Surface effects on dynamic stability and loading during outdoor running using wireless trunk accelerometry

Despite frequently declared benefits of using wireless accelerometers to assess running gait in real-world settings, available research is limited. The purpose of this study was to investigate outdoor surface effects on dynamic stability and dynamic loading during running using tri-axial trunk accelerometry. Twenty eight runners (11 highly-trained, 17 recreational) performed outdoor running on three outdoor training surfaces (concrete road, synthetic track and woodchip trail) at self-selected comfortable running speeds. Dynamic postural stability (tri-axial acceleration root mean square (RMS) ratio, step and stride regularity, sample entropy), dynamic loading (impact and breaking peak amplitudes and median frequencies), as well as spatio-temporal running gait measures (step frequency, stance time) were derived from trunk accelerations sampled at 1024 Hz. Results from generalized estimating equations (GEE) analysis showed that compared to concrete road, woodchip trail had several significant effects on dynamic stability (higher AP ratio of acceleration RMS, lower ML inter-step and inter-stride regularity), on dynamic loading (downward shift in vertical and AP median frequency), and reduced step frequency (p < 0.05). Surface effects were unaffected when both running level and running speed were added as potential confounders. Results suggest that woodchip trails disrupt aspects of dynamic stability and loading that are detectable using a single trunk accelerometer. These results provide further insight into how runners adapt their locomotor biomechanics on outdoor surfaces in situ.     

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.     

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

ObjectivesThis prospective study examined differences in kinetic variables between injured and noninjured novice female and male runners and their potential contribution to RRIs.DesignA prospective cohort study.MethodsAt baseline vertical ground reaction forces 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. Primary outcome measure was a running related injury (RRI). Participants were novice female and male recreational runners and were followed during a 9-week running program with three running sessions a week.ResultsOne hundred thirty three female and seventy seven male runners participated in this study. Mean age was 37.2 years and the BMI was 23.9 kg m^?2. During the nine week running program 16.2% of the participants sustained an injury and no difference in incidence between female and male runners was seen. In injured male runners loading rate was significantly higher compared to noninjured male runners at both running speeds and contact time in the injured male group was significantly shorter at 9 km h^?1. In the group of female injured and noninjured runners no differences on kinetic or spatio-temporal variables were observed. Female runners had significantly higher loading rates compared to male runners but this did not have an effect on the incidence of RRIs.ConclusionsThis study showed that male injured runners had higher loading rates and shorter contact times than noninjured male runners. In female runners, however, no differences in kinetic or spatio-temporal variables were observed between injured and noninjured novice runners.     

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.     

Whole-body biomechanical load in running-based sports: The validity of estimating ground reaction forces from segmental accelerations

ObjectivesUnlike physiological loads, the biomechanical loads of training in running-based sports are still largely unexplored. This study, therefore, aimed to assess the validity of estimating ground reaction forces (GRF), as a measure of external whole-body biomechanical loading, from segmental accelerations.MethodsFifteen team-sport athletes performed accelerations, decelerations, 90° cuts and straight running at different speeds including sprinting. Full-body kinematics and GRF were recorded with a three-dimensional motion capture system and a single force platform respectively. GRF profiles were estimated as the sum of the product of all fifteen segmental masses and accelerations, or a reduced number of segments.ResultsErrors for GRF profiles estimated from fifteen segmental accelerations were low (1–2 N kg⁻¹) for low-speed running, moderate (2–3 N kg⁻¹) for accelerations, 90° cuts and moderate-speed running, but very high (>4 N kg⁻¹) for decelerations and high-speed running. Similarly, impulse (2.3–11.1%), impact peak (9.2–28.5%) and loading rate (20.1–42.8%) errors varied across tasks. Moreover, mean errors increased from 3.26 ± 1.72 N kg⁻¹ to 6.76 ± 3.62 N kg⁻¹ across tasks when the number of segments was reduced.ConclusionsAccuracy of estimated GRF profiles and loading characteristics was dependent on task, and errors substantially increased when the number of segments was reduced. Using a direct mechanical approach to estimate GRF from segmental accelerations is thus unlikely to be a valid method to assess whole-body biomechanical loading across different dynamic and high-intensity activities. Researchers and practitioners should, therefore, be very cautious when interpreting accelerations from one or several segments, as these are unlikely to accurately represent external whole-body biomechanical loads.     

