Touchdown Angle Research Articles

Spatiotemporal and kinematic adjustments in master runners may be associated with the relative physiological effort during running.

Master runners maintain a similar running economy to young runners, despite displaying biomechanical characteristics that are associated with a worse running economy. This apparent paradox may be explained by a greater physiological effort-i.e., percentage of maximal oxygen uptake (VO2-max)-that master runners perform at a given speed. Moreover, age-related responses to non-exhaustive sustained running are yet underexplored. The aims of this study were, therefore, to examine if biomechanical adjustments in master runners are physiological-effort dependent, and to explore the age-related biomechanical changes during a non-exhaustive sustained run. Young (23.9 ± 6; n = 12) and master (47.3 ± 6.9; n = 12) runners performed a sustained 30-minute treadmill run matched for relative physiological effort (70% VO2-max), while spatiotemporal and lower-limb kinematic characteristics were collected during the 1st and 30th minute. Group differences were observed in step/stride length, knee touch-down angle, and knee stiffness. However, both groups of runners had a similar step frequency, vertical center of mass oscillation, and knee range of motion. Age-related adjustment in these latter characteristics may thus not be an inevitable result of the aging process but rather a strategy to maintain running economy. The relative physiological effort of runners should, therefore, be considered when examining age-related adjustments in running biomechanics.

Effects of particle size and thickness of quartz sand on the webbed foot kinematics of mallard (Anas platyrhynchos).

The webbed foot structure of mallards (Anas platyrhynchos) exhibits effective anti-subsidence properties when walking on soft ground. To investigate the effects of quartz sand particle size and thickness on joint angles and the movement patterns of webbed feet, we created a testing substrate with quartz sand and utilized high-speed cameras and kinematic analysis tools for data acquisition. Mallards mainly adjusted the tarsometatarso-phalangeal joint (TMTPJ) during touch-down and lift-off stages in response to increasing particle size or enhanced ground roughness. Conversely, adjustments to the intertarsal joint (ITJ) predominantly took place during mid-stance. Conversely, mallards predominantly adjusted the ITJ during touch-down and lift-off when coping with increased quartz sand thickness, with TMTPJ adjustments mainly occurring at touch-down. As quartz sand particle size increased, the TMTPJ angle increased, the ITJ angle decreased, toe closure advanced, and the duty factor decreased throughout the entire stride cycle. In contrast, increasing quartz sand thickness led to more delayed TMTPJ adjustments, slower webbed foot closure, and an increased duty factor throughout the stride cycle. Mallards modify their leg posture to notably decrease the touch-down foot angle upon encountering sandy terrain. This action subsequently forms a depression beneath their feet, contributing to sand consolidation and limiting flow. During the stance phase, the mallard's weight is distributed across the webbed foot, generating minimal pressure and preventing significant subsidence while walking on sandy ground.

Validity of IMU measurements on running kinematics in non-rearfoot strike runners across different speeds

ABSTRACT This study aims to determine the validity of the lower extremity joint kinematics measured by inertial measurement units (IMUs) in non-rearfoot strike pattern (NRFS) runners across different speeds. Fifteen NRFS runners completed three 2-min running tests on a treadmill in random order at 8, 10 and 12 km/h, whilst data were synchronously collected using the IMU system and an optical motion capture system. Before the offset was corrected, the validity of the knee angle waveform was higher than that of the hip and ankle; after the offset was corrected, the validity increased in all three joints. The correlation between the touchdown angles in the sagittal plane measured by the two systems was relatively high after the offset was corrected. The running speed influenced the offset-corrected measurements, with higher error values at higher speeds. The IMU system was able to provide measurements of running kinematics in the sagittal plane of NRFS runners at different running speeds but was unable to reliably measure motion in the frontal and horizontal planes. Future research should analyse the 3D gait of NRFS runners under a larger range of speed conditions to provide evidentiary support for the use of IMUs in running analysis outside the laboratory.

Energy variations and periodic solutions in a switched inverted pendulum model of human running gaits

In the paper, we investigate the dynamics of a switched spring loaded inverted pendulum (SLIP) model of running. We first show how switching between two sets of differential equations, corresponding to two phases of running namely to the support and flight phase, lead to discontinuities in the system’s overall vector field. These discontinuities allow for the existence of asymptotically stable solutions in an otherwise conservative system. We then present a modification to the standard SLIP model by introducing an additional parameter ξ, which can be thought of as a parameter encapsulating energy dissipation and energy generation during running. Conditions for the existence of periodic running in the model, under small angle approximation and a constraint on the touch-down angle, are then given. A one-dimensional reduced mapping, which captures the system’s dynamics, is then introduced. A linearisation of this mapping, which includes discontinuity mappings, is obtained, which, in turn, allows to determine the stability of periodic solutions. Finally, a one-parameter orbit diagram in ξ parameter depicts numerically found stable asymmetric periodic solutions which terminate in the fold bifurcation.

