Exploring the relationship between the supination resistance test and the effects of foot orthoses on the foot and ankle biomechanics during walking.

BACKGROUND: The effects of foot orthoses on lower limb biomechanics during walking have been studied extensively. However, the lack of knowledge regarding the effects of various foot orthoses models for the same population complicates model selection in clinical practice and research. Additionally, there is a critical need to enhance our ability to predict the outcomes of foot orthoses using clinical tests, such as the supination resistance test. RESEARCH QUESTION: What are the effects of two commonly prescribed types of FO (thin-flexible and medially wedged) on lower limb biomechanics during gait? Is there a correlation on these effects with the results of the supination resistance test? METHODS: Twenty-three participants with flat feet were enrolled in this cross-sectional descriptive study. Participants underwent walking trials under three conditions: shod, thin-flexible FOs and medially wedged FOs. Midfoot, ankle, knee and hip angles, moments were calculated. Repeated measure ANOVAs were employed for within-group comparison across conditions. Correlations between the effects of FOs on foot and ankle angles/moments and supination resistance were determined using regression analyses using a statistical parametric mapping approach. RESULTS: Thin-flexible and medially wedged FOs reduced midfoot dorsiflexion angles and ankle inversion moments. Medially wedged FOs also decreased midfoot and ankle abduction angles, midfoot plantarflexion moments compared to thin-flexible FOs and shoes. Moderate to good correlations between the supination resistance test and the medially wedged FOs were observed for the frontal and transverse ankle angles and moments. SIGNIFICANCE: Medially wedged FOs are more effective in modifying lower limb biomechanics during walking compared to thin-flexible FOs. Greater supination resistance was associated with more pronounced effects for medially wedged FOs on foot and ankle biomechanics. These findings hold promise for refining orthotic prescription strategies, potentially offering advantages to individuals with musculoskeletal disorders.

The importance of foot posture when recording lower leg electromyography when walking in non-textured and textured foot orthoses.

Foot posture describes the anatomical variance in an individual's overall foot shape, an important consideration in the provision of foot orthoses. Current orthoses designs could be optimized by considering the topographical organization of cutaneous mechanoreceptors. Currently, the effect of foot orthoses designs to enhance skin stimulation across different anatomical foot posture remains unknown. Thus, the purpose of this study was to investigate how foot posture variance modulates lower leg muscle activity when walking in non-textured orthoses and in textured orthoses which facilitates cutaneous mechanoreceptors under five different regions of the foot sole. Fifty-one (51) healthy young adults were subdivided by the Foot Posture Index and completed level walking trials wearing non-textured and textured foot orthoses. Surface and fine-wire electromyography (EMG) recorded muscle activity in 8 lower leg muscles. Statistically significant interactions were observed in each muscle's average EMG across textured location and Foot Posture Index score. For example, in pes cavus compared to pes planus feet, texture under the calcaneus generated greater aEMG of the tibialis anterior (44.9 mV ± 22.7 mV to 30.9 mV ± 11.4 mV) medial gastrocnemius (26.1 mV ± 16.7 mV to 17.5 mV ± 6.0 mV), and tibialis posterior (84.4 mV ± 77.1 mV to 64.4 mV ± 44.5 mV) muscles. This study demonstrates that lower leg muscle activity is modulated across the foot posture spectrum wearing non-textured and textured foot orthoses. Furthermore, in the development of new orthoses designs, specifically with texture, foot posture remains an important consideration when clinicians interpret EMG results and academics are designing new experimental protocols.

Medially wedged foot orthoses generate greater biomechanical effects than thin-flexible foot orthoses during a unilateral drop jump task on level and inclined surfaces.

