Test-retest reliability of ultrasound measures of intrinsic foot motor function

Association between running biomechanics and lower limb musculotendinous changes over an adolescent marathon training program

BACKGROUND

Prospective musculotendinous changes have been observed among adolescents completing marathon training programs. However, examinations of potential factors influencing musculotendinous characteristics do not currently exist. Evaluations of biomechanical parameters and the influence on musculotendinous features and changes over time are warranted.

RESEARCH QUESTION

What are the relationships between adolescent running biomechanics and 1) lower extremity musculotendinous characteristics cross-sectionally, and 2) changes in musculotendinous properties over 6-months?

METHODS

Thirty-three adolescent runners participated in this study (19 F, 14 M; 15.8 ± 1.6 years). Ultrasound images of lower extremity musculotendinous structures were obtained to determine thickness and echogenicity. Following ultrasound measures, outdoor running biomechanics were assessed using wearable sensors to collect spatiotemporal, kinetic, and kinematic measures. A subset of participants had repeat ultrasound evaluations following a 6-month running program (n = 11; 6 F, 5 M). Hierarchical linear models were used to assess the relationships between biomechanics and ultrasound measures. Pearson's correlations were used to assess the relationship between biomechanics the change in musculotendinous characteristics (baseline to 6-months).

RESULTS

The strongest relationships between measures were for the Achilles tendon (R2=0.39, F=0.85, p = 0.10), and flexor digitorum brevis (R2=0.38, F=2.38, p = 0.06). The interaction between pronation excursion and velocity was a significant predictor for Achilles tendon thickness (p = 0.03), and medial gastrocnemius thickness (p = 0.05). Contact time was a significant predictor for intrinsic foot muscle thickness (p = 0.01). There were moderate correlations across biomechanical measures and changes in musculotendinous thickness and echogenicity.

SIGNIFICANCE

Biomechanical characteristics often noted with running-related injuries were moderately related to tissue-level characteristics, and changes during running training.

Discussion on the validity of commonly used reliability indices in sports medicine and exercise science: a critical review with data simulations

Apart from objectivity and validity, reliability is considered a precondition for testing within scientific works, as unreliable testing protocols limit conclusions, especially for practical application. Classification guidelines commonly refer to relative reliability, focusing on Pearson correlation coefficients (rp) and intraclass correlation coefficients (ICC). On those, the standard error of measurement (SEM) and the minimal detectable change (MDC) are often calculated in addition to the variability coefficient (CV). These, however, do not account for systematic or random errors (e.g., standardization problems). To illustrate, we applied common reliability statistics in sports science on simulated data which extended the sample size of two original counter-movement-jump sessions from (youth) elite basketball players. These show that excellent rp and ICC (≥ 0.9) without a systematic bias were accompanied by a mean absolute percentage error of over 20%. Furthermore, we showed that the ICC does not account for systematic errors and has only limited value for accuracy, which can cause misleading conclusions of data. While a simple re-organization of data caused an improvement in relative reliability and reduced limits of agreement meaningfully, systematic errors occurred. This example underlines the lack of validity and objectivity of commonly used ICC-based reliability statistics (SEM, MDC) to quantify the primary and secondary variance sources. After revealing several caveats in the literature (e.g., neglecting of the systematic and random error or not distinguishing between protocol and device reliability), we suggest a methodological approach to provide reliable data collections as a precondition for valid conclusions by, e.g., recommending pre-set acceptable measurement errors.

Reliability of direct and indirect measures of intrinsic foot muscle strength in adults: A systematic review

BACKGROUND

The aim of this systematic review was to summarize the existing literature on evaluation methods developed to measure intrinsic foot muscle strength in both symptomatic and asymptomatic individuals. The specific objectives was to provide an overview of the evaluation methods with their protocols and reliability.

METHODS

Five databases (PubMed, Embase, Web of Science, Cochrane Library and SPORTDiscus) were searched up to August 2023. Studies reporting direct or indirect measures of intrinsic foot muscle evaluation with no limitation to sex, BMI or ethnicity were included. The inclusion criteria were applied systematically, and the methodological quality of the selected articles was assessed using The Downs and Black Checklist.