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.     

Water depth effects on impact loading,kinematic and physiological variables during water treadmill running

PurposeThe purpose of this study was to compare impact loading, kinematic and physiological responses to three different immersion depths (mid-shin, mid-thigh, and xiphoid process) while running at the same speed on a water based treadmill.MethodsParticipants (N = 8) ran on a water treadmill at three depths for 3 min. Tri-axial accelerometers were used to identify running dynamics plus measures associated with impact loading rates, while heart rate data were logged to indicate physiological demand.ResultsParticipants had greater peak impact accelerations (p < 0.01), greater impact loading rates (p < 0.0001), greater stride frequency (p < 0.05), shorter stride length (p < 0.01), and greater rate of acceleration development at toe-off (p < 0.0001) for the mid-shin and mid-thigh compared to running immersed to the xiphoid process. Physiological effort determined by heart rate was also significantly less (p < 0.0001) when running immersed to the xiphoid process.ConclusionWater immersed treadmill running above the waistline alters kinematics of gait, reduces variables associated with impact, while decreasing physiological demand compared to depths below the waistline.     

Change in foot strike patterns and performance in recreational runners during a road race: A cross-sectional study

ObjectivesTo characterise foot strike and observe change in foot strike patterns with increasing distance during a 15 km recreational running road race. To assess the impact of foot strike on running performance.DesignObservational cross-sectional study.MethodsFoot strike patterns were determined at the 3 km and 13 km checkpoints for 459 participants during the 2017 Melbourne City to Sea recreational running event. Foot strike patterns were categorised as either rearfoot strike (RFS) or non-rearfoot strike (NRFS) at both checkpoints and analyses were conducted on intra-individual change in foot strike as well as relationship to finishing time.ResultsThe most prevalent foot strike pattern at 3 km and 13 km was RFS with 76.9% (95% CI: 73.2%–80.5%) and 91.0% (95% CI: 88.7%–93.1%) using this pattern, respectively. Of the 105 participants who ran with a NRFS at 3 km, 61% changed to RFS at 13 km. Race completion time differed by foot strike pattern, where mean time for consistent NRFS (62.64 ± 11.20 min) was significantly faster than consistent RFS (72.58 ± 10.84 min; p < 0.001) and those who changed from NRFS to RFS between checkpoints (67.93 ± 10.60 min; p = 0.040).ConclusionsWhile the majority of recreational distance runners RFS within race settings, the fastest runners were those who consistently ran with a NRFS. In runners that use a NRFS early, a large proportion change to RFS as distance increases. Further research is warranted to determine whether interventions aimed at reducing muscular fatigue can attenuate this change and enhance running performance.     

Widening margin in activity profile between elite and sub-elite Australian football: A case study

ObjectivesIt is not known if the activity profile of elite Australian football players changes across two levels of competition. The aims of this study were therefore to: (1) classify the activity profile of elite and sub-elite Australian football for players from one elite Australian football club; and (2) compare the activity profile of elite footballers across both elite and sub-elite competitions.DesignQuantitative case-study approach.MethodsMovement was recorded by 5 Hz global positioning system and expressed relative to game time for total; and high-velocity running distance (4.17–10.00 m s^?1) and maximal accelerations (2.78–10.00 m s^?2). The difference was expressed as a percentage and effect size statistic with confidence intervals.ResultsElite Australian football players had 8% greater total 11% more high intensity running; and 16% more maximal accelerations during matches in 2009 compared to 2008. Players at a sub-elite level had no change in total; 9% less high intensity running but 23% greater maximal accelerations during the same period. In 2008 there was a 5% lower total covered by players in sub-elite competition; no difference in high intensity running; and 28% less maximal accelerations compared to elite. In 2009 the gap was larger for distance of running as sub-elite had 15% less total and 20% less high intensity running than elite. Similar to 2008, sub-elite players had 23% less maximal accelerations in 2009.ConclusionsThe activity profile of players in the elite competition has increased over these two seasons, but not in the sub-elite. This has implications for teams where players must move between competitions during the season.     

