Forefoot Strike Research Articles

The effect of uneven terrain conditions during shod vs. barefoot running

Background: The majority of research on barefoot running focuses on acute changes in altering footwear without regard to the runner's experience with barefoot or minimalist footwear running. Objective: The objective of this study was to compare the effect of footwear (standard cushioned running shoes, barefoot) and running surface (flat surface, uneven terrain) on gait in experienced runners using minimalist shoes. Methods: Terrain running was simulated by three custom-made mats with randomly placed firmly attached stones. Seven experienced trail runners participated in this study. All participants were forefoot strikers. Participants underwent three-dimensional kinematic and kinetic analysis consisting of five running trials in each combination of footwear and surface. A trial was successful when the participant maintained a velocity of 3.2 ± 0.16 m/s without targeting a force platform. Results: Uneven terrain conditions along with barefoot conditions led to significantly decreased peak moment of ankle plantarflexion (terrain: p = .041, footwear: p = .026) and decreased second peak of vertical ground reaction force in comparison with other conditions (terrain: p = .026, footwear: p = .004). Uneven terrain conditions also significantly decreased ankle dorsiflexion at initial contact with the ground for both footwear conditions (p = .021). Conclusions: We conjecture that net ankle moments could be decreased by barefoot running in terrain conditions in skilled forefoot runners. Experienced runners using minimalist shoes may incorporate trail running into their barefoot running regime without risk of higher Achilles tendon loading compared to even running.

계단과 경사로 하강 동작 중의 발목관절 충격량 비교

The purpose of this study was to compare ankle joint loads (Linear and Angular Impulses) while descending the stairs and ramp. Ten young male subjects participated in this study. Stairs and ramp of identical slope (30 degrees) were custom-made to include force plates in the middle of pathways. Subjects descended the stairs and ramp at a comfortable speed and posture. The stance period was divided into three phases, weight acceptance (WA), single limb stance, and pre-swing. Three-directional impulses and their sum were derived from the reaction forces and moments at the ankle joint. Differences in impulse sums (Both Linear and Angular) between stairs and ramp were significant only in the early (WA) phase, whereas those of stairs were greater than the ramp. All subjects adopted forefoot strike strategy for the stairs and 80% of the subjects adopted rearfoot strike strategy for the ramp. An increase in the GRF and moment arm of the GRF at the ankle joint in case of forefoot strike may have contributed to the increase in the linear and angular impulse in the early phase of stair descent compared to ramp descent. The results are in agreement with the preference of ramp in the elderly.

Exerted running results in altered impact mechanics and footstrike patterns following gait retraining

ABSTRACT Exertion may alter running mechanics and increase injury risk. Effects of exertion following gait-retraining are unknown. Objectives: To determine how exertion effects load rates, footstrike, and cadence in runners following a transition to forefoot strike (FFS) or increased cadence (CAD) gait-retraining. Methods: 33 (9 M, 24 F) healthy rearfoot strike runners were randomized into CAD or FFS groups. All runners received strengthening exercises and gait-retraining. 3D kinetic and kinematic motion analysis with instrumented treadmill at self-selected speed was performed at baseline & 1-week post-intervention, including an exerted run. Exertion was ≥17 on Borg’s Rating of Perceived Exertion scale or voluntary termination of running. Results: Within group comparisons between fresh and exerted running: Cadence not affected in either group. Foot angle at contact became less plantarflexed in FFS (−2.2°, ±0.4) and was unchanged in CAD. Both groups increased vertical average load rate (FFS +16.9%, CAD +13.6%). CAD increased vertical stiffness (+8.6 kN/m). FFS reduced ankle excursion (1.8°). (p ≤ 0.05 for all values listed). Conclusion: Both FFS and CAD exhibited increased load rates with exertion. Variables that may have increased load rates were different for each group. CAD runners had increased vertical stiffness while FFS runners had reduced plantarflexion at contact and reduced ankle dorsiflexion excursion.