Adaptive locomotion: Foot strike pattern and limb mechanical stiffness while running over an obstacle

Previous studies of level running suggest runners adjust foot strike to control leg stiffness. This study aimed to determine how runners adjusted mechanical stiffness and foot strike prior to, during, and after a drop in surface height. Ten healthy subjects (5 male, 5 female; 24.32 ± 5.0 years) were video recorded as they ran on an outdoor path with a single drop in surface height (12.5 cm). Foot strike was recorded, while subject velocity, duty factor (DF), normalized maximum ground reaction force (GRFbw), vertical hip displacement (Δy), leg compression (ΔL), vertical (Kvert) and leg stiffness (Kleg), touchdown (TD) and takeoff angle (TO), and flight (Tf) and contact time (Tc) were calculated. Compared to the step before the drop, Tf, GRFbw, Kvert, Kleg, and TO increased, while Tc, DF, Δy, ΔL, and TD decreased in the step after the drop. Across trials, runners had either consistent or variable foot strike patterns. Runners using a consistent pattern most often shifted from rear to fore-foot strike in the steps before and after the drop, while those with a variable pattern showed less dramatic shifts. All parameters, except TD, were significantly different (p < 0.04) based on foot strike pattern, and comparisons between steps before and after the drop (except TD) were significantly different (p < 0.004). Runners with a variable foot strike pattern experienced smaller shifts within mechanical parameters when traveling over the drop, suggesting these runners may be able to stabilize limb mechanics on interrupted surfaces.

3D-SLIP model based dynamic stability strategy for legged robots with impact disturbance rejection

Inspired by biomechanical studies, the spring-loaded inverted pendulum model is an effective behavior model to describe the running movement of animals and legged robots in the sagittal plane. However, when confronted with external lateral disturbances, the model has to move out of the 2-D plane and be extended to 3-D locomotion. With the degree of freedom increasing, the computational complexity is higher and the real-time control is more and more difficult, especially when considering the complex legged model. Here, we construct a control strategy based on the classical Raibert controller for legged locomotion under lateral impact disturbances. This strategy, named 3D-HFC, is composed of three core modules: touchdown angle control, body attitude angle control and energy compensation. The energy loss in each step is taken into consideration, and the real-time measured energy loss of the current step is adopted to predict that of the next step. We demonstrate the efficiency of the proposed control strategy on a simulated 3D-SLIP lower order model and a simulated running quadruped, which are perturbed by different impact forces. Furthermore, a quadruped bionic prototype named MBBOT was set up, on which lateral impact experiments were designed and implemented. Both simulation and experimental results show that the proposed approach can realize the impact disturbance rejection.

Tendon‐Driven Auxetic Tubular Springs for Resilient Hopping Robots

Compliance in jumping robots improves gait stability and enables energy‐efficient locomotion. Here, 3D printable auxetic tubular springs from thermoplastic polyurethane (TPU) for rapid and sustainable hopping are developed. Because the springs have negative Poisson's ratios, they become stiffer as compression proceeds and theoretically stores 35.2% more energy than a linear spring with the same stiffness. As the stress concentrates on the hinges, it is revealed through experimental, numerical, and analytical investigations that hinge geometries, for example, the lattice angle and hinge radius, governs the global stiffness and robustness of the springs. The hopping robot leg composed of three auxetic tubular springs in parallel sustains more than 1,000 cycles of repeated, one‐degree‐of‐freedom (1‐DOF) vertical hopping and two‐degree‐of‐freedom (2‐DOF) forward hopping. The 2.5 kg‐robot system requires minimum 420 mJ of elastic energy for repeated hopping. The springs are pre‐compressed by tendon‐driven actuators and stores 1.08 J during jumping and release the springs when touching the ground. The power stroke is calculated as 15–18 W. The average velocity of the hopping robot reaches 0.06 m s−1 with the increase of touchdown angle to 0.125 rad. The cost of transport is calculated as 6.7, similar to those of the living organisms.