BACKGROUND: Foot orthoses are therapeutic insoles designed to induce various effects on lower limb biomechanics. However, conflicting findings in previous research, highlight the need to better understand how foot orthoses with different features affect lower limb biomechanics during challenging tasks, particularly during unilateral drop jump landings. METHODS: Seventeen participants with flat feet were recruited to participate in this cross-sectional descriptive study that examined the effects of thin-flexible foot orthoses and medially wedged foot orthoses on lower limb biomechanics during unilateral drop jump landings on level and valgus inclined surfaces. Midfoot, ankle, knee, and hip angles and moments were calculated and compared across conditions with repeated measures ANOVAs, using a statistical parametric mapping approach. FINDINGS: Medially wedged and thin-flexible foot orthoses reduced ankle pronation and arch flattening during unilateral drop jump landings on level and valgus inclined surfaces. Medially wedged foot orthoses further decreased midfoot dorsiflexion and ankle eversion angles compared to thin-flexible foot orthoses. Medially wedged foot orthoses also generated greater effects on ankle kinetics and hip kinematics during unilateral drop jump landings. INTERPRETATION: Medially wedged foot orthoses are more effective than thin-flexible foot orthoses in optimizing lower limb biomechanics during unilateral drop jump landings. While the biomechanical effects did not increase on inclined surfaces, medially wedged foot orthoses generated greater effects on proximal joints, highlighting their potential to improve hip stability and enhance overall lower limb function. Personalized foot orthoses selection based on specific biomechanical profiles should be further explored to optimize orthotic interventions benefiting individuals with musculoskeletal conditions.

The topographical attenuation of cutaneous input is modulated at the ankle joint during gait.

The attenuation of sensory inputs via various methods has been demonstrated to impair balance control and alter locomotor behavior during human walking; however, the effects of attenuating foot sole sensation under distinct areas of the foot sole on lower extremity motor output remains poorly understood. Thus, the purpose of this study was to attenuate cutaneous feedback via regional hypothermia under five different areas of the foot sole and investigate the resultant modulation of kinematic and muscle activity during level walking. Electromyography from eight lower leg muscles, kinematics, and location of center of pressure was recorded from 48 healthy young adults completing walking trials with normal and reduced cutaneous sensation from bilateral foot soles. The results of this study highlight the modulatory response of the tibialis anterior in terminal stance (propulsion and toe-off) and medial gastrocnemius muscle throughout the entire stance phase of gait. The topographical organization of foot sole skin in response to the attenuation of cutaneous feedback from different areas of the foot sole significantly modified locomotor activity. Furthermore, the locomotor response to cutaneous attenuation under the same regions that we previously facilitated with tactile feedback do not oppose each other, suggesting different physiological changes to foot sole skin generate unique gait behaviors.

Capitalizing on skin in orthotics design: the effects of texture on plantar intrinsic foot muscles during locomotion.

Foot orthoses (FO) are a commonly prescribed intervention to alter foot function during walking although their effects have been primarily studied in the extrinsic muscles of the foot. Furthermore, enhancing sensory feedback under the foot sole has been recently shown to alter extrinsic muscle activity during gait; however, the effects of FOs with enhanced sensory feedback on plantar intrinsic foot muscles (PIFMs) remain unknown. Thus, the purpose of this study was to investigate the effect of FOs with and without sensory facilitation on PIFM activity during locomotion. Forty healthy adults completed a series of gait trials in non-textured and textured FOs when walking over hard and soft flooring. Outcome measures included bilateral joint kinematics and electromyography (EMG) of four PIFMs. Results of this study highlight the distinct onset and cessations of each PIFM throughout the stance phase of gait. PIFMs remained active during mid-stance when wearing FOs and textured FOs facilitated muscle activity across the stance phase of gait. Increasing cutaneous input from foot sole skin, via the addition of texture under the foot sole, appears to alter motor-neuron pool excitation of PIFMs. Future academics are encouraged to increase our understanding on which pathologies, diseases, and/or medical conditions would best benefit from textured FOs.

The effects of foot orthoses and sensory facilitation on lower limb electromyography: A scoping review.

