Effect of custom-made and prefabricated insoles on plantar loading parameters during running with and without fatigue

Effects of foot orthoses on running kinetics and kinematics: A systematic review and meta-analysis

BACKGROUND

Foot orthoses (FOs) are often prescribed by clinicians to treat foot and ankle conditions, prevent running injuries, and enhance performance. However, the lack of higher-order synthesis of clinical trials makes it challenging for clinicians to adopt an evidence-based approach to FOs' prescriptions.

RESEARCH QUESTION

Do FOs with different modifications alter lower extremity running kinematics and kinetics?

METHODS

A systematic search of seven databases was conducted from inception to February 2023. The analysis was restricted to healthy adults without foot musculoskeletal impairments and studies that compared the FOs effects with the controls. The methodological quality of the 35 studies that met the eligibility criteria was evaluated using the modified Downs and Black checklist. The random effects model estimated the standardized mean difference (SMD) with 95% confidence intervals and effect sizes. Sub-group analyses based on FOs type were performed to assess the potential effects of the intervention.

RESULTS

Our findings indicated that both custom and off-the-shelf arch-support FOs reduced peak plantar pressure at the medial heel (SMD=-0.35, and SMD=-1.03), lateral heel (SMD=-0.50, and SMD=-0.53), and medial forefoot (SMD=-0.20, and SMD=-0.27), but increased plantar pressure at the mid-foot (SMD=0.30, and SMD=0.56). Compared with the controls, significant increases (SMD=0.36) in perceived comfort were found with custom FOs. A reduction (SMD=-0.58) in initial ankle inversion was found when a raised heel cup was integrated with arch-support FOs. A medial post integrated with arch support exhibited a reduced ankle (SMD=-1.66) and tibial (SMD=-0.63) range of motion. Custom FOs, however, unfavorably affected the running economy (SMD=-0.25) and perceived exertion (SMD=0.20).

SIGNIFICANCE

Although FOs have been reported to have some positive biomechanical effects in healthy populations without musculoskeletal impairments or running-related issues, they need to be optimized and generalized to achieve better running performance and prevent injury.

Effect of Foot Orthoses on Angular Velocity of Feet

There is some uncertainty regarding how foot orthoses (FO) affect the biomechanics of the lower extremities during running in non-injured individuals. This study aims to describe the behavior of the angular velocity of the foot in the stride cycle measured with a low-sampling-rate IMU device commonly used by podiatrists. Specific objectives were to determine if there are differences in angular velocity between the right and left foot and to determine the effect of foot orthoses (FO) on the 3D angular velocity of the foot during running. The sample was composed of 40 male adults (age: 43.0 ± 13.8 years, weight: 72.0 ± 5.5 kg, and height: 175.5 ± 7.0 cm), who were healthy and without any locomotor system alterations at the time of the test. All subjects use FO on a regular basis. The results show that there are significant differences in the transverse plane between feet, with greater differences in the right foot. Significant differences between FO and non-FO conditions were observed in the frontal and transverse planes on the left foot and in the sagittal and transverse planes on the right foot. FO decreases the velocity of the foot in dorsi-plantar flexion and abduction and increases the velocity in inversion. The kinematic changes in foot velocity occur between 30% and 60% of the complete cycle, and the FO reduces the velocity in abduction and dorsi-plantar flexion and increases the velocity in inversion-eversion, which facilitates the transition to the oscillating leg and with it the displacement of the center of mass. Quantifying possible asymmetries and assessing the effect of foot orthoses may aid in improving running mechanics and preventing injuries in individuals.

Relationship between muscular extensibility, strength and stability and the transmission of impacts during fatigued running

The aim was to analyse the relationship between isokinetic strength, dynamic stability, muscular extensibility and impacts transmission during fatigued running. Low- and high-frequency impacts-related to body movements and the severity of impacts, respectively-were assessed in 17 male recreational runners, before and after a treadmill running fatigue protocol, using a triaxial accelerometry system. High-frequency impacts in the tibia were negatively correlated to the knee angle at which the quadriceps peak torque was reached (p = 0.014), and also to the extensibility of the hamstrings and soleus (p = 0.001 and p = 0.023, respectively). The increases of high-frequency impacts in tibia caused by fatigue were positively related to the knee angle at which the hamstrings peak torque was reached (p = 0.001) and to stability after landing (p = 0.007). The attenuation of high-frequency impacts was positively related to hamstrings/quadriceps ratio of strength (p = 0.010) and to stability (p = 0.006). Limiting possible deficits in hamstring and soleus range of motion, improving stability after landing, developing hamstring and quadriceps strength in elongated muscle range, and maintaining a balanced ratio of hamstring/quadriceps strength could help to reduce the injury risk in running.

Can a shoe-mounted IMU identify the effects of orthotics in ways comparable to gait laboratory measurements?

BACKGROUND

Footwear and orthotic research has traditionally been conducted within laboratories. With increasing prevalence of wearable sensors for foot and ankle biomechanics measurement, transitioning experiments into the real-world is realistic. However wearable systems must effectively detect the direction and magnitude of response to interventions to be considered for future usage.