Experimental and numerical study of shallow‐buried high‐density polyethylene pipeline under collapse touchdown impact

AbstractThe debris from structures produced during the blasting demolition of engineered buildings (structures) may fall near buried pipelines, which threaten the integrity of the buried gas pipeline. In this paper, the dynamic response of nearby shallow‐buried high‐density polyethylene (HDPE) gas pipelines under collapse impact loads was investigated. The stress‐strain curve and material parameters of the HDPE pipe were obtained through uniaxial tensile tests. The strain distribution of buried pipelines under collapse loading was obtained. Subsequently, a 3D nonlinear finite element (FE) model of a buried HDPE pipeline impacted by a collapsed body was established. Finally, the effects of the impact velocity, touchdown angle, touchdown mode, offset distance, and pavement structure on the mechanical behavior of buried HDPE pipelines were analyzed in detail. The results show that, as the touchdown velocity and angle of the collapsed body increase, the von Mises stress of the pipeline is significantly affected. The pipe section close to the center of the impact zone tends to be damaged due to the von Mises stress reaching the maximum tensile strength. The maximum von Mises stress of the pipeline that is impacted by the edge of the collapsed body is the smallest, but the buried pipeline undergoes the largest displacement. The rigidity of the overlying pavement structure has a significant impact on the reliability of the buried HDPE gas pipeline. The stress concentration areas of buried pipelines mainly appear on the top, bottom, and the arches of the pipeline.

Asymmetry in sprinting: An insight into sub-10 and sub-11 s men and women sprinters.

We assessed sprint mechanical asymmetry in world-class competitors and evaluated whether inter-limb sex-based differences in sprinting mechanics exist. The eight finalists in the men's and women's 100m events at the 2017 IAAF World Championships were studied. Five high-speed cameras (150Hz) were used to capture two consecutive steps of the whole body between 47.0m and 55.5m from the start, while four additional cameras (250Hz) focussed on the lower extremities. A total of 33 spatio-temporal, touchdown and toe-off joint angles, and horizontal and vertical foot velocity parameters were extracted through three-dimensional analysis. Group mean asymmetry scores were assessed using the symmetry angle (SA) where scores of 0% and 100% represent perfect symmetry and perfect asymmetry, respectively. Although considered generally low (SA <3% for 22 out of 33 parameters), the magnitude of mechanical asymmetry varied widely between sprinters of the same sex. However, there was no mean SA scores difference between men and women for any stride mechanical parameters (all p≥0.064). Asymmetry scores were inconsistent between parameters and phases (touchdown vs toe-off instants), and sprinting mechanics were generally not related to asymmetry magnitudes. In summary, low to moderate asymmetry is a natural phenomenon in elite sprinting. Asymmetry was inconsistent between parameters and competitors during near maximum velocity running, yet mean values for a given parameter generally did not differ between sexes. Sprinters' performances were not related to their SA scores.

Kinematic determinants of acceleration in skeleton push phase

ABSTRACT This study aimed to characterise the push phase kinematics in skeleton sport and explore the relationship between kinematic indicators and push performance. Nine male Chinese skeleton athletes performed three 15-metre pushes on an indoor simulated push track. Kinematic data were recorded with a 3-dimensional motion system (VICON; UK) consisting of 14 cameras sampling at a rate of 200 Hz. The linear relationships between the kinematic indicators and push performance were determined by Pearson correlation analysis. Statistical significance was set at p ≤ 0.05. Step velocity (SV), step length (SL), toe-off distance (TOD), and toe-off angle (TOA) were significantly different between the inside and outside foot in the first four steps. Positively significant correlations were found between touchdown distance (TD), touchdown angle (TA), and SV in step 1 (r = 0.696; r = 0.682), and negative correlations were found between contact time (CT), TOA, and SV in step 1 and step 4, respectively (r = −0.839; r = −0.763). Effective acceleration was achieved by shortening contact, increasing TA and TD in the first step, and maintaining a relatively small TOA and a relatively long TOD in the steps 2 to 4.

Improving spring-mass parameter estimation in running using nonlinear regression methods.

