Heel-toe Running Research Articles

Effects of Shoe Midfoot Bending Stiffness on Multi-Segment Foot Kinematics and Ground Reaction Force during Heel-Toe Running.

We investigated how midfoot stiffness of running shoes influences foot segment kinematics and ground reaction force (GRF) during heel-toe running. Nineteen male rearfoot strike runners performed overground heel-toe running at 3.3 m/s when wearing shoes with different midfoot bending stiffnesses (low, medium, and high) in a randomized order. A synchronized motion capture system (200 Hz) and force plate (1000 Hz) were used to collect the foot-marker trajectories and GRF data. Foot kinematics, including rearfoot-lab, midfoot-rearfoot, forefoot-rearfoot, and forefoot-midfoot interactions, and kinetics, including GRF characteristics, were analyzed. Our results indicated that high midfoot stiffness shoes reduced the forefoot-rearfoot range of motion (mean ± SD; high stiffness, 7.8 ± 2.0°, low stiffness, 8.7 ± 2.1°; p < 0.05) and forefoot-midfoot range of motion (mean ± SD; high stiffness, 4.2 ± 1.1°, medium stiffness, 4.6 ± 0.9°; p < 0.05) in the frontal plane. No differences were found in the GRF characteristics among the shoe conditions. These findings suggest that an increase in midsole stiffness only in the midfoot region can reduce intersegmental foot medial-lateral movements during the stance phase of running. This may further decrease the tension of the foot muscles and tendons during prolonged exercises.

Foot strike determines the center of pressure behavior and affects impact severity in heel-toe running

ABSTRACT This study assessed the centre of pressure (COP) behaviour and the relationship with impact severity during heel-toe running in conventional athletic footwear. We hypothesized that the COP behaviour depends on its location at foot strike, which would be associated with the vertical loading rate and peak tibial accelerations in heel-toe running. Ground reaction force and tibial acceleration were measured in 104 distance runners running level at ~3.2 m/s. High-speed plantar pressure captured at high temporal resolution (500 Hz) and spatial resolution (7.62 · 5.08 mm/sensor) allowed for localization of the COP directly in the footprint during running in self-selected athletic footwear. More lateral X-coordinates of the COP at first foot contact had, in general, more anterior Y-coordinates (adj.R2:0.609). In heel-toe running, a more anterior foot strike had a greater refined strike index, which was associated with a quicker roll-over in the rearfoot zone. This strike index contributed to greater maximum vertical loading rates (R2:0.121), and greater axial (R2:0.047) and resultant (R2:0.247) peak tibial accelerations. These findings indicate that (1) the COP progression is dependend on the COP location at foot strike; (2) more anterior rearfoot strikes are more likely to have greater impact severity than posterior rearfoot strikes.

Effects Of Shoe Midfoot Bending Stiffness On Inner-foot Joints Rom During Heel-toe Running

Shoe manufacturers focus on footwear design which might affect the function of the footwear as well as foot motion and joint loading to improve running performance and prevent running injury. The longitudinal bending stiffness is considered to be a key feature in running shoe development. However, the majority of the longitudinal bending stiffness studies focus on the forefoot region, little investigation is carried out for midfoot bending stiffness. It is expected that changes in shoe midfoot bending stiffness would alter the foot motion. PURPOSE: The purpose of this study was to examine whether midfoot bending stiffness affects inner-foot joints ROM on frontal plane, thus providing scienticfic priciples for midfoot structure design of running footwear to enhance foot stability during heel-toe running. METHODS: The midfoot bending stiffness of experimental running shoe conditions were 0.069 Nm/°, 0.091 Nm/° and 0.163 Nm/°. Nineteen male runners with a rearfoot strike pattern, and running at least 10 Km/week, were recruited for this study. Kinematic and ground reaction force data were collected at 3.3 m/s using motion capture system (Vicon T20&T40, 200 Hz) and force platform (AMTI OR6-GT, 1000 Hz) during heel-toe running. A custom-made sock technology and a multi-segmental foot model were used to find the internal movements of foot segment in the shoe. RESULTS: Forefoot to midfoot interaction indicated the frontal plane ROM (p = 0.020, η2 = 0.196) was significantly greater in both the low stiffness (4.7 ± 1.3°) and medium stiffness (4.6 ± 0.9°) shoes compared to the high stiffness shoe (4.2 ± 1.1°) during running stance phase. A significant main effect was seen for the frontal plane ROM (p = 0.005, η2 = 0.258) on the forefoot to rearfoot discrete joint. The amplitude was greater in low stiffness (8.7 ± 2.1°) and medium stiffness (8.4 ± 2.0°) shoes relative to high stiffness shoe (7.8 ± 2.0°) during running stance phase. No difference was found for midfoot to rearfoot frontal plane ROM. CONCLUSIONS: The increased stiffness shoe had a splinting effect on the midfoot and rearfoot by reducing ROM in frontal plane to increase the stability of foot segments movement during running stance phase.