Tibial impact accelerations in gait of primary school children: The effect of age and speed

Tibial stress fractures are associated with increased lower extremity loading at initial foot-ground contact, reflected in high peak positive acceleration (>8 g) of the tibia in adults. There is no reported data on peak positive acceleration of the tibia in children during walking and running. The aim of this study was to establish tibial peak positive acceleration responses in children across a range of age and gait speeds. Twenty-four children aged 8.5 ± 1.4 years with no known gait pathology comprised two age groups; Young (7–9 year, n = 12) and Older (10–12 years, n = 12). Wireless Inertial Measurement Unit comprising a tri-axial accelerometer was securely taped to the anteromedial aspect of the distal tibia to measure peak positive acceleration responses while walking and running on the treadmill at 3 different speeds (20% below baseline, baseline, and 20% above baseline). Results showed significant increase in peak positive acceleration with increased gait speed and greater variability in young children compared to older children. The study suggests that ground impact in walking, but not running, is mature by age 7 years. Future studies should explore strategies using peak positive acceleration responses to monitor ground impact during sport activities and its application in gait retraining.     

Biomechanics of starting,sprinting and submaximal running in athletes with brain impairment: A systematic review

ObjectivesPara athletes with brain impairment are affected by hypertonia, ataxia and athetosis, which adversely affect starting, sprinting and submaximal running. The aim was to identify and synthesise evidence from studies that have compared the biomechanics of runners with brain impairments (RBI) and non-disabled runners (NDR).DesignSystematic review.MethodsFive journal databases were systematically searched from inception to March 2020. Included studies compared the biomechanics of RBI (aged > 14 years) and NDR performing either block-starts, sprinting, or submaximal running.ResultsEight studies were included, analysing a total of 100 RBI (78M:22F; 18–38 years) diagnosed with either cerebral palsy (n = 44) or traumatic brain injury (n = 56). Studies analysed block-starts (n = 3), overground sprinting (n = 3) and submaximal running (n = 2), and submaximal treadmill running (n = 1). Horizontal velocity during starts, sprinting and self-selected submaximal speeds were lower in RBI. During sprinting and submaximal running, compared with NDR, RBI had shorter stride length, step length, and flight time, increased ground-contact time, increased cadence, and reduced ankle and hip range of motion. In submaximal running, RBI had decreased ankle-power generation at toe-off.ConclusionsThere is limited research and small sample sizes in this area. However, preliminary evidence suggests that RBI had lower sprint speeds and biomechanical characteristics typical of submaximal running speeds in NDR, including increased ground-contact times and reduced stride length, step length, and flight times. Meaningful interpretation of biomechanical findings in RBI is impeded by impairment variability (type, severity and distribution), and methods which permit valid, reliable impairment stratification in larger samples are required.     

Effects of different hydration supports on stride kinematics,comfort, and impact accelerations during running

BackgroundDifferent supports for hydration can influence total body mass and affect running biomechanics.Research questionDo different hydration supports affect the perceived exertion and comfort, stride kinematics, and impact accelerations during running?MethodsThis was a crossover study design. Thirteen trail runners completed a treadmill running test divided into four different durations and randomized hydration supports conditions, lasting 8 min each at moderate intensity: A) waist bag (0.84 kg); B) medium load backpack (0.84 kg); C) full load backpack (3.40 kg); and D) a control condition without water support. Impact accelerations were measured for 30 s in 4, 6, and 8 min. The rate of perceived exertion and heart rate were registered on minutes 4 and 8. At the last minute of each condition, comfort perception was registeredResults and significanceNo condition affected the stride kinematics. Full load backpack condition reduced head acceleration peak (−0.21 g; p = 0.04; ES=0.4) and head acceleration magnitude (−0.23 g; p = 0.03; ES=0.4), and increased shock attenuation (3.08 g; p = 0.04; ES=0.3). It also elicited higher perceived exertion (p < 0.05; ES>0.8) being considered heavier (p < 0.01; ES > 1.1). The waist bag condition was more comfortable in terms of noise (p = 0.006; ES=1.3) and humidity/heat (p = 0.001; ES=0.8). The waist bag was the most comfortable support. On the other hand, the full backpack elicited lower comfort and was the only generating compensatory adjustments. These results may help to improve design of full load backpack aiming at comfort for runners.     

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.     