Foot joint coupling variability differences between habitual rearfoot and forefoot runners prior to and following an exhaustive run

As joint coupling variability has been associated with running-related lower extremity injury, the purpose of this study was to identify how variability within the foot may be different between forefoot (FFS) and rearfoot strike (RFS) runners. Identifying typical variability in uninjured runners may contribute to understanding of ideal coordination associated with running foot strike patterns.Fifteen FFS and 15 RFS runners performed a maximal-effort 5 km treadmill run. A 7-segment foot model identified 6 functional articulations (rearfoot, medial and lateral midfoot and forefoot, and 1st metatarsophalangeal) for analysis. Beginning and end of the run motion capture data were analyzed. Vector coding was used to calculate 6 joint couples. Standard deviations of the coupling angles were used to identify variability within subphases of stance (loading, mid-stance, terminal, and pre-swing). Mixed between-within subjects ANOVAs compared differences between the foot strikes, pre and post run.Increased variability was identified within medial foot coupling for FFS and within lateral foot coupling for RFS during loading and mid-stance. The exhaustive run increased variability during mid-stance for both groups.Interpretation. Joint coupling variability profiles for FFS and RFS runners suggest different foot regions have varying coordination needs which should be considered when comparing the strike patterns.

Energy absorption at lower limb joints in different foot contact strategies while descending stairs.

BACKGROUND: Joint loads in different walking strategies during stair descent have been investigated in terms of the joint moment in association with the risk of osteoarthritis. However, the absorption mechanisms of the potential energy loss are not known.OBJECTIVE: This study aims to compare the mechanical energy absorptions in lower limb joints in different initial foot contact strategies.METHODS: Nineteen young subjects walked down on instrumented stairs with two different strategies, i.e., forefoot and rearfoot strike. Power and energy at lower limb joints during stance phase were compared between strategies.RESULTS: Lower limb joints absorbed 73 11% of the potential energy released by descending stairs and there was no difference between strategies. Rearfoot strategy absorbed less energy than forefoot strategy at the ankle joint in the 1st phase, which was compensated mainly by more energy absorption at the knee in the 2nd phase and less energy generation at the hip joints in the 3rd phase.CONCLUSION: The results suggest that a leg absorbs most of the potential energy while descending stairs irrespective of the walking strategies and that any reduction of energy absorption at one joint is compensated by other joints. Greater energy absorption at the knee joint compared to the other joints suggests high burden of knee joint muscles and connective tissues during stair-descent, which is even more significant for the rearfoot strike strategy.

Lower extremity stiffness in habitual forefoot strikers during running on different overground surfaces

Sports surface is one of the known external factors affecting running performance and injury. To date, we have found no study that examined the lower extremity stiffness in habitual forefoot strikers running on different overground surfaces. Therefore, the objective of this study was to investigate lower extremity stiffness and relevant kinematic adjustments in habitual forefoot strikers while running on different surfaces. Thirty-one male habitual forefoot strikers were recruited in this study. Runners were instructed to run at a speed of 3.3 m/s (±5%) on three surfaces, named synthetic rubber, concrete, and artificial grass. No significant differences were found in leg stiffness, vertical stiffness, and joint stiffness in the sagittal plane during running on the three surfaces ( p > 0.05). Running on artificial grass exerted a greater displacement in knee joint angle than running on synthetic rubber ( p = 0.002, 95% CI = 1.52-7.35 degrees) and concrete ( p = 0.006, 95% CI = 1.04-7.25 degrees). In the sagittal plane, peak knee moment was lower on concrete than on artificial grass ( p = 0.003, 95% CI = 0.11-0.58 Nm/kg), whereas peak ankle moment was lower on synthetic rubber than on concrete ( p < 0.001, 95% CI = 0.03-0.07 Nm/kg) and on artificial grass ( p < 0.001, 95% CI = 0.02-0.06 Nm/kg). Among the three surfaces, the maximal ground reaction forces on concrete were the lowest ( p < 0.05). This study indicated that running surfaces cannot influence lower extremity stiffness in habitual forefoot strikers at current running speed. Kinematic adjustments of knee and ankle, as well as ground reaction forces, may contribute to maintaining similar lower extremity stiffness.