FINDINGS

Sixteen studies provided results of direct measures of intrinsic foot muscle strength, while indirect measures were reported in 19 articles. Direct measurement methods such as dynamometry (ICC 0.75-0.99) and plantar pressure (ICC 0.75-0.95) show high reliability. Among the indirect methods, both MRI (ICC 0.99) and ultrasound showed mostly high (ICC 0.66-0.99) reliability values.

INTERPRETATION

Direct methods like dynamometry and plantar pressure show excellent reliability, but validity is uncertain. MRI is considered gold standard among indirect measurement techniques. However, portable ultrasound devices have gained popularity due to their strong agreement with MRI.

Long-Term Effects and Impressions of Minimal Footwear in Older Adults

INTRODUCTION

Foot pathologies can lead to difficulty walking and falls in older adults. Intrinsic foot muscles contribute to the structural support and alignment of the foot and provide somatosensory input from the ground. Minimally cushioned footwear may naturally strengthen intrinsic foot muscles and enhance sensory input to the foot; however, these effects are largely unknown in older adults. Further, there is little evidence regarding the prescription of minimal footwear and the perceptions of this footwear by older adults.

METHODS

Twenty-four adults age ≥65 volunteered to use minimal footwear for prescribed times during daily activities for 16 weeks. The cross-sectional area (CSA) of 5 intrinsic foot muscles was measured using ultrasound imaging at baseline, 8 weeks, and 16 weeks. Semi-structured interviews were recorded regarding participants' impressions of the footwear, the progressive wear schedule, the footwear's effects on orthopedic-related pain, balance, and foot awareness/sensation.

RESULTS

Across the cohort, there was no significant difference in CSA of the 5 muscles after 16 weeks of minimal footwear use. Thirteen participants had clinically meaningful increased CSA of the abductor hallucis muscle (Abh). These positive responders had no significant differences in age, grip strength, foot structure, or fall risk scores compared to participants with little to no CSA change. Interview results indicated a generally positive experience with minimal footwear for 68.1% of the cohort. A large percentage of the cohort reported no difficulty with the progressive wear schedule (77.2%), no aggravation of preexisting conditions and no new pain (77.2%), improved balance (63.6%), and improved foot awareness/sensation (72.7%) with minimal footwear use. The progressive wear schedule was perceived as inconvenient by some in the first few weeks (22.8%), but resulted in mild to no adverse effects when followed as prescribed.

CONCLUSION

Sixteen weeks of progressive minimal footwear use in older adults did not lead to changes in intrinsic foot muscle CSA; however, half of the cohort had clinically meaningful increased CSA in the Abh muscle. It is unclear what individual qualities were associated with this positive response. Older adults reported generally positive experiences with minimal footwear with self-reported improvements in balance and foot awareness/sensation. The wear schedule may have been too conservative or not long enough to produce foot muscle hypertrophy, but subjective reports suggest beneficial neuromuscular adaptations and sensory changes occurred. Future research may need a greater length of time and larger samples to further determine the effects of long-term minimal footwear use in older adults.

Effect of Neuromuscular Electrostimulation With Blood Flow Restriction on Acute Muscle Swelling of the Abductor Hallucis

CONTEXT

Plantar intrinsic foot muscle strength training is difficult to master to a degree sufficient to elicit muscle hypertrophy in most individuals. It is possible that combining neuromuscular electrostimulation (NMES) and blood flow restriction (BFR) can elicit plantar intrinsic foot muscle hypertrophy regardless of the individual's technique. This study aimed to determine the effects of NMES training with BFR on acute muscle swelling in the abductor hallucis.

DESIGN

Randomized, controlled, single-blind trial design.

METHODS

Forty-eight participants were randomly allocated to the NMES + BFR, NMES, or Sham NMES + BFR groups. All participants received abductor hallucis NMES for 15 minutes. Participants in the NMES + BFR and Sham NMES + BFR groups received NMES with BFR. The intensity of NMES was the sensory threshold in the Sham NMES + BFR group. The cross-sectional area of the abductor hallucis was measured pretraining and posttraining using ultrasonography by a single investigator blinded to the participants' allocations.

RESULTS

After 15 minutes of training, the cross-sectional area of the abductor hallucis was significantly increased in the NMES + BFR (P < .001) and the Sham NMES + BFR (P = .004) groups. Moreover, the rate of increase was significantly higher in the NMES + BFR group than in the NMES or the Sham NMES + BFR groups (P < .001 and P = .001, respectively).

