Acute and delayed peripheral and central neuromuscular alterations induced by a short and intense downhill trail run

Downhill sections are highly strenuous likely contributing to the development of neuromuscular fatigue in trail running. Our purpose was to investigate the consequences of an intense downhill trail run (DTR) on peripheral and central neuromuscular fatigue at knee extensors (KE) and plantar flexors (PF). Twenty‐three runners performed a 6.5‐km DTR (1264‐m altitude drop) as fast as possible. The electromyographic activity of vastus lateralis (VL) and gastrocnemius lateralis (GL) was continuously recorded. Neuromuscular functions were assessed Pre‐, Post‐, and 2‐day Post‐DTR (Post2d). Maximal voluntary torques decreased Post (～ ?19% for KE, ～ ?25% for PF) and Post2d (～ ?9% for KE, ～ ?10% for PF). Both central and peripheral dysfunctions were observed. Decreased KE and PF voluntary activation (VA), evoked forces, VL M‐wave amplitude, and KE low‐frequency fatigue were observed at Post. Changes in VL M‐wave amplitude were negatively correlated to VL activity during DTR. Changes in PF twitch force and VA were negatively correlated to GL activity during DTR. The acute KE VA deficit was about a third of that reported after ultramarathons, although peripheral alterations were similar. The prolonged force loss seems to be mainly associated to VA deficit likely induced by the delayed inflammatory response to DTR‐induced ultrastructural muscle damage.     

Influence of step length and landing pattern on patellofemoral joint kinetics during running

Elevated patellofemoral joint kinetics during running may contribute to patellofemoral joint symptoms. The purpose of this study was to test for independent effects of foot strike pattern and step length on patellofemoral joint kinetics while running. Effects were tested relative to individual steps and also taking into account the number of steps required to run a kilometer with each step length. Patellofemoral joint reaction force and stress were estimated in 20 participants running at their preferred speed. Participants ran using a forefoot strike and rearfoot strike pattern during three different step length conditions: preferred step length, long (+10%) step length, and short (?10%) step length. Patellofemoral kinetics was estimated using a biomechanical model of the patellofemoral joint that accounted for cocontraction of the knee flexors and extensors. We observed independent effects of foot strike pattern and step length. Patellofemoral joint kinetics per step was 10–13% less during forefoot strike conditions and 15–20% less with a shortened step length. Patellofemoral joint kinetics per kilometer decreased 12–13% using a forefoot strike pattern and 9–12% with a shortened step length. To the extent that patellofemoral joint kinetics contribute to symptoms among runners, these running modifications may be advisable for runners with patellofemoral pain.     

Effects of marathon fatigue on running kinematics and economy

The influence of marathon fatigue on both running kinematics and economy was investigated with 8 subjects. The measurements included a treadmill test at 3 steady submaximal speeds performed before and after the marathon. One complete left leg cycle was videotaped at 100 Hz from the left side at each speed. The analysis included contact time (braking and push-off) and flight time as well as displacements and angular velocities of the left hip and knee. This analysis was complemented by the measurements of the electromyographic (EMG) activity of the gastrocnemius muscle at each running velocity, and energy expenditure (Ė) of the last 30 s at the 2 slowest speeds. The results revealed significant increases of Ė at these 2 speeds, but the changes were not related to kinematic changes, which were greatly individual. However, the relative duration of the push-off phase was significantly increased at the 2 slowest speeds, and the gastrocnemius muscle presented higher integrated EMG values in the respective braking (NS) and push-off phases at the 2 fastest speeds. This might indicate a loss of tolerance to impact during the belt contact. The results failed, however, to demonstrate that running kinematics and running economy are interrelated when fatigue progresses. It is also possible that observed kinematic changes might reflect some adaptation to fatigue more than real failure to compensate for it.     

