The effect of footwear and footfall pattern on running stride interval long-range correlations and distributional variability

The presence of long-range correlations (self-similarity) in the stride-to-stride fluctuations in running stride interval has been used as an indicator of a healthy adaptable system. Changes to footfall patterns when running with minimalist shoes could cause a less adaptable running gait. The purpose of this study was to investigate stride interval variability and the degree of self-similarity of stride interval in runners wearing minimalist and conventional footwear. Twenty-six trained habitual rearfoot footfall runners, unaccustomed to running in minimalist footwear, performed 6-min sub-maximal treadmill running bouts at 11, 13 and 15 km·h⁻¹ in minimalist and conventional shoes. Force sensitive resistors were placed in the shoes to quantify stride interval (time between successive foot contacts). Footfall position, stride interval mean and coefficient of variation (CV), were used to assess performance as a function of shoe type. Long-range correlations of stride interval were assessed using detrended fluctuation analysis (α). Mean stride interval was 1-1.3% shorter (P = 0.02) and 27% of runners adopted a midfoot footfall (MFF) in the minimalist shoe. There was a significant shoe effect on α and shoe*speed*footfall interaction effect on CV (P < 0.05). Runners that adopted a MFF in minimalist shoes, displayed reduced long-range correlations (P < 0.05) and CV (P < 0.06) in their running stride interval at the 15 km·h⁻¹ speed. The reduced variability and self-similarity observed for runners that changed to a MFF in the minimalist shoe may be suggestive of a system that is less flexible and more prone to injury.     

The influence of shoe aging on children running biomechanics

Athletic children are prone to overuse injuries, especially at the heel and knee. Since footwear is an extrinsic factor of lower limb injury risk, the aim of this study was to assess the influence of shoe aging on children running biomechanics. Fourteen children active in sports participated in a laboratory biomechanical evaluation. A new pair of shoes was provided to each participant at an inclusion visit. Four months later, the participants performed a running task and their kinematics and kinetics were assessed both with their used shoes and with a new pair of shoes identical to the first. Furthermore, mechanical cushioning properties of shoes were evaluated before and after in-vivo aging. After 4 months of use, the sole stiffness increased by 16% and the energy loss capacity decreased by 18% (p < 0.001). No ankle or knee kinematic adjustment was found at foot strike in used shoes but changes were observed later during stance. Running with used shoes produced a higher loading rate of the vertical ground reaction force (+23%, p = 0.016), suggesting higher compressive forces under the heel and placing children at risk to experience impact-related injuries. Nevertheless, the decreased peak ankle and knee power absorption in used shoes (−11%, p = 0.010 and −12%, p = 0.029, respectively) suggests a lower ankle and knee joints loading during the absorption phase that may be beneficial regarding stretch-related injuries.     

Biomechanics of slow running and walking with a rocker shoe

Evidence suggests a link between the loading of the Achilles tendon and the magnitude of the ankle internal plantar flexion moment during late stance of gait, which is clinically relevant in the management of Achilles tendinopathy. Some studies showed that rocker shoes can reduce the ankle internal plantar flexion moment. However, the existing evidence is not conclusive and focused on walking and scarce in running. Sixteen healthy runners participated in this study. Lower extremity kinetics, kinematics and electromyographic (EMG) signals of triceps surae and tibialis anterior were quantified for two types of shoes during running and walking. The peak ankle plantar flexion moment was reduced significantly in late stance of running (0.27 Nm/kg; p < 0.001) and walking (0.24 Nm/kg; p < 0.001) with the rocker shoe compared to standard shoe. The ankle power generation and plantar flexion moment impulse were also reduced significantly when running and walking with the rocker shoe (p < 0.001). No significant changes in the knee and hip moments were found in running and walking. A significant delay of the EMG peak, approximately 2% (p < 0.001), was present in the triceps surae when walking with rocker shoes. There were no significant changes in the EMG peak amplitude of triceps surae in running and walking. The peak amplitude of tibialis anterior was significantly increased (64.7 μV, p < 0.001) when walking with rocker shoes. The findings show that rocker shoes reduce the ankle plantar flexion moment during the late stance phase of running and walking in healthy people.     