CONCLUSIONS

Since it is possible that the amount of muscle swelling immediately after training correlates with muscle hypertrophy when training is continued, the results of this study suggest that NMES training with BFR is a training method that can be expected to produce plantar intrinsic foot muscle hypertrophy. Further studies are needed to confirm the long-term effects of NMES training with BFR.

Relationship between foot morphologic characteristic and postural control after jump-landing in youth competitive athletes

BACKGROUND

Foot arch dynamics play an important role in dynamic postural control. Association between foot arch dynamics and postural control among adolescent athletes remains poorly explored.

OBJECTIVE

To examine the relationship between foot arch dynamics, intrinsic foot muscle (IFM) morphology, and toe flexor strength and dynamic postural stability after jump landing and repetitive rebound jump performance in competitive adolescent athletes.

METHODS

Based on foot arch dynamics, evaluated from relative change in the foot arch height in sitting and standing positions, 50 adolescent athletes were classified as stiff, normal, or flexible. IFM morphology was evaluated by ultrasonography. Dynamic postural stability index (DPSI) was measured as participants jumped and landed with the right leg onto a force plate, whereas repetitive rebound jumping performance was assessed using the jump height and reactive jump index.

RESULTS

The stiff group had a significantly worse DPSI and vertical stability index than the normal group (p= 0.26, p= 0.44, respectively), and worse anteroposterior stability index (APSI) values than the flexible group (p= 0.005). Multivariate regression models of the relationship between the APSI and foot arch dynamics showed adequate power (probability of error = 0.912).

CONCLUSIONS

Increased foot arch stiffness negatively affects dynamic balance during jump-landing, which may deteriorate their performance.

Adolescent exercise-related lower leg pain musculotendinous characteristics

BACKGROUND

Exercise-related lower leg pain (ERLLP) is one of the most common injuries among adolescent runners; however, there is limited information available on lower extremity musculotendinous characteristics in relationship to injury. Ultrasound imaging has previously been used to evaluate musculotendinous structures among adults with chronic lower limb injuries. Similar measurement approaches may be adopted to assess young runners with ERLLP.

OBJECTIVE

To compare ultrasound-derived lower extremity musculotendinous thickness, echogenicity, and muscle fiber pennation angles between adolescent runners with and without ERLLP.

DESIGN

Cross-sectional design.

SETTING

Hospital-affiliated sports injury prevention center.

PARTICIPANTS

Twenty-eight adolescent runners with (N = 14) and without ERLLP (N = 14).

INTERVENTIONS

Runners' patellar and Achilles tendons, and tibialis anterior, medial gastrocnemius, abductor hallicus, and flexor digitorum brevis muscles were assessed with ultrasound imaging using standardized procedures.

MAIN OUTCOME MEASURES

Separate repeated measures multivariate analyses of covariance (covariate: gender) were used to compare groups and limbs for mass-normalized musculotendinous thickness, musculotendinous echogenicity, and extrinsic ankle muscle fiber pennation angles.

RESULTS

The adolescent ERLLP group had reduced average muscle size for all structures except the tibialis anterior compared to the uninjured group (mean difference [MD] range: -0.12-0.49 mm/kg; p range: .002-.05), and reduced average medial gastrocnemius pennation angles on their case limb compared to their contralateral limb and the uninjured group (MD range: -3.7-6.4°; p < .001). The ERLLP group additionally had reduced average patellar and Achilles tendon size (MD range: -0.14--0.15 mm/kg; p range: .02-.03), and lower Achilles tendon echogenicity compared to uninjured counterparts (MD: -18; p = .02).

CONCLUSIONS

Adolescent runners with ERLLP exhibited morphological musculotendinous changes that may occur either as a result of or as a contributing factor to pain and persistent dysfunction. The findings highlight key targets for rehabilitation for young, injured runners, particularly intrinsic foot muscle strengthening.

Current evidence regarding 2D ultrasonography monitoring of intrinsic foot muscle properties: A systematic review

Background

Ultrasonography can discriminate between intrinsic and extrinsic foot muscle properties and has therefore gained considerable popularity as an indirect strength evaluation. However, an overview on the use of ultrasound for assessing intrinsic foot musculature (IFM) is currently lacking.