Acute fatigue-induced changes in muscle mechanical properties and neuromuscular activity in elite handball players following a handball match

The purpose of the present study was to determine the acute fatigue development in muscle mechanical properties and neuromuscular activity in response to handball match play. Male elite handball players ( n = 10) were tested before and after a simulated handball match for maximal isometric strength [maximal voluntary contraction (MVC)] and rate of force development (RFD) with synchronous electromyography (EMG) recording, while maximal vertical jump parameters were assessed using force plate analysis. Quadriceps and hamstrings MVC and RFD decreased significantly post-match (∼10%, P <0.05 and ∼16–21%, P <0.05, respectively). During quadriceps, MVC mean EMG amplitude [mean average voltage (MAV)] decreased for the vastus lateralis (VL) and rectus femoris (RF) (21–42%, P ≤0.05), while MAV also decreased in the antagonist biceps femoris (BF) muscle (48–55%, P <0.01). During hamstring MVC, MAV was reduced in BF (31%, P <0.01). Maximum EMG amplitude during quadriceps MVC was reduced for the VL (28%, P <0.01) and the RF (5%, P <0.05). During hamstring MVC, maximum EMG was reduced for BF (21%, P <0.01). Post-match maximal jump height was reduced (5.2%, P <0.01), as was also work (6.8%, P <0.01), velocity of center of mass (2.4–4.0%, P <0.01) and RFD (∼30%, P <0.05). In conclusion, maximal (MVC) and rapid muscle force characteristics (RFD, impulse) were acutely affected concurrently with marked reductions in muscle EMG following handball match play, which may potentially lead to impaired functional performance.     

Immediate effect of visual,auditory and combined feedback on foot strike pattern

BackgroundA growing body of literature supports the promising effect of real-time feedback to re-train runners. However, no studies have comprehensively assessed the effects of foots trike and cadence modification using different forms of real-time feedback provided via wearable devices.Research questionThe purpose of the present study was to determine if a change could be made in foot strike pattern and plantar loads using real-time visual, auditory and combined feedback provided using wearable devices.MethodsVisual, auditory and combined feedback were provided using wearable devices as fifteen recreational runners ran on a treadmill at self-selected speed and increased cadence. Plantar loads and location of initial contact were measured with a flexible insole system. Repeated measures ANOVAs with Bonferroni adjusted pair-wise comparisons were used to assess statistical significance.Results and significanceA significant effect of condition was noted on location of center of pressure (p < 0.01). Bonferroni-adjusted post-hoc comparisons showed that feedback conditions differed from baseline as well as the new cadence conditions, however did not differ from each other. A significant interaction effect (region x feedback) was found for plantar loads (maximum force P < 0.001). Significant effects of feedback were noted at the heel (P < 0.001), medial midfoot (P < 0.001), lateral midfoot (P < 0.001), medial forefoot (P = 0.003), central forefoot (P = 0.003), and great toe (P = 0.004) but not at the lateral forefoot (P = 0.6) or lateral toes (P = 0.507).SignificanceThe unique findings of our study showed that an anterior shift of the center of pressure, particularly when foot strike modification was combined with 10% increased cadence. We found lower heel and midfoot loads along with higher forefoot and great toe loads when foot strike modification using real-time feedback was combined with increased cadence. Our findings also suggest that auditory feedback might be more effective than visual feedback in foot-strike modification.     

Effects of a 10-week running-retraining programme on the foot strike pattern of adolescents: A longitudinal intervention study

BackgroundThe purpose of this study was to analyse the effects of ten weeks of different running-retraining programmes on rearfoot strike (RFS) prevalence in adolescents.Research questionit is possible to change foot strike pattern in adolescents?MethodsA total of 180 children (45.3% girls), aged 13–16 years, participated in this intervention study. The children were randomly assigned to one of three experimental groups (EGs) that each carried out a different retraining programme, based on running technique (n = 39), a 15% increased step frequency (SF) (n = 37) and barefoot training (n = 30), performed for three days each week. A control group (CG) (n = 43) did not perform any retraining. A 2D video-based analysis (240 Hz) was used to determine the RFS.ResultsAt baseline, no significant differences in RFS prevalence were found between the EGs and the CG in either the left (χ² = 2.048; p = 0.559) or the right foot (χ² = 0.898; p = 0.825). In the post-test, no significant differences were found for the left foot (χ² = 7.102; p = 0.069), but there were significant differences for the right foot (χ² = 9.239; p = 0.025) were observed. In the re-test, no significant differences were found for either the left foot (χ² = 2.665; p = 0.273) or the right foot (χ² = 2.182; p = 0.325). In addition, no group displayed significant changes in RFS prevalence from the pre-test to the re-test. There was a trend towards a reduction in the RFS prevalence in both the increased SF group and the barefoot group.MeaningThe main finding of this study was that certain running-retraining programmes performed three times per week for ten weeks are not enough to modify the adolescent foot strike pattern (FSP).     