Is midsole thickness a key parameter for the running pattern?

Many studies have highlighted differences in foot strike pattern comparing habitually shod runners who ran barefoot and with running shoes. Barefoot running results in a flatter foot landing and in a decreased vertical ground reaction force compared to shod running. The aim of this study was to investigate one possible parameter influencing running pattern: the midsole thickness. Fifteen participants ran overground at 3.3 m s⁻¹ barefoot and with five shoes of different midsole thickness (0 mm, 2 mm, 4 mm, 8 mm, 16 mm) with no difference of height between rearfoot and forefoot. Impact magnitude was evaluated using transient peak of vertical ground reaction force, loading rate, tibial acceleration peak and rate. Hip, knee and ankle flexion angles were computed at touch-down and during stance phase (range of motion and maximum values). External net joint moments and stiffness for hip, knee and ankle joints were also observed as well as global leg stiffness. No significant effect of midsole thickness was observed on ground reaction force and tibial acceleration. However, the contact time increased with midsole thickness. Barefoot running compared to shod running induced ankle in plantar flexion at touch-down, higher ankle dorsiflexion and lower knee flexion during stance phase. These adjustments are suspected to explain the absence of difference on ground reaction force and tibial acceleration. This study showed that the presence of very thin footwear upper and sole was sufficient to significantly influence the running pattern.     

Effect of shoe type on plantar pressure: A gender comparison

Despite the differences in materials, racing flats have begun to be used not only for racing, but also for daily training. As there are data suggesting a gender difference in overuse injuries in runners, shoe choice may affect loading patterns during running. The purpose was to determine differences in plantar pressure between genders when running in training shoes and racing flats. In-shoe plantar pressure data were collected from 34 subjects (17m, 17f) who ran over-ground in both a racing flat and training shoe. Contact area (CA), maximum force (MF), and contact time under the entire foot and beneath eight foot regions were collected. Each variable was analyzed using a shoe by gender repeated measures ANOVA (α = 0.05). In men, MF was increased in the racing flats (p = 0.016) beneath the medial midfoot (MMF), yet was increased beneath the medial forefoot (MFF) in the training shoe (p = 0.018). Independent of gender, CA was decreased in the racing flats beneath the entire foot (p = 0.029), the MMF (p = 0.013), and the MFF (p = 0.030), and increased beneath the lateral forefoot (LFF) (p = 0.023). In the racing flats, MF was increased beneath the entire foot (p < 0.001) and the LFF (p < 0.001). Independent of the shoe, CA was decreased in men beneath the MFF (p = 0.007) and middle forefoot (p < 0.001), while MF was increased in the LFF (p = 0.002). The LFF is an area of increased stress fracture risk in men. Based on the gender differences in loading, running shoe design should be gender specific in an attempt to prevent injuries.     

How do elite endurance runners alter movements of the spine and pelvis as running speed increases?

Elite endurance runners are characterised by their performance ability and higher running economy. However, there is relatively little research aimed at identifying the biomechanical characteristics of this group. This study aimed to understand how motions of the pelvis, lumbar spine and thorax change with speed in a cohort of elite endurance runners (n = 14) and a cohort of recreational runners (n = 14). Kinematic data were collected during over ground running at four speeds ranging from 3.3 to 5.6 m s⁻¹ and a linear mixed model used to understand the effect of speed on both range of motion and mean sagittal inclination. The results showed the two groups to exhibit similar changes in range of motion as speed was increased, with the most pronounced increases being observed in the transverse plane. However, the adaptation of thorax inclination with speed differed between the two groups. Whereas the recreational runners increased thorax inclination as running speed was increased, elite endurance runners consistently maintained a more upright thorax position. This is the first study to identify specific differences in upper body motions between recreational and elite runners and the findings may have implications for training protocols aimed at improving running performance.     