Effectiveness of a knee-ankle-foot orthosis with a knee extension aid in gait training for stroke patients.

To evaluate the effectiveness of a knee-ankle-foot orthosis (KAFO) with a newly developed knee extension aid in gait training for stroke patients with severe leg paralysis. The participants were 7 recovering stroke patients prescribed a KAFO. With the KAFO knee joint set to allow free flexion, knee flexion angle, lower limb muscle activity, and time of plantar ground contact were measured during assisted walking with the knee extension aid or a conventional support loop. When first using the knee extension aid, knee flexion angle at initial ground contact was significantly decreased and time from heel strike on the paralyzed side to forefoot strike was prolonged compared with the support loop. After using the knee extension aid for 1 week, in addition to the two parameters above, maximum knee flexion angle during the swing phase, knee extension displacement from the maximum flexion angle to initial ground contact, and the muscle activity ratio of the biceps femoris during the swing phase were significantly increased compared with the support loop. This knee extension aid may be indicated for patients who have difficulty in initial heel strike due to excessive knee flexion at the end of the swing phase.

Relationships Between Arch Height Flexibility and Medial–Lateral Ground Reaction Forces in Rearfoot and Forefoot Strike Runners

Higher medial-lateral forces have been reported in individuals with stiffer foot arches. However, this was in a small sample of military personnel who ran with a rearfoot strike pattern. Therefore, our purpose was to investigate whether runners, both rearfoot and forefoot strikers, show different associations between medial-lateral forces and arch stiffness. A group of 118 runners (80 rearfoot strikers and 38 forefoot strikers) were recruited. Ground reaction force data were collected during running on an instrumented treadmill. Arch flexibility was assessed as the difference in arch height from sitting to standing positions, and participants were classified into stiff/flexible groups. Group comparisons were performed for the ratio of medial:vertical and lateral:vertical impulses. In rearfoot strikers, runners with stiff arches demonstrated significantly higher medial:vertical impulse ratios (P = .036). Forefoot strikers also demonstrated higher proportions of medial forces; however, the mean difference did not reach statistical significance (P = .084). No differences were detected in the proportion of lateral forces between arch flexibility groups. Consistent with previous findings in military personnel, our results indicate that recreational runners with stiffer arches have a higher proportion of medial forces. Therefore, increasing foot flexibility may increase the ability to attenuate medial forces.

Duty Factor Reflects Lower Limb Kinematics of Running

The aim was to identify the differences in lower limb kinematics used by high (DFhigh) and low (DFlow) duty factor (DF) runners, particularly their sagittal plane (hip, knee, and ankle) joint angles and pelvis and foot segment angles during stance. Fifty-nine runners were divided in two DF groups based on their mean DF measured across a range of speeds. Temporal characteristics and whole-body three-dimensional kinematics of the running step were recorded from treadmill runs at 8, 10, 12, 14, 16, and 18 km/h. Across speeds, DFhigh runners, which limit vertical displacement of the COM and promote forward propulsion, exhibited more lower limb flexion than DFlow during the ground contact time and were rearfoot strikers. On the contrary, DFlow runners used a more extended lower limb than DFhigh due to a stiffer leg and were midfoot and forefoot strikers. Therefore, two different lower limb kinematic mechanisms are involved in running and the one of an individual is reflected by the DF.

Rearfoot, Midfoot, and Forefoot Motion in Naturally Forefoot and Rearfoot Strike Runners during Treadmill Running