Effects of running-induced fatigue on plantar pressure distribution in runners with different strike types

BackgroundRunning induced-fatigue is an important factor in running related injuries. Runners with different strike types have different running mechanics and suffer from different injury patterns. Underlying mechanism of this difference is not well understood.Research questionThe aim of this study was to examine the effects of running-induced fatigue on plantar pressure distribution in runners with different strike types.Methods30 rearfoot (age = 21.56 ± 2.28 years; height = 1.67 ± 0.08 m; mass = 61.43 ± 11.57 kg; BMI = 21.77 ± 2.9 kg∙m⁻²) and 30 forefoot (age = 19.73 ± 1.68 years; height = 1.71 ± 0.08 m; mass = 65.7 ± 13.45; BMI = 22.53 ± 3.39 kg∙m⁻²) strike male and female recreational runners were recruited to this study. Participants ran in 3.3 m/s barefoot along the plantar pressure measuring device (Footscan®, Rsscan International) before and after running-induced fatigue. Fatigue protocol was performed on a treadmill. Peak plantar pressure and peak plantar force (% body weight), contact time and medio-lateral force ratio were calculated while running. Repeated measures ANOVA test was used to investigate the effect of running-induced fatigue on plantar pressure variables (p ≤ 0.05).ResultsAfter running-induced fatigue, in the rearfoot strike group, increases in loading of medial and lateral portions of the heel, first metatarsal and big toe was observed, and in lesser toes and in the forefoot push off phase, the medio-lateral force ratio decreased. While, in the forefoot strike group first to third metatarsals loading increased and fifth metatarsal loading decreased after fatigue, and medio-lateral force ratio in the foot flat and forefoot push off phase increased. In both groups contact time increased after fatigue.SignificanceOur data indicate that running-induced fatigue has different effects on plantar pressure distribution pattern in runners with different strike type. These different effects reflect different adaptation strategies in runners with different strike types, and could explain existence of different injury patterns in runners with different strike types.     

Classification of medial longitudinal arch kinematics during running and characteristics of foot muscle morphology in novice runners with pronated foot

BackgroundNovice runners with pronated feet are at an increased risk of running-related injuries. However, not all runners with pronated feet have increased foot pronation during running. Moreover, although foot muscle morphology is related to static foot alignment, the relationship between foot muscle morphology and foot kinematics during running remains unclear. We aimed to determine foot kinematic patterns during running among novice runners with pronated feet and the presence of a relationship between these foot kinematic patterns and foot muscle morphology.MethodsTwenty-one novice runners with pronated feet participated in this study, and data on 39 lower limbs were collected. Data on foot kinematics during running (rearfoot strike) were collected using a three-dimensional motion capture system in terms of navicular height (NH) at initial contact and dynamic navicular drop (DND). A hierarchical cluster analysis method was used to identify the optimal number of clusters based on these two foot-related kinematic variables. Following identification of the clusters, differences in cluster variables and cross-sectional areas of selected foot muscles assessed using ultrasonography in each cluster were examined. The muscles of interest included the abductor hallucis, flexor hallucis brevis and longus, flexor digitorum brevis and longus, and peroneus longus.ResultsThree subgroups were identified based on foot kinematics during running: cluster 1, lowest NH at initial contact and larger DND; cluster 2, moderate NH at initial contact and smaller DND; and cluster 3, highest NH at initial contact and larger DND. Clusters 1 and 3 had a larger abductor hallucis compared with cluster 2, and cluster 3 had a larger flexor hallucis brevis compared with cluster 2.SignificanceThese subgroups may differ in terms of resistance to and type of running-related injury. Moreover, foot kinematics during running is possibly impacted by the morphology and function of medial intrinsic foot muscles.     

