Three-dimensional impact kinetics with foot-strike manipulations during running

The biomechanics of running and running styles: a synthesis

Running movements are parametrised using a wide variety of devices. Misleading interpretations can be avoided if the interdependencies and redundancies between biomechanical parameters are taken into account. In this synthetic review, commonly measured running parameters are discussed in relation to each other, culminating in a concise, yet comprehensive description of the full spectrum of running styles. Since the goal of running movements is to transport the body centre of mass (BCoM), and the BCoM trajectory can be derived from spatiotemporal parameters, we anticipate that different running styles are reflected in those spatiotemporal parameters. To this end, this review focuses on spatiotemporal parameters and their relationships with speed, ground reaction force and whole-body kinematics. Based on this evaluation, we submit that the full spectrum of running styles can be described by only two parameters, namely the step frequency and the duty factor (the ratio of stance time and stride time) as assessed at a given speed. These key parameters led to the conceptualisation of a so-called Dual-axis framework. This framework allows categorisation of distinctive running styles (coined 'Stick', 'Bounce', 'Push', 'Hop', and 'Sit') and provides a practical overview to guide future measurement and interpretation of running biomechanics.

Assessing the effects of foot strike patterns and shoe types on the control of leg length and orientation in running

This research investigates the stabilization of leg length and orientation during the landing phase of running, examining the effects of different footwear and foot strike patterns. Analyzing kinematic data from twenty male long-distance runners, both rearfoot and forefoot strikers, we utilized the Uncontrolled Manifold approach to assess stability. Findings reveal that both leg length and orientation are indeed stabilized during landing, challenging the hypothesis that rearfoot strikers exhibit less variance in deviations than forefoot strikers, and that increased footwear assistance would reduce these deviations. Surprisingly, footwear with a lower minimalist index enhanced post-landing stability, suggesting that cushioning contributes to both force dissipation and leg length stability. The study indicates that both foot strike patterns are capable of effectively reducing task-relevant variance, with no inherent restriction on flexibility for rearfoot strikers. However, there is an indication of potential reliance on footwear for stability. These insights advance our understanding of the biomechanics of running, highlighting the role of footwear in stabilizing leg length and orientation, which has significant implications for running efficiency and injury prevention.

Comparative analysis of ankle injury kinematics and dynamics in basketball players: forefoot landing vs. rearfoot landing modes

OBJECTIVE

To compare the differences in ankle joint parameters of basketball athletes between the forefoot and rearfoot landing and to investigate the injury mechanism of ankle joints in different landing modes.

METHODS

Twenty level II male basketball athletes were selected as subjects in this study. The landing movements of these athletes were assigned into a forefoot landing mode and a rearfoot landing mode. The former includes movements such as running emergency stop, two-leg jump and forefoot landing, while the latter includes actions such as running emergency stop, two-leg jump and rearfoot landing. The motion capture system and three-dimensional force measuring table were used for collecting the kinematic and dynamic data of the subjects.

RESULTS

The initial landing angles, including ankle dorsiflexion and medial ankle rotation of the forefoot were larger than those of the rearfoot (all P<0.05). Compared to those in the rearfoot landing mode, the forefoot landing exhibited a greater peak angle of ankle plantar flexion and ankle varus, as well as a smaller peak angle of ankle dorsiflexion and ankle internal rotation (all P<0.05). In comparison to the rearfoot landing mode, the forefoot landing showed a larger range of ankle varus and valgus, as well as a smaller range of ankle dorsiflexion and plantar flexion (all P<0.05). The ankle plantar flexion torque of forefoot landing was higher than that of rearfoot landing, while the peak ankle dorsiflexion torque of forefoot landing was smaller than that of rearfoot landing (all P<0.05). Compared to those in the rearfoot landing mode, the outward peak ground reaction force was smaller and the forward peak ground reaction was larger in forefoot landing mode (all P<0.05). No obvious differences were observed in other indicators between two landing modes.

CONCLUSIONS

There are kinematic and dynamic differences between the forefoot and rearfoot landing. Forefoot landing may increase the risk of ankle injury during landing.