METHODS

RunScribe IMU was used simultaneously with motion capture, accelerometers, and force plates during straight-line walking. Three orthotics (A, B, C) were used to change lower limb biomechanics from a control (SHOE) including: Ground reaction force (GRF) loading rate (A), pronation excursion (A and B), maximum pronation velocity (A and B), and impact shock (C) to test whether RunScribe detected effects consistent with laboratory measurements. Sensitivity was evaluated by assessing: 1. Significant differences (t-test) and effect sizes (Cohen's d) between measurement systems for the same orthotic, 2. Statistical significance (t-test and ANOVA) and effect size (Cohen's d & f) for orthotic effect across measurement systems 3. Direction of orthotic effect across measurement systems.

RESULTS

GRF loading rate (SHOE: p = 0.138 d = 0.403, A: p = 0.541 d = 0.165), impact shock (SHOE: p = 0.177 d = 0.405, C: p = 0.668 d = 0.132), pronation excursion (A: p = 0.623 d = 0.10, B: p = 0.986 d = 0.00) did not significantly differ between measurement systems with low effect size. Significant differences and high effect sizes existed between systems in the control condition for pronation excursion (p = 0.005 d = 0.68), and all conditions for pronation velocity (SHOE: p < 0.001 d = 1.24, A: p = 0.001 p = 1.21, B: p = 0.050 d = 0.64). RunScribe (RS) and Laboratory (LM) recorded the same significant effect of orthotic but inconsistent effect sizes for GRF loading rate (LM: p = 0.020 d = 0.54, RS: p = 0.042 d = 0.27), pronation excursion (LM: p < 0.001 f = 0.31, RS: p = 0.042 f = 0.15), and non-significant effect of orthotic for impact shock (LM: p = 0.182 d = 0.08, RS: p = 0.457 d = 0.24). Statistical significance was different between systems for effect of orthotic on pronation velocity (LM: p = 0.010 f = 0.18, RS: p = 0.093 f = 0.25). RunScribe and Laboratory agreed on the direction of change of the biomechanics variables for 69% (GRF loading rate), 40%-70% (pronation excursion), 47%-65% (pronation velocity), and 58% (impact shock) of participants.

CONCLUSION

The RunScribe shows sensitivity to orthotic effect consistent with the laboratory at the group level for GRF loading rate, pronation excursion, and impact shock during walking. There were however large discrepancies between measurements in individuals. Application of the RunScribe for group analysis may be appropriate, however implementation of RunScribe for individual assessment and those including pronation may lead to erroneous interpretation.

Effects of Central and Peripheral Fatigue on Impact Characteristics during Running

Fatigue and impact can represent an injury risk factor during running. The objective of this study was to compare the impact transmission along the locomotor system between the central and peripheral fatigued states during running. Tibial and head acceleration as well as shock attenuation in the time- and frequency-domain were analyzed during 2-min of treadmill running in the pre- and post-fatigue state in eighteen male popular runners (N = 18). The impact transmission was measured before and after a 30-min central fatigue protocol on the treadmill or a peripheral fatigue protocol in the quadricep and hamstring muscles using an isokinetic dynamometer. The time-domain acceleration variables were not modified either by peripheral or central fatigue (p > 0.05). Nevertheless, central fatigue increased the maximum (p = 0.006) and total (p = 0.007) signal power magnitude in the high-frequency range in the tibia, and the attenuation variable in the low- (p = 0.048) and high-frequency area (p = 0.000), while peripheral fatigue did not cause any modifications in the frequency-domain variables (p > 0.05). Furthermore, the attenuation in the low (p = 0.000)- and high-frequency area was higher with central fatigue than peripheral fatigue (p = 0.003). The results demonstrate that central fatigue increases the severity of impact during running as well as the attenuation of low and high components.

Higher Hamstrings Strength and Stability Are Related to Lower Kinematics Alteration during Running after Central and Peripheral Fatigue

Fatigue can be classified as peripheral or central depending on the extent of its effects. Muscle strength reduction, associated with the appearance of fatigue during running, produces kinetics and kinematics modifications which could lead to an increased risk of injury. This study aimed to analyze the effect of peripheral and central fatigue protocols in running kinematics and to investigate the relationship between isokinetic strength and dynamic stability in fatigue related changes. Eighteen male recreational runners participated in the study. The dynamic postural stability index (DPSI) and quadriceps and hamstring isokinetic strength were assessed before the fatigue test. Then, angular kinematics during treadmill running were evaluated in pre- and post-fatigue states (central and peripheral). The results showed that runners with higher hamstring isokinetic strength and better DPSI had lower modifications after central fatigue of stance time, knee flexion, vertical and leg stiffness, and ankle dorsiflexion during the absorption and propulsion phases (r > 0.400, p < 0.05). Moreover, small changes in ankle dorsiflexion at initial contact after peripheral fatigue are related to a better DPSI and higher hamstring isokinetic strength (r > 0.400, p < 0.05). In summary, high values of hamstring isokinetic concentric strength and dynamic stability are related to lower increases of range of movements during running after central and peripheral fatigue. So, fatigue may affect to a lesser extent the running technique of those runners with higher hamstring strength and stability values.