Effect of foot orthoses on magnitude and timing of rearfoot and tibial motions,ground reaction force and knee moment during running

Changes in magnitude and timing of rearfoot eversion and tibial internal rotation by foot orthoses and their contributions to vertical ground reaction force and knee joint moments are not well understood. The objectives of this study were to test if orthoses modify the magnitude and time to peak rearfoot eversion, tibial internal rotation, active ground reaction force and knee adduction moment and determine if rearfoot eversion, tibial internal rotation magnitudes are correlated to peak active ground reaction force and knee adduction moment during the first 60% stance phase of running. Eleven healthy men ran at 170 steps per minute in shod and with foot orthoses conditions. Video and force-plate data were collected simultaneously to calculate foot joint angular displacement, ground reaction forces and knee adduction moments. Results showed that wearing semi-rigid foot orthoses significantly reduced rearfoot eversion 40% (4.1°; p = 0.001) and peak active ground reaction force 6% (0.96 N/kg; p = 0.008). No significant time differences occurred among the peak rearfoot eversion, tibial internal rotation and peak active ground reaction force in both conditions. A positive and significant correlation was observed between peak knee adduction moment and the magnitude of rearfoot eversion during shod (r = 0.59; p = 0.04) and shod/orthoses running (r = 0.65; p = 0.02). In conclusion, foot orthoses could reduce rearfoot eversion so that this can be associated with a reduction of knee adduction moment during the first 60% stance phase of running. Finding implies that modifying rearfoot and tibial motions during running could not be related to a reduction of the ground reaction force.     

Effects of footwear on treadmill running biomechanics in preadolescent children

While recent research debates the topic of natural running in adolescents and adults, little is known about the influence of footwear on running patterns in children. The purpose of this study was to compare shod and barefoot running gait biomechanics in preadolescent children. Kinematic and ground reaction force data of 36 normally developed children aged 6–9 years were collected during running on an instrumented treadmill. Running conditions were randomized for each child in order to compare barefoot running with two different shod conditions: a cushioned and a minimalistic running shoe. Primary outcome was the ankle angle at foot strike. Secondary outcomes were knee angle, maximum and impact ground reaction forces, presence of rear-foot strike, step width, step length and cadence. Ankle angle at foot strike differed with statistical significance (p < 0.001) between conditions. Running barefoot reduced the ankle angle at foot strike by 5.97° [95% CI, 4.19; 7.75] for 8 km h⁻¹ and 6.18° [95% CI, 4.38; 7.97] for 10 km h⁻¹ compared to the cushioned shoe condition. Compared to the minimalistic shoe condition, running barefoot reduced the angle by 1.94° [95% CI, 0.19°; 3.69°] for 8 km h⁻¹ and 1.38° [95% CI, −3.14°; 0.39°] for 10 km h⁻¹. Additionally, using footwear significantly increased maximum and impact ground reaction forces, step length, step width and rate of rear-foot strike. In conclusion, preadolescent running biomechanics are influenced by footwear, especially by cushioned running shoes. Health professionals and parents should keep this in mind when considering footwear for children.     

In-shoe plantar pressure distribution during running on natural grass and asphalt in recreational runners

The type of surface used for running can influence the load that the locomotor apparatus will absorb and the load distribution could be related to the incidence of chronic injuries. As there is no consensus on how the locomotor apparatus adapts to loads originating from running surfaces with different compliance, the objective of this study was to investigate how loads are distributed over the plantar surface while running on natural grass and on a rigid surface—asphalt. Forty-four adult runners with 4 ± 3 years of running experience were evaluated while running at 12 km/h for 40 m wearing standardised running shoes and Pedar insoles (Novel). Peak pressure, contact time and contact area were measured in six regions: lateral, central and medial rearfoot, midfoot, lateral and medial forefoot. The surfaces and regions were compared by three ANOVAS (2 × 6). Asphalt and natural grass were statistically different in all variables. Higher peak pressures were observed on asphalt at the central (p < 0.001) [grass: 303.8(66.7) kPa; asphalt: 342.3(76.3) kPa] and lateral rearfoot (p < 0.001) [grass: 312.7(75.8) kPa; asphalt: 350.9(98.3) kPa] and lateral forefoot (p < 0.001) [grass: 221.5(42.9) kPa; asphalt: 245.3(55.5) kPa]. For natural grass, contact time and contact area were significantly greater at the central rearfoot (p < 0.001). These results suggest that natural grass may be a surface that provokes lighter loads on the rearfoot and forefoot in recreational runners.     