Effect of Running Speed and Midsole Type on Foot Loading in Heel-Toe Running.

The purpose of this study was to explore the immediate effects of running speed and midsole type on foot loading during heel-toe running. Fifteen healthy male college students were required to complete 3 running trials on an indoor 45-m tartan runway at 4 different speeds (3, 4, 5, and 6m/s) using 2 different running footwear types (engineering thermoplastic polyurethane elastomer, polyurethane elastomer; and ethylene vinyl acetate, vinyl acetate). The ground reaction force and plantar pressure data were quantified. Significant speed effects were detected both in ground reaction force and plantar pressure-related data (P < .05). Vertical average loading rate was significantly less, and time to first peak occurred later for the polyurethane elastomer compared with vinyl acetate footwear (P < .05). The peak pressure of the heel, medial forefoot, central forefoot, lateral forefoot, and big toe was significantly less when subjects wore a polyurethane elastomer than vinyl acetate footwear (P < .05). Overall, our results suggested that, compared with the vinyl acetate footwear, the special polyurethane elastomer footwear that is adhered with thousands of polyurethane elastomer granules was effective at reducing the mechanical impact on the foot.

Midsole Properties Affect the Amplitude of Soft Tissue Vibrations in Heel-Toe Runners.

Soft tissue vibrations can generate discomfort and may necessitate a greater energy demand to preserve an efficient motion in running. Vibration damping is thus of interest from a comfort and performance standpoint. Our purpose was to assess whether changes in midsole material affect the properties of (a) soft tissue vibrations and (b) myoelectric activity. Two midsole conditions were compared. The control condition corresponded to a full ethylene-vinyl acetate foam midsole. The experimental condition was a bimaterial midsole with a material combination of viscous and viscoelastic materials. Twelve participants ran on an indoor track in both conditions while recording the longitudinal acceleration and the EMG activity of vastus medialis (VM) and gastrocnemius medialis (GM). Wavelet transforms were performed for EMG and acceleration signals to assess the intensity of the muscle activity at low and high frequencies (37-128 and 170-395 Hz, respectively) and to calculate the damping coefficient (D) for soft tissue vibrations. The soft tissue vibrations were also characterized by the peak of acceleration (apeak), the frequency of the power peak (fpeak), and the power of the soft tissue vibrations (PSD[8-55]). The variables apeak and PSD[8-55] decreased for VM and GM in the viscous condition. Before heel strike, low-frequency EMG activity decreased for VM, and high-frequency EMG activity tended to decrease for GM in the viscous condition. The damping D was reduced only for VM, and fpeak was unchanged. A more viscous midsole substantially reduced the amplitude of soft tissue vibrations, but not their frequency. Looking at individual results, it was noted that muscle activity was tuned in response to the acceleration input, and that the damping of soft tissue vibrations was affected by the intensity of muscle activity.