Research question

What is the current evidence regarding (1) 2D ultrasonography protocols and its reliability? (2) Reference values for cross-sectional area and dorso-plantar thickness evaluation in asymptomatic and symptomatic persons?

Methods

The PRISMA guidelines were used to conduct this systematic review. Eight databases (PubMed, Embase, Web of Science, Cochrane Library, Scopus, CINAHL, SPORTDiscus and EuropePMC) were searched up to November 1, 2021. Studies reporting quantitative 2D ultrasound findings of the intrinsic foot muscles with no limitation to sex, BMI, ethnicity or physical activity were included. Studies were assessed for methodological quality using the Downs and Black checklist.

Results

Fifty-three studies were retained. Protocols showed an overall good to great reliability, suggesting limits of agreement between 8 and 30% of relative muscle size with minimal detectable changes varying from 0.10 to 0.29 cm² for cross-sectional area and 0.03-0.23 cm for thickness. Reference values are proposed for both cross-sectional area and thickness measurements of the abductor hallucis, flexor digitorum brevis, flexor hallucis brevis and quadratus plantae in asymptomatic persons. This could not be performed in the symptomatic studies due to a limited number of relevant studies addressing the symptomatic population, therefore a clinical overview is outlined. Clinically, IFM properties have been studied in ten distinct pathological conditions, predominantly pointing towards decreased muscle properties of the abductor hallucis.

Significance

We provide a clear and comprehensive overview of the literature regarding 2D ultrasonography of the IFM, making the available evidence more accessible to decision makers and researchers.

Adolescent Marathon Training: Prospective Evaluation of Musculotendinous Changes During a 6-Month Endurance Running Program

OBJECTIVES

Assess changes in lower extremity musculotendinous thickness, tissue echogenicity, and muscle pennation angles among adolescent runners enrolled in a 6-month distance running program.

METHODS

We conducted prospective evaluations of adolescent runners' lower extremity musculotendinous changes at three timepoints (baseline, 3 months, and 6 months) throughout a progressive marathon training program. Two experienced researchers used an established protocol to obtain short- and long-axis ultrasound images of the medial gastrocnemius, tibialis anterior, flexor digitorum brevis, abductor hallicus, and Achilles and patellar tendons. ImageJ software was used to calculate musculotendinous thickness and echogenicity for all structures, and fiber pennation angles for the ankle extrinsic muscles. Repeated measures within-subject analyses of variance were conducted to assess the effect of endurance training on ultrasound-derived measures.

RESULTS

We assessed 11 runners (40.7% of eligible runners; 6F, 5M; age: 16 ± 1 years; running experience: 3 ± 2 years) who remained injury-free and completed all ultrasound evaluation timepoints. Medial gastrocnemius muscle (F_2,20  = 3.48, P = .05), tibialis anterior muscle (F_2,20  = 7.36, P = .004), and Achilles tendon (F_2,20  = 3.58, P = .05) thickness significantly increased over time. Echogenicity measures significantly decreased in all muscles (P-range: <.001-.004), and increased for the patellar tendon (P < .001) during training. Muscle fiber pennation angles significantly increased for ankle extrinsic muscles (P < .001).

CONCLUSIONS

Adolescent runners' extrinsic foot and ankle muscles increased in volume and decreased in echogenicity, attributed to favorable distance training adaptations across the 6-month timeframe. We noted tendon thickening without concomitantly increased echogenicity, signaling intrasubstance tendon remodeling in response to escalating distance.

Effects of foot intensive rehabilitation (FIRE) on clinical outcomes for patients with chronic ankle instability: a randomized controlled trial protocol

BACKGROUND

Lateral ankle sprains account for a large proportion of musculoskeletal injuries among civilians and military service members, with up to 40% of patients developing chronic ankle instability (CAI). Although foot function is compromised in patients with CAI, these impairments are not routinely addressed by current standard of care (SOC) rehabilitation protocols, potentially limiting their effectiveness. The purpose of this randomized controlled trial is to determine if a Foot Intensive REhabilitation (FIRE) protocol is more effective compared to SOC rehabilitation for patients with CAI.

