Toe flexor forces in dancers and non-dancers

Foot arch height, toe flexor strength, and dynamic balance ability in collegiate female dancers and non-dancers

[Purpose] To characterize the foot arch height, toe flexor strength, and dynamic balance ability of collegiate female dancers and age-matched non-dancers. [Participants and Methods] This study included 20 healthy college-aged female dancers (21.6 ± 0.8 years) and 20 age-matched females (19.7 ± 1.0 years) with no previous experience in sports as non-dancers. Foot arch height was determined by measuring the height of the navicular tuberosity in the standing position using a ruler. Toe flexor strength was measured while seated on a chair using a toe grip dynamometer. Dynamic balance ability was evaluated based on the reach distance measured using a professional Y-balance test kit. [Results] The collegiate dancers had higher foot arches, greater toe flexor strength, and longer Y-balance test reach distance than the non-dancers. [Conclusion] The foot arch height, toe flexor strength, and dynamic balance ability of collegiate female dancers were adapted through years of training and were superior to those of non-dancers.

Flexor hallucis longus tendinous slips and the relationship to toe flexor strength

BACKGROUND

In the general population, the flexor hallucis longus (FHL) often has tendinous slips to lesser toes and the number of FHL slips varies between individuals. The purpose of this study was to investigate the relationship between the number of FHL tendinous slips in an individual foot and its toe flexor strength.

METHODS

Forty healthy men were included in the study. The FHL branch test was used to assess each subject for the number of FHL tendinous slips. Toe flexor strength in each toe was measured using a force gauge. A two-way ANOVA was used to compare toe flexor strength between groups classified according to the number of FHL slips.

RESULTS

The group of subjects with FHL branching to the second toe was the most common (20/40). The toe flexor strength ratio of the third toe was significantly lower in feet lacking FHL branching to the third toe than in those feet which did have branching to the third toe (P = 0.005).

CONCLUSIONS

Toe flexor strength was affected by FHL tendinous slips. Considering the number of the FHL tendinous slips an individual foot has may be useful in clinical practice for rehabilitation or training of toe flexor muscles.

A new simpler approach to measure the strength of toe plantar flexion requiring no mechanical restraint with a light-weight device

Conventionally, the strength of toe plantar flexion (STPF) is measured in a seated position, in which not only the target toe joints but also the knee and particularly ankle joints, are usually restrained. We have developed an approach for the measurement of STPF which does not involve restraint and considers the interactions of adjacent joints of the lower extremities. This study aimed to evaluate this new approach and comparing with the seated approach. A thin, light-weight, rigid plate was attached to the sole of the foot in order to immobilize the toe area. Participants were 13 healthy young women (mean age: 24 ± 4 years). For measurement of STPF with the new approach, participants were instructed to stand, raise the device-wearing leg slightly, plantar flex the ankle, and push the sensor sheet with the toes to exert STPF. The sensor sheet of the F-scan II system was inserted between the foot sole and the plate. For measurement with the seated approach, participants were instructed to sit and push the sensor with the toes. They were required to maintain the hip, knee, and ankle joints at 90°. The mean values of maximum STPF of the 13 participants obtained with each approach were compared. There was no significant difference in mean value of maximum STPF when the two approaches were compared (new: 59 ± 23 N, seated: 47 ± 33 N). The coefficient of variation of maximum STPF was smaller for data obtained with the new approach (new: 39%, seated: 70%). Our simple approach enables measurement of STPF without the need for the restraints that are required for the conventional seated approach. These results suggest that the new approach is a valid method for measurement of STPF.

Effects of a "toes-off" modified heel raise on muscle coordination in non-dancers, dancers, and dancers with flexor hallucis longus tendinopathy

BACKGROUND

Tendinopathy of the flexor hallucis longus, commonly called "dancer's tendinitis", is a prevalent injury among female ballet dancers. Limited success of non-surgical interventions leads to many dancers undergoing tenolysis surgeries with risks and recovery times that can be detrimental to a dance career. The purpose of this study was to evaluate lower limb kinematics and muscle coordination during a modified traditional heel raise exercise where the toes hang off the edge of the support surface. We hypothesized this would decrease activation of the flexor hallucis longus and increase activation of larger plantarflexors.

METHODS

Healthy non-dancers (n = 11), healthy dancers (n = 10), and dancers with flexor hallucis longus tendinopathy (n = 9) performed traditional ("toes-on") and modified ("toes-off") heel raises with kinematic and electromyographic instrumentation of the lower leg.

FINDINGS

Participants maintained ankle excursion with the toes-off modification, while metatarsophalangeal joints had reduced excursion and greater excursion variability. Most healthy dancers (9/10) decreased flexor hallucis longus activation as predicted, but dancers with flexor hallucis longus tendinopathy showed a variable response with some decreasing activation (3/9) but others increasing activation up to 4-times. There were no changes in activation of other plantarflexors. Across groups, intrinsic foot muscle activation decreased with the toes-off modification.