Interaction between body composition and impact-related parameters in male and female heel-toe runners

BackgroundBone fatigue resistance and more generally the ability to dissipate the stress sustained in dynamic tasks are partly affected by tissue properties. Men and women demonstrate substantial differences in body composition. Research questionTo assess whether gender, as a function of body composition, affects impact-related parameters in running. MethodsA qualitative study has been conducted. Twelve females and eighteen males performed four 2-min running trials at 2.8 m∙s−1, 3.3 m∙s−1, 3.9 m∙s−1, and 4.4 m∙s−1 while recording axial and transverse tibial acceleration. Peak acceleration and power spectral density within the impact-related frequency range (vibration content) were measured. Bone mineral content, fat mass, lean mass, and muscle mass were assessed using an impedance meter. Two-way (gender × speed) ANOVAs were computed. Multiple linear regressions were then used to assess the magnitude of the effect of body composition indicators on impact-related parameters. ResultsSignificant gender and speed effects were observed. Females and high running speeds were associated with greater peak acceleration and vibration content at the tibia. Small interactions were observed between muscle mass and axial peak acceleration and vibration content, and between bone mineral content and transverse peak acceleration and vibration content, and axial vibration content. SignificanceWomen demonstrated greater mechanical stress than men during running. High mechanical stress was associated with low bone mineral content and muscle mass. These findings may have implications in the prevention and management of bone overuse injuries in runners.

Cushioning perception is associated with both tibia acceleration peak and vibration magnitude in heel-toe running

Objective: To investigate the relationship between the perception of cushioning and variable measured using tibia acceleration in heel–toe running. Method: Ten rearfoot strikers’ runners ran at 3.9 m.s−1 on a stiff treadmill in seven footwear conditions presenting different mechanical properties through midsole geometries and/or materials. The perceived cushioning was quantified through a 100-mm visual analogic scale. Tibia accelerations were measured using a triaxial accelerometer from which six variables of interest were extracted based on time and frequency analyses. After pooling data of each subject in each condition (n = 70), Pearson correlation coefficients were calculated to test the correlation between the perceived cushioning and each biomechanical variables. The Cohen’s d effect size was calculated for significant correlation. Results: Significant correlations were found between the perceived cushioning and three axial acceleration-related variables which are the axial acceleration peak (r = −0.246, p = .04, small correlation), the kurtosis coefficient of the axial acceleration peak (r = −0.281, p = .056, small correlation), and the power spectral density of the axial acceleration within the 10–20 Hz bandwidth (r = −0.300, p = .018, small correlation). Conclusion: The present study highlights that the perception of running footwear cushioning was correlated to tibia impact peak and tibia vibration magnitude. Besides, no variable extracted from the transverse component of tibia acceleration was correlated to cushioning perception. These findings could have practical implications in running footwear design.

Effect of rocker shoes and running speed on lower limb mechanics and soft tissue vibrations

Previous studies have shown a possible effect of running speed and the sole material of footwear on lower-limb mechanics and soft tissue vibrations, while little information has been offered concerning the influence of the shape of the footwear’s sole. The purpose of this study is to assess the effect of running speed and rocker shoes on muscular activity, ground reaction force, and soft tissue vibrations. Twenty participants performed heel-toe running with two shoes, differentiated only by their sole shape (i.e. rocker and non-rocker), at four running speeds. Ground reaction force and electromyograms of the gastrocnemius medialis and vastus lateralis were measured, and soft tissue accelerations of the same muscles were recorded with tri-axial accelerometers. A continuous wavelet transform was applied to the accelerometer’s signals to analyse them in the time-frequency domain. The rocker of the shoes did not change the muscular activations, ground reaction force, nor power of soft tissue vibrations. In opposite, increased running speed led to an augmentation of all of the measured parameters. Interestingly, running speed augmentation led to a greater increase in high frequencies component of soft tissue vibrations (25–50 Hz, 242%) than lower ones (8–25 Hz, 111%). Consequently, we indicated a 10% increase in the relative part of the high frequencies of the total power. In conclusion, although rocker shoes have shown an effect on lower-limb kinetics in some studies, no influence on soft tissue vibration is denoted. By contrast, soft tissue vibrations may be modulated by changing running speed.

Do Strike Patterns or Shoe Conditions Have a Predominant Influence on Foot Loading?