METHODS

This study will use a three-site, single-blind, randomized controlled trial design with data collected over four data collection points (baseline and post-intervention with 6-, 12-, and 24-month follow-ups) to assess variables related to recurrent injury, sensorimotor function, and self-reported function. A total of 150 CAI patients (50 per site) will be randomly assigned to one of two rehabilitation groups (FIRE or SOC). Rehabilitation will consist of a 6-week intervention composed of supervised and home exercises. Patients assigned to SOC will complete exercises focused on ankle strengthening, balance training, and range of motion, while patients assigned to FIRE will complete a modified SOC program along with additional exercises focused on intrinsic foot muscle activation, dynamic foot stability, and plantar cutaneous stimulation.

DISCUSSION

The overall goal of this trial is to compare the effectiveness of a FIRE program versus a SOC program on near- and long-term functional outcomes in patients with CAI. We hypothesize the FIRE program will reduce the occurrence of future ankle sprains and ankle giving way episodes while creating clinically relevant improvements in sensorimotor function and self-reported disability beyond the SOC program alone. This study will also provide longitudinal outcome findings for both FIRE and SOC for up to two years. Enhancing the current SOC for CAI will improve the ability of rehabilitation to reduce subsequent ankle injuries, diminish CAI-related impairments, and improve patient-oriented measures of health, which are critical for the immediate and long-term health of civilians and service members with this condition. Trial Registration Clinicaltrials.gov Registry: NCT #NCT04493645 (7/29/20).

Immediate association of navicular bone height and plantar intrinsic muscle size with toe flexion task: An ultrasound-based study

BACKGROUND: Intrinsic foot muscle (IFM) dysfunction and poor foot arch are associated with various foot conditions. Toe flexor exercise (TFE) has been used to improve it; however, the immediate effects of TFE on each IFM and how it relates to changes in navicular bone height (NH) are unclear. OBJECTIVE: This study aimed to investigate acute muscle swelling in the IFM after TFE and the association between changes in NH and IFM size. METHODS: Fourteen adults participated in this study. NH and cross-sectional area (CSA) of the IFM were acquired pre and post- TFE. The CSA of the IFM, including the abductor hallucis (AbH), flexor hallucis brevis, flexor digitorum brevis, and quadratus plantae, was acquired with ultrasonography. In the TFE, each participant completed five sets of eight repetitions with maximum strength. RESULTS: The NH and CSA of all IFM significantly increased significantly post-TFE (p< 0.01). Only the increase in AbH was moderately and positively correlated with the change in NH (r= 0.54, p< 0.01). CONCLUSION: This study suggests that the acute swelling of AbH after TFE is associated with an immediate increase in NH, supporting the important role of AbH in the formation of foot arch.

Ultrasound Measures of Intrinsic Foot Muscle Size and Activation Following Lateral Ankle Sprain and Chronic Ankle Instability

CONTEXT

Tibial nerve impairment and reduced plantarflexion, hallux flexion, and lesser toe flexion strength have been observed in individuals with recent lateral ankle sprain (LAS) and chronic ankle instability (CAI). Diminished plantar intrinsic foot muscles (IFMs) size and contraction are a likely consequence.

OBJECTIVES

To assess the effects of ankle injury on IFM size at rest and during contraction in young adults with and without LAS and CAI.

SETTING

Laboratory.

DESIGN

Cross-sectional.

PATIENTS

A total of 22 healthy (13 females; age = 19.6 [0.9], body mass index [BMI] = 22.5 [3.2]), 17 LAS (9 females; age =21.8 [4.1], BMI = 24.1 [3.7]), 21 Copers (13 females; age = 20.8 [2.9], BMI = 23.7 [2.9]), and 20 CAI (15 females; age = 20.9 [4.7], BMI = 25.1 [4.5]).

MAIN OUTCOME MEASURES

Foot Posture Index (FPI), Foot Mobility Magnitude (FMM), and ultrasonographic cross-sectional area of the abductor hallucis, flexor digitorum brevis, quadratus plantae, and flexor hallucis brevis were assessed at rest, and during nonresisted and resisted contraction.

