities in individuals with pronated, compared to normal, feet, using the voluntary response index (VRI).
Methods:
In this cross sectional study, 15 asymptomatic pronated foot individuals (mean age 23.27 ± 3.28 years) and 15 normal subjects (mean age 23.40 ± 3.11 years) were recruited by simple non-random sampling. Electrical activities of gluteus medius (GM), vastus lateralis (VL), vastus medialis (VM), biceps femoris, semitendinosus (ST), and medial gastrocnemius (MG) muscles were recorded during a forward jump landing task. Voluntary response index (VRI) variables, included similarity index (SI) and magnitude (Mag) were also evaluated.
Results:
Muscle activity of VM (p < 0.001) and ST (p = 0.010) were significantly higher but VL (p = 0.039) and MG (p = 0.001) were significantly lower in pronated foot, compared to normal subjects. Similarity index was found to be different (p < 0.001) between pronated foot and healthy individuals. No significant difference was found in terms of Mag between the two groups (p = 0.576).
Conclusion:
The altered pattern of lower limb muscle activation identified in the pronated foot during landing may be attributed to the different activation involving VL, VM, MG and ST muscles. Adaptations to the biomechanical effects, due to the pronated foot causing altered activation of VL, VM, MG, and ST muscles, results in an altered pattern of muscle activation. This change in activation pattern may harm the effectiveness of movement control processes; and might also predispose individuals with pronated feet, to injuries. It seems that an altered motor strategy with the aim of minimizing biomechanical changes, predisposes individuals to injuries. However, further large scale studies are needed to support the findings of the present study.
... This proportion suggests that flat foot are occurring more prevalently in the adult population and have become a common structural abnormality of the foot. Flat foot not only harm strength and balance performance [13][14][15][16] but also reduce muscle activation during walking [56]. However, it remains uncertain whether flat foot affect vertical jump. ...
Objective
The necessity to exclude flat foot when selecting athletes is a controversial issue. This study aimed to investigate whether flat foot affects vertical jump.
Methods
The quality of the literature was assessed using the observational study quality assessment tool provided by the Joanna Briggs Institute (JBI) Centre for Evidence-Based Health Care in Australia. Meta-analysis, heterogeneity testing, sensitivity analysis, subgroup analysis, and forest plot were conducted using Review Manager 5.4.
Results
In the end, 9 articles met the meta-analysis criteria. Due to the heterogeneity of the studies, only vertical jump height was used as an indicator for meta-analysis. Meta-analysis results showed low heterogeneity among studies (I² = 6%, P = 0.39), and the combined effect size showed no significant difference in jumping height between flat foot and normal foot (P = 0.73, ES = 0.13, 95%CI [-0.58, 0.83]). Subgroup analyses showed no significant differences in jump heights between flat and normal foot in either the adolescent subgroup (ES = 0.07, 95% CI [-1.04, 1.18]) or the adult subgroup (ES = 0.16, 95% CI [-0.76, 1.08]). Subgroups were divided according to training background, and jump height was unaffected by flat foot in both athletes (ES = -0.08, 95%CI [-1.07, 0.90]) and amateur (ES = 0.34, 95%CI [-0.67, 1.35]).
Conclusion
Overall, flat foot do not affect vertical jump height, although flat foot have different vertical jump biomechanics. This study breaks the bias that flat foot have poorer athletic performance. The meta-analysis has been registered with PROSPERO under registration number CRD42023481326.
... Возможно, ЭНМГ-особенности, полученные у детей, могут коренным образом повлиять на выбор хирургической тактики лечения ПС, поскольку выявленные изменения в возрасте 7-14 лет практически не поддаются коррекции. К сожалению, мы встретили лишь единичные работы, посвященные состоянию нейромышечного аппарата нижних конечностей при плоскостопии у детей, что не позволяет составить целостную картину[14,15].В программу был включен алгоритм анализа степени нарушений при статических деформациях стоп у детей, в частности плоской стопы, основанный на оценке кластерных данных со статистической значимостью: -фактор 1 «Рентгенологический показатель стопы» (угол продольного медиального свода, высота продольного медиального свода, угол пяточной инклинации -все измерения в боковой проекции); -фактор 2 «Динамометрический показатель» (период общей опоры -период -фактор 3 «Стабилометрический показатель» (L, mm; V, mm/s)); -фактор 4 «Рентгенологические угловые показатели стопы» (таранно-горизонтальный угол в боковой проекции). электронейромиографических показателей предназначено для скрининга патологии стоп у детей. ...