This study aimed to explore the effects of strike patterns and shoe conditions on foot loading during running. Twelve male runners were required to run under shoe (SR) and barefoot conditions (BR) with forefoot (FFS) and rearfoot strike patterns (RFS). Kistler force plates and the Medilogic insole plantar pressure system were used to collect kinetic data. SR with RFS significantly reduced the maximum loading rate, whereas SR with FFS significantly increased the maximum push-off force compared to BR. Plantar pressure variables were more influenced by the strike patterns (15 out of 18 variables) than shoe conditions (7 out of 18 variables). The peak pressure of midfoot and heel regions was significantly increased in RFS, but appeared in a later time compared to FFS. The influence of strike patterns on running, particularly on plantar pressure characteristics, was more significant than that of shoe conditions. Heel-toe running caused a significant impact force on the heel, whereas wearing cushioned shoes significantly reduced the maximum loading rate. FFS running can prevent the impact caused by RFS. However, peak plantar pressure was centered at the forefoot for a long period, thereby inducing a potential risk of injury in the metatarsus/phalanx.

Mechanical Fatigue of Bovine Cortical Bone Using Ground Reaction Force Waveforms in Running.

Stress fractures are a common overuse injury among runners associated with the mechanical fatigue of bone. Several in vivo biomechanical studies have investigated specific characteristics of the vertical ground reaction force (vGRF) in heel-toe running and have observed an association between increased loading rate during impact and individuals with a history of stress fracture. The purpose of this study was to examine the fatigue behavior of cortical bone using vGRF-like loading profiles, including those that had been decomposed into their respective impact and active phase components. Thirty-eight cylindrical cortical bone samples were extracted from bovine tibiae and femora. Hydrated samples were fatigue tested at room temperature in zero compression under load control using either a raw (n = 10), active (n = 10), low impact (n = 10), or high impact (n = 8) vGRF profile. The number of cycles to failure was quantified and the test was terminated if the sample survived 105 cycles. Fatigue life was significantly greater for both impact groups compared to the active (p < 0.001) and raw (p < 0.001) groups, with all low impact samples and 6 of 8 high impact samples surviving 105 cycles. The mean (± SD) number of cycles to failure for the active and raw groups was 12,133±11,704 and 16,552±29,612, respectively. The results suggest that loading rates associated with the impact phase of a typical vGRF in running have little influence on the mechanical fatigue behavior of bone relative to loading magnitude, warranting further investigation of the mechanism by which increased loading rates are associated with stress fracture.

The Preferred Movement Path Paradigm: Influence of Running Shoes on Joint Movement.

(A) To quantify differences in lower extremity joint kinematics for groups of runners subjected to different running footwear conditions, and (B) to quantify differences in lower extremity joint kinematics on an individual basis for runners subjected to different running footwear conditions. Three-dimensional ankle and knee joint kinematics were collected for 35 heel-toe runners when wearing three different running shoes and when running barefoot. Absolute mean differences in ankle and knee joint kinematics were computed between running shoe conditions. The percentage of individual runners who displayed differences below a 2°, 3°, and 5° threshold were also calculated. The results indicate that the mean kinematics of the ankle and knee joints were similar between running shoe conditions. Aside from ankle dorsiflexion and knee flexion, the percentage of runners maintaining their movement path between running shoes (i.e., less than 3°) was in the order of magnitude of about 80% to 100%. Many runners showed ankle and knee joint kinematics that differed between a conventional running shoe and barefoot by more than 3°, especially for ankle dorsiflexion and knee flexion. Many runners stay in the same movement path (the preferred movement path) when running in various different footwear conditions. The percentage of runners maintaining their preferred movement path depends on the magnitude of the change introduced by the footwear condition.

Effects of a leaf spring structured midsole on joint mechanics and lower limb muscle forces in running.