Different location and incidence of lower extremity injuries have been reported in rearfoot strike (RFS) and forefoot strike (FFS) recreational runners. These might be related to functional differences between the two footstrike patterns affecting foot kinematics and thus the incidence of running injuries. The aim of this study was to investigate and compare the kinematic patterns of foot joints between naturally RFS and FFS runners. A validated multi-segment foot model was used to measure 24 foot kinematic variables in long-distance recreational runners while running on a treadmill. These variables included the three-dimensional relative motion between rearfoot, midfoot, and forefoot segments. The footstrike pattern was identified using kinematic data and slow-motion videos. Functional analysis of variance was used to compare the time series of these variables between RFS (n = 49) and FFS (n = 25) runners. In FFS runners, the metatarsal bones were less tilted with respect to the ground, and the metatarsus was less adducted with respect to the calcaneus during stance. In early stance, the calcaneus was more dorsiflexed with respect to the shank and returned to a more plantarflexed position at push-off. FFS runners showed a more adducted calcaneus with respect to the shank and a less inverted midfoot to the calcaneus. The present study has showed that the footstrike angle characterizes foot kinematics in running. These data may help shed more light on the relationship between foot function and running-related injuries.

Effects of Foot Strike Techniques on Running Biomechanics: A Systematic Review and Meta-analysis.

Distance running is one of the most popular physical activities, and running-related injuries (RRIs) are also common. Foot strike patterns have been suggested to affect biomechanical variables related to RRI risks. To determine the effects of foot strike techniques on running biomechanics. The databases of Web of Science, PubMed, EMBASE, and EBSCO were searched from database inception through November 2018. The initial electronic search found 723 studies. Of these, 26 studies with a total of 472 participants were eligible for inclusion in this meta-analysis. Systematic review and meta-analysis. Level 4. Means, standard deviations, and sample sizes were extracted from the eligible studies, and the standard mean differences (SMDs) were obtained for biomechanical variables between forefoot strike (FFS) and rearfoot strike (RFS) groups using a random-effects model. FFS showed significantly smaller magnitude (SMD, -1.84; 95% CI, -2.29 to -1.38; P < 0.001) and loading rate (mean: SMD, -2.1; 95% CI, -3.18 to -1.01; P < 0.001; peak: SMD, -1.77; 95% CI, -2.21 to -1.33; P < 0.001) of impact force, ankle stiffness (SMD, -1.69; 95% CI, -2.46 to -0.92; P < 0.001), knee extension moment (SMD, -0.64; 95% CI, -0.98 to -0.3; P < 0.001), knee eccentric power (SMD, -2.03; 95% CI, -2.51 to -1.54; P < 0.001), knee negative work (SMD, -1.56; 95% CI, -2.11 to -1.00; P < 0.001), and patellofemoral joint stress (peak: SMD, -0.71; 95% CI, -1.28 to -0.14; P = 0.01; integral: SMD, -0.63; 95% CI, -1.11 to -0.15; P = 0.01) compared with RFS. However, FFS significantly increased ankle plantarflexion moment (SMD, 1.31; 95% CI, 0.66 to 1.96; P < 0.001), eccentric power (SMD, 1.63; 95% CI, 1.18 to 2.08;P < 0.001), negative work (SMD, 2.60; 95% CI, 1.02 to 4.18; P = 0.001), and axial contact force (SMD, 1.26; 95% CI, 0.93 to 1.6; P < 0.001) compared with RFS. Running with RFS imposed higher biomechanical loads on overall ground impact and knee and patellofemoral joints, whereas FFS imposed higher biomechanical loads on the ankle joint and Achilles tendon. The modification of strike techniques may affect the specific biomechanical loads experienced on relevant structures or tissues during running.

Relationship Between Wearable Sensor Foot Strike Outcomes And Ankle Sagittal Plane Kinematics During Treadmill Running