EFFECT OF FATIGUE AND GRADED RUNNING ON KINEMATICS AND KINETICS PARAMETERS IN TRIATHLETES

This study aimed to evaluate the effect of cycling-induced fatigue on subsequent running with different ground inclinations on triathletes. Twenty male triathletes ran on a treadmill at individual speeds, on three inclines: level (0%), 7% uphill (7%), and 7% downhill (-7%). Subsequently, the athletes performed an incremental ramp-to-exhaustion (RTE) protocol on an ergometric bicycle until task failure and repeated the running protocol (POST-RTE). During running and cycling was monitored perceived exertion (RPE) and heart rate (HR). Plantar pressure distribution, peak plantar pressure, total foot area, and ground contact time were measured by an in-shoe sensor. Analysis of variance showed that HR (p=0.001; η2=0.63) and RPE (p=0.001; η2=0.82 large effect) were higher in POST-RTE, without interactions between slopes and fatigue. The heel load showed difference between 0% and 7% and 7% and -7% (p=0.001; η2=0.44 large effect) with higher value in -7%. The midfoot showed differences between 0% and -7% with higher value in 0% (p=0.03; η2=0.15 small effect). The contact time showed interactions between fatigue and slopes with a higher value in POST-RTE. Coaches should be aware that training on the uphill and downhill surfaces can alter the plantar load on different foot parts.

Effects of Minimalist Footwear and Foot Strike Pattern on Plantar Pressure during a Prolonged Running

The use of minimalist shoes (MS) in running involves changes in running mechanics compared to conventional shoes (CS), but there is still little research analysing the effects of this footwear on plantar pressure, which could help to understand some risk injury factors. Moreover, there are no studies examining the effects of a prolonged running and foot strike patterns on baropodometric variables in MS. Therefore, the aim of this study was to analyse the changes produced using MS on plantar pressure during a prolonged running, as well as its interaction with the time and foot strike pattern. Twenty-one experienced minimalist runners (age 38 ± 10 years, MS running experience 2 ± 1 years) ran with MS and CS for 30 min at 80% of their maximal aerobic speed, and mean pressure, peak pressure, contact time, centre of pressure velocity, relative force and contact area were analysed using a pressure platform. Foot strike pattern and time were also considered as factors. The multivariable linear regression mixed models showed that the use of MS induced, at the end of a prolonged running, higher peak pressure (p = 0.008), lower contact time (p = 0.004) and lower contact area (p < 0.001) than using CS. Also, runners with forefoot strike pattern using MS, compared to midfoot and rearfoot patterns, showed higher mean and peak pressure (p < 0.001) and lower contact time and area (p < 0.05). These results should be considered when planning training for runners using MS, as higher peak pressure values when using this type of footwear could be a risk factor for the development of some foot injuries.

Acute intense fatigue does not modify the effect of EVA and TPU custom foot orthoses on running mechanics, running economy and perceived comfort

We determined whether fatigue modifies the effect of custom foot orthoses manufactured from ethyl-vinyl acetate (EVA) and expanded thermoplastic polyurethane (TPU) materials, both compared to standardized footwear (CON), on running mechanics, running economy, and perceived comfort. Eighteen well-trained, males ran on an instrumented treadmill for 6 min at the speed corresponding to their first ventilatory threshold (13.8 ± 1.1 km/h) in three footwear conditions (CON, EVA, and TPU). Immediately after completion of a repeated-sprints exercise (8 × 5 s treadmill sprints, rest = 25 s), these run tests were replicated. Running mechanics, running economy and perceived comfort were determined. Two-way repeated measures ANOVA [condition (CON, EVA, and TPU) × fatigue (fresh and fatigued)] were conducted. Flight time shortened (P = 0.026), peak braking (P = 0.016) and push-off (P = 0.032) forces decreased and vertical stiffness increased (P = 0.014) from before to after the repeated-sprint exercise, independent of footwear condition. There was a global fatigue-induced deterioration in running economy (- 1.6 ± 0.4%; P < 0.001). There was no significant condition × fatigue [except mean loading rate (P = 0.046)] for the large majority of biomechanical, cardio-respiratory [except minute ventilation (P = 0.020) and breathing frequency (P = 0.019)] and perceived comfort variables. Acute intense fatigue does not modify the effect of custom foot orthoses with different resilience characteristics on running mechanics, running economy and perceived comfort.

Plantar pressure distribution during running with a self-customized foot orthosis in a home microwave

The individualization of a custom-made foot orthosis could provide improvements in plantar loading distribution regarding a prefabricated one. However, not all runners can afford it because of its high cost. A new type of low-cost prefabricated foot orthoses with self-customization could be the solution. The aim of the study was to evaluate if self-customized prefabricated foot orthoses (SCFO) could improve plantar pressure distribution with respect to generic prefabricated ones without customization, during the intense prolonged running. Thirty healthy recreational runners performed two tests of 30 min running on a treadmill, each one with a foot orthosis condition, on different days. Mean peak pressure, pressure-time integral, relative pressure and stance time were measured at the beginning and at the end of the tests. Plantar pressure data were analyzed in nine foot regions. Two-way repeated-measures ANOVAs were performed. SCFO reduced relative pressure in metatarsals (P < 0.005) and lateral heel (P = 0.004), thanks to a greater involvement of arch area in mean peak pressure (medial: P = 0.006 and lateral: P = 0.019) and relative pressure (P < 0.001). In general, prolonged run increased pressures in forefoot, in both foot orthosis, but with lower values in metatarsals with SCFO (P < 0.022), which also helped reduce relative pressure in midfoot (P = 0.007) and medial heel (P = 0.035). Stance time was not modified in any case (P > 0.05). In conclusion, customization and better fit of a low-cost prefabricated foot orthosis can improve plantar pressure distribution during a prolonged run, being a good prevention mechanism for plantar overloading in healthy runners.