Injury and performance related biomechanical differences between recreational and collegiate runners

Introduction

Running related injuries (RRI) are common, but factors contributing to running performance and RRIs are not commonly compared between different types of runners.

Methods

We compared running biomechanics previously linked to RRIs and performance between 27 recreational and 35 collegiate runners. Participants completed 5 overground running trials with their dominant limb striking a force plate, while outfitted with standardised footwear and 3-dimensional motion capture markers.

Results

Post hoc comparisons revealed recreational runners had a larger vertical loading rate (194.5 vs. 111.5 BW/s, p < 0.001) and shank angle (6.80 vs. 2.09, p < 0.001) compared with the collegiate runners who demonstrated greater vertical impulse (0.349 vs. 0.233 BWs, p < 0.001), negative impulse (-0.022 vs. -0.013 BWs, p < 0.001), positive impulse (0.024 vs. 0.014 BWs, p < 0.001), and propulsive force (0.390 vs. 0.333 BW, p = 0.002). Adjusted for speed, collegiate runners demonstrated greater total support moment (TSM), plantar flexor moment, knee extensor moment, hip extensor moment, and had greater proportional plantar flexor moment contribution and less knee extensor moment contribution to the TSM compared with recreational runners. Unadjusted for speed, collegiate runners compared with recreational had greater TSM and plantar flexor moment but similar joint contributions to the TSM.

Discussion

Greater ankle joint contribution may be more efficient and allow for greater capacity to increase speed. Improving plantarflexor function during running provides a strategy to improve running speed among recreational runners. Moreover, differences in joint kinetics and ground reaction force characteristics suggests that recreational and collegiate runners may experience different types of RRI.

Changes in acceleration load as measured by inertial measurement units manifest in the upper body after an extended running task

The purpose of this study was to investigate the behaviour of physiological load measures as well as ground reaction forces (GRF) and acceleration load during a prolonged running task that simulated the running demands of an intermittent team sport. Nineteen males completed a maximal aerobic fitness test and an extended running protocol across two sessions. Participants wore a portable metabolic system, and four inertial measurement units (IMU), one on each foot, the lower back and upper back. GRF were measured via an instrumented treadmill. Change in metabolic, IMU and GRF variables across five blocks during the running protocol were assessed using a one-way repeated measures ANOVA. The running protocol elicited large increases in heart rate and oxygen consumption over time. No statistically significant changes in any peak impact accelerations were observed. Resultant acceleration area under the curve (AUC) increased at the lower and upper back locations but was unchanged at the foot. GRF active peak but not impact peak increased during the prolonged run. The results of this study indicate that the effect of an extended running task on IMU measures of external mechanical load is manifested in the upper body, and is effectively measured by AUC.

One hundred marathons in 100 days: Unique biomechanical signature and the evolution of force characteristics and bone density

BACKGROUND

An extraordinary long-term running performance may benefit from low dynamic loads and a high load-bearing tolerance. An extraordinary runner (age = 55 years, height = 1.81 m, mass = 92 kg) scheduled a marathon a day for 100 consecutive days. His running biomechanics and bone density were investigated to better understand successful long-term running in the master athlete.

METHODS

Overground running gait analysis and bone densitometry were conducted before the marathon-a-day challenge and near its completion. The case's running biomechanics were compared pre-challenge to 31 runners who were matched by a similar foot strike pattern.

RESULTS

The case's peak vertical loading rate (Δx̄ = -61.9 body weight (BW)/s or -57%), peak vertical ground reaction force (Δx̄ = -0.38 BW or -15%), and peak braking force (Δx̄ = -0.118 BW or -31%) were remarkably lower (p < 0.05) than the control group at ∼3.3 m/s. The relatively low loading-related magnitudes were attributed to a remarkably high duty factor (0.41) at the evaluated speed. The foot strike angle of the marathoner (29.5°) was greater than that of the control group, affecting the peak vertical loading rate. Muscle powers in the lower extremity were also remarkably low in the case vs. controls: peak power of knee absorption (Δx̄ = -9.16 watt/kg or -48%) and ankle generation (Δx̄ = -3.17 watt/kg or -30%). The bone mineral density increased to 1.245 g/cm² (+2.98%) near completion of the challenge, whereas the force characteristics showed no statistically significant change.