INTERPRETATION

The toes-off modification decreased flexor hallucis longus activation in most of the healthy dancers but was insufficient to shift muscle coordination from the flexor hallucis longus to larger plantarflexors in dancers with flexor hallucis longus tendinopathy. Future work should investigate clinical cues or modifications to this "toes-off" heel raise intervention.

Functional assessments of foot strength: a comparative and repeatability study

Background

Evaluating the strength of the small muscles of the foot may be useful in a variety of clinical applications but is challenging from a methodology standpoint. Previous efforts have focused primarily on the functional movement of toe flexion, but clear methodology guidelines are lacking. A novel foot doming test has also been proposed, but not fully evaluated. The purposes of the present study were to assess the repeatability and comparability of several functional foot strength assessment techniques.

Methods

Forty healthy volunteers were evaluated across two testing days, with a two-week doming motion practice period between them. Seven different measurements were taken using a custom toe flexion dynamometer (seated), custom doming dynamometer (standing), and a pressure mat (standing). Measurements from the doming dynamometer were evaluated for reliability (ICCs) and a learning effect (paired t-tests), while measurements from the toe flexion dynamometer and pressure mat were evaluated for reliability and comparability (correlations). Electromyography was also used to descriptively assess the extent of muscle isolation in all measurements.

Results

Doming showed excellent within-session reliability (ICCs > 0.944), but a clear learning effect was present, with strength (p < 0.001) and muscle activity increasing between sessions. Both intrinsic and extrinsic muscles were engaged during this test. All toe flexion tests also showed excellent reliability (ICCs > 0.945). Seated toe flexion tests using the dynamometer were moderately correlated to standing toe flexion tests on a pressure mat (r > 0.54); however, there were some differences in muscle activity. The former may better isolate the toe flexors, while the latter appeared to be more functional for many pathologies. On the pressure mat, reciprocal motion appeared to display slightly greater forces and reliability than isolated toe flexion.

Conclusions

This study further refines potential methodology for foot strength testing. These devices and protocols can be duplicated in the clinic to evaluate and monitor rehabilitation progress in clinical populations associated with foot muscle weakness.

Reliability of doming and toe flexion testing to quantify foot muscle strength

Background

Quantifying the strength of the intrinsic foot muscles has been a challenge for clinicians and researchers. The reliable measurement of this strength is important in order to assess weakness, which may contribute to a variety of functional issues in the foot and lower leg, including plantar fasciitis and hallux valgus. This study reports 3 novel methods for measuring foot strength – doming (previously unmeasured), hallux flexion, and flexion of the lesser toes.

Methods

Twenty-one healthy volunteers performed the strength tests during two testing sessions which occurred one to five days apart. Each participant performed each series of strength tests (doming, hallux flexion, and lesser toe flexion) four times during the first testing session (twice with each of two raters) and two times during the second testing session (once with each rater). Intra-class correlation coefficients were calculated to test for reliability for the following comparisons: between raters during the same testing session on the same day (inter-rater, intra-day, intra-session), between raters on different days (inter-rater, inter-day, inter-session), between days for the same rater (intra-rater, inter-day, inter-session), and between sessions on the same day by the same rater (intra-rater, intra-day, inter-session).

Results

ICCs showed good to excellent reliability for all tests between days, raters, and sessions. Average doming strength was 99.96 ± 47.04 N. Average hallux flexion strength was 65.66 ± 24.5 N. Average lateral toe flexion was 50.96 ± 22.54 N.

Conclusions

These simple tests using relatively low cost equipment can be used for research or clinical purposes. If repeated testing will be conducted on the same participant, it is suggested that the same researcher or clinician perform the testing each time for optimal reliability.

Correlation between toe flexor strength and ankle dorsiflexion ROM during the countermovement jump

[Purpose] This study assessed the relationships between peak toe flexor muscle strength, ankle dorsiflexion range of motion, and countermovement jump height. [Subjects and Methods] Eighteen healthy volunteers participated in the study. Each participant completed tests for peak toe flexor muscle strength, ankle dorsiflexion range of motion, and countermovement jump height. [Results] The results showed (1) a moderate correlation between ankle dorsiflexion range of motion and countermovement jump height and (2) a high correlation between peak first toe flexor muscle strength and countermovement jump height. Peak first toe flexor muscle strength and ankle dorsiflexion range of motion are the main contributors to countermovement jump performance. [Conclusion] These findings indicate that the measurement of peak first toe flexor muscle strength and ankle dorsiflexion range of motion may be useful in clinical practice for improving jump performance in athletes training for sports such as volleyball and basketball.