PURPOSE: Wearable sensors are capable of measuring biomechanical running outcomes. Traditional gait analyses have determined a strong relationship between ankle angle at initial contact and foot strike. However, there is currently no information available on how sensor-derived metrics of foot strike type relate to ankle sagittal motion during running as a means of validation. Therefore, the purpose of this study was to validate the sensor-derived foot strike type outcome by determining the relationship between foot strike type and ankle sagittal plane kinematics during a treadmill running analysis. We hypothesized that a rearfoot strike (RFS) would highly correlate to increased ankle dorsiflexion, while a forefoot strike (FFS) would highly correlate to increased ankle plantarflexion. METHODS: Twenty collegiate cross-country athletes (12 females) ran on an instrumented treadmill with 3-D motion capture at standard (2.68 m/s) and fast (3.60 m/s) speeds. Foot strike outcomes were obtained bilaterally using running wearable sensors, and sagittal plane ankle kinematics were simultaneously recorded. Pearson’s r correlation coefficients were used to determine the relationship between sensor-derived foot strike categories (1 to 16), and ankle angles at initial contact. Dorsiflexion was defined as in the positive axis. Alpha was set a priori to .05 for all analyses. RESULTS: Eight hundred total steps were included for analysis. Foot strike type and ankle angles at initial contact had a strong, inverse correlation, such that a higher foot strike value was strongly related to increased ankle plantarflexion angles (r = -0.85, p<.001, Figure). CONCLUSIONS: Sensor-derived foot strike metrics were highly correlated to sagittal plane ankle measures, thus confirming our initial hypotheses. These outcomes support that the running wearable sensors are a valid means to assess foot strike patterns during distance running.

Foot strike pattern during running alters muscle-tendon dynamics of the gastrocnemius and the soleus

Running is thought to be an efficient gait due, in part, to the behavior of the plantar flexor muscles and elastic energy storage in the Achilles tendon. Although plantar flexor muscle mechanics and Achilles tendon energy storage have been explored during rearfoot striking, they have not been fully characterized during forefoot striking. This study examined how plantar flexor muscle-tendon mechanics during running differs between rearfoot and forefoot striking. We used musculoskeletal simulations, driven by joint angles and electromyography recorded from runners using both rearfoot and forefoot striking running patterns, to characterize plantar flexor muscle-tendon mechanics. The simulations revealed that foot strike pattern affected the soleus and gastrocnemius differently. For the soleus, forefoot striking decreased tendon energy storage and fiber work done while the muscle fibers were shortening compared to rearfoot striking. For the gastrocnemius, forefoot striking increased muscle activation and fiber work done while the muscle fibers were lengthening compared to rearfoot striking. These changes in gastrocnemius mechanics suggest that runners planning to convert to forefoot striking might benefit from a progressive eccentric gastrocnemius strengthening program to avoid injury.

Plantar Loads of Habitual Forefoot Strikers during Running on Different Overground Surfaces

The objective of this study is to investigate plantar loads characteristics of habitual forefoot strike runners while running on different surfaces. Twenty-six runners (age: 28.2 ± 6.8 y, height: 172.9 ± 4.1 cm, weight: 67.7 ± 9.6 kg, BMI (body mass index): 22.6 ± 2.8 kg/m2, running age: 5.0 ± 4.2 y, running distance per week: 14.6 ± 11.7 km) with habitual forefoot strike participated in the study. Runners were instructed to run at 3.3 ± 0.2 m/s on three surfaces: grass, synthetic rubber and concrete. An in-shoe pressure measurement system was used to collect and analyze plantar loads data. Running on the synthetic rubber surface produced a lower plantar pressure in the lateral forefoot (256.73 kPa vs. 281.35 kPa, p = 0.006) than running on concrete. Compared with the concrete surface, lower pressure–time integrals were shown at the central forefoot (46.71 kPa⋅s vs. 50.73 kPa⋅s, p = 0.001) and lateral forefoot (36.13 kPa⋅s vs. 39.36 kPa⋅s, p = 0.004) when running on the synthetic rubber surface. The different surfaces influence plantar loads of habitual forefoot strikers and runners should choose appropriate overground surface to reduce the risk of lower extremity musculoskeletal injuries.

Twelve-Week Gait Retraining Reduced Patellofemoral Joint Stress during Running in Male Recreational Runners.