CONCLUSION

The remarkable pattern of the high-mileage runner may be useful in developing or evaluating load-shifting strategies in distance running.

Human balance control in 3D running based on virtual pivot point concept

Balance control is one of the crucial challenges in bipedal locomotion. Humans need to maintain their trunk upright while the body behaves like an inverted pendulum which is inherently unstable. Instead, the virtual pivot point (VPP) concept introduced a new virtual pendulum model to the human balance control paradigm by analyzing the ground reaction forces (GRF) in the body coordinate frame. This paper presents novel VPP-based analyses of the postural stability of human running in a 3D space. We demonstrate the relation between the VPP position and the gait speed. The experimental results suggest different control strategies in frontal and sagittal planes. The ground reaction forces intersect below the center of mass in the sagittal plane and above the center of mass in the frontal plane. These VPP locations are found for the sagittal and frontal planes at all running speeds, respectively. We introduced a 3D VPP-based model which can replicate the kinematic and kinetic behavior of human running. The similarity between the experimental and simulation results indicates the ability of the VPP concept in predicting human balance control in running and can support its applicability for gait assistance.

Using statistical parametric mapping to assess the association of duty factor and step frequency on running kinetic

Duty factor (DF) and step frequency (SF) were previously defined as the key running pattern determinants. Hence, this study aimed to investigate the association of DF and SF on 1) the vertical and fore-aft ground reaction force signals using statistical parametric mapping; 2) the force related variables (peaks, loading rates, impulses); and 3) the spring-mass characteristics of the lower limb, assessed by computing the force-length relationship and leg stiffness, for treadmill runs at several endurance running speeds. One hundred and fifteen runners ran at 9, 11, and 13 km/h. Force data (1000 Hz) and whole-body three-dimensional kinematics (200 Hz) were acquired by an instrumented treadmill and optoelectronic system, respectively. Both lower DF and SF led to larger vertical and fore-aft ground reaction force fluctuations, but to a lower extent for SF than for DF. Besides, the linearity of the force-length relationship during the leg compression decreased with increasing DF or with decreasing SF but did not change during the leg decompression. These findings showed that the lower the DF and the higher the SF, the more the runner relies on the optimization of the spring-mass model, whereas the higher the DF and the lower the SF, the more the runner promotes forward propulsion.

Vibration transmissibility and apparent mass changes from vertical whole-body vibration exposure during stationary and propelled walking

Whole-Body Vibration (WBV) is an occupational hazard affecting employees working with transportation, construction or heavy machinery. To minimize vibration-induced pathologies, ISO identified WBV exposure limits based on vibration transmissibility and apparent mass studies. The ISO guidelines do not account for variations in posture or movement. In our study, we measured the transmissibility and apparent mass at the mouth, lower back, and leg of participants during stationary and propelled walking. Stationary walking transmissibility was significantly higher at the lumbar spine and bite bar at 5 and 10 Hz compared to all higher frequencies while the distal tibia was lower at 5 Hz compared to 10 and 15 Hz. Propelled walking transmissibility was significantly higher at the bite bar and knee at 2 Hz than all higher frequencies. These results vary from previously published transmissibility values for static participants, showing that ISO standards should be adjusted for active workers.

Ground reaction force profiles during inclined running at iso-efficiency speeds

While running provides an accessible form of cardiovascular stimulus, many runners report lower extremity musculoskeletal injuries. Additionally, runners who develop overuse injuries, such as tibial stress fractures, also have higher loading rates (LR) and impact forces.

PURPOSE

Therefore, the purpose of this study was to investigate how uphill treadmill running at iso-efficient speeds (IES; a speed-incline combination having the same metabolic intensity as level running) influences impact LR, and peak vertical ground reaction forces (GRF).

METHODS

Eleven collegiate distance runners completed 3 experimental running conditions (0%, 4%, and 8% treadmill inclination). During each running condition, the metabolic intensity was controlled by implementing an IES for each runner.

RESULTS

All variables of interest were significantly reduced as treadmill incline increased (0% > 4% > 8%).