Importance and challenges of measuring intrinsic foot muscle strength

BACKGROUND

Intrinsic foot muscle weakness has been implicated in a range of foot deformities and disorders. However, to establish a relationship between intrinsic muscle weakness and foot pathology, an objective measure of intrinsic muscle strength is needed. The aim of this review was to provide an overview of the anatomy and role of intrinsic foot muscles, implications of intrinsic weakness and evaluate the different methods used to measure intrinsic foot muscle strength.

METHOD

Literature was sourced from database searches of MEDLINE, PubMed, SCOPUS, Cochrane Library, PEDro and CINAHL up to June 2012.

RESULTS

There is no widely accepted method of measuring intrinsic foot muscle strength. Methods to estimate toe flexor muscle strength include the paper grip test, plantar pressure, toe dynamometry, and the intrinsic positive test. Hand-held dynamometry has excellent interrater and intrarater reliability and limits toe curling, which is an action hypothesised to activate extrinsic toe flexor muscles. However, it is unclear whether any method can actually isolate intrinsic muscle strength. Also most methods measure only toe flexor strength and other actions such as toe extension and abduction have not been adequately assessed. Indirect methods to investigate intrinsic muscle structure and performance include CT, ultrasonography, MRI, EMG, and muscle biopsy. Indirect methods often discriminate between intrinsic and extrinsic muscles, but lack the ability to measure muscle force.

CONCLUSIONS

There are many challenges to accurately measure intrinsic muscle strength in isolation. Most studies have measured toe flexor strength as a surrogate measure of intrinsic muscle strength. Hand-held dynamometry appears to be a promising method of estimating intrinsic muscle strength. However, the contribution of extrinsic muscles cannot be excluded from toe flexor strength measurement. Future research should clarify the relative contribution of intrinsic and extrinsic muscles during intrinsic foot muscle strength testing.

The potential of toe flexor muscles to enhance performance

The metatarsal phalangeal joint (MPJ) and its crossing toe flexor muscles (TFM) represent the link between the large energy generating leg extensor muscles and the ground. The purpose of this study was to examine the functional adaptability of TFM to increased mechanical stimuli and the effects on walking, running and jumping performance. Fifteen men performed a heavy resistance TFM strength training with 90% of the maximal voluntary isometric contraction (MVIC) for 7 weeks (560 contractions) for the left and right foot. Maximal MPJ and ankle plantar flexion moments during MVICs were measured in dynamometers before and after the intervention. Motion analyses (inverse dynamics) were performed during barefoot walking, running, and vertical and horizontal jumping. Athletic performance was determined by measuring jump height and distance. Left (0.21 to 0.38 Nm · kg(-1); P < 0.001) and right (0.24 to 0.40 Nm · kg(-1); P < 0.001) MPJ plantar flexion moments in the dynamometer, external MPJ dorsiflexion moments (0.69 to 0.75 Nm · kg(-1); P = 0.012) and jump distance (2.25 to 2.31 m; P = 0.006) in horizontal jumping increased significantly. TFM responded highly to increased loading within a few weeks. The increased force potential made a contribution to an athlete's performance enhancement.

The potential of human toe flexor muscles to produce force

The maximal force a muscle produces depends among others on the length of the muscle and therefore on the positions of the joints the muscle crosses. Long and short toe flexor muscles (TFM) cross the ankle joints and metatarsal phalangeal joints (MPJ) and work against gravity during human locomotion. The purpose of this study was to describe the maximal moments around the MPJ during maximal voluntary isometric contractions (MVIC) of the TFM as a function of ankle joint and MPJ position. Twenty men performed MVIC of the TFM in a custom-made dynamometer. Ankle and MPJ angles were modified after each contraction. External moments of force around the MPJ were determined. Moments ranged between 6.3 ± 2.6 Nm and 14.2 ± 5.8 Nm. Highest moments were produced at 0°-10° ankle joint dorsal flexion and 25°-45° MPJ dorsal flexion. Lowest moments were generated at 35° ankle joint plantar flexion and 0° MPJ dorsal flexion. In conclusion, if the ankle is plantar-flexed, dorsal flexion of the MPJ avoids a disadvantage of the force-length relationship of TFM. Therefore, MPJ dorsal flexion is a necessary function in the push-off phase of human locomotion to work against the loss of the mechanical output at the forefoot caused by plantar flexion of the ankle.

The effect of a foot gymnastic exercise programme on gait performance in older adults: a randomised controlled trial

BACKGROUND

Aged-related loss of ankle dorsiflexion range of motion (ROM) and toe plantarflexor strength play an important role in gait performance. Further, conventional strength, balance and gait training can significantly improve the lower extremity muscle power and functional abilities of older individuals. It remains unclear, however, whether training effects can be enhanced by augmenting ankle ROM and toe plantarflexor strength complementary to training.

OBJECTIVE

This study investigated the effect of physical exercise combined with foot gymnastics on the gait performance in older adults.