Purpose To explore the changes in knee sagittal angle and moment and patellofemoral joint (PFJ) force and stress before and after 12-week gait retraining. Methods A total of 30 healthy male recreational runners were randomized into a control group (n = 15) who ran in their original strike pattern using minimalist shoes or experimental group (n = 15) who ran in a forefoot strike pattern using minimalist shoes during the 12-week gait retraining. The kinematic and kinetic data of the dominant leg of the participants during the 12 km/h running were collected by 3D motion capture systems and 3D force platforms. Besides, the biomechanical property of the PFJ was calculated on the basis of the joint force model and the regression equation of the contact area. Results After the 12-week gait retraining, 78% of the rearfoot strikers turned into forefoot strikers. Peak knee extension moment and peak PFJ stress decreased by 13.8% and 13.3% without altering the running speed, respectively. Meanwhile, no changes in maximum knee flexion angle/extension moment and PFJ force/stress were observed for the control group. Conclusion The 12-week gait retraining effectively reduced the PFJ stress, thereby providing a potential means of reducing the risk of patellofemoral pain syndrome while running.

Tibial Acceleration Measured from Wearable Sensors Is Associated with Loading Rates in Injured Runners.

The loadrate of the vertical ground reaction force at impact has been associated with a variety of running injuries. Peak tibial shocks occur during the early stance phase and has been shown to be correlated to the loadrates in healthy runners using a rearfoot strike pattern. As a result, tibial accelerometry has been used as a surrogate for loadrates. However, these correlations have not been assessed in injured runners nor in runners with differing footstrike patterns. To examine the relationship between tibial acceleration and loadrates in injured runners who are habitual rearfoot (RFS), midfoot (MFS), and forefoot (FFS) strikers. Tibial acceleration was expected to be positively associated with loadrates across all footstrike patterns. Cross-sectional cohort. Academic medical center with biomechanics laboratory. One hundred sixty-nine injured runners (age 38.7 ± 13.1 years, 127 RFS, 17 MFS, 25 FFS). Each participant completed a biomechanical assessment for injury including evaluation on a force treadmill with a triaxial accelerometer fastened by a Velcro strap to the distal medial tibia. Peak vertical and resultant tibial acceleration (VTA, RTA) were measured from the accelerometer. Vertical average and instantaneous loadrates (VALR, VILR) and the resultant instantaneous loadrate (RILR) were determined from the force data. The relationship between tibial acceleration and loadrates measured using Pearson's correlation coefficient (r). Loadrates were each associated with VTA (r = 0.66-0.82, P < .001) and RTA (r = 0.41-0.68, P < .05) across all footstrike groups with the exception of association of VILR to RTA in the FFS group. The strength in correlations was lowest between RTA and loadrates for the FFS runners (r = 0.41-0.47, P < .05). Vertical tibial acceleration is the stronger surrogate for loadrates in injured runners across differing footstrike patterns.

Alterations in Running Biomechanics after 12 Week Gait Retraining with Minimalist Shoes

Purpose: The intervention of 12 week gait retraining with minimalist shoes was established to examine its effect on impact forces, joint mechanics, and vertical stiffness during running. Methods: Thirty male recreational runners were randomly assigned to the gait retraining + minimalist shoe (n = 15, GR) and minimalist shoe (n = 15, MIN) groups. The ground reaction force and marker trajectories were collected before and after intervention at a speed of 3.33 ± 5% m/s. Results: A total of 17 participants (9 in the GR group and 8 in the MIN group) completed the training. After training, (1) the loading rate of both groups decreased significantly, and the loading rate of the GR group was lower than that of the MIN group. (2) The foot strike angle of the GR group decreased significantly after training, and the plantarflexion angle and hip joint angular extension velocity increased in both groups. (3) The moment of ankle joint increased in the GR group, and the stiffness of lower limbs was significantly improved in both groups. Conclusion: The 12 week gait retraining with minimalist shoes converted rearfoot strikers into forefoot strikers with a rate of 78% (7/9). More importantly, such a combined program, compared to the training with only minimalist shoes, can avoid the peak impact force and decrease the loading rate more effectively, thus providing a potential means of reducing risk of running injury caused by impact forces. Moreover, the increased vertical stiffness of lower extremity after gait retraining may improve running economy and corresponding energy utilization. However, these observations also suggest that the sole use of minimalist footwear may have limited effects on reducing running-related impacts.