To enhance running performance in heel-toe running, a leaf spring structured midsole shoe (LEAF) has recently been introduced. The purpose of this study was to investigate the effect of a LEAF compared to a standard foam midsole shoe (FOAM) on joint mechanics and lower limb muscle forces in overground running. Nine male long-distance heel strike runners ran on an indoor track at 3.0 ± 0.2 m/s with LEAF and FOAM shoes. Running kinematics and kinetics were recorded during the stance phase. Absorbed and generated energy (negative and positive work) of the hip, knee and ankle joint as well as muscle forces of selected lower limb muscles were determined using a musculoskeletal model. A significant reduction in energy absorption at the hip joint as well as energy generation at the ankle joint was found for LEAF compared to FOAM. The mean lower limb muscle forces of the m. soleus, m. gastrocnemius lateralis and m. gastrocnemius medialis were significantly reduced for LEAF compared to FOAM. Furthermore, m. biceps femoris showed a trend of reduction in running with LEAF. The remaining lower limb muscles analyzed (m. gluteus maximus, m. rectus femoris, m. vastus medialis, m. vastus lateralis, m. tibialis anterior) did not reveal significant differences between the shoe conditions. The findings of this study indicate that LEAF positively influenced the energy balance in running by reducing lower limb muscle forces compared to FOAM. In this way, LEAF could contribute to an overall increased running performance in heel-toe running.

Effect of torsional stiffness on biomechanical variables of the lower extremity during running

Torsion, the relative in-/eversion between forefoot and rearfoot, is a concept that has been incorporated into running shoes for almost 30 years. Studies have shown an influence of footwear torsional stiffness on lower extremity biomechanics during running but results are inconclusive. However, the influence of the torsion axis of the shoe on kinematics and kinetics of running has not been examined. Therefore, the goal was to examine the effect of shoes with a specially designed torsion element on running biomechanics of the lower extremities. Twenty runners performed heel–toe running at 4.0 ms−1 with three shoes and barefoot. All shoes had a torsion element based on a rearfoot and a forefoot element connected by bushings that had a defined rotation axis. The torsional stiffness was altered by modifications made to the torsion element and the surrounding midsole. A force plate and camera system were used to collect kinetics and kinematics. Foot torsion, ankle eversion, ankle and knee moments in the frontal and transverse plane and ground reaction forces were compared between conditions using paired t-tests. The shoe with the lowest torsional stiffness did not result in larger torsion range of motion compared to a stiffer shoe. Ankle eversion decreased with decreasing torsional stiffness while the changes in ankle kinetics were not consistent between the frontal and transverse plane. Torsional stiffness did not have a systematic influence on knee joint kinetics. While shoe torsional stiffness influences foot kinematics significantly, it does not affect lower extremity running biomechanics in a way that would alter the risk of running injuries.

Relationship between Attenuation of Impact Shock at High Frequency and Flexion-Extension of the Lower Extremity Joints during Downhill Running

Objective: The purpose of this study was to determine the interrelationship between ranges of motion ofthe knee and ankle joints on the sagittal plane and the attenuation magnitude of impact shock at highfrequency (9~20 Hz) in the support phase during downhill running.Method: Fifteen male heel-toe runners with no history of lower extremity injuries were recruited for thisstudy (age, 25.07 ± 5.35 years; height, 175.4 ± 4.6 cm; mass, 75.8 ± .70 kg). Two uniaxial accelerometers weremounted to the tuberosity of tibia and sacrum, respectively, to measure acceleration signals. The participantswere asked to run at their preferred running speed on a treadmill set at 0°, 7°, and 15° downhill. Sixoptical cameras were placed around the treadmill to capture the coordinates of the joints of the lowerextremities. The power spectrum densities of the two acceleration signals were analyzed and used in thetransfer function describing the gain and attenuation of impact shock between the tibia and the sacrum.Angles of the knee and ankle joints on the sagittal plane and their angle ranges were calculated. ThePearson correlation coefficient was used to test the relationship between two variables, the magnitude ofimpact shock, and the range of joint angle under three downhill conditions. The alpha level was set at .05.Results: Close correlations were observed between the knee joint range of motion and the attenuationmagnitude of impact shock regardless of running slopes (p<.05), and positive correlations were foundbetween the ranges of motion of the knee and ankle joints and the attenuation magnitude of impact shockin 15° downhill running (p<.05).Conclusion: In conclusion, increased knee flexion might be required to attenuate impact shock duringdownhill and level running through change in stride or cadence while maintaining stability, and strongand flexible ankle joints are also needed in steeper downhill running.