... A number of studies have performed kinematic analysis of flatfoot. Kim et al. 6) analyzed the features of gait of adults with flatfoot on an ascending slope using a three dimensional gait analysis system, and Kim et al. 7) analyzed muscle activity on an ascending slope, level ground, and a descending slope. Lee et al. 8) analyzed the muscle activities of the lower extremity during gait by adults with flatfoot on an ascending slope. ...
[Purpose] This study was conducted to determine the difference in foot pressures between flat and normal feet at different gait speeds on an ascending slope. [Subjects] This study enrolled 30 adults with normal (n=15) and flat feet (n=15), with ages from 21 to 30 years old, who had no history of neurological disorders or gait problems. A treadmill was used for the analysis of kinematic features during gait, using a slope of 10%, and gait velocities of slow, normal, and fast. [Methods] A foot pressure analyzer was used to measure changes in foot pressure. [Results] Compared to the normal subjects, the foot pressure of the flatfoot subjects showed a significant increase in the 2–3rd metatarsal region with increasing gait speed, whereas there were significant decreases in the 1st toe and 1st metatarsal regions with increasing gait speed. [Conclusion] The body weight of adults with flatfoot was concentrated on the 2–3rd metatarsal region during the stance phase and increased with walking speed on the ascending slope due to weakening of function of the medial longitudinal arch.
[Purpose] The purpose of this study was to clarify the relationship between aspects of the alteration of Physiological Cost Index (PCI) and surface electromyography and the walking speed. [Participants and Methods] The subjects were 35 healthy persons. They walked at five different walking speeds relative to their most comfortable walking, the free walking speed (FWS): –50%FWS, –25%FWS, FWS, 25%FWS and 50%FWS. Surface electromyography and the heart rate were measured, and the integrated value (IEMG), the median power frequency (MdPF), the mean power frequency (MPF) and the PCI were calculated. [Results] PCI at –50%FWS and 50%FWS was significantly increased compared with that of FWS. Although the IEMG increased with increase in walking speed, MdPF and MPF showed activity in the low and medium frequency bands. [Conclusion] The results of this study suggest that the PCI increased faster or slower than FWS, and IEMG increased with the increase in the walking speed.
[Purpose] The purpose of this study was to clarify the characteristics of the muscle activities of the gastrocnemius during increases of walking speed. [Participants and Methods] The subjects were 10 healthy persons. Surface electromyography of the gastrocnemius was performed during walking. During increases of the walking speed from 2.5 km/h to 4.0 km/h (acceleration phase I), and from 4.0 km/h to 5.5 km/h (acceleration phase II), the integrated electromyography value (IEMG) of the gastrocnemius was calculated and examined. [Results] IEMG of the medialis was significantly higher than that of the lateralis in both acceleration periods I and II (p<0.05); and IEMGs of the medialis and lateralis were significantly higher in acceleration period II than in acceleration period I (p<0.05). [Conclusion] The muscle activity of the gastrocnemius medialis was larger than that of the gastrocnemius lateralis muscle during acceleration in progressive walking.
Cerium-doped nanosheet-based porous δ-MnO2 microspheres have been successfully prepared via a simple hydrothermal process. Electrochemical measurements showed that appropriate amount of cerium doping can significantly increase the speicific capacitance of δ-MnO2. It is found that 1.5% cerium-doped manganese oxides exhibit the best specific capacitance of 382.38 F g-1 at a current density of 1 A g-1. In terms of ion transport kinetics, cerium doping can shorten the diffusion path length and increase the ion transfer rate by changing the partical size, porosity density and conductivity of manganese oxides materials.