RESULTS

Multiple linear regression analyses assessing group, sex, BMI, FPI, and FMM on resting and contracted IFM size found sex (B = 0.45; P < .001), BMI (B = 0.05; P = .01), FPI (B = 0.07; P = .05), and FMM × FPI interaction (B = -0.04; P = .008) accounted for 19% of the variance (P = .002) in resting abductor hallucis measures. Sex (B = 0.42, P < .001) and BMI (B = 0.03, P = .02) explained 24% of resting flexor digitorum brevis measures (P < .001). Having a recent LAS (B = 0.06, P = .03) and FMM (B = 0.04, P = .02) predicted 11% of nonresisted quadratus plantae contraction measures (P = .04), with sex (P < .001) explaining 13% of resting quadratus plantae measures (B = 0.24, P = .02). Both sex (B = 0.35, P = .01) and FMM (B = 0.15, P = .03) predicted 16% of resting flexor hallucis brevis measures (P = .01). There were no other statistically significant findings.

CONCLUSIONS

IFM resting ultrasound measures were primarily determined by sex, BMI, and foot phenotype and not injury status. Routine ultrasound imaging of the IFM following LAS and CAI cannot be recommended at this time but may be considered if neuromotor impairment is suspected.

Ultrasound Imaging Is Reliable for Tibialis Posterior Size Measurements

OBJECTIVES

The tibialis posterior (TP) is a vital muscle for controlling the medial longitudinal arch of the foot during weight-bearing activities. Dysfunction of this muscle is associated with a variety of pathologic conditions; thus, it is important to reliably assess its morphologic characteristics. Ultrasound (US) has been used to assess characteristics of TP tendons but not the muscle cross-sectional area (CSA). The purpose of this study was to establish a reliable US technique to measure the TP CSA and thickness.

METHODS

Twenty-three healthy volunteers participated. We evaluated the CSA and thickness at 4 measurement locations (anterior and posterior views at both 30% and 50% of the shank length).

RESULTS

The participants included 12 female and 11 male volunteers (mean age ± SD, 31.23 ± 14.93 years). Excellent reliability was seen for the CSA and thickness at all locations (intraclass correlation coefficients, 0.988-0.998). Limits of agreement (LoA) and standard errors of the measurement (SEMs) were slightly lower at the 30% locations (LoA at 30%, 4.6-9.2; LoA at 50%, 6.4-9.7; SEM at 30%, 0.03-0.05; SEM at 50%, 0.04-0.07). Strong correlations were seen between anterior and posterior measurements of the CSA (30%, r = 0.99; P < .0001; 50%, r = 0.94; P < .0001) and thickness (30%, r = 0.98; P < .0001; 50%, r = 0.95; P = .0001).

CONCLUSIONS

Based on these results, the TP can be measured accurately with US at any of the tested locations. Due to the ease of collection and the quality of the data, we recommend the anterior view at 30% of the shank length to measure the CSA. The ability to assess muscle size of the TP will aid in a variety of medical and research applications.

Current advances and research in ultrasound imaging to the assessment and management of musculoskeletal disorders

Currently evidence-based practice has given scientific weight to the physical therapist profession; it is essential that all medical professional and physical therapists know the usefulness of new tools that optimize the effectiveness of their interventions and allow the growing of the scientific knowledge base. The use of ultrasound imaging (USI) by physiotherapists has evolved in recent years, consolidating as an increasingly standardized technique, low cost compared to other imaging techniques, quickly of execution, feasible and reliable tool. USI offers a wide range of opportunities in clinical practice as well as in different research areas. Therefore, ultrasound has been currently used as a diagnostic tool by physicians and in recent years there has been an expansion of the use of ultrasound equipment by non-physicians professionals such as physical therapist or physical trainers, who incorporates USI as a means of assessing musculoskeletal system architecture and composition, musculoskeletal changes in dysfunction, pain or injury conditions, as an interventional technique assisting echo-guided procedures or using the visual real-time information as a biofeedback in control motor approaches, as guiding tool in clinical decisions as well as to improve the understanding of tissue adaptations to exercise or movement. The purpose of this article is to review and provide an overview about the currently research of the USI applications and their benefits for the diagnosis and management in individuals with musculoskeletal conditions.

Use of Cine Loops and Structural Landmarks in Ultrasound Image Processing Improves Reliability and Reduces Error in the Assessment of Foot and Leg Muscles

OBJECTIVES

Foot and leg muscle strength and size are crucial to proper function. It is important to assess these characteristics reliably. Our primary objective was to compare the measurement of still images to cine loops. The secondary purpose was to determine interoperator and intraoperator reliability between operators of different experience levels using video clips and internal and external landmarks.