Motion analysis of axial rotation and gait stability during turning in people with Parkinson's disease

BackgroundAxial rigidity and postural instability in people with Parkinson's disease (PD) may contribute to turning difficulty. This study examined the rotation of axial segments and gait instability during turning in people with PD.MethodsThirteen PD and twelve age-matched healthy adults were recruited. Participants performed the timed Up-and-Go test and were recorded by a 3D motion capture system. Axial rotation was evaluated by the rotation onset of the head, thorax and pelvis. Gait stability was evaluated by the center of mass and center of pressure inclination angle. Turning performance was evaluated by turning time and turning steps.ResultsDuring turning, PD adults rotated the head, thorax and pelvis simultaneously, whereas healthy adults rotated in a cranial to caudal sequence. Further, PD adults had a smaller sagittal inclination angle (p < 0.001) but larger frontal inclination angle (p = 0.006) than healthy adults. PD adults also turned slower (p = 0.002) with a greater number of steps (p < 0.001) than healthy adults. Last, PD adults showed a significant correlation between the sagittal inclination angle and turning steps (Spearman's ρ = −0.63), while healthy adults showed a significant correlation between frontal inclination angle and turning steps (Spearman's ρ = −0.67).ConclusionThis study demonstrated the axial rigidity in PD adults during turning may reduce forward progression and increase lateral instability. The reduced progression is associated with extra turning steps and the increased lateral instability may result in great fall risk.     

Do novice runners have weak hips and bad running form?

First, we sought to better understand the predisposition of novice female runners to injury by identifying potential differences in running mechanics and strength between experienced female runners and active novice runners. Secondly, we aimed to assess the relationship between hip and trunk strength with non-sagittal hip kinematics during running. Two female populations were recruited: 19 healthy experienced runners and 19 healthy active novice runners. Strength measurements of the hip abductors and external rotators were measured using a hand held dynamometer while trunk endurance was assessed via a side-plank. Next, an instrumented gait analysis was performed while each participant ran at 3.3 m/s. Group comparisons were made using an independent t-test to identify differences in the impact peak, loading rate, peak non-sagittal hip joint angles, trunk endurance, and hip strength. Pearson's correlation coefficients were calculated between hip kinematics and strength measurements. There were no statistically significant differences in impact peak, loading rate, peak non-sagittal hip kinematics, or strength. However, the novice runners did show a clinically meaningful trend toward increased peak hip internal rotation by 3.8° (effect size 0.520). A decrease in trunk side-plank endurance was associated with an increased peak hip internal rotation angle (r = −0.357, p = 0.03), whereas isometric strength was not related to kinematics. Programs aiming to prevent injuries in novice runners should target trunk performance and possibly hip neuromuscular control, rather than hip strength.     

Body borne loads impact walk-to-run and running biomechanics

The purpose of this study was to perform a biomechanics-based assessment of body borne load during the walk-to-run transition and steady-state running because historical research has limited load carriage assessment to prolonged walking. Fifteen male military personnel had trunk and lower limb biomechanics examined during these locomotor tasks with three different load configurations (light, ∼6 kg, medium, ∼20 kg, and heavy, ∼40 kg). Subject-based means of the dependent variables were submitted to repeated measures ANOVA to test the effects of load configuration. During the walk-to-run transition, the hip decreased (P = 0.001) and knee increased (P = 0.004) their contribution to joint power with the addition of load. Additionally, greater peak trunk (P = 0.001), hip (P = 0.001), and knee flexion (P < 0.001) moments and trunk flexion (P < 0.001) angle, and reduced hip (P = 0.001) and knee flexion (P = 0.001) posture were evident during the loaded walk-to-run transition. Body borne load had no significant effect (P > 0.05) on distribution of lower limb joint power during steady-state running, but increased peak trunk (P < 0.001), hip (P = 0.001), and knee (P = 0.001) flexion moments, and trunk flexion (P < 0.001) posture were evident. During the walk-to-run transition the load carrier may move joint power production distally down the kinetic chain and adopt biomechanical profiles to maintain performance of the task. The load carrier, however, may not adopt lower limb kinematic adaptations necessary to shift joint power distribution during steady-state running, despite exhibiting potentially detrimental larger lower limb joint loads. As such, further study appears needed to determine how load carriage impairs maximal locomotor performance.     