CONCLUSION

Incline running is more metabolically demanding compared to level running at the same speed. But, if speed is controlled to maintain metabolic output, runners could decrease LR and peak vertical GRF while achieving the same metabolic training stimulus as level running.

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

CONTENT

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.

OBJECTIVE

To determine the effects of foot strike techniques on running biomechanics.

DATA SOURCES

The databases of Web of Science, PubMed, EMBASE, and EBSCO were searched from database inception through November 2018.

STUDY SELECTION

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.

STUDY DESIGN

Systematic review and meta-analysis.

LEVEL OF EVIDENCE

Level 4.

DATA EXTRACTION

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.

RESULTS

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.

CONCLUSION

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.

Foot Angle and Loading Rate during Running Demonstrate a Nonlinear Relationship

Vertical loading rates are typically found to be lower in forefoot compared to rearfoot strikers, promoting the idea that forefoot striking is desirable and may reduce running injury risk. However, prior work using linear models has shown that foot inclination angle (FIA) at initial contact is a poor predictor of vertical loading rate, suggesting a more complex association exists.

PURPOSE

To determine if a nonlinear model superiorly describes the relationship between FIA and average vertical loading rate (AVLR). Secondary analyses assessed the influence of sex and sport on the association between FIA and AVLR.

METHODS

Whole body kinematics and vertical ground reaction forces were collected for 170 healthy National Collegiate Athletic Association Division I athletes (97 males; 81 cross-country runners) during treadmill running at 2.68, 3.35, and 4.47 m·s. Foot inclination angle and AVLR were calculated for 15 strides and averaged across strides for each limb. Polynomial mixed effects models assessed linear and nonlinear trends in the relationship between FIA and AVLR across the entire sample and accounting for sex and sport participation.

RESULTS

Average vertical loading rate was lowest at the extremes of FIA (i.e., -15°, 20°), whereas greater AVLR were observed between 5° and 10°. The cubic model resulted in a significantly better fit than the linear model (P < 0.001). Average vertical loading rate was also more variable among FIA associated with rearfoot and midfoot strike than forefoot strike. Adding sex to the model did not influence model fit; though, controlling for sport minimally improved model fit.

CONCLUSIONS

The relationship between FIA and AVLR is best represented by a cubic model. Consequently, FIA should be treated as a continuous variable. Reducing FIA into categories may misrepresent the relationship between FIA and other gait variables.

Difference in the running biomechanics between preschoolers and adults

BACKGROUND

High vertical loading rate is associated with a variety of running-related musculoskeletal injuries. There is evidence supporting that non-rearfoot footstrike pattern, greater cadence, and shorter stride length may reduce the vertical loading rate. These features appear to be common among preschoolers, who seem to experience lower running injury incidence, leading to a debate whether adults should accordingly modify their running form.

OBJECTIVE

This study sought to compare the running biomechanics between preschoolers and adults.

METHODS

Ten preschoolers (4.2±1.6 years) and ten adults (35.1±9.5 years) were recruited and ran overground with their usual shoes at a self-selected speed. Vertical average (VALR) and vertical instantaneous loading rate (VILR) were calculated based on the kinetic data. Footstrike pattern and spatiotemporal parameters were collected using a motion capture system.

RESULTS

There was no difference in normalized VALR (p=0.48), VILR (p=0.48), running speed (p=0.85), and footstrike pattern (p=0.29) between the two groups. Preschoolers demonstrated greater cadence (p<0.001) and shorter normalized stride length (p=0.01).

CONCLUSION

By comparing the kinetic and kinematic parameters between children and adults, our findings do not support the notion that adults should modify their running biomechanics according to the running characteristics in preschoolers for a lower injury risk.