Manganese oxide/carbon (MnOx/C) composites have been successfully prepared via a high temperature heat treatment method followed by the electrochemical oxidation. The presence of carbon not only enhances the electronic conductivity of manganese oxides (MnOx), but also provides more active sites for the transformation of manganese monoxide (MnO) during the galvanostatic charge–discharge process. Simultaneity, the interconnected porous structures of MnOx/C samples are believed to provide a continuous channel for the diffusion of electrolyte ion and shorten the diffusion length of ions involved in the charge/discharge cycling processes. Consequently, these advantages endow the MnOx/C electrode a better capacitance performance, a superior long-term cyclic stability and outstanding rate capability compared with pristine MnOx. More importantly, the composites show a fascinating capacitance of 807 F g−1 at 1 A g−1, which is much higher than the reported hydrous RuO2 electrodes. It can be easily speculated that MnOx/C composites will act as a promising electrode materials for designing high-performance supercapacitors.
OBJECTIVE: To identify the influence of static subtalar pronation (as measured by weight-bearing navicular drop [ND]) on ground impact forces and rate of loading during a single-leg landing. DESIGN AND SETTING: Subjects were grouped (n = 16 per group) on the basis of weight-bearing ND scores (supinators, <5 mm; neutral, 5-10 mm; pronators, >10 mm). Subjects performed 5 single-leg landings, dropping from a 0.3-m height onto a force platform. An electrogoniometer simultaneously recorded sagittal knee range of motion during the landing task. SUBJECTS: Forty-eight healthy volunteers participated. MEASUREMENTS: Peak vertical force was defined as the highest force recorded in the F(z) direction during landing. Rate of loading was defined as the peak vertical force divided by the time to reach the peak vertical force. Knee-flexion excursion was defined as the change in knee-flexion range from initial contact to peak vertical force. RESULTS: Peak vertical force (P =.769) and rate of loading (P =.703) did not differ among groups. Although secondary analyses identified significant negative correlations between peak force and rate of loading with knee excursion, the amount of knee excursion was similar among groups (P =.744). CONCLUSIONS: Our results de-emphasize the influence of static anatomical foot alignment on impact forces and absorption during a single-leg drop landing and provide further support for the role of knee flexion in dissipation of landing forces. Further investigations are needed to fully elucidate the role of subtalar pronation and other lower extremity alignment factors in force dissipation during dynamic functional activities.
Much of the work describing support of the medial longitudinal arch has focused on the plantar fascia and the extrinsic muscles. There is little research concerning the function of intrinsic muscles in the maintenance of the medial longitudinal arch. Ten healthy volunteer adults served as subjects for this study, which was approved by the University Investigational Review Board. The height of the navicular tubercle above the floor was measured in both feet while subjects were seated with the foot in a subtalar neutral position and then when standing in a relaxed calcaneal stance. Subtalar neutral was found by palpating for talar congruency. Recordings of muscle activity from the abductor hallucis muscle were performed while the subjects maintained a maximal voluntary contraction in a supine position by plantarflexing their great toes. An injection of lidocaine (1% with epinephrine) was then administered by a Board-certified orthopedic surgeon in the region of the tibial nerve, posterior and inferior to the medial malleolus. Measurements were repeated and compared by using a paired t test. After the nerve block, the muscle activity was 26.8% of the control condition (P =.011). This corresponded with an increase in navicular drop of 3.8 mm. (P =.022). The observation that navicular drop increased when the activity of the intrinsic muscles decreased indicates that the intrinsic pedal muscles play an important role in support of the medial longitudinal arch.
The study of neuromuscular activity at very slow walking speeds may lead to a better understanding of the mechanisms underlying speed regulation during walking, and may aid the interpretation of gait data in patients who walk slowly. Extreme reductions in walking speed will cause changes in locomotor task demands that may eventually result in modifications of the patterning of muscle activity that underlies walking. The aim of the present study was to investigate patterns of lower limb muscle activity during very slow walking (< 0.28 m s(-1)), and to study the neuromuscular gain functions that reflect the phase dependent effects of walking speed on electromyographic (EMG) amplitude. Nine healthy young adults walked at seven different walking speeds (1.39, 0.83, 0.28, 0.22, 0.17, 0.11, and 0.06 m s(-1)) while EMG was recorded from eight lower extremity muscles. Results showed that the phasing of muscle activity remained relatively stable over walking speeds despite substantial changes in its amplitude. However, between 1.39 and 0.28 m s(-1), epochs of Rectus femoris, Biceps femoris and Tibialis anterior activities were found that were typical for specific speed ranges. When walking speed decreased further to almost standing still (0.06 m s(-1)), negative gain values were found in Peroneus longus during midstance and Rectus femoris in late swing, indicating the emergence of new bursts of activity with decreasing walking speed. It is proposed that these extra activities may be attributed to increased demands on postural stability, and the altered dynamics of the swinging limb at very slow speeds.