Fatigue effects of marathon running on neuromuscular performance

Nine experienced endurance runners performed individual marathon runs that involved several tests of neuromuscular performance before, during and after the marathon. The tests were performed with special force platform and dynamometer techniques. The results showed an overall decrease in performance from the marathon. The maximal sprint velocity decreased parabolically during the marathon, reaching the final value of 84% of the pre-marathon one. Similarly, the other test results after marathon indicated that maximal isometric knee extension torque was 78%, the performance in a special rebound test (drop jump) 84% and the 5-jump performance 92% of the pre-marathon values. These reductions were accompanied by alteration in the ground reaction force curves in the sprint and jump tests, suggesting reduced tolerance to stretch load as well as loss in the recoil characteristics of the muscles.     

Ontogenetic changes in foot strike pattern and calcaneal loading during walking in young children

The assumption that the morphology of the human calcaneus reflects high and cyclical impact forces at heel strike during adult human walking has never been experimentally tested. Since a walking step with a heel strike is an emergent behavior in children, an ontogenetic study provides a natural experiment to begin testing the relationship between the mechanics of heel strike and calcaneal anatomy. This study examined the ground reaction forces (GRFs) of stepping in children to determine the location of the center of pressure (COP) relative to the calcaneus and the orientation and magnitude of ground reaction forces during foot contact. Three-dimensional kinematic and kinetic data were analyzed for 18 children ranging in age from 11.5 to 43.1 months. Early steppers used a flat foot contact (FFC) and experienced relatively high vertical and resultant GRFs with COP often anterior to the calcaneus. More experienced walkers used an initial heel contact (IHC) in which GRFs were significantly lower but the center of pressure remained under the heel a greater proportion of time. Thus, during FFC the foot experienced higher loading, but the heel itself was relatively wider and the load was distributed more evenly. In IHC walkers load was concentrated on the anterior calcaneus and a narrower heel, suggesting a need for increased calcaneal robusticity during development to mitigate injury. These results provide new insight into foot loading outside of typical mature contact patterns, inform structure-function relationships during development, and illuminate potential causes of heel injury in young walkers.     

两种肌肉调理方法对新学员5km越野后肌疲劳干预效果的比较

 目的 观察本体感觉神经肌肉促进法(proprioceptive neuromuscular facilitation,PNF)与心理肌肉放松法对新学员5 km越野训练肌疲劳的影响,以得出最佳运动后疲劳的恢复方式.方法 选择南京某院校2006-09入学的144名新学员作为研究对象,随机分为A组(PNF干预组)、B组(心理肌肉放松干预组)和C组(对照组),在训练前、训练后第3天、第5天分别评定肌疲劳度并行相关血液生化指标检查.结果 PNF干预组训练后第3天、第5天的肌疲劳程度及血液生化指标增幅较心理肌肉放松干预组及对照组低,心理肌肉放松干预组训练后第3天、第5天的肌疲劳程度及血液生化指标增幅仅较对照组低.3组新学员肌疲劳变化程度差异和相关血液生化指标平均增幅差异均有统计学意义(P<0.05),其中PNF干预组<心理肌肉放松干预组<对照组.结论 PNF法与心理肌肉放松训练法均能有效降低参训人员运动后疲劳,其中PNF法作用更显著.     

Differences in in vivo muscle fascicle and tendinous tissue behavior between the ankle plantarflexors during running

The primary human ankle plantarflexors, soleus (SO ), medial gastrocnemius (MG ), and lateral gastrocnemius (LG ) are typically regarded as synergists and play a critical role in running. However, due to differences in muscle‐tendon architecture and joint articulation, the muscle fascicles and tendinous tissue of the plantarflexors may exhibit differences in their behavior and interactions during running. We combined in vivo dynamic ultrasound measurements with inverse dynamics analyses to identify and explain differences in muscle fascicle, muscle‐tendon unit, and tendinous tissue behavior of the primary ankle plantarflexors across a range of steady‐state running speeds. Consistent with their role as a force generator, the muscle fascicles of the uniarticular SO shortened less rapidly than the fascicles of the MG during early stance. Furthermore, the MG and LG exhibited delays in tendon recoil during the stance phase, reflecting their ability to transfer power and work between the knee and ankle via tendon stretch and storage of elastic strain energy. Our findings add to the growing body of evidence surrounding the distinct mechanistic functions of uni‐ and biarticular muscles during dynamic movements.     