Runners are commonly modeled as spring-mass systems, but the traditional calculations of these models rely on discrete observations during the gait cycle (e.g. maximal vertical force) and simplifying assumptions (e.g. leg length), challenging the predicative capacity and generalizability of observations. We present a method to model runners as spring-mass systems using nonlinear regression (NLR) and the full vertical ground reaction force (vGRF) time series without additional inputs and fewer traditional parameter assumptions. We derived and validated a time-dependent vGRF function characterized by four spring-mass parameters - stiffness, touchdown angle, leg length and contact time - using a sinusoidal approximation. Next, we compared the NLR-estimated spring-mass parameters with traditional calculations in runners. The mixed-effect NLR method (ME NLR) modeled the observed vGRF best (RMSE:155N) compared with a conventional sinusoid approximation (RMSE: 230N). Against the conventional methods, its estimations provided similar stiffness approximations (-0.2±0.6 kN m-1) with moderately steeper angles (1.2±0.7deg), longer legs (+4.2±2.3 cm) and shorter effective contact times (-12±4 ms). Together, these vGRF-driven system parameters more closely approximated the observed vertical impulses (observed: 214.8Ns; ME NLR: 209.0Ns; traditional: 223.6Ns). Finally, we generated spring-mass simulations from traditional and ME NLR parameter estimates to assess the predicative capacity of each method to model stable running systems. In 6/7 subjects, ME NLR parameters generated models that ran with equal or greater stability than traditional estimates. ME NLR modeling of the vGRF in running is therefore a useful tool to assess runners holistically as spring-mass systems with fewer measurement sources or anthropometric assumptions. Furthermore, its utility as statistical framework lends itself to more complex mixed-effects modeling to explore research questions in running.

DYNAMIC MODELLING FOR THE SECOND FLIGHT PHASE OF THE YURCHENKO LAYOUT VAULT BASED ON MSC. ADAMS

Gymnasts attempt to increase the angles of rotation about transversal and longitudinal axes during the post-flight of vaulting, and these angles are related to different mechanical properties. The present study uses a 3D angle-driven computer simulation model of a gymnast who performs Yurchenko layout vault using ADAMS software. Simulation initial conditions are horizontal and vertical velocities of gymnast’s pelvis center and angular velocities about the transversal and longitudinal axes which can be easily measured. The initial linear and angular velocity conditions of the simulation model are each changed in certain increments from measurement data collected from an elite woman gymnast. Increasing initial horizontal velocity results in an increased horizontal flight distance, but has no connection with the duration of flight and angle of twists. The overall angle of twists is concerned with initial vertical velocity and angular velocities about the transversal and longitudinal axes. Also, increasing initial vertical velocity and angular velocity about transverse axis leads to increase in touchdown angle between ground’s horizontal axis and gymnast’s longitudinal axis.&#x0D;

Precision Robotic Leaping and Landing Using Stance-Phase Balance

Prior work has addressed control of continuous jumping using touchdown angle from flight, but greater precision can be obtained by directing individual leaps using liftoff angle from stance. We demonstrate targeted leaping as well as balanced landing on a narrow foot with a small, single leg hopping robot, Salto-1P. Accurate and reliable leaping and landing are achieved by the combination of stance-phase balance control based on angular momentum, a launch trajectory that stabilizes the robot at a desired launch angle, and an approximate expression for selecting touchdown angle before landing. Dynamic transitions between standing, hopping, and standing again are now possible in a robot with a narrow foot. We also present approximate bounds on acceptable velocity estimate and angle errors beyond which balanced landing is infeasible. Compared to a prior Spring Loaded Inverted Pendulum (SLIP)-like gait, the jump distance standard deviation is reduced from 9.2 cm to 1.6 cm for particular jumps, now enabling precise jumps to narrow targets.

Validity and reliability of a smartphone motion analysis app for lower limb kinematics during treadmill running

ObjectiveTo investigate the validity and reliability of a smartphone application for selected lower-limb kinematics during treadmill running. DesignValidity and reliability study. SettingBiomechanics laboratory. ParticipantsTwenty healthy female runners. Main outcome measure(s)Sagittal-plane hip, knee, and ankle angle and rearfoot eversion were assessed using the Coach’s Eye Smartphone application and a 3D motion capture system. Paired t-test and intraclass correlation coefficients (ICC) established criterion validity of Coach’s Eye; ICC determined test-retest and intrarater/interrater reliability. Standard error of measurement (SEM) and minimal detectable change (MDC) were also reported. ResultsSignificant differences were found between Coach’s Eye and 3D measurements for ankle angle at touchdown and knee angle at toe-off (p < 0.05). ICCs for validity of Coach’s Eye were excellent for rearfoot eversion at touchdown (ICC = 0.79) and fair-to-good for the other kinematics (range 0.51–0.74), except for hip at touchdown, which was poor (ICC = 0.36). Test-retest (range 0.80–0.92), intrarater (range 0.95–0.99) and interrater (range 0.87–0.94) ICC results were excellent for all selected kinematics. ConclusionCoach’s Eye can be used as a surrogate for 3D measures of knee and rearfoot in/eversion at touchdown, and hip, ankle, and rearfoot in/eversion at toe-off, but not for hip and ankle at touchdown or knee at toe-off. Reliable running kinematics were obtained using Coach’s Eye, making it suitable for repeated measures.