Footwear and footstrike change loading patterns in running

Loading rates have been linked to running injuries, revealing persistent impact features that change direction among three-dimensional axes in different footwear and footstrike patterns. Extracting peak loads from ground reaction forces, however, can neglect the time-varying loading patterns experienced by the runner in each footfall. Following footwear and footstrike manipulations during laboratory-based overground running, we examined three-dimensional loading rate-time features in each direction (X, Y, Z) using principal component analysis. Twenty participants (9 M, 11 F, age: 25.3 ± 3.6 y) were analysed during 14 running trials in each of two footwear (cushioned and minimalist) and three footstrike conditions (forefoot, midfoot, rearfoot). Two principal components (PC) captured the primary loading rate-time features (PC1: 42.5% and PC2: 22.8% explained variance) and revealed interaction among axes, footwear, and footstrike conditions (PC1: F _{(2.1, 40.1)} = 5.6, p = 0.007, η ² = 0.23; PC2: F _{(2.0, 38.4)} = 62.3, p < 0.001, η ² = 0.77). Rearfoot running in cushioned footwear attenuated impact loads in the vertical direction, and forefoot running in minimalist footwear attenuated impact loads in the anterior-posterior and medial-lateral directions relative to forefoot running in cushioned shoes. Loading patterns depend on footwear and footstrike interactions, which require shoes that match the runner's footstrike pattern.

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.

The effects of midfoot strike gait retraining on impact loading and joint stiffness

OBJECTIVE

To assess the biomechanical changes following a systematic gait retraining to modify footstrike patterns from rearfoot strike (RFS) to midfoot strike (MFS).

DESIGN

Pre-post interventional study. All participants underwent a gait retraining program designed to modify footstrike pattern to MFS.

SETTING

Research laboratory.

PARTICIPANTS

Twenty habitual RFS male runners participated.

MAIN OUTCOME MEASURES

Gait evaluations were conducted before and after the training. Footstrike pattern, vertical loading rates, ankle and knee joint stiffness were compared.

RESULTS

Participants' footstrike angle was reduced (p < 0.001, Cohen's d = 1.65) and knee joint stiffness was increased (p = 0.003, Cohen's d = 0.69). No significant difference was found in the vertical loading rates (p > 0.155). Further subgroup analyses were conducted on the respondents (n = 8, 40% of participants) who exhibited MFS for over 80% of their footfalls during the post-training evaluation. Apart from the increased knee joint stiffness (p = 0.005, Cohen's d = 1.14), respondents exhibited a significant reduction in the ankle joint stiffness (p = 0.019, Cohen's d = 1.17) when running with MFS.

CONCLUSIONS

Gait retraining to promote MFS was effective in reducing runners' footstrike angle, but only 40% of participants responded to this training program. The inconsistent training effect on impact loading suggests a need to develop new training protocols in an effort to prevent running injuries.

Reliability and minimum detectable change of measures of gait in children during walking and running on an instrumented treadmill

BACKGROUND

Instrumented treadmills that incorporate pressure platforms are increasingly used to characterize gait in children. Although footprint size is known to influence the measurement performance of pressure platforms, published evidence on the reliability of such systems for children's gait is lacking.

RESEARCH QUESTION

This study evaluated the test-retest reliability of temporospatial gait parameters and vertical ground reaction forces measured in healthy children during barefoot walking and running on a capacitance-based treadmill system.

METHODS

Temporospatial gait parameters, including cadence, stride length, stride duration, stance and swing phase durations and the magnitude and timing of conventional vertical ground reaction force peaks were determined on two occasions in 17 healthy children (mean age, 11 ± 2 years; height, 148.4 ± 9.3 cm; and mass, 43.3 ± 10 kg) during walking and running at preferred speed on an instrumented treadmill. Reliability was assessed using Intra Class Correlation Coefficients (ICC) and the standard error of measurement (SEM). The minimum detectable change (MDC95%) was also calculated.

RESULTS

ICC values ranged from 0.91-0.99 for all variables. When expressed as a percentage of the mean, the SEM was <5% for all gait parameters assessed during walking and running. The MDC95% values for gait parameters were typically higher during running than walking, and were ±4% of the gait cycle for temporal parameters, ±55 cm for stride length and ±0.1 bodyweights for peak vertical ground reaction force.

SIGNIFICANCE

Children's gait parameters varied by <5% between test occasions and were more consistent during walking than running. These findings provide clinicians and researchers with an index of the reliability and sensitivity of the treadmill to detect changes in common spatiotemporal gait parameters and vertical ground reaction forces in children.

