The effect of foot orthoses on sprinting biomechanics on flat footed individuals

Introduction: Sprinting involves running at near maximum speeds. Sprinting produces high ground reaction forces (GRF) and loading rates which predisposes sprinters to injuries. Compared to non-flatfooted individuals, flatfooted individuals exhibit different lower extremity biomechanics during locomotion which are associated with an increased risk of overuse injuries. Flat-footed individuals are therefore possibly more susceptible to sprint injuries. Foot orthoses are usually prescribed to flatfooted individuals to better control the rearfoot and reduce GRF. However, there is a lack of studies investigating the efficacy of foot orthoses during sprinting. This study investigated the effects of foot orthoses on GRF in flatfooted individuals during sprinting. In addition, the comfort perception of foot orthoses were evaluated. Method: Ten flatfooted university male athletes (age 24.9 ± 1.10 years, Body Mass 70.45 ± 8.89 kg) ran on an instrumented treadmill at three different speeds (5m/s, 6m/s and 7m/s) under two different orthoses conditions (prefabricated foot orthoses and flat control insoles). The order of running speed and orthotic conditions were randomized. The GRF of the last eight complete steps of each trial were collected. Comfort perception was measured using a 150mm visual analogue scale after completion of the entire trial. A two-way repeated ANOVA was performed on GRF variables. A paired sample t-test was performed on the comfort perception ratings. Results: There was no significant interaction effect between speed and foot orthosis conditions for the GRF variables (P > 0.05). Compared to flat control insoles, the prefabricated foot orthoses were found to reduce the time to peak vertical GRF by 12% resulting in a corresponding increase in loading rate by 32.3% (P < 0.05) while peak propulsive force was reduced by 3.93% (P < 0.05). The participants responded that the prefabricated orthotics provided better arch support but poorer overall comfort compared to the flat control insoles (P < 0.05). Discussion: The findings suggest that the prefabricated foot orthoses do not reduce shock at foot strike. Therefore, no inference can be made regarding the potential for prefabricated orthosis to prevent impact related injuries during sprints. The poor overall comfort perceived when using the prefabricated foot orthoses may be due to minimal wear-in time. In conclusion, this study shows that there is no clear beneficial effect of foot orthosis in flat-footed individuals during sprinting

Changes in inertial parameters of the lower limb during the impact phase of dynamic tasks

Mechanical analysis at the whole human body level typically assumes limbs are rigid bodies with fixed inertial parameters, however, as the human body consists mainly of deformable soft tissue, this is not the case. The aim of this study was to investigatechanges in the inertial parameters of the lower limb during landing and stamping tasks using high frequency three-dimensional motion analysis. Seven males performed active and passive drop landings from 30 and 45 cm and a stamp onto a force plate. A sixteen-camera 750 Hz Vicon system recorded markers for standardrigid body analysis using inverse kinematics in Visual 3D and 7×8 and 7×9 marker arrays on the shank and thigh. Frame by frame segment volumes from marker arrays were calculated as a collection of tetrahedra using the Delaunay triangulation method in 3D and further inertial parameters were calculated using the method of Tonon (2004). Distance between the centres of mass (COM) of the rigid and soft tissues changed during impact in a structured manner indicative of a damped oscillation. Group mean amplitudes for COM motion of the soft tissues relative to therigid body of up to 1.4 cm, and changes of up to 17% in moment of inertia of the soft tissue about the rigid body COM were found. This study has shown that meaningful changes in inertial parameters can be observed and quantified during even moderate impacts. Further examination of the effects these could have onmovement dynamics and energetics seems pertinent.</div

Examining the interaction of different factors on pointing precision when using handheld laser pointers

Objective: Laser pointers are common teaching tools used during lessons. The pointing precision may influence the teaching effectiveness. In this study, we examined the effect of four external factors, namely aiming distance, target size, light condition and colour of the laser beam on the pointing precision. Results: Thirty participants (15 males and 15 females; age = 23.2 ± 4.3) were asked to aim at the target black circles with different sizes (diameters = 4 mm, 8 mm, 12 mm and 16 mm) from five various distances (2 m, 4 m, 6 m, 8 m and 10 m) at two brightness conditions (i.e., bright and dark) using two different coloured laser pointers (red and green). Three aiming parameters, namely number of hits, duration per hit and pointing precision were measured. Results showed that the aiming parameters were the highest with the aiming distance of 2 m and the use of green laser pointer towards larger target sizes regardless of the environmental brightness. Among all factors, aiming distance was the most important external factor that could influence pointing precision.</div

Fiber Bragg grating sensors for clinical measurement of the first metatarsophalangeal joint quasi-stiffness