The pathology manifested in posterior tibial tendon insufficiency (PTTI) is not limited to the posterior tibial tendon. The association of ligament failure with deformity has been discussed in numerous publications, but extensive documentation of the structures involved has not been performed. The purpose of this observational study was to identify the pattern of ligament involvement using standardized, high-resolution magnetic resonance imaging (MRI) in a series of 31 consecutive patients diagnosed with PTTI compared to an age matched control group without PTTI.
The structures evaluated by MRI were the posterior tibial tendon, superomedial and inferomedial components of the spring ligament complex, talocalcaneal interosseous ligament, long and short plantar ligaments, plantar fascia, deltoid ligament, plantar naviculocuneiform ligament, and tarsometatarsal ligaments. Structural derangement was graded on a five-part scale (0 to IV) with level 0 being normal and level IV indicating a tear of more than 50% of the cross-sectional area of the ligament. Standard flatfoot measurements taken from preoperative plain standing radiographs were correlated with the MRI grading system.
Statistically significant differences in frequency of pathology in the PTTI group and controls were found for the superomedial calcaneonavicular ligament (p < 0.0001), inferomedial calcaneonavicular ligament (p < 0.0001), interosseous ligament (p = 0.0009), anterior component of the superficial deltoid (p < 0.0001), plantar metatarsal ligaments (p = 0.0002) and plantar naviculocuneiform ligament (p = 0.0006). The ligaments with the most severe involvement were the spring ligament complex (superomedial and inferomedial calcaneonavicular ligaments) and the talocalcaneal interosseous ligament.
Ligament involvement is extensive in PTTI, and the spring ligament complex is the most frequently affected. Because ligament pathology in PTTI is nearly as common as posterior tibial tendinopathy, treatment should seek to protect or prevent progressive failure of these ligaments.
Objectives. To compare the effectiveness of a traditional balance training program and a balance training program that emphasizes foot positioning, in improving postural control.Design. Randomized control study using a pre-post design.Setting. A laboratory setting.Participants. Forty-five healthy college students participated. Sixteen completed a traditional balance training program (TRAD), 14 completed a training program emphasizing foot positioning (POS), and 15 received no intervention (CONT). Subjects in the TRAD and POS group performed balance training on their dominant lower extremity for 4 weeks.Main outcome measure. Center of pressure excursion velocity (COPV) assessed during single leg quiet standing on a force plate during eyes open and eyes closed trials on both the trained and untrained limbs.Results. The TRAD group improved substantially more than did the POS or CONT groups. Improvements in COPV measures were seen in the TRAD group for both the trained and untrained limbs. The most substantial improvements occurred on the trained leg in the eyes closed condition.Conclusion. Traditional balance training appears to be more effective than balance training emphasizing active foot positioning in healthy individuals. Bilateral improvement in balance for the TRAD group suggests a central nervous system control of postural control.
Delay onset of the vastus medialis obliquus (VMO) has often been reported to happen in people with patellofemoral pain (PFP). Previous studies revealed that a motion control shoe could check rearfoot pronation in overpronators. Literature suggested that movements of the lower leg could affect patellar tracking; thus motion control shoe may help prevent PFP by controlling excessive foot movements. This study aimed to compare the vasti muscle activities in people with excessive foot pronation when running with different footwear.
Twenty female subjects with rearfoot pronation >6 degrees were tested by running for 10 km on a treadmill on two separate days. During each test, subjects either wore a motion-control running shoe or a neutral running shoe. EMG activities of their right VMO and vastus lateralis (VL) were recorded. Their EMG onset timing and median frequency (MF) were compared between the two shoe conditions.