Is There a Relationship Between Strike Pattern and Injury During Running: A Review

<strong>Object:</strong> Recently people have shown an interest in running barefoot or with minimalist shoes, which result in forefoot strike (FFS) patterns that are different from running in normal shod with the rearfoot strike (RFS). To date, there is a dispute whether runners’ footfall pattern has an important impact on running injuries. Therefore, the purpose of this review is to investigate whether there is a relationship between different strike patterns and running injuries by reviewing the literature. <strong>Materials and Methods:</strong> A database retrieval and reference search were carried out with PubMed, Scopus, Google Scholar, and ScienceDirect. In the final review, 10 papers were included by matching the inclusion criteria. <strong>Results:</strong> Barefoot running exhibited smaller impact forces, short stride length, higher strike frequency, and shorter contact times compared to the standard shod condition. The forefoot strike pattern showed an increase in the plantarflexed foot, more ankle compliance during impact, smaller loading at the knee and lowered vertical loading rate in the FFS pattern than RFS. <strong>Discussion:</strong> Although the running injury is driven by multi-factorial variables, our literature review did not show any scientific evidence to suggest that footfall patterns are directly related to running injury.

Influence of Swing-Foot Strike Pattern on Balance Control Mechanisms during Gait Initiation over an Obstacle to Be Cleared

Gait initiation (GI) over an obstacle to be cleared is a functional task that is highly challenging for the balance control system. Two swing-foot strike patterns were identified during this task—the rearfoot strike (RFS), where the heel strikes the ground first, and the forefoot strike (FFS), where the toe strikes the ground first. This study investigated the effect of the swing-foot strike pattern on the postural organisation of GI over an obstacle to be cleared. Participants performed a series of obstacle clearance tasks with the instruction to strike the ground with either an FFS or RFS pattern. Results showed that anticipatory postural adjustments in the frontal plane were smaller in FFS than in RFS, while stability was increased in FFS. The vertical braking of the centre of mass (COM) during GI swing phase was attenuated in FFS compared to RFS, leading to greater downward centre of mass velocity at foot contact in FFS. In addition, the collision forces acting on the foot were smaller in FFS than in RFS, as were the slope of these forces and the slope of the C7 vertebra acceleration at foot contact. Overall, these results suggest an interdependent relationship between balance control mechanisms and foot strike pattern for optimal stability control.

Effects of Foot-Strike Patterns on Biomarkers S100 Calcium-Binding Protein B/Neuron-Specific Enolase in Running-A Pilot Study.

Foot-strike patterns (FSP) in running are related to certain impact kinetics during ground contact. A rear-foot strike (RFS) has been associated with higher impact forces, whereas a forefoot strike (FFS) is assumed to minimize these impact forces. This study investigated the effects of running with RFS or FFS on impact-sensitive neuronal biomarkers S100 calcium-binding protein B (S100B), neuron-specific enolase (NSE), and lactate dehydrogenase (LDH). In this randomized crossover study, 18 healthy recreational runners (14 male, mean [SD] age 28.2 [4.7]y, body mass index 22.8 [1.9]) ran 2 separate 5-mile runs with RFS or FFS, respectively. Blood samples were taken before (pre), 30min after (post 0), and 24h after (post 24) the run. S100B, NSE, and LDH concentrations were determined and analyzed (3 × 2 data model). S100B, NSE, and LDH concentrations increased from pre to post 0 and decreased within 24 h back to the baseline level, demonstrating a significant time effect (all P < .01, all ηpart2>.3). No main effect for FSP or any significant interaction effect indicating FSP-specific differences between FFS or RFS was found (all P > .05, all ηpart2<.07), except for LDH (P < .001, ηpart2=.77). NSE, S100B, and LDH concentration increased in the short term after running and returned to normal in 24h. FSP with varying impact forces does not influence the increase of these biomarkers. LDH findings favor peripheral origins, but mixed effects are possible. Thus, further research is needed to estimate the risk of mild traumatic encephalopathy.