Predicting ground contact events for a continuum of gait types: An application of targeted machine learning using principal component analysis

An ongoing challenge in the application of gait analysis to clinical settings is the standardized detection of temporal events, with unobtrusive and cost-effective equipment, for a wide range of gait types. The purpose of the current study was to investigate a targeted machine learning approach for the prediction of timing for foot strike (or initial contact) and toe-off, using only kinematics for walking, forefoot running, and heel-toe running. Data were categorized by gait type and split into a training set (∼30%) and a validation set (∼70%). A principal component analysis was performed, and separate linear models were trained and validated for foot strike and toe-off, using ground reaction force data as a gold-standard for event timing. Results indicate the model predicted both foot strike and toe-off timing to within 20ms of the gold-standard for more than 95% of cases in walking and running gaits. The machine learning approach continues to provide robust timing predictions for clinical use, and may offer a flexible methodology to handle new events and gait types.

편평족 달리기 시 충격 쇼크의 성분과 흡수

Objective : The purpose of this study was to determine the differences in the head and tibial acceleration signal magnitudes, and their powers and shock attenuations between flat-footed and normal-footed running. Methods : Ten flat-footed and ten normal-footed subjects ran barefoot on a treadmill with a force plate at 3.22m/s averaged from their preferred running speed using heel-toe running pattern while the head and tibial acceleration in the vertical axis data was collected. The accelerometers were sampled at 2000 Hz and voltage was set at 100 mv, respectively. The peak magnitudes of the head and tibial acceleration signals in time domain were calculated. The power spectral density(PSD) of each signal in the frequency domain was also calculated. In addition to that, shock attenuation was calculated by a transfer function of the head PSD relative to the tibia PSD. A one-way analysis of variance was used to determine the difference in time and frequency domain acceleration variables between the flat-footed and normal-footed groups running. Results : Peaks of the head and tibial acceleration signals were significantly greater during flat-footed group running than normal-footed group running(p

Increased vertical impact forces and altered running mechanics with softer midsole shoes.

To date it has been thought that shoe midsole hardness does not affect vertical impact peak forces during running. This conclusion is based partially on results from experimental data using homogeneous samples of participants that found no difference in vertical impact peaks when running in shoes with different midsole properties. However, it is currently unknown how apparent joint stiffness is affected by shoe midsole hardness. An increase in apparent joint stiffness could result in a harder landing, which should result in increased vertical impact peaks during running. The purpose of this study was to quantify the effect of shoe midsole hardness on apparent ankle and knee joint stiffness and the associated vertical ground reaction force for age and sex subgroups during heel-toe running. 93 runners (male and female) aged 16-75 years ran at 3.33 ± 0.15 m/s on a 30 m-long runway with soft, medium and hard midsole shoes. The vertical impact peak increased as the shoe midsole hardness decreased (mean(SE); soft: 1.70BW(0.03), medium: 1.64BW(0.03), hard: 1.54BW(0.03)). Similar results were found for the apparent ankle joint stiffness where apparent stiffness increased as the shoe midsole hardness decreased (soft: 2.08BWm/º x 100 (0.05), medium: 1.92 BWm/º x 100 (0.05), hard: 1.85 BWm/º x 100 (0.05)). Apparent knee joint stiffness increased for soft (1.06BWm/º x 100 (0.04)) midsole compared to the medium (0.95BWm/º x 100 (0.04)) and hard (0.96BWm/º x 100 (0.04)) midsoles for female participants. The results from this study confirm that shoe midsole hardness can have an effect on vertical impact force peaks and that this may be connected to the hardness of the landing. The results from this study may provide useful information regarding the development of cushioning guidelines for running shoes.

Running shoe crash-pad design alters shoe touchdown angles and ankle stability parameters during heel–toe running