Modification of Angular Kinematics and Spatiotemporal Parameters during Running after Central and Peripheral Fatigue

Fatigue causes kinematics modifications during running, and it could be related to injuries. The aim was to identify and compare the effects of central and peripheral fatigue on angular kinematics and spatiotemporal parameters during running. Angular kinematics and spatiotemporal parameters were evaluated using an infrared motion capture system and were registered during 2 min treadmill running in pre- and post-fatigue states in eighteen male recreational runners. Central fatigue was induced by a 30 min running fatigue protocol on a treadmill, while peripheral fatigue in quadriceps and hamstrings muscles was induced by an isokinetic dynamometer fatigue protocol. Central fatigue increased the anterior shank oscillation during the initial contact, knee flexion during the maximum absorption, posterior shank oscillation during propulsion, and stance time (p < 0.05). Peripheral fatigue decreased ankle dorsiflexion during initial contact and increased knee flexion and posterior shank oscillation during propulsion (p < 0.05). Moreover, central fatigue increased to a greater extent the hip and knee flexion and ankle dorsiflexion during initial contact and maximum absorption as well as stance time and propulsion time (p < 0.05). These results suggested that central fatigue causes greater increases in the range of movements during the midstance than peripheral fatigue.

Plantar forefoot pain: ultrasound findings before and after treatment with custom-made foot orthoses

PURPOSE

No prior studies investigated the role of ultrasound in the assessment of response of patients undergoing treatment of metatarsalgia with custom-made orthoses. Our aim was to describe ultrasound findings of patients with plantar forefoot pain treated with custom-made foot orthoses.

METHODS

Twenty patients (15 females; mean age: 62.6 ± 11 years) affected by metatarsalgia in 27/40 feet underwent clinical evaluation before, three months and six months after treatment with custom-made full foot insole with a support proximal and an excavation below the painful metatarsals. Ultrasound was performed before and three months after the use of orthoses to examine the presence of intermetatarsal/submetatarsal bursitis, metatarsophalangeal joints effusion, anterior plantar fat pad oedema, flexor tendinitis/tenosynovitis, and Morton's neuroma. Outcome measures were clinical response with Foot Function Index (FFI)/Visual Analogue Scale (VAS) and ultrasound features changes.

RESULTS

Median VAS and FFI before treatment were 8[5-8.5] and 45.85[32.4-59.4], respectively. After 3 and 6 months of insoles use, both median VAS (2.5 [0-5] and 0 [0-2.75], respectively) and median FFI (7.9 [3.95-20] and 0 [0-3.95], respectively) showed a significant reduction in pain and disability (p < .001). Before treatment, ultrasound revealed 22 intermetatarsal bursitis, 16 submetatarsal bursitis, 10 joint effusions, 20 fat pad oedema, 3 flexor tendinitis/tenosynovitis and 3 Morton's neuromas. After 3 months of treatment, a significant decrease of intermetatarsal bursitis (7, p < .001) was observed. No significant changes were observed in any other ultrasound parameters.

CONCLUSION

Ultrasound might be able to detect some imaging features associated with the response of forefoot pain to custom-made foot orthoses, especially intermetatarsal bursitis.

Successful Application of an Insole with a Metatarsal Inhibition Bar and Deep Heel Cup for Improving Gait Dysfunction in a Patient with Poor Coordination with Disrupted Corticoreticular Tracts: A Case Report

We report the successful management of gait dysfunction in a patient with coordination problems using an insole with a metatarsal inhibition bar (MIB) and a deep heel cup. Furthermore, we investigated the state of the neural tracts via diffusion tensor tractography (DTT). A 23-month-old boy with gait dysfunction presented with toe walking with a wide base and decreased hip flexion. Motor weakness or spasticity was not observed. Conventional brain magnetic resonance imaging did not reveal any abnormal findings, but DTT revealed disrupted bilateral corticoreticulospinal tracts (CRTs). No abnormalities were observed in the corticospinal tract or the medial lemniscus. We applied a custom-made insole with an MIB and a deep heel cup. Immediately after application, the patient’s gait pattern stabilized significantly and was nearly normalized. Our therapeutic experience indicates that the application of an insole with an MIB and deep heel cups could be beneficial for patients with coordination problems and gait dysfunction. Our DTT results showed that CRTs could be the causative brain pathology for gait dysfunction in patients with coordination problems.