A more significant delay in VMO onset of the running duty cycle was observed in the neutral shoe condition than in the motion control shoe (p<0.001). In the neutral shoe condition, the delay in VMO increased with running mileage (Pearson correlation = 0.948), whereas no such pattern was observed in the motion control shoe. A significant drop in MF of the quadriceps after the 10 km run in both shoe conditions was observed (p ranged from <0.001 to 0.008), and there was a larger drop in VMO MF when running with the neutral shoe.
The findings suggest that the motion control shoe may facilitate a stable temporal activation of VMO during running.
A biomechanical model was used to calculate the mechanical properties of the foot at a load of 683 newtons, while changing arch height with and without the plantar fascia. An increase in arch height from 20 mm to 60 mm decreased predicted vertical displacement of the foot from 11.8 mm to 5.5 mm with the plantar fascia intact and from 13.5 mm to 7.5 mm without the plantar fascia. The amount of horizontal elongation decreased from 8.6 mm to 8.4 mm with the plantar fascia and increased from 9.8 mm to 11.7 mm without. A 60-mm arch height yielded a 40% increase in horizontal elongation and a 36% increase in vertical displacement when the plantar fascia was cut, whereas a 20-mm arch height yielded a 13% increase in horizontal elongation and a 14% increase in vertical displacement. A change in arch height from 20 mm to 60 mm increased stiffness of the foot with and without the plantar fascia.
Investigation into the effects of foot structure on foot function, and the risks of injury, has been at the core of many studies, sometimes with conflicting results. Often different methods of foot type classification have been used, making comparison of the results and drawing sound conclusions impossible. This article aims to critically review current methods of foot type classification. It is concluded that if a classification method combines data on structure with information on foot function in dynamic loading situations, it should relate more closely to the functional behaviour of the foot during locomotion.
This paper examined if an electromyography (EMG) driven musculoskeletal model of the human knee could be used to predict knee moments, calculated using inverse dynamics, across a varied range of dynamic contractile conditions. Muscle-tendon lengths and moment arms of 13 muscles crossing the knee joint were determined from joint kinematics using a three-dimensional anatomical model of the lower limb. Muscle activation was determined using a second-order discrete non-linear model using rectified and low-pass filtered EMG as input. A modified Hill-type muscle model was used to calculate individual muscle forces using activation and muscle tendon lengths as inputs. The model was calibrated to six individuals by altering a set of physiologically based parameters using mathematical optimisation to match the net flexion/extension (FE) muscle moment with those measured by inverse dynamics. The model was calibrated for each subject using 5 different tasks, including passive and active FE in an isokinetic dynamometer, running, and cutting manoeuvres recorded using three-dimensional motion analysis. Once calibrated, the model was used to predict the FE moments, estimated via inverse dynamics, from over 200 isokinetic dynamometer, running and sidestepping tasks. The inverse dynamics joint moments were predicted with an average R(2) of 0.91 and mean residual error of approximately 12 Nm. A re-calibration of only the EMG-to-activation parameters revealed FE moments prediction across weeks of similar accuracy. Changing the muscle model to one that is more physiologically correct produced better predictions. The modelling method presented represents a good way to estimate in vivo muscle forces during movement tasks.
The hypothesis tested was that the increased load on the medial arch in the adult flat foot can be reduced through a 6 mm subtalar arthroereisis.
A three-dimensional multisegment biomechanical model was used in conjunction with experimental data and data from the literature.
Biomechanical models have been used to study the plantar fascia, medial arch height, subtalar motion, medial displacement calcaneal osteotomy and distribution of forces in the foot.
Responses of a normal foot, a flat foot, and a flat foot with a subtalar arthroereisis to an applied load of 683 N were analyzed and the distribution of support among the metatarsal heads and the moment about various joints were computed.
The flattened foot results in an increase in the load on the head of the first metatarsal from 10% to 24% of the body weight, and an increase in the moment about the talo-navicular joint from 3.4 to 11.9 Nm. Insertion of a 6 mm cylinder into the sinus tarsi, subtalar arthroereisis, results in a shift of the load back toward the lateral column, decreasing the load on the first metatarsal to 6% of the body weight and decreasing the moment about the talo-navicular joint to 6.0 Nm.