Assessing the mobility of the first metatarsophalangeal joint (MTPJ) of a human foot is useful in clinical practice but there are no standard methods of measurement. The present study developed a new instrumentation using Fiber Bragg grating (FBG) sensor and load cell to quantify the first MTPJ quasi-stiffness in a clinical setting. This system is portable, lightweight, and allows quantification of quasi-stiffness over different ranges of motion in both loading and unloading directions. The laboratory setting validation results showed that FBG sensors could measure MTPJ angular displacement with reasonably good accuracy. The proposed system was successfully trialed in a hospital setting operated by a clinician on eight human subjects. Non-linear torque-angular displacement relationship was observed in both loading and unloading phases, with varying MTPJ quasi-stiffness in the early [loading 6.30 (2.62) Nmm/o unloading 8.46 (2.29) Nmm/ o], middle [loading 7.13 (2.17) Nmm/ o, unloading 11.11 (2.94) Nmm/ o], and late [loading 24.54 (7.14) Nmm/ o, unloading 14.50 (4.77) Nmm/ o] ranges of motion. The new method for measuring the first MTPJ quasi-stiffness established in the present study serves as a reference and opens up opportunities for future clinical investigations

Validity of a FBG-based smart sock system for measuring toe grip function in human foot

This study developed a smart sock system using optical fiber technology to measure the toe grip function of individual toes. The system comprised Fiber Bragg grating (FBG) sensors incorporated into a sock garment for measuring maximum toe flexion displacements. Calibration equation of each FBG sensor was determined from 3D motion capture system on 10 female subjects. The validity of the smart sock system was checked by comparing maximum toe flexion displacement against the gold standard of 3D motion capture. The root mean squared error was 0.95 (0.57) cm across 10 toes. The magnitude of toe displacement and error were similar between the left and right foot. In conclusion, the FBG-based smart sock system can successfully measure maximum toe flexion displacements of individual toes simultaneously. This system can be developed to support the evaluation of toe grip function in clinical and field settings.</div

A clinician-free method utilising top-view photograph for screening and monitoring hallux valgus

Abstract will be added following publication.</div

Test-retest reliability of a clinical foot assessment device for measuring first metatarsophalangeal joint quasi-stiffness

Background: The stiffness of the first metatarsophalangeal joint (MTPJ) is of interest in cases such as hallux rigidus and apropulsive gait. Subjective rating of joint mobility as ‘hypermobile, normal, or stiff’ is an unreliable method. Previous instruments for the assessment of first MTPJ stiffness can be too hard and uncomfortable for test subjects. Recently, a new device using a load cell and optical fiber with fiber Bragg grating (FBG) sensors was developed to provide a comfortable means of clinical foot assessment. This study aimed to evaluate the test-retest reliability of this FBG-load cell device in measuring the first MTPJ quasi-stiffness.Methods: The left foot of 13 female subjects were measured twice for their first MTPJ quasistiffness, approximately seven days apart. The FBG-load cell device measured the MTPJ range of motion from a resting position to maximum dorsiflexion and then returning to the resting start-position. The force applied by a clinician to displace the toe was simultaneously recorded using a load cell. The quasi-stiffness over the “working range” in loading and unloading directions were determined from the slope of the torque-angular displacement graph. The test-retest reliability of the MTPJ quasi-stiffness was evaluated using intra-class correlation coefficient [ICC (2,1)].Results: The reliability was almost perfect for MTPJ quasi-stiffness over the loading phase (ICC = 0.814), moderate for MTPJ quasi-stiffness over the unloading phase (ICC = 0.477) and moderate for MTPJ maximum range (ICC = 0.486).Conclusion: The foot assessment device based on FBG and load cell was able to reliably measure the first MTPJ quasi-stiffness in a clinical setting. The measurement reliability was higher during the loading phase than the unloading phase. </div

Within-day and between-day reliability of a FBG-based smart sock system for measuring active toe flexion displacement of the hallux

This study examined the test-retest reliability of hallux flexion displacement measured using a smart sock system with embedded fiber Bragg grating (FBG) sensors. Thirty female participants consisted of 15 hallux valgus (HV) patients and 15 control participants were recruited. Maximum active hallux flexion displacement was measured twice on each participant in the first visit; the same procedures were repeated 7 days later. Intraclass correlation coefficients (ICC2,1) and standard error of measurement (SEM) were applied to test within-day and between-day reliability. Paired-samples T-test was performed to compare the displacements between trials. Results showed almost perfect within-day reliability for both HV and control groups (ICC = .984 and .977, respectively) with small SEM (both 0.5 cm). However, fair to moderate between-day reliability was found (.323 and .438, respectively). Significant differences were found between repeated measurements taken on the same day (mean difference = 0.3 cm, p = .023) and on different days (mean difference = 1.6 cm, p = .027), though the effect size was small. The poorer between-day reliability is likely due to the inconsistency in fitting the sock onto the foot. Future optimization of the prototype design is called for to improve the fitting consistency of wearable sensors onto patients

Reporting guidelines for running biomechanics and footwear studies using three-dimensional motion capture

Editorial – Reporting guidelines for running biomechanics and footwear studies using 3D motion capture.</p