Running mechanics adjustments to perceptually-regulated interval runs in hypoxia and normoxia

ObjectivesWe determined whether perceptually-regulated, high-intensity intermittent runs in hypoxia and normoxia induce similar running mechanics adjustments within and between intervals.DesignWithin-participants repeated measures.MethodsNineteen trained runners completed a high-intensity intermittent running protocol (4 × 4-min intervals at a perceived rating exertion of 16 on the 6–20 Borg scale, 3-min passive recoveries) in either hypoxic (FiO₂ = 0.15) or normoxic (FiO₂ = 0.21) conditions. Running mechanics were collected over 10 consecutive steps, at constant velocity (∼15.0 ± 2.0 km.h⁻¹), at the beginning and the end of each 4-min interval. Repeated measure ANOVA were used to assess within intervals (onset vs. end of each interval), between intervals (interval 1, 2, 3 vs. 4) and FiO₂ (0.15 vs. 0.21) main effects and any potential interaction.ResultsParticipants progressively reduced running velocity from interval 1–4, and more so in hypoxia compared to normoxia for intervals 2, 3 and 4 (P < 0.01). There were no between intervals (across all intervals P > 0.298) and FiO₂ (across all intervals P > 0.082) main effects or any significant between intervals × within intervals × FiO₂ interactions (all P > 0.098) for any running mechanics variables. Irrespective of interval number or FiO₂, peak loading rate (+10.6 ± 7.7%; P < 0.001) and duration of push-off phase (+2.0 ± 3.1%; P = 0.001) increased from the onset to the end of 4-min intervals, whereas peak push-off force decreased (−4.0 ± 4.0%; P < 0.001).ConclusionsWhen carrying out perceptually-regulated interval treadmill runs, runners adjust to progressively slower velocities in hypoxia compared to normoxia. However, only subtle constant-velocity modifications of their mechanical behaviour occurred within each set, independently of FiO₂ or interval number.     

Biomechanical strategies implemented to compensate for mild leg length discrepancy during gait

Although mild leg length discrepancy is related to lower limb injuries, there is no consensus regarding its effects on the biomechanics of the lower limbs during gait. Biomechanical data of 19 healthy participants were collected while they walked under different conditions as described: (1) control condition—wearing flat thick sandals; (2) short limb condition—wearing a flat thick sandal on the left and a flat thin sandal on the right foot; (3) long limb condition: wearing flat thin sandal on the left and flat thick sandal on the right foot. The thick and thin sandals had 1.45 cm of mean thickness difference. The right lower limb data were analyzed for all conditions. Ankle, knee, hip and pelvis kinematics and internal moments were measured with a motion capture system and six force platforms. Principal component analysis was used to compare differences between conditions. The scores of the principal components were compared between conditions using one-way repeated measures ANOVA. Twelve gait variables were different between conditions: rearfoot dorsiflexion and inversion (p < 0.001); ankle dorsiflexion and inversion moments (p < 0.001); knee flexion angle and moment (p < 0.001); knee adduction moment (p < 0.001); hip flexion angle and moment (p < 0.001); hip adduction angle (p = 0.001) and moment (p = 0.022); and pelvic ipsilateral drop (p < 0.001). Mild leg length discrepancy caused compensatory changes during gait, apparently to equalize the functional length of the lower limbs. However, these strategies did not fully succeed, since both short and long limb conditions affected pelvic motion in the frontal plane. These results suggest that mild leg length discrepancy should not be overlooked in clinical settings.     