Medial Gastrocnemius Muscle Activity during Single-Leg Hopping to Exhaustion

This study described changes in leg muscle activation characteristics during exhaustive single-leg hopping. Twenty-seven healthy men performed trials (132 hops/min) to exhaustion, without a target height, to a target height with visual feedback and target height with tactile feedback. Mean muscle activation amplitude of the medial gastrocnemius (MG) decreased during the anticipatory period while duration of MG activity was maintained when hopping to a target height and contrasted the changes during hopping without a target height. Changes to MG activity were specific to whether the hopping height had been maintained or not. Changes during the anticipatory period of MG activity, indicative of adaptation in descending motor pathways, implicate utility of a motor learning strategy to allow completion of an exhaustive task.

Real-Time Biofeedback of Performance to Reduce Braking Forces Associated With Running-Related Injury: An Exploratory Study

BACKGROUND

The high rate of running-related injury may be associated with increased peak braking forces (PBFs) and vertical loading rates. Gait retraining has been suggested by some experts to be an effective method to reduce loading parameters.

OBJECTIVES

To investigate whether PBF could be decreased following an 8-session gait retraining program among a group of female recreational runners and which self-selected kinematic strategies could achieve this decrease.

METHODS

In this exploratory study, 12 female recreational runners with high PBFs (greater than 0.27 body weight) completed an 8-session gait retraining program with real-time biofeedback of braking forces over the course of a half-marathon training program. Baseline and follow-up kinetics and kinematics were analyzed with a repeated-measures analysis of variance.

RESULTS

There was an average reduction of 15% in PBF (-0.04 body weight; 95% confidence interval [CI]: -0.07, -0.02 body weight; P = .001; effect size, 0.62), accompanied by a 7% increase in step frequency (11.3 steps per minute; 95% CI: 1.8, 20.9 steps per minute; P = .024; effect size, 0.38) and a 6% decrease in step length (-5.5 cm; 95% CI: -9.9, -1.0 cm; P = .020; effect size, 0.40), from baseline to follow-up.

CONCLUSION

The gait retraining program significantly reduced the PBF among a group of female recreational runners. This was achieved through a combination of increased step frequency and decreased step length. Furthermore, the modified gait pattern was incorporated into the runners' natural gait pattern by the completion of the program. Based on these results, the outlined gait retraining program should be further investigated to assess whether it may be an effective injury prevention strategy for recreational runners. This study was registered with ClinicalTrials.gov (NCT03302975).

LEVEL OF EVIDENCE

Prevention, level 4. J Orthop Sports Phys Ther 2019;49(3):136-144. Epub 7 Dec 2018. doi:10.2519/jospt.2019.8587.

Effects of Exercise-Induced Fatigue on Lower Extremity Joint Mechanics, Stiffness, and Energy Absorption during Landings

The aim of this study was to determine the effects of two fatigue protocols on lower-limb joint mechanics, stiffness and energy absorption during drop landings. Fifteen male athletes completed landing tasks before and after two fatigue protocols (constant speed running [R-FP] and repeated shuttle sprint plus vertical jump [SJ-FP]). Sagittal plane lower-limb kinematics and ground reaction forces were recorded. Compared with R-FP, SJ-FP required significantly less intervention time to produce a fatigue state. The ranges of motion (RoM) of the hip were significantly greater when the athletes were fatigued for both protocols. Knee RoM significantly increased after SJ-FP but not after R-FP (p > 0.05), whereas the RoM of the ankle was significantly greater after R-FP but lower after SJ-FP. When fatigued, the first peak knee extension moment was significantly greater in R-FP but lower in SJ-FP; the second peak ankle plantar flexion moment was lower, regardless of protocols. After fatigue, vertical, hip, and knee stiffness was lower, and more energy was absorbed at the hip and knee for both protocols. Hip and knee extensors played a crucial role in altering movement control strategies to maintain similar impact forces and to dissipate more energy through a flexed landing posture when fatigued compared to when non-fatigued. Furthermore, SJ-FP seems to be a more efficient method to induce fatigue due to less intervention time than R-FP.

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.