Diagnostic of footwork characteristics and running speed demands in tennis on different ground surfaces

BackgroundAnalysis of court surface effects on foot work and running speed and analysis of correlation between general speed and jump performance and the complex running performance in tennis.Materials and Methods12 male tennis players performed a tennis specific baseline shuttle run test including one change of direction (SR), either on clay or on an indoor carpet court. Additionally, subjects completed a linear sprint test, a counter movement jump (CMJ), and a drop jump (DJ).ResultsSR running time (clay: 3.63 ± 0.08 s; carpet: 3.31 ± 0.15 s), change direction time (clay: 1.24 ± 0.09; carpet: 1.09 ± 0.04 s) and ground contact time during the last step while changing direction (clay: 0.92 ± 0.13; carpet: 0.47 ± 0.13 s) were significantly longer on clay (P < 0.05). Linear sprint and jump tests showed no or only weak correlations with SR on both surfaces.ConclusionFoot work and running speed demands in tennis are different depending on the court surface and require specific training interventions and testing procedures.     

Identifying symmetry in running gait using a single inertial sensor

Running gait has been shown to alter due to changes in intensity. It was hypothesised that a sacral mounted single inertial sensor could identify the centre of mass (COM) vertical accelerations. This study aimed to validate this new technique against a criterion measure and to determine the influence of changes in running intensity on COM vertical acceleration and the symmetry of COM vertical acceleration between left and right steps. Ten athletes ran for 5 min at their self-selected pace, plus 1 km/h above and below this velocity. Validity of the single inertial sensor was determined by comparing COM vertical acceleration against that measured with a six-camera infrared system. Large correlation (r = 0.96), a small typical error of estimate (1.84), and mean bias (0.02) were found between the two systems. The greatest magnitude in COM vertical acceleration occurred at the slowest running pace and decreased as pace increased. Sixty percent of the athletes exhibited asymmetry during at least one running pace; 30% were asymmetrical across all three velocities. While significant changes in COM vertical acceleration occurred between the different running velocities, this did not always result in a change in symmetry. This study found that a single inertial sensor can be used as a valid means of measuring COM vertical acceleration. This technique can detect changes in the COM vertical acceleration that may change with running velocity. Gait symmetry (using COM vertical acceleration) during running was also quantified using the inertial sensor.     

About some factors influencing safety mattress performances in head impact collisions: A pilot study

ObjectivesIn recreational snow sports activities, safety mattresses are placed on obstacles to prevent injuries from a collision with users. However, the performances of these devices in field conditions remain unclear. The objective of this study is to evaluate the effect of mattress thickness, impact speed, impacting mass and atmospheric conditions on head acceleration during an in-field impact on safety mattress.Design42 in-field experimental drop tests of a normative metallic head were conducted on safety mattress to assess the influence of impact speed (5.8 m/s or 7.3 m/s), impacting mass (6 kg or 11.6 kg), outside conditions (3 conditions) and mattress thickness (24 cm, 32 cm, 44 cm) on head acceleration at impact.MethodsLinear accelerations were measured and Head Injury Criteria 15 ms (HIC₁₅) was computed. A statistical analysis (ANOVA) was used to characterize the effects of the varying parameters on maximal acceleration and HIC₁₅.ResultsReduced impact speed, increased mattress thickness and change in the outside conditions significantly decreased the head acceleration and HIC₁₅ (p < 0.001). The effect of the impacting mass on head acceleration was not significant.ConclusionsThis study highlights the influence of impact speed, atmospheric condition and mattress construction on absorption capacities of safety mattresses. It is a first step toward a better understanding and evaluation of safety mattresses performances.     