The effect of pain on hip and knee kinematics during running in females with chronic patellofemoral pain

PurposeDespite the growing recognition of the role of abnormal hip and knee mechanics in patellofemoral pain (PFP), few studies have assessed if or how these mechanics change when the person experiences pain while running. Therefore, the purpose of this study was to determine if the development of pain while running resulted in altered hip and knee kinematics in female runners with PFP as compared to healthy female runners.MethodsThirty female runners (15 PFP, 15 controls) participated in an instrumented gait analysis while running for 30 min at a self-selected pace. Pain and fatigue were recorded every minute while participants ran. Variables of interest included peak hip adduction, hip internal rotation, knee abduction, knee external rotation, pain, and fatigue.ResultsThere were significant group by pain interactions for hip adduction (p < 0.01) and hip internal rotation (p < 0.01). The healthy group, who did not develop pain had significant increases in both motions compared to the PFP group, who did develop pain. There was also a trend toward less knee external rotation in the PFP group in presence of pain (p = 0.059). No differences were found for knee abduction (p = 0.32). A group main effect was found for hip internal rotation (p = 0.008) in which the PFP group had significantly larger values.ConclusionRunners with PFP did not alter their hip mechanics over the course of the run. This may have resulted in repetitive stress to the same aspect of the patellofemoral joint and contributed to the initial development of pain. However, the PFP group did attempt to make a compensation once in pain by reducing knee external rotation.     

Differences in kinetic asymmetry between injured and noninjured novice runners: A prospective cohort study

PurposeThe purpose of this prospective study was to describe natural levels of asymmetry in running, compare levels of asymmetry between injured and noninjured novice runners and compare kinetic variables between the injured and noninjured lower limb within the novice runners with an injury.MethodsAt baseline vertical ground reaction forces and symmetry angles (SA) were assessed with an instrumented treadmill equipped with three force measuring transducers. Female participants ran at 8 and 9 km h^?1 and male runners ran at 9 and 10 km h^?1. Participants were novice female and male recreational runners and were followed during a 9-week running program.ResultsTwo hundred and ten novice runners enrolled this study, 133 (63.3%) female and 77 (36.7%) male runners. Thirty-four runners reported an RRI. At baseline SA values varied widely for all spatio-temporal and kinetic variables. The inter-individual differences in SA were also high. No significant differences in SA were found between female and male runners running at 9 km h^?1. In injured runners the SA of the impact peak was significantly lower compared to noninjured runners.ConclusionsNatural levels of asymmetry in running were high. The SA of impact peak in injured runners was lower compared to noninjured runners and no differences were seen between the injured and noninjured lower limbs.     

Is passive metatarsophalangeal joint stiffness related to leg stiffness,vertical stiffness and running economy during sub-maximal running?

This study examined whether passive metatarsophalangeal joints (MPJ) stiffness was associated with leg stiffness (K_leg) vertical stiffness (K_vert) and running economy (RE) during sub-maximal running. Nine male experienced runners underwent passive MPJ stiffness measurements in standing and sitting positions followed by sub-maximal running on an instrumented treadmill. With the individual foot position properly aligned, the MPJ passive stiffness in both sitting (MPJ_sit) and standing positions (MPJ_stand) were measured with a computerized dynamometer. Data were collected at a running speed of 2.78 m/s, representing a stabilized level of energy expenditure. Pedar pressure insole was used to determine the contact time (t_c) and peak reaction force for the calculation of K_leg and K_vert. A respiratory gas analysis system was used to estimate the RE. Bivariate correlation test was performed to examine the correlation among MPJ stiffness, contact time, K_leg, K_vert, and RE. The results showed that MPJ_sit and MPJ_stand were inversely correlated with RE (p = 0.04, r = −0.68 to −0.69), suggesting that stiffer MPJ improves RE. In addition, MPJ_sit was correlated positively with K_leg (p < 0.01, r = 0.87), K_vert (p = 0.03, r = 0.70) but inversely with t_c (p = 0.02, r = −0.76), while MPJ_stand was correlated positively with the K_vert (p = 0.02, r = 0.77). These findings suggested that strength of toe plantar flexors provides stability and agility in the stance phase for more effective and faster forward movement.     