Altered forefoot function following a military training activity

BackgroundInjury rates are high in populations that regularly undertake weight-bearing physical activity, particularly military populations. Military training activities, that often include load carriage, have been associated with lower limb injury occurrence, specifically stress fractures. Research questionRecent work identified plantar loading variables as risk factors for lower limb stress fractures in Royal Marines recruits that were assessed during barefoot running. This study aimed to quantify how those plantar loading variables changed in Royal Marines recruits following a prolonged military load carriage activity, to further understand potential mechanisms for lower limb stress fractures. MethodsBilateral, synchronised plantar pressure and lower limb kinematic data were recorded during barefoot running at 3.6 m s−1 (±5%) pre- and post- a 12.8-km training activity (∼150 min). The training activity was completed with an average speed typical of walking (1.4 m.s-1), and 35.5 kg of additional load was carried throughout. Data were collected from 32 male Royal Marines recruits who completed the training activity in week-21 of the 32-week training programme. Plantar pressure variables and ankle dorsiflexion were compared between pre- and post-activity. ResultsPost-activity there was reduced loading under the forefoot and increased loading under the rearfoot and midfoot. There was no change in dorsiflexion touchdown angle, but an increase in peak dorsiflexion and range of motion post-activity. SignificanceThe increased rearfoot loading, reduced forefoot loading and increased ankle dorsiflexion following a prolonged military load carriage activity suggest a reduced transfer of loading from the rearfoot to the forefoot during stance, which may have implications for the development of stress fractures, particularly of the metatarsals.

A Detailed Look at the SLIP Model Dynamics: Bifurcations, Chaotic Behavior, and Fractal Basins of Attraction

This paper provides a comprehensive numerical analysis of a simple 2D model of running, the spring-loaded inverted pendulum (SLIP). The model consists of a point-mass attached to a massless spring leg; the leg angle at touch-down is fixed during the motion. We employ numerical continuation methods combined with extensive simulations to find all periodic motions of this model, determine their stability, and compute the basins of attraction of the stable solutions. The result is a detailed and complete analysis of all possible SLIP model behavior, which expands upon and unifies a range of prior studies. In particular, we demonstrate and explain the following effects: (i) saddle-node bifurcations, which lead to two distinct solution families for a range of energies and touch-down angles; (ii) period-doubling (PD) bifurcations which lead to chaotic behavior of the model; and (iii) fractal structures within the basins of attraction. In contrast to prior work, these effects are found in a single model with a single set of parameters while taking into account the full nonlinear dynamics of the SLIP model.

Passive Dynamic Bounding Control using Symmetry Condition Control Laws

Legged locomotion is preferred over the wheeled locomotion as it can be used both for flat and rough terrains. Quadruped robots are preferred since they can offer better stability with considerable reliability. In recent years, passive dynamics has been used to obtain near zero-energy bounding gaits. Although theoretically such gaits consume no energy, in practice some additional energy is required to overcome losses. Existence and stability of such gaits have been thoroughly studied in literature for quadruped models with the assumption that the mass distribution and stiffness in the front and back legs are symmetric. Fixed points found using Poincare map indicate touchdown angle-liftoff angle symmetry between front and back legs. This property can be used to search for fixed points with ease. However, the range of initial conditions where the bounding gait is stable is highly limited. Control laws based on symmetry conditions observed are proposed in this paper to improve the stability region. One such control law based on body-fixed touchdown angles theoretically allows redesign of quadruped robot with physical cross coupling between legs to achieve inherent stability without leg actuation.

A Torque-actuated dissipative spring loaded inverted pendulum model with rolling contact and Its application to hexapod running