Our analysis indicates that a 6 mm subtalar arthroereisis in an adult flat foot model decreases the load on the medial arch.
Surface electromyography (SEMG) is still rarely used in clinical settings for the detection and analysis of myoelectric signals. The electromyographic signal detected on the skin surface includes information from a greater proportion of the muscle of interest than conventional clinical EMG, acquired using needle electrodes. SEMG is therefore more representative than the localised, and thus very selective needle EMG signals currently used. However, both reliability and interpretation of surface EMG need to be questioned. This review looks at the studies concerned with the characterisation of neuromuscular pathologies using EMG parameters. After introducing principles and limitations of surface EMG, an overview of the main results obtained in clinical settings is presented and discussed. There is a particular focus on high spatial resolution surface EMG as it is currently the best compromise between the selectivity of needle EMG and the representative nature of classical SEMG. Several perspectives are proposed that underline the fact that surface EMG is an evolving discipline and should be worthy of a place in routine clinical examinations.
Reflexes are exquisitely sensitive to the motor task that is being performed at the time they are evoked; in other words, they are "task-dependent". The purpose of this study was to investigate the extent to which the pattern of reflex modulation is conserved across three locomotor tasks that differ in muscle activity, joint kinematics, and stability demands. Subjects performed continuous level and incline walking on a treadmill and stair climbing on a stepping mill. Cutaneous reflexes were evoked by delivering trains of electrical stimulation to the sural nerve at the ankle at an intensity of two times the radiating threshold. Electromyographic (EMG) recordings were collected continuously from muscles in the arms, legs and trunk. Results showed that middle-latency reflex modulation patterns were generally conserved across the three locomotor tasks with a few notable exceptions related to specific functional requirements. For example, a reflex reversal was observed for tibialis anterior during stair climbing, which may be indicative of a specific adaptation to the task constraints. Overall our data suggest that the underlying neural mechanisms involved in coordinating level walking can be modified to also coordinate other locomotor tasks such as incline walking and stair climbing. Therefore, there may be considerable overlap in the neural control of different forms of locomotion.
Investigations using quadrupeds have suggested that the motor programs used for slope walking differ from that used for level walking. This idea has not yet been explored in humans. The aim of this study was to use electromyographic (EMG) signals obtained during level and slope walking to complement previously published joint angle and joint moment data in elucidating such control strategies. Nine healthy volunteers walked on an instrumented ramp at each of five grades (-39%, -15%, 0%, +15%, +39%). EMG activity was recorded unilaterally from eight lower limb muscles (gluteus maximus (GM), rectus femoris (RF), vastus medialis (VM), biceps femoris (BF), semimembranosus (SM), soleus (Sol), medial gastrocnemius (MG), and tibialis anterior (TA)). The burst onset, duration, and mean activity were calculated for each burst in every trial. The burst characteristics were then averaged within each grade and subject and submitted to repeated measures ANOVAs to assess the effect of grade (alpha=0.05, a priori). Power production increased during upslope walking, as did the mean activity and burst durations of most muscles. In this case, the changes in muscle activity patterns were not predictable based on the changes in joint moments because of the activation of biarticular muscles as antagonists. During downslope walking power absorption increased, as did knee extensor activity (mean and duration) and the duration of the ankle plantarflexor activity. The changes in muscle activity during this task were directly related to the changes in joint moments. Collectively these data suggest that the nervous system uses different control strategies to successfully locomote on slopes, and that joint power requirements are an important factor in determining these control strategies.
Our aim with this study was to establish the prevalence of flat foot in a population of 3- to 6-year-old children to evaluate cofactors such as age, weight, and gender and to estimate the number of unnecessary treatments performed.
A total of 835 children (411 girls and 424 boys) were included in this study. The clinical diagnosis of flat foot was based on a valgus position of the heel and a poor formation of the arch. Feet of the children were scanned (while they were in a standing position) by using a laser surface scanner, and rearfoot angle was measured. Rearfoot angle was defined as the angle of the upper Achilles tendon and the distal extension of the rearfoot.