Plantarflexor passive-elastic properties related to BMI and walking performance in older women

The objective of this study was to examine the influence of BMI on the passive-elastic properties of the ankle plantarflexors in older women. Twenty-three women, 65–80 yr, were separated into normal weight (NW, BMI < 25.0 kg m⁻², n = 11) and overweight-obese (OW, BMI ≥ 25.0 kg m⁻², n = 12) groups. Resistive torque of the ankle plantarflexors was recorded on an isokinetic dynamometer by passively moving the ankle into dorsiflexion. Stiffness, work absorption, and hysteresis were calculated across an ankle dorsiflexion angle of 10–15°. Maximal plantarflexor strength was assessed, then participants walked at maximal speed on an instrumented gait analysis treadmill while muscle activation (EMG) was recorded. Plantarflexor stiffness was 34% lower in OW (26.4 ± 12.7 Nm rad⁻¹) than NW (40.0 ± 15.7 Nm rad⁻¹, p = 0.032). Neither work absorption nor hysteresis were different between OW and NW. Stiffness per kg was positively correlated to strength (r = 0.66, p < 0.001), peak vertical ground reaction force during walking (r = 0.72, p < 0.001), weight acceptance rate of force (r = 0.51, p = 0.007), push-off rate of force (r = 0.41, p = 0.026), maximal speed (r = 0.61, p = 0.001), and inversely correlated to BMI (r = −0.61, p = 0.001), and peak plantarflexor EMG (r = −0.40, p = 0.046). Older women who are OW have low plantarflexor stiffness, which may limit propulsive forces during walking and necessitate greater muscle activation for active force generation.     

Investigation of treadmill and overground running: Implications for the measurement of oxygen cost in children with developmental coordination disorder

Differences in the kinematics and kinetics of overground running have been reported between boys with and without developmental coordination disorder (DCD). This study compared the kinematics of overground and treadmill running in children with and without DCD to determine whether any differences in technique are maintained, as this may influence the outcome of laboratory treadmill studies of running economy in this population. Nine boys with DCD (10.3 ± 1.1 year) and 10 typically developing (TD) controls (9.7 ± 1 year) ran on a treadmill and overground at a matched velocity (8.8 ± 0.9 km/h). Kinematic data of the trunk and lower limb were obtained for both conditions using a 12-camera Vicon MX system. Both groups displayed an increase in stance time (p < 0.001), shorter stride length (p < 0.001), higher cadence (p < 0.001) and reduced ankle plantar flexion immediately after toe-off (p < 0.05) when running on the treadmill compared with overground. The DCD group had longer stance time (p < 0.009) and decreased knee flexion at mid-swing (p = 0.04) while running overground compared to their peers, but these differences were maintained when running on the treadmill. Treadmill running improved ankle joint symmetry in the DCD group compared with running overground (p = 0.019). Overall, these findings suggest that there are limited differences in joint kinematics and lower limb symmetry between overground and treadmill running in this population. Accordingly, laboratory studies of treadmill running in children with DCD are likely representative of the energy demands of running.     

A mechanical protocol to replicate impact in walking footwear

Impact testing is undertaken to quantify the shock absorption characteristics of footwear. The current widely reported mechanical testing method mimics the heel impact in running and therefore applies excessive energy to walking footwear. The purpose of this study was to modify the ASTM protocol F1614 (Procedure A) to better represent walking gait. This was achieved by collecting kinematic and kinetic data while participants walked in four different styles of walking footwear (trainer, oxford shoe, flip-flop and triple-density sandal). The quantified heel-velocity and effective mass at ground-impact were then replicated in a mechanical protocol. The kinematic data identified different impact characteristics in the footwear styles. Significantly faster heel velocity towards the floor was recorded walking in the toe-post sandals (flip-flop and triple-density sandal) compared with other conditions (e.g. flip-flop: 0.36 ± 0.05 m s⁻¹ versus trainer: 0.18 ± 0.06 m s⁻¹). The mechanical protocol was adapted by altering the mass and drop height specific to the data captured for each shoe (e.g. flip-flop: drop height 7 mm, mass 16.2 kg). As expected, the adapted mechanical protocol produced significantly lower peak force and accelerometer values than the ASTM protocol (p < .001). The mean difference between the human and adapted protocol was 12.7 ± 17.5% (p < .001) for peak acceleration and 25.2 ± 17.7% (p = .786) for peak force. This paper demonstrates that altered mechanical test protocols can more closely replicate loading on the lower limb in walking. This therefore suggests that testing of material properties of footbeds not only needs to be gait style specific (e.g. running versus walking), but also footwear style specific.