Foot orthoses (FO) are used as a treatment for biomechanical abnormalities, overuse injuries, and neuropathologies, but study of their mechanism remains inconclusive. The neuromotor paradigm has proposed that FOs may manipulate sensory input from foot sole skin to reduce muscle activity for movement optimization. This review argues that a FO likely alters the incoming mechanical stimuli transmitted via cutaneous mechanoreceptors and nociceptors as the foot sole interfaces with the surface of the orthotic. Thus, all FOs with or without intentional sensory facilitation, likely changes sensory information from foot sole cutaneous afferents. Additionally, in light of understanding and applying knowledge pertaining to the cutaneous reflex loop circuitry, FO's increasing sensory input to the motorneuron pool can change EMG to either reflex sign (increase or decrease). The purpose of this scoping review was to synthesize FO and sensory augmentation literature and summarize how FO designs can capitalize on foot sole skin to modulate lower limb electromyography (EMG). Six database searches resulted in 30 FO studies and 22 sensory studies that included EMG as an outcome measure. Results revealed task and phase specific responses with some consistencies in EMG outcomes between testing modalities, however many inconsistencies remain. Electrical stimulation reflex research provides support for a likely sensory-to-motor factor contributing to muscle activity modulation when wearing FOs. The discussion divides trends in FO treatment modalities by desired increase or decrease in each compartment musculature. The results of this review provides a benchmark for future academics and clinicians to advance literature in support of a revised neuromotor paradigm while highlighting the importance of foot sole skin in FO design.

The effect of texture under distinct regions of the foot sole on human locomotion.

Sensory feedback from the foot sole plays an important role in shaping human locomotion. While net muscle activity and kinematic changes have been correlated with electrical stimulation to five topographical regions of the foot, it remains unknown if these responses are similar with tactile stimulation. The purpose of this study was to use texture in foot orthosis design, applied to five distinct regions under the foot sole, and measure joint kinematics, location of center of pressure, and muscle activity of eight lower leg muscles during level and incline walking. Fifty-five healthy adults completed 48 walking trials in textured and non-textured foot orthoses. Study results confirm that tactile stimulation is stimulation-site and gait-phase specific in modulating lower leg muscle activity during walking. For example, texture under the lateral forefoot consistently generated a suppression of EMG and texture under the lateral midfoot always generated a facilitation. In early stance, adding texture under the medial midfoot or calcaneus facilitated extensor muscle activity and suppressed flexor muscle activity. Texture under the lateral midfoot or medial forefoot facilitated tibialis posterior activation. These results support the topographical organization of cutaneous mechanoreceptors in foot sole skin while considering how texture can be used in foot orthosis design to target lower leg muscular changes during locomotion.

Effects of foot orthoses on the biomechanics of the lower extremities in adults with and without musculoskeletal disorders during functional tasks: A systematic review.

BACKGROUND: Foot orthoses are among the most commonly used external supports to treat musculoskeletal disorders. It remains unclear how they change the biomechanics of the lower extremities during functional tasks. This systematic review aimed to determine the effects of foot orthoses on primary outcomes (i.e., kinematics, kinetics and electromyography of the lower extremities) in adults with and without musculoskeletal disorders during functional tasks. METHODS: A literature search was conducted for articles published from inception to June 2021 in Medline, CINAHL, SPORTDiscus, Cochrane libraries and PEDro electronic databases. Two investigators independently assessed the titles and abstracts of retrieved articles based on the inclusion criteria. Of the 5578 citations, 24 studies were included in the qualitative synthesis as they reported the effects of foot orthoses on the primary outcomes. Risk of bias of included studies was determined using the modified Downs and Black Quality Index. FINDINGS: During low impact tasks, foot orthoses decrease ankle inversion and increase midfoot plantar forces and pressure. During higher impact tasks, foot orthoses had little effects on electromyography and kinematics of the lower extremities but decreased ankle inversion moments. INTERPRETATION: Even though the effects of foot orthoses on the biomechanics of the lower extremities seem task-dependent, foot orthoses mainly affected the biomechanics of the distal segments during most tasks. However, few studies determined their effects on the biomechanics of the foot. It remains unclear to what extent foot orthoses features induce different biomechanical effects and if foot orthoses effects change for different populations.

The role of enhanced plantar-surface sensory feedback on lower limb EMG during planned gait termination.