We report on the development and analysis of a new torque-actuated dissipative spring loaded inverted pendulum model with rolling contact (TDR-SLIP), which is a successor to the previously developed spring loaded inverted pendulum model with rolling contact (R-SLIP) model. The stability properties of the models were analyzed numerically via steps-to-fall analysis and return map analysis, wherein the dimensionless parameters are varied to analyze their effects on the dynamic performance of the model, including torque, damping constant, spring constant, touchdown angle, touchdown speed, and landing angle. Because the involvement of torque and damping in the TDR-SLIP model is similar to other recently developed torque-actuated dissipative spring loaded inverted pendulum studies, their performance was compared so that the unique features of the TDR-SLIP model, such as rolling contact, could be investigated. To undertake the comparison, a method for yielding parameter equivalency between these two models is also reported. In addition to its analytical role, the TDR-SLIP model served as a template to initiate the stable running behavior of the empirical robot acted as the anchor. Two sets of legs were evaluated—the original compliant half-circular leg of the robot and the new mechanical legs, which resemble the morphology of the TDR-SLIP model. Two types of control strategies were tested—position-based control and hybrid control. The experimental results reveals that the low-damped compliant half-circular leg and the mechanical leg match the behaviors of the R-SLIP model and the TDR-SLIP model, respectively, and the robot with hybrid control performs more stably and more closely to the model profile. In addition, when the robot’s motion follows the template’s stable dynamics, the energy cost of the leg in stance can be significantly lower than that in flight.

Dynamic elastic response prostheses alter approach angles and ground reaction forces but not leg stiffness during a start-stop task

In a dynamic elastic response prosthesis (DERP), spring-like properties aim to replace the loss of musculature and soft tissues and optimise dynamic movement biomechanics, yet higher intact limb (IL) loading exists. It is unknown how amputees wearing a DERP will perform in start-stop movements and how altering the prosthetic stiffness will influence the performance and loading. This study assessed movement dynamics through comparisons in spatiotemporal, kinematic and kinetic variables and leg stiffness of intact, prosthetic and control limbs. The effect of prosthetic stiffness on movement dynamics was also determined. Eleven male unilateral transtibial amputees performed a start-stop task with one DERP set at two different stiffness – Prescribed and Stiffer. Eleven control participants performed the movement with the dominant limb. Kinematic and kinetic data were collected by a twelve-camera motion capture system synchronised with a Kistler force platform. Selected variables were compared between intact, prosthetic and control limbs, and against prosthetic stiffness using ANOVA and effect size. Pearson’s Correlation was used to analyse relationship between leg stiffness and prosthetic deflection. Amputees showed a more horizontal approach to the bound during the start-stop movement, with lower horizontal velocities and a longer stance time on the IL compared to controls. In both stiffness conditions, the IL showed selected higher anteroposterior and vertical forces and impulses when compared to the controls. Leg stiffness was not significantly different between limbs as a result of the interplay between angle swept and magnitude of force, even with the change in prosthetic stiffness. A main effect for prosthetic stiffness was found only in higher impact forces of the prosthetic limb and more horizontal touchdown angles of the IL when using the prescribed DERP. In conclusion, amputees achieve the movement with a horizontal approach when compared to controls which may reflect difficulty of movement initiation with a DERP and a difficulty in performing the movement dynamically. The forces and impulses of the IL were high compared to control limbs. The consistent leg stiffness implies compensation strategies through other joints.

Running Technique is an Important Component of Running Economy and Performance.

ABSTRACTDespite an intuitive relationship between technique and both running economy (RE) and performance, and the diverse techniques used by runners to achieve forward locomotion, the objective importance of overall technique and the key components therein remain to be elucidated.PurposeThis study aimed to determine the relationship between individual and combined kinematic measures of technique with both RE and performance.MethodsNinety-seven endurance runners (47 females) of diverse competitive standards performed a discontinuous protocol of incremental treadmill running (4-min stages, 1-km·h−1 increments). Measurements included three-dimensional full-body kinematics, respiratory gases to determine energy cost, and velocity of lactate turn point. Five categories of kinematic measures (vertical oscillation, braking, posture, stride parameters, and lower limb angles) and locomotory energy cost (LEc) were averaged across 10–12 km·h−1 (the highest common velocity < velocity of lactate turn point). Performance was measured as season's best (SB) time converted to a sex-specific z-score.ResultsNumerous kinematic variables were correlated with RE and performance (LEc, 19 variables; SB time, 11 variables). Regression analysis found three variables (pelvis vertical oscillation during ground contact normalized to height, minimum knee joint angle during ground contact, and minimum horizontal pelvis velocity) explained 39% of LEc variability. In addition, four variables (minimum horizontal pelvis velocity, shank touchdown angle, duty factor, and trunk forward lean) combined to explain 31% of the variability in performance (SB time).ConclusionsThis study provides novel and robust evidence that technique explains a substantial proportion of the variance in RE and performance. We recommend that runners and coaches are attentive to specific aspects of stride parameters and lower limb angles in part to optimize pelvis movement, and ultimately enhance performance.