Validity and Reliability of an Instrumented Treadmill with an Accelerometry System for Assessment of Spatio-Temporal Parameters and Impact Transmission

Running retraining programs focused on concurrent feedback of acceleration impacts have been demonstrated to be a good strategy to reduce running-related injuries (RRI), as well as to improve running economy and reduce acceleration impacts and injury running incidence. Traditionally, impacts have been registered by mean of accelerometers attached directly to the athletes, which is inaccessible to the entire population, because it requires laboratory conditions. This study investigated the validity and reliability of a new device integrated directly into the treadmill, compared to a traditional acceleration impact system. Thirty healthy athletes with no history of RRI were tested on two separate days over the instrumented treadmill (AccTrea) and simultaneously with an acceleration impact system attached to the participant (AccAthl). AccTrea was demonstrated to be a valid and reliable tool for measuring spatio-temporal parameters like step length (validity intraclass correlation coefficient (ICC) = 0.94; reliability ICC = 0.92), step time (validity ICC = 0.95; reliability ICC = 0.96), and step frequency (validity ICC = 0.95; reliability ICC = 0.96) during running. Peak acceleration impact variables showed a high reliability for the left (reliability ICC = 0.88) and right leg (reliability ICC = 0.85), and peak impact asymmetry showed a modest validity (ICC = 0.55). These results indicated that the AccTrea system is a valid and reliable way to assess spatio-temporal variables, and a reliable tool for measuring acceleration impacts during running.

Effectiveness and Reliability of Foot Orthoses on Impact Loading and Lower Limb Kinematics When Running at Preferred and Nonpreferred Speeds

This study examined the effect of foot orthoses used on ground reaction forces, ankle, and knee kinematics when running at preferred and nonpreferred speeds. Sixteen runners ran on instrumented treadmills at various speeds (90%, 100%, and 110% of preferred speed) when wearing arch-support and flat-control orthoses. Two-way repeated analysis of variance (ANOVA) was performed on the mean and coefficient of variation of all variables. Results indicated that arch-support orthoses experienced larger maximum loading rates than flat-control orthoses (P = .017, 95% CI, 2.22 to 19.53). Slower speed was related to smaller loading rates (preferred: P = .002, 95% CI, -17.02 to -4.20; faster: P = .003, 95% CI, -29.78 to -6.17), shorter stride length (preferred: P < .001, 95% CI, -0.204 to -0.090; faster: P < .001, 95% CI, -0.382 to -0.237), and longer contact time (preferred: P < .001, 95% CI, 0.006-0.021; faster: 95% CI, 0.012-0.042). In arch-support condition, preferred speed induced higher stride length coefficient of variation (P = .046, 95% CI, 0.035-1.117) than faster speed, while displaying no differences in flat-control condition. These findings suggest that the use of arch-support orthoses would influence impact loading, but not spatial-temporal and joint kinematics in recreational runners.

An individually moulded insole with 5-mm medial arch support reduces peak impact and loading at the heel after a one-hour treadmill run

BACKGROUND

Foot pain experienced by long-distance runners could be relieved by functional insoles which aim at evenly distributing the plantar pressure.

RESEARCH QUESTION

We hypothesised that an individually moulded insole with medial arch support would reduce the impact and loading under the heel and metatarsal regions.

METHODS

Twelve male recreational runners ran on a treadmill at 10 km/h for 1 hour with flat insoles and medial arch supported insoles. A pressure insole system (Novel Pedar, Germany) was used to obtain the peak pressure, peak force, time normalised pressure-time integrals, and the percentage of the total force-time integrals under 10 regions.

RESULTS

Medial arch supported insoles reduced the peak force under the heel (medial: -15.3%, p = 0.001; lateral: -19.2%, p = 0.037) during the initial run, and reduced peak pressure under the heel (medial: -13.3%, p = 0.005; lateral: -9.9%, p = 0.006), and peak force under the medial heel (-17.8%, p = 0.006) after the run. The percentage of the total force-time integrals under the heel was reduced (medial: -23.8%, p = 0.004; lateral: -13.6%, p = 0.022) after the run. No significant difference was found under the metatarsal regions. There is shift of load from the metatarsal regions to the medial mid-foot as indicated by the change of the percentage of total force-time integrals.

SIGNIFICANCE

Medial arch supported insoles were effective in reducing the impact and loading under the heel region in prolonged running on a treadmill.

LEVEL OF EVIDENCE

Controlled laboratory study, Level V.

Development and evaluation of a dual density insole for people standing for long periods of time at work

BACKGROUND

Appropriate footwear is important for those who stand for prolonged periods of time at work, enabling them to remain comfortable, healthy and safe. Preferences for different footwear cushioning or hardness are often person specific and one shoe or insole will not be the choice for all. The aim of this study was to develop a range of insole options to maintain comfort during long periods of standing at work and test insole material preferences in the workplace.

METHODS

The study consisted of two parts. Part one evaluated 9 insoles of the same geometry that varied in hardness under 2 different plantar regions (n = 34). Insole preference, plantar pressure and selected anthropometric foot measures were taken. Three insole designs based on the most preferred options were identified from this part. In part two, these three insoles were evaluated with 22 workers immediately after trying them on (1 min) and after a working day. Foot anthropometric measures and subjective questions concerning material hardness preferences and self-reported foot characteristics were used to investigate whether either had a relationship with insole preference.