METHODS

Fifty-six independent living, older adults aged 66-91 years were randomly assigned to either foot gymnastics group (FG; n = 28) or training group (TG; n = 28). Further, 14 subjects were integrated as a control group (CG; n = 14) (no exercise). The FG and TG completed the same training program consisting of aerobic exercises, progressive resistance strength training and stretching exercises twice per week for 12 weeks, whereas the FG performed additional foot gymnastic exercises at the end of the training session and a 10-min foot gymnastics home-program daily. Assessments included the Falls Efficacy Scale - International (FES-I), Expanded Timed Get-up-and-Go test (ETGUG), gait analysis and muscle power measurements of the knee and ankle joint at pre- and post-training. Results. No significant change in FES-I score occurred in either group. The FG showed a significant improvement of ankle ROM. There were significant time x group interactions in walking speed, step length, in several muscle power measurements and in ETGUG. The positive effects of gait parameters ranged between 1 and 11% and between 2 and 12%, of muscle power between 14 and 34% and 14 and 46% and of ETGUG were 10 and 8% for the FG and TG, respectively. The FG and TG did not differ significantly in their improvements. The CG showed a trend to deteriorations between 0 and -6% for gait parameters, between -4 and -14% for muscle power and 0% for ETGUG.

CONCLUSIONS

The results of this study provide evidence of significant improvements in gait performance, muscle power and ETGUG after a conventional training program in independent living, older adults. However, there is no additional effect on physical performance after foot gymnastic exercises.

Muscle imbalance and reduced ankle joint motion in people with hammer toe deformity

BACKGROUND

Multiple factors may contribute to hammer toe deformity at the metatarsophalangeal joint. The purposes of this study were to (1) compare the ratio of toe extensor/flexor muscle strength in toes 2-4 among groups with and without hammer toe deformity, (2) to determine correlations between the ratio of toe extensor/flexor muscle strength in toes 2-4, and metatarsophalangeal joint deformity (3) to determine if other clinical measures differ between groups and if these measures are correlated with metatarsophalangeal joint angle.

METHODS

Twenty-seven feet with visible hammer toe deformity and 31 age matched feet without hammer toe deformity were tested. Toe muscle strength was measured using a dynamometer and the ratio of toe extensor muscle strength to flexor muscle strength was calculated. Metatarsophalangeal joint angle was measured from a computerized tomography image. Ankle and subtalar joint range of motion, and tibial torsion were measured using goniometry.

FINDINGS

Extensor/flexor toe muscle strength ratio was 2.3-3.0 times higher in the hammer toe group compared to the non-hammer toe group, in toes 2-4. The ratios of extensor/flexor toe muscle strength for toes 2-4 and metatarsophalangeal joint angle were highly correlated (r=0.69-0.80). Ankle dorsiflexion and metatarsophalangeal joint angle were negatively correlated for toes 2-4 (r=-0.38 to -0.56) as were eversion and metatarsophalangeal joint angle.

INTERPRETATION

These results provide insight into potential risk factors for the development of hammer toe deformity. Additional research is needed to determine the causal relationship between hammer toe deformity and the ratio of toe extensor/flexor muscle strength in toes 2-4.

Plantarflexion strength of the toes: age and gender differences and evaluation of a clinical screening test

BACKGROUND

The toes play an important stabilizing role in weightbearing activities. However, the factors that influence toe plantarflexion strength are poorly understood, and there are no validated measures for assessing toe weakness in the clinical setting. Therefore, the objectives of this study were to determine whether plantarflexion strength of the toes differs according to age and gender and to evaluate the validity of a clinical screening test for assessing toe plantarflexor weakness (the paper grip test).

METHODS

Plantarflexion strength of the hallux and lesser toes was measured in 40 young participants (20 men and 20 women, mean age 20.8 +/- 2.2 years) and 40 older participants (20 men and 20 women, mean age 74.6 +/- 5.7 years) using a pressure platform in conjunction with clinical assessment using the paper grip test.

RESULTS

Older participants exhibited 32% less plantarflexion strength of the hallux and 27% less plantarflexion strength of the lesser toes compared to younger participants, and women exhibited 42% less hallux plantarflexor strength than men. Gender did not influence lesser toe plantarflexor strength. Participants who failed the paper grip test exhibited significantly reduced plantarflexion strength for both the hallux and lesser toes. The sensitivity and specificity of the paper grip test of the hallux to predict plantarflexor strength less than 2.6 kg was 80% and 79%, respectively, and the sensitivity and specificity of the paper grip test of the lesser toes to predict plantarflexor strength less than 2.2 kg was 75% and 74%, respectively.

CONCLUSIONS

These findings indicate that aging is associated with reduced plantarflexion strength of the toes. The paper grip test may be a useful screening tool to detect toe weakness in the clinical setting.