Assessment of dehydration using body mass changes of elite marathoners in the tropics

ObjectivesThe ACSM recommends drinking to avoid loss of body mass >2% during exercise to avert compromised performance. Our study aimed to assess the level of dehydration in elite runners following a city marathon in a tropical environment.DesignProspective cohort design.MethodsTwelve elite runners (6 males, 6 females; age 24–41 y) had body mass measured to the nearest 0.01 kg in their race attire immediately before and after the 2017 Standard Chartered Singapore Marathon 2017. Body mass change was corrected for respiratory water loss, gas exchange, and sweat retained in clothing, and expressed as % of pre-race mass (i.e. % dehydration).ResultsData are expressed as means ± SD (range). Dry bulb temperature and humidity were 27.9 ± 0.1 °C (27.4–28.3 °C) and 79 ± 2% (73–82%). Finish time was 155 ± 10 min (143−172 min). Male runners finishing positions ranged from 2–12 out of 7627 finishers, whilst female runners placed 1–8 out of 1754 finishers. Body mass change (loss) and % dehydration for all runners were 2.5 ± 0.5 kg (1.8–3.5 kg) and 4.6 ± 0.9% (3.6–6.8%). Male runners experienced body mass loss of 2.8 ± 0.5 kg and 4.9 ± 1.2% while females experienced body mass loss of 2.1 ± 0.2 kg and 4.3 ± 0.6%.ConclusionsDespite experiencing dehydration (4.6% body mass loss) two-fold higher than current fluid replacement guidelines recommend (≤2%), elite male and female runners performed successfully and without medical complication in a hot weather marathon.     

Footwear characteristics are related to running mechanics in runners with patellofemoral pain

Running footwear is known to influence step rate, foot inclination at foot strike, average vertical loading rate (VLR) and peak patellofemoral joint (PFJ) force. However, the association between the level of minimalism of running shoes and running mechanics, especially with regards to these relevant variables for runners with patellofemoral pain (PFP), has yet to be investigated. The objective of this study was to explore the relationship between the level of minimalism of running shoes and habitual running kinematics and kinetics in runners with PFP. Running shoes of 69 runners with PFP (46 females, 23 males, 30.7 ± 6.4 years) were evaluated using the Minimalist Index (MI). Kinematic and kinetic data were collected during running on an instrumented treadmill. Principal component and correlation analyses were performed between the MI and its subscales and step rate, foot inclination at foot strike, average VLR, peak PFJ force and peak Achilles tendon force. Higher MI scores were moderately correlated with lower foot inclination (r = −0.410, P < 0.001) and lower peak PFJ force (r = −0.412, P < 0.001). Moderate correlations also showed that lower shoe mass is indicative of greater step rate (ρ = 0.531, P < 0.001) and lower peak PFJ force (ρ = −0.481, P < 0.001). Greater shoe flexibility was moderately associated with lower foot inclination (ρ = −0.447, P < 0.001). Results suggest that greater levels of minimalism are associated with lower inclination angle and lower peak PFJ force in runners with PFP. Thus, this population may potentially benefit from changes in running mechanics associated with the use of shoes with a higher level of minimalism.     

Biomechanical effects following footstrike pattern modification using wearable sensors

ObjectivesThis study sought to examine the biomechanical effects of an in-field sensor-based gait retraining program targeting footstrike pattern modification during level running, uphill running and downhill running.DesignQuasi-experimental design.MethodsSixteen habitual rearfoot strikers were recruited. All participants underwent a baseline evaluation on an instrumented treadmill at their preferred running speeds on three slope settings. Participants were then instructed to modify their footstrike pattern from rearfoot to non-rearfoot strike with real-time audio biofeedback in an 8-session in-field gait retraining program. A reassessment was conducted to evaluate the post-training biomechanical effects. Footstrike pattern, footstrike angle, vertical instantaneous loading rate (VILR), stride length, cadence, and knee flexion angle at initial contact were measured and compared.ResultsNo significant interaction was found between training and slope conditions for all tested variables. Significant main effects were observed for gait retraining (p-values ≤ 0.02) and slopes (p-values ≤ 0.01). After gait retraining, 75% of the participants modified their footstrike pattern during level running, but effects of footstrike pattern modification were inconsistent between slopes. During level running, participants exhibited a smaller footstrike angle (p ≤ 0.01), reduced VILR (p ≤ 0.01) and a larger knee flexion angle (p = 0.01). Similar effects were found during uphill running, together with a shorter stride length (p = 0.01) and an increased cadence (p ≤ 0.01). However, during downhill running, no significant change in VILR was found (p = 0.16), despite differences found in other biomechanical measurements (p-values = 0.02–0.05).ConclusionAn 8-session in-field gait retraining program was effective in modifying footstrike pattern among runners, but discrepancies in VILR, stride length and cadence were found between slope conditions.