RESULTS

Part one found insole preference predominantly varied according to material hardness under the medial arch rather than the heel/forefoot. Softer material under the heel and forefoot was associated with a reduction in peak pressures in these regions (p < 0.05). The most preferred insole had lower pressures under the hallux and first metatarsal phalangeal joint, and greater pressures and contact area under the medial midfoot (p < 0.05) compared to the least preferred insole. Height and foot anthropometrics were related to insole preference. In part two, under real world conditions, insole preference changed for 65% of participants between the immediate assessment (1 min) and after a whole workday, with dorsum height related to the latter (p < 0.05). Subjective questions for self-assessed arch height and footwear feel identified 66.7% of the insole preferences after 1 day at work, compared to 36% using immediate assessment of insole preference.

CONCLUSION

Preference for material hardness varies underneath the medial arch of the foot and is time dependent. Simple foot measures and questions about comfort can guide selection of preferred insoles.

Custom foot orthoses improve performance, but do not modify the biomechanical manifestation of fatigue, during repeated treadmill sprints

PURPOSE

We determined the effect of custom foot orthotics manufactured from ethyl-vinyl acetate (EVA) and expanded thermoplastic polyurethane (TPU) materials, both compared to a control condition (CON; shoes only) during repeated sprints on running mechanical alterations.

METHODS

Eighteen males performed eight, 5-s sprints with 25-s recovery on an instrumented sprint treadmill in three footwear conditions (EVA, TPU and CON). Mechanical data consisted of continuous (step-by-step) measurement of running kinetics and kinematics, which were averaged for each sprint for further analysis.

RESULTS

Distance ran in 5 s decreased from first to last sprint (P < 0.001), yet with higher sprints 1-8 values for both EVA (P = 0.004) and TPU (P = 0.018) versus CON. Regardless of footwear condition, mean horizontal forces, step frequency, vertical and leg stiffness decreased from sprint 1 to sprint 8 (all P < 0.001). Duration of the propulsive phase was globally shorter for both EVA (P = 0.002) and TPU (P = 0.021) versus CON, while braking phase duration was similar (P = 0.919). In the horizontal direction, peak propulsive (P < 0.001), but not braking (P = 0.172), forces also decreased from sprint 1 to sprint 8, independently of conditions.

CONCLUSION

Compared to shoe only, wearing EVA or TPU custom foot orthotics improved repeated treadmill sprint ability, yet provided similar fatigue-induced changes in mechanical outcomes.

Effects of arch-support orthoses on ground reaction forces and lower extremity kinematics related to running at various inclinations

While foot orthoses are commonly used in running, little is known regarding biomechanical risk potentials during uphill running. This study investigated the effects of arch-support orthoses on kinetic and kinematic variables when running at different inclinations. Sixteen male participants ran at different inclinations (0°, 3° and 6°) when wearing arch-support and flat orthoses on an instrumented treadmill. Arch-support orthoses induced longer contact time, larger initial ankle dorsiflexion, maximum ankle eversion, and knee sagittal range of motion (RoM) (p < 0.05). As incline slopes increased, vertical impact peak and loading rate, stride length, and ankle coronal RoM decreased, but contact time, stride frequency, initial ankle dorsiflexion and inversion, maximum dorsiflexion, initial knee flexion, and ankle sagittal RoM increased (p < 0.05). Furthermore, knee sagittal RoM was lowest when running at an inclination of 3°. The interaction effect indicated that in arch-support condition, participants running at 6° induced higher maximum ankle eversion than running at 0° (p < 0.05), while no differences were found in flat orthosis condition. These findings suggest that the use of arch-support orthoses would influence running biomechanics that is related to injury risks. Running at higher inclination led to more alterations to biomechanical variables than at lower inclination.

Validation of a novel Kinect-based device for 3D scanning of the foot plantar surface in weight-bearing

Background

Advancements in additive manufacturing, along with new 3D scanning tools, are increasingly fulfilling the technological need for custom devices in personalized medicine. In podiatry and in the footwear industry, custom orthotic and footwear solutions are often required to address foot pathologies or morphological alterations which cannot be managed with standard devices. While laser scanners are the current gold-standard for 3D digitization of the foot shape, their costs limit their applications and diffusion, therefore traditional operator-dependent casting methods are still in use. The aim of this study was to design and validate a novel 3D foot scanner based on the Microsoft Kinect sensor, allowing a 3D scan of the plantar shape of the foot to be acquired in weight-bearing.

Methods

The accuracy and repeatability of the prototypal foot scanner were investigated in a population of 14 asymptomatic healthy subjects, with no history of foot or lower limb injuries. The accuracy was estimated by comparing the Kinect foot scans with those obtained with a high-resolution laser scanner used as reference. The repeatability was assessed by comparing scans of the same foot acquired in different sessions.

Results

The inter-subject average Root Mean Square Error (RMSE) of the Kinect scans was lower than 3 mm for the whole plantar surface, and lower than 1.6 mm for the arch region alone, both in left and right feet. The repeatability, quantified as the average RMSE of pairwise comparisons between sessions, was 1.2 ± 0.4 mm.