Prevalence of flexible flat foot in the group of 3- to 6-year-old children was 44%. Prevalence of pathological flat foot was < 1%. Ten percent of the children were wearing arch supports. The prevalence of flat foot decreases significantly with age: in the group of 3-year-old children 54% showed a flat foot, whereas in the group of 6-year-old children only 24% had a flat foot. Average rearfoot angle was 5.5 degrees of valgus. Boys had a significant greater tendency for flat foot than girls: the prevalence of flat foot in boys was 52% and 36% in girls. Thirteen percent of the children were overweight or obese. Significant differences in prevalence of flat foot between overweight, obese, and normal-weight children were observed.
This study is the first to use a three-dimensional laser surface scanner to measure the rearfoot valgus in preschool-aged children. The data demonstrate that the prevalence of flat foot is influenced by 3 factors: age, gender, and weight. In overweight children and in boys, a highly significant prevalence of flat foot was observed; in addition, a retarded development of the medial arch in the boys was discovered. At the time of the study, > 90% of the treatments were unnecessary.
Our purpose was to assess the effect of foot intrinsic muscle fatigue on pronation, as assessed with navicular drop, during static stance. Twenty-one healthy young adults participated. Navicular drop was measured before and after fatiguing exercise of the plantar foot intrinsic muscles. Surface electromyography of the abductor hallucis muscle was recorded during maximum voluntary isometric contractions (MVIC) in order to find the baseline median frequency (MedF). Subjects then performed sets of 75 repetitions of isotonic flexion contractions of the intrinsic foot muscles against a 4.55 kg weight on a custom pulley system. After each set an MVIC was performed to track shifts in MedF. After a MedF shift of at least 10%, navicular drop measurements were repeated. Subjects exhibited 10.0+/-3.8mm of navicular drop at baseline and 11.8+/-3.8mm after fatigue (p<0.0005). The change in navicular drop was significantly correlated with change in MedF (r=.47, p=.03). The intrinsic foot muscles play a role in support of the medial longitudinal arch in static stance. Disrupting the function of these muscles through fatigue resulted in an increase in pronation as assessed by navicular drop.
Most studies of degenerative flatfoot have focused on the posterior tibial muscle, an extrinsic muscle of the foot. However, there is evidence that the intrinsic muscles, in particular the abductor hallucis (ABH), are active during late stance and toe-off phases of gait. The purpose of this study was to analyze the kinematic effect of a simulated contraction of the abductor hallucis muscle on a cadaver lower limb specimen.
Eight below-knee cadaver specimens were prepared. The abductor hallucis muscle was exposed and the entire muscle-tendon unit excised. A suture secured to the calcaneal origin of the muscle and tendon was passed through a pulley at the ABH sesamoid attachment. The specimen was mounted on an experimental rig in a 'standing' position. Motions in the first metatarsal, tibia, and calcaneus were tracked using the 'Flock of Birds' motion analysis system (Ascension Technology, Burlington, VT). Muscle contraction was simulated by applying tension on the suture.
All eight specimens showed an origin from the posteromedial calcaneus and an insertion at the tibial sesamoid. All specimens also demonstrated a fascial sling in the hindfoot, lifting the abductor hallucis muscle to give it an inverted 'V' shaped configuration. Simulated contraction of the abductor hallucis muscle caused flexion and supination of the first metatarsal, inversion of the calcaneus, and external rotation of the tibia, consistent with elevation of the arch.
The abductor hallucis muscle acts as a dynamic elevator of the arch. Understanding this mechanism may change the way we understand and treat pes planus, posterior tibial tendon dysfunction, hallux valgus, and Charcot neuroarthropathy.
Kinesiology of the musculoskeletal system: Foundations for physical rehabilitation
- D A Neumann
Neumann DA: Kinesiology of the musculoskeletal system: Foundations for
physical rehabilitation. Mosby, 2002.
Principles of manual medicine
- P Greenman
Greenman P: Principles of manual medicine. 2nd ed. Baltimore; Lippincott, Williams & Wilkins, 2003.