Purpose/aim of the study: Generation of smooth movement relies on the central nervous system (CNS) having information from the visual, vestibular and somatosensory systems to effectively execute motor behaviour. Recently, cutaneous afferent inputs have been linked to lower leg motorneuron pools, resulting in a growing interest of adding texture to the plantar foot sole interface as a novel method to facilitate cutaneous feedback. The aim of this study was to characterize the changes in magnitude and temporal organization of muscle activity, and to investigate motor output changes from enhanced tactile feedback during perturbed gait termination.Materials and methods: Thirty young adults experienced an unpredictable platform perturbation when completing planned gait termination. The study manipulated two experimental variables: 1) direction of platform tilt (anterior, posterior, medial, lateral), and 2) foot sensory facilitation (non-facilitated, facilitated). Upper and lower leg EMG onset, cessation time and integrated EMG (iEMG) were measured in addition to common gait parameters (walking velocity, step length, step width).Results: Gait termination over a textured surface resulted in significantly earlier upper leg EMG onset times and modified iEMG of rectus femoris, vastus medialis and biceps femoris muscles.Conclusions: Results of this study suggest that the addition of cutaneous feedback under the plantar-surface of the foot increases the ability to generate an earlier muscle response, consequently improving response ability to an unexpected perturbation. Secondly, enhanced tactile feedback appears to inform the CNS of the magnitude of the threat to the balance control system, providing additional insight into how the CNS uses enhanced tactile feedback during a gait termination task.

Fine-wire electromyography of the transverse head of adductor hallucis during locomotion.

BACKGROUND: Previous literature on the transverse head of adductor hallucis (AddH-T) has largely focused on muscle morphology. This data provides insight into muscle architecture, yet fails to inform it's functional implication during walking. The role of the AddH-T, which runs parallel to the distal transverse metatarsal arch, has never been studied using fine-wire EMG during locomotion. RESEARCH QUESTION: The purpose of this study is to explain a novel method of recording fine-wire EMG of the adductor hallucis muscle of the foot, and secondly, to report phasic AddH-T muscle activity during level walking on hard and soft surfaces. METHODS: Ultrasound-guided fine-wire EMG was recorded from the AddH-T of each foot, in ten asymptomatic young adults. Participants completed ten walking trials per experimental conditions (hard and soft surface). Ensemble averages were calculated from the time normalized linear-envelopes of each participant, and represented from 0 to 100 percent of the gait cycle. RESULTS: Using the described ultrasound-guided fine-wire protocol, successful EMG signals were generated in 19 of 20 feet. When walking over hard or soft flooring, the AddH-T muscle has two bursts in EMG, occurring between 0-20 % and 50-65 % of the gait cycle. The magnitude of peak activity was often reduced at initial contact when walking over foam. 45 % of participants experienced a third burst in EMG activity at midstance, corresponding to 30-40 % of the gait cycle. SIGNIFICANCE: This study has successfully explained a novel method of recording finewire electromyography (EMG) of the adductor hallucis (transverse head) muscle of the foot. Results suggest that the AddH-T stabilizes the forefoot at initial contact and toeoff, while further anchoring the hallux during propulsion. These results provide preliminary insight into the functional role of the AddH-T during human locomotion.

Textured Foot Orthotics on Dynamic Stability and Turning Performance in Parkinson's Disease.

The purpose of this study was to facilitate sensory feedback, with textured foot orthotics, to evaluate dynamic stability and turning behavior in Parkinson's disease individuals. Seven participants with a diagnosis of idiopathic Parkinson's disease, aged 55-80 years old, participated in this study. Participants completed three testing sessions; baseline, 4 weeks post-baseline, and 5 weeks post-baseline. Three experimental conditions were tested: footwear only (F), footwear + non-textured orthotic (FO), and footwear + textured orthotic (FOT). Kinematic, kinetic, and video data were collected during the steps preceding a turn task. Variables of interest included dynamic stability (maximum mediolateral (ML), minimum ML, and ML range of the center of mass (COM)-base of support (BOS) relationship) and turning performance (gait velocity and step count). There was a statistically significant increase in maximum ML COM-BOS distance (week 4 [0.1298 m ± 0.054] compared to week 0 [0.1069 m ± 0.050] p = .0076), and a significant decrease in step count (week 0-F [5.52 steps ± 1.08] to week 0-FO [5.23 steps ± 0.87] p = .0296) and (week 4-FO [5.24 steps ± 1.31] to week 4-FOT [4.67 steps ± 0.76] p = .0004). Textured foot orthotics modified dynamic stability and turning performance in Parkinson's disease individuals completing a 180° degree turn. These preliminary results support this potential treatment option for rehabilitation professionals treating Parkinson's disease.