Conclusions

The present Kinect-based 3D foot scanner showed optimal intra-operator repeatability and its accuracy appears adequate to obtain 3D scans of the foot plantar surface suitable for different clinical applications. This device could represent a valid low-cost alternative to expensive laser-based scanners and could be used for automatic foot measurements, supporting the design of custom insoles and footwear.

Plantar Pressure Differences between Nordic Walking Techniques

High plantar pressure has been associated with increased risk of injury. The characteristics of each physical activity determine the load on the lower limbs. The influence of Nordic Walking (NW) technique on plantar pressure is still unknown. The aim of this study was to analyze the differences between plantar pressure during NW with the Diagonal technique (DT) versus Alpha technique (AT) and compare them with the pressure obtained during normal walking (W). The normality and sphericity of the plantar pressure data were checked before performing a two-way repeated measures ANOVA in order to find differences between speeds (preferred, fast) and the gait (NW, W) as within-subject factors. Then, a t-test for independent measures was used to identify the specific differences between NW techniques. The strength of the differences was calculated by means of the effect size (ES). The results demonstrated that during NW with AT at preferred speed the pressure was lower under the Calcaneus, Lateral Metatarsal and Toes compared to the DT group (p = 0.046, ES = 1.49; p = 0.015, ES = 1.44; p = 0.040, ES = 1.20, respectively). No differences were found at the fast speed (p > 0.05). Besides the increase in walking speed during NW (p < 0.01), both technique groups showed lower pressure during NW compared to W under the Hallux and Central Metatarsal heads (F = 58.321, p = 0.000, ES = 2.449; F = 41.917, p = 0.012, ES = 1.365, respectively). As a practical conclusion, the AT technique may be the most effective of the NW techniques at reducing plantar pressure while allowing NW practitioners to achieve the physiological benefits of NW.

[Forefoot relief with shoe inserts : Effects of different construction strategies]

BACKGROUND

Shoe inserts and shoe modifications are used to reduce plantar peak pressure. The effects of different shoe inserts and shoe construction strategies for relief of the forefoot have not yet been sufficiently evaluated.

PURPOSE

The aim of this study was to analyze the effects of shoe inserts and shoe construction strategies (e.g. metatarsal pad, forefoot cushioning and control) and shoe modifications (e.g. flexible or stiff) on the peak plantar pressure in the forefoot region.

MATERIAL AND METHODS

In this study 15 healthy subjects were recruited. Plantar pressure distribution was measured using an in-shoe system during walking (3.5km∙h^-1) on a treadmill and the average plantar peak pressure (kPa) in the forefoot was calculated. The statistics for testing the hypothesis were carried out using 2‑factorial ANOVA with repeat measurements (factors: shoe, insert; α = 0.05).

RESULTS

The metatarsal pad and forefoot cushioning led to a reduction of peak pressure, which was statistically significant compared to the control condition (p = 0.009). No differences were observed between both shoe inserts (p > 0.05). A comparison between stiff and flexible shoes revealed a statistically significant pressure reduction in favor of stiff shoes (p = 0.0001). The metatarsal pad led to a peak pressure increase in the midfoot of 12% and by 21% compared to control and forefoot cushioning, respectively.

DISCUSSION

A peak pressure reduction in the forefoot can be achieved with a metatarsal pad or with cushioning; however, the metatarsal pad resulted in a subsequent increase in midfoot pressure. Moreover, shoe construction is crucial because a stiff shoe contributes to a better peak pressure reduction compared to a flexible shoe. Prospective clinical studies should be carried out to prove whether this results in beneficial effects for patients with metatarsalgia.

Influence of custom-made and prefabricated insoles before and after an intense run

Each time the foot contacts the ground during running there is a rapid deceleration that results in a shock wave that is transmitted from the foot to the head. The fatigue of the musculoskeletal system during running may decrease the ability of the body to absorb those shock waves and increase the risk of injury. Insoles are commonly prescribed to prevent injuries, and both custom-made and prefabricated insoles have been observed to reduce shock accelerations during running. However, no study to date has included a direct comparison of their behaviour measured over the same group of athletes, and therefore great controversy still exists regarding their effectiveness in reducing impact loading during running. The aim of the study was to analyse the acute differences in stride and shock parameters while running on a treadmill with custom-made and prefabricated insoles. Stride parameters (stride length, stride rate) and shock acceleration parameters (head and tibial peak acceleration, shock magnitude, acceleration rate, and shock attenuation) were measured using two triaxial accelerometers in 38 runners at 3.33 m/s before and after a 15-min intense run while using the sock liner of the shoe (control condition), prefabricated insoles and custom-made insoles. No differences in shock accelerations were found between the custom-made and the control insoles. The prefabricated insoles increased the head acceleration rate (post-fatigue, p = 0.029) compared to the control condition. The custom-made reduced tibial (pre-fatigue, p = 0.041) and head acceleration rates (pre-fatigue and post-fatigue, p = 0.01 and p = 0.046) compared to the prefabricated insoles. Neither the stride nor the acceleration parameters were modified as a result of the intense run. In the present study, the acute use of insoles (custom-made, prefabricated) did not reduce shock accelerations compared to the control insoles. Therefore, their effectiveness at protecting against injuries associated with elevated accelerations is not supported and remains unclear.