METHODS

Twelve healthy volunteers participated in our study. Internal (navicular tuberosity) and external (lateral leg length at 30% and 50% from the knee joint line) landmarks were used. Two operators each captured and later measured still and cine loop images of selected foot and leg muscles.

RESULTS

The 12 participants included 8 male and 4 female volunteers (mean age ± SD, 23.5 ± 1.9 years). Good to excellent intraoperator and interoperator reliability was seen (intraclass correlation coefficient range of 0.946-0.998). The use of cine loops improved the intraclass correlation coefficients for both intraoperator and interoperator reliability (0.5%-4% increases). The use of cine loops decreased the intraoperator standard error of the measurement and limits of agreement of the novice operator (decreases of 45%-73% and 24%-51%, respectively), and these became comparable to those of experienced operators using still images. The interoperator standard errors of the measurement dropped by 42% to 53%, whereas the limits of agreement dropped by 27% to 40%. No substantial changes were noted in the tibialis anterior across reliability metrics.

CONCLUSIONS

Improved protocols that take advantage of using internal bony landmarks and cine loops during both the image-gathering and measurement processes improve the reliability of research examining muscle size changes in the lower leg or foot associated with muscle changes due to exercise, injury, disuse, or disease.

The evalaution of the foot core system in individuals with plantar heel pain

OBJECTIVE

To compare foot posture, plantar sensation, plantar fascia thickness, intrinsic foot muscle performance, and abductor hallucis morphology in individuals with and without plantar heel pain (PHP).

DESIGN

Cross-Sectional.

SETTING

Laboratory.

PARTICIPANTS

Sixteen individuals with PHP and sixteen matched healthy participants.

MAIN OUTCOME MEASURES

Static foot posture, plantar sensation, plantar fascia thickness, intrinsic foot muscle performance and abductor hallucis morphology were evaluated. Foot posture was assessed with the Foot Posture Index-6. Abductor hallucis morphology and plantar fascia thickness were measured utilizing diagnostic ultrasound. Plantar foot sensation was assessed at the head of the first metatarsal and medial longitudinal arch using Semmes-Weinstein Monofilaments. Intrinsic foot muscle performance was assessed using the intrinsic foot muscle test (IFMT). Mann-Whitney U and independent t-tests were used to examine between group differences.

RESULTS

Individuals with PHP exhibited a more pronated foot posture and greater plantar fascia thickness at the proximal insertion compared to healthy controls. Plantar sensation thresholds were higher in the PHP compared to healthy controls at the head of the first metatarsal. There were no group differences in abductor hallucis morphology or IFMT performance.

CONCLUSIONS

Individuals with PHP exhibited a more pronated foot posture, thicker plantar fascia, and diminished plantar tactile sensation.

Effects of a 4-Week Intrinsic Foot Muscle Exercise Program on Motor Function: A Preliminary Randomized Control Trial

Context: Intrinsic foot muscle (IFM) exercises are utilized clinically in the treatment of foot and ankle conditions. However, the effectiveness of training on IFM motor function is unknown. Objective: To study the effects of a 4-week IFM exercise program on motor function, perceived difficulty, and IFM motor activation measured using ultrasound imaging (USI) during 3 IFM exercises. Design: Single-blinded randomized control trial. Setting: Laboratory. Participants: A total of 24 healthy, recreationally active young adults without history of ankle-foot injury who have never performed IFM exercises participated (12 males and 12 females; mean age = 21.5 [4.8] y; body mass index = 23.5 [2.9] kg/m²) Intervention: Following randomization, participants allocated to the intervention group received a 4-week progressive home IFM exercise program performed daily. Participants in the control group did not receive any intervention. Main Outcome Measures: Clinician-assessed motor performance (4-point scale: 0 = does not initiate movement and 3 = performs exercise in standard pattern), participant-perceived difficulty (5-point Likert scale: 1 = very easy and 5 = very difficult), and USI motor activation measures (contracted measurementresting measurement) of the abductor hallucis, flexor digitorum brevis, quadratus plantae, and flexor hallucis brevis were assessed during toe-spread-out, hallux-extension, and lesser-toe-extension exercises. Results: The intervention group demonstrated significant improvement in motor performance in the toe-spread-out exercise (pre = 1.9 [0.5], post = 2.6 [0.5], P = .008) and less perceived difficulty in the toe-spread-out (pre = 3.1 [1.3], post = 2.3 [1.2], P = .01), hallux-extension (pre = 3.2 [1.5], post = 2.0 [1.2], P = .005), and lesser-toe-extension (pre = 1.9 [0.7], post = 1.2 [0.4], P = .03) exercises. Both groups demonstrated increased USI motor activation in the abductor hallucis during the toe-spread-out exercise (intervention: pre = 1.07 [0.06], post = 1.11 [0.08] and control: pre = 1.08 [0.06], post = 1.11 [0.06]; P = .05). No other significant main effects or group by time interactions were observed. Conclusion: A 4-week IFM exercise intervention resulted in improved motor performance and decreased perceived difficulty when performing the exercises, but not changes in USI measures of IFM activation compared with a control group.