Purpose: Running shoe crash-pads are commonly used to improve cushioning during heel–toe running. However, guidelines regarding shape and positioning of crash-pads are rare. This research examined the effect of systematically modified running shoe crash-pads on vertical ground reaction force characteristics and lower extremity kinematics during heel–toe running.Methods: Four custom-made running shoes featured crash-pad variations regarding horizontal extent and vertical position embedded within ethylene-vinyl acetate (EVA) midsoles. Crash-pads were located at the posterior-lateral midsole and had two sizes (narrow and wide) and two positions (top and bottom). Twenty-four runners performed five valid laboratory running trials per shoe while capturing ground reaction forces and lower extremity kinematics. Perception of cushioning, stability, and overall preference was assessed during outdoor loop running. Shoe variable means were compared for main (p < .05) and interaction (simple) effects (p < .05) by two within participants’ factors (size and position) repeated measures analyses of variance (ANOVA) and effect size estimation (pη2).Results: Rearfoot motion variables indicated biomechanical effects on running shoe stability induced by crash-pad size and position. Shock attenuation was marginally affected by shoe modifications and was not perceived by runners. Runners also did not perceive rearfoot stability alterations among shoes.Conclusion: Crash-pad modifications at the posterior-lateral region of EVA midsoles do not necessarily change substantially biomechanical and perceived running shoe cushioning properties. However, crash-pads applied in this research influenced rearfoot stability characteristics during running. In addition to dual density use at the medial shoe border, dual density use at the posterior-lateral midsole can provide opportunities to control rearfoot stability during heel–toe running.

Biomechanical and metabolic effects of a leaf spring structured midsole in heel–toe running

Purpose: The purpose of this study was to investigate effects of a novel leaf spring midsole construction on biomechanical variables affecting running economy. The midsole construction is designed to exploit the directionality of the ground reaction force to shift the shoe anteriorly during the stance phase in running.Methods: Nine male long-distance runners ran 5 min on a treadmill (3 m s−1) with two types of shoes: a leaf spring structured midsole shoe and a standard reference shoe with a standard ethylene vinyl acetate foam midsole. Runner and shoe kinematics were analysed using a three-dimensional motion capture system, and oxygen cost was measured by an open circuit breath-by-breath spirometer. Group differences for all variables were tested using paired t-tests (p < 0.05).Results: The leaf spring structured midsole shoe significantly increased the anterior shift of the foot by 8 ± 4 mm (p = 0.001) during stance leading to an increased stride length (1%; p = 0.044), while oxygen cost (2%; p = 0.031) and stride rate (1%; p = 0.039) were significantly reduced compared to the reference shoe.Conclusion: It is concluded that the leaf spring structured midsole contributes to a more economic running style in heel–toe running at moderate running speeds.

Segmented midsole hardness in the midfoot to forefoot region of running shoes alters subjective perception and biomechanics during heel-toe running revealing potential to enhance footwear

Purpose: Dual density midsole constructions at the lateral rearfoot and medial midfoot provide opportunities to improve cushioning and stability of running shoes. By similar mechanisms, non-uniform midsole density across the medio-lateral direction at the midfoot to forefoot may allow better negotiation of different loading magnitudes of the medial and lateral midfoot to forefoot during running. Thus, the effect of segmented midsole hardness at the midfoot to forefoot of running shoes on perception and biomechanics was examined.Methods: Four custom-made running shoes featured a three section longitudinal hardness pattern at midfoot to forefoot. The central section as well as the rearfoot section always had consistent medium hardness, whereas medial and lateral sections were systematically softer or harder. A sample of 24 runners participated in visual analogue scale based perception measurements and in recording of in-shoe plantar pressures, ground reaction forces, and multi-segment foot kinematics. Shoe effects were analysed by repeated measures analyses of variance (ANOVA) (p<.05), followed by least significant difference (LSD) and Bonferroni adjusted post-hoc tests (p<.05) for discrete variables. Interaction of shank and foot segments was also analysed using motion-time curves.Results: Runners distinguished midsole hardness at the medial (p = .009) but not at the lateral midfoot to forefoot and indicated a trend (p = .069) preferring softer medial hardness. Plantar peak pressure (medial: p = .006, lateral: p = .000) and relative loads (medial: p = .000, lateral: p = .000) were increased when midsole sections were harder. Ground contact time (p = .045) and maximum loading rate I (p = .016) were higher for shoes having softer medial hardness, while rearfoot (p = .040) and forefoot (p = .001) showed increased maximum ankle eversion for these conditions.Conclusion: Segmented running shoe midsole hardness across the medio-lateral direction of the midfoot to forefoot influences subjective comfort and biomechanical forefoot stability. Findings allow systematic approaches to improve both features, thereby creating enhanced running footwear.