The effect of foot orthoses with forefoot cushioning or metatarsal pad on forefoot peak plantar pressure in running

Background

Foot orthoses are frequently used in sports for the treatment of overuse complaints with sufficient evidence available for certain foot-related overuse pathologies like plantar fasciitis, rheumatoid arthritis and foot pain (e.g., metatarsalgia). One important aim is to reduce plantar pressure under prominent areas like metatarsal heads. For the forefoot region, mainly two common strategies exist: metatarsal pad (MP) and forefoot cushioning (FC). The aim of this study was to evaluate which of these orthosis concepts is superior in reducing plantar pressure in the forefoot during running.

Methods

Twenty-three (13 female, 10 male) asymptomatic runners participated in this cross-sectional experimental trial. Participants ran in a randomised order under the two experimental (MP, FC) conditions and a control (C) condition on a treadmill (2.78 ms⁻¹) for 2 min, respectively. Plantar pressure was measured with the in-shoe plantar pressure measurement device pedar-x®-System and mean peak pressure averaged from ten steps in the forefoot (primary outcome) and total foot was analysed. Insole comfort was measured with the Insole Comfort Index (ICI, sum score 0–100) after each running trial. The primary outcome was tested using the Friedman test (α = 0.05). Secondary outcomes were analysed descriptively (mean ± SD, lower & upper 95%-CI, median and interquartile-range (IQR)).

Results

Peak pressure [kPa] in the forefoot was significantly lower wearing FC (281 ± 80, 95%-CI: 246–315) compared to both C (313 ± 69, 95%-CI: 283–343; p = .003) and MP (315 ± 80, 95%-CI: 280–350; p = .001). No significant difference was found between C and MP (p = .858). Peak pressures under the total foot were: C: 364 ± 82, 95%-CI: 328–399; MP: 357 ± 80, 95%-CI: 326–387; FC: 333 ± 81 95%-CI: 298–368. Median ICI sum scores were: C 50, MP 49, FC 64.

Conclusions

In contrast to the metatarsal pad orthosis, the forefoot cushioning orthosis achieved a significant reduction of peak pressure in the forefoot of recreational runners. Consequently, the use of a prefabricated forefoot cushioning orthosis should be favoured over a prefabricated orthosis with an incorporated metatarsal pad in recreational runners with normal height arches.

Electronic supplementary material

The online version of this article (doi:10.1186/s13047-016-0176-z) contains supplementary material, which is available to authorized users.

In shoe pressure measurements during different motor tasks while wearing safety shoes: The effect of custom made insoles vs. prefabricated and off-the-shelf

Health and safety regulations in many countries require workers at risk to wear safety shoes in a factory environment. These shoes are often heavy, rigid, and uncomfortable. Wearing safety shoes daily leads to foot problems, discomfort and fatigue, resulting also in the loss of numerous working days. Currently, knowledge of the biomechanical effects of insoles in safety shoes, during working activities, is very limited. Seventeen workers from a metalworking factory were selected and clinically examined for any foot conditions. Workers feet were 3D scanned, with regards to their plantar view, and the images used to design 34 custom-insoles, based on foot and safety shoe models. Three insoles were blind-tested by each worker: custom (CUS); prefabricated with the safety-shoe (PSS), and off-the-shelf (OTS). Foot-to-insole pressure distribution was measured in seven motor tasks replicating typical working activities: single and double-leg standing; weight lifting; stair ascending and descending; normal and fast walking. Wearing CUS within safety shoes resulted in a greater uniform pressure distribution across plantar regions for most of the working activities. Peak pressure at the forefoot during normal walking was the lowest in the custom insole (CUS 275.9±55.3kPa; OTS 332.7±75.5kPa; PSS 304.5±54.2kPa). Normal and fast walking were found to be the most demanding activities in terms of peak pressure. Wearing safety shoes results in high pedobarographic parameters in several foot regions. The use of custom insoles designed on the foot morphology helps decrease peak pressure and pressure-time integral compared to prefabricated featureless insoles.

Ankle muscle strength influence on muscle activation during dynamic and static ankle training modalities

Muscle weakness is considered a risk factor for ankle injury. Balance training and barefoot running have been used in an attempt to strengthen the muscles crossing the ankle. It is expected that training tasks that successfully strengthen the ankle would elicit increased muscular activity. However, it is unknown how an individual's ankle strength will influence the muscle activity used during a given task. Twenty-six participants performed dynamic (shod, barefoot running) and static tasks (squat on ground, squat on ®Bosu Ball) believed to strengthen the muscles surrounding the ankle. Electromyographic signals of the tibialis anterior, peroneus longus, gastrocnemius lateralis (GL) and gastrocnemius medialis (GM) were recorded and analysed using a non-linearly scaled wavelet analysis. Participants were divided into a strong group and a weak group according to their isometric plantar-flexion torque. The weak group required more relative GL and GM muscle activity during each training task compared to the strong group. No difference was observed between shod and barefoot running. There was a significant effect of training task on muscle activation level for the weak group. Differences in ankle strength had a significant impact on muscle activation.