Intrinsic foot muscle size can be measured reliably in weight bearing using ultrasound imaging

BACKGROUND

The intrinsic foot muscles (IFMs) are important contributors to optimal foot function. While assessment of IFM morphology using ultrasound imaging in non-weight bearing has been established, this does not evaluate the foot in its primary functional position of weight bearing.

RESEARCH QUESTION

Is ultrasound imaging a reliable and clinically feasible method of measuring IFM morphology in weight bearing, do these measures differ to those from non-weight bearing and are they associated with participant characteristics?

METHODS

Ultrasound images were obtained by a single rater from twenty-four healthy participants on two occasions, one week apart. Images were taken in weight bearing (bilateral stance) and non-weight bearing (seated). Cross-sectional area and thickness of the abductor hallucis muscle, and dorsoplantar thickness of the muscles of the first interstitium were measured from acquired images. A second rater also acquired images at the first session. Participant characteristics included age, height, weight, sex, foot posture and foot mobility.

RESULTS

Measurements of IFM morphology demonstrated high reliability within and between test sessions, as well as between raters (ICCs > 0.8). Our findings suggest that changes of 10-18% could be considered to exceed measurement error. Larger IFM size was related to larger body size (taller, heavier), foot posture (longer foot, higher arch, wider midfoot) and male sex.

SIGNIFICANCE

This study is the first to describe a reliable and clinically feasible method of measuring IFM morphology in weight bearing. These measurements could be used in future studies to assess IFM morphology in patient populations and to evaluate the effect of intervention. Body size and foot posture explained between 20 and 41% of the variance in measurements and should be considered when comparing IFM morphology between individuals. The establishment of reliable measurements in weight bearing provides a crucial step towards the future evaluation of IFM function using ultrasound imaging.

Rehabilitative ultrasound imaging of the bilateral intrinsic plantar muscles and fascia in post-stroke survivors with hemiparesis: A case-control study

Purpose: The study main aim was to compare the cross-sectional area (CSA) and thickness of the plantar muscles and fascia in the hemiparesis and contralateral feet of poststroke survivors with respect to healthy feet of matched controls. Methods: A case-control observational study was performed using B-mode rehabilitative ultrasound imaging. A convenience sampling method was used to select 60 feet. The sample was divided into 20 feet ipsilateral and 20 feet contralateral to the hemiparesis lower limb from poststroke survivors, as well as 20 healthy feet from matched controls. The CSA and thickness of the abductor hallucis, flexor digitorum brevis and flexor hallucis brevis, as well as the thickness for the posterior, middle and anterior plantar fascia portions were measured. Comparisons and multivariate predictive analyses were carried out for ultrasound measurements. In all analyses, a P-value<.01 with a 99% confidence interval was considered as statistically significant. Results: Statistically significant differences (P<.01) were shown for a flexor hallucis brevis thickness increase as well as middle and anterior plantar fascia thickness decrease of the hemiparesis feet and contralateral feet with respect to the healthy matched control feet. The rest of measurements did not show any statistically significant difference (P>.01). Conclusions: The thickness of the flexor hallucis brevis muscle as well as the middle and anterior plantar fascia portions of the hemiparesis and contralateral feet from poststroke survivors presented morphology changes with respect to the healthy matched control feet.