Exhaustive stretch-shortening cycle exercise: no contralateral effects on muscle activity in maximal motor performances

Minor cross-over effects of unilateral muscle fatigue have been reported after isometric exercises. The present study re-examined this possibility after an exhaustive stretch-shortening cycle (SSC)-type exercise. Twenty-five subjects performed on a sledge apparatus a unilateral exhaustive rebound exercise involving mostly the triceps surae muscle group. Ipsilateral vs contralateral fatigue effects were compared in uni- and bilateral tests that included a maximal isometric voluntary contraction (MVC) and a series of 10 maximal drop jumps (DJ). These tests were carried out just before and after (POST) the exhaustive SSC exercise, and were repeated 2 days later (D2), at the expected time of major inflammation and pain. The exercised (fatigued) leg analysis revealed significant declines in MVC and DJ performances at POST and D2, the latter ones being associated with significant decreases in voluntary muscle activity. In contrast, no significant change was found for the non-fatigued leg. These results do not support the existence of cross-over effects after exhaustive SSC exercise, at least when tested in maximal static and dynamic unilateral motor tasks.     

Effects of a 30-min running performed daily after downhill running on recovery of muscle function and running economy

This study investigated the effects of a 30-min level running performed daily for 6 days after downhill running (DHR) on indicators of muscle damage and running economy (RE). Fifty men were placed into five groups – control (CON), 40%, 50%, 60% and 70% (10 subjects per group) – by matching the baseline maximal oxygen consumption () among the groups. Subjects in the 40%, 50%, 60% and 70% groups had a treadmill (0°) run for 30 min at 40%, 50%, 60% and 70% of the pre-determined , respectively, at 1–6 days after a bout of 30-min DHR at −15% (−8.5°). Maximal voluntary isometric strength of the knee extensors, muscle soreness, plasma creatine kinase and lactate dehydrogenase activities were measured before, immediately after and every day for 7 days after DHR. RE was assessed by oxygen consumption, minute ventilation, respiratory exchange ratio, lactate, heart rate and rating of perceived exertion during a 5-min level running at 85% performed before and at 2, 5 and 7 days after DHR. All muscle damage markers changed significantly (P < 0.05) after DHR without significant differences among the groups. The RE parameters showed a significant decrease in RE for 7 days after DHR, but no significant differences in the changes were evident among the groups. These results suggest that the daily running performed after DHR did not have any beneficial or adverse effects on recovery of muscle damage and RE regardless of the intensity.     

Changes in gluteal muscle forces with alteration of footstrike pattern during running

Gait retraining is a common form of treatment for running related injuries. Proximal factors at the hip have been postulated as having a role in the development of running related injuries. How altering footstrike affects hip muscles forces and kinematics has not been described. Thus, we aimed to quantify differences in hip muscle forces and hip kinematics that may occur when healthy runners are instructed to alter their foot strike pattern from their habitual rear-foot strike to a forefoot strike. This may gain insight on the potential etiology and treatment methods of running related lower extremity injury. Twenty-five healthy female runners completed a minimum of 10 running trials in a controlled laboratory setting under rear-foot strike and instructed forefoot strike conditions. Kinetic and kinematic data were used in an inverse dynamic based static optimization to estimate individual muscle forces during running. Within subject differences were investigated using a repeated measures multi-variate analysis of variance. Peak gluteus medius and minimus and hamstring forces were reduced while peak gluteus maximus force was increased when running with an instructed forefoot strike pattern. Peak hip adduction, hip internal rotation, and heel-COM distance were also reduced. Therefore, instructing habitual rearfoot strike runners to run with a forefoot strike pattern resulted in changes in peak gluteal and hamstring muscle forces and hip kinematics. These changes may be beneficial to the development and treatment of running related lower extremity injury.     

Determinant factors in climbing ability: Influence of strength,anthropometry, and neuromuscular fatigue

The goal of this study was to (i) assess the physical and anthropometric differences between three levels of climbers and (ii) predict climbing ability by using a multiple regression model. The participants were divided into novice (n = 15), skilled (n = 16), and elite (n = 10) climbers. Anthropometric characteristics such as height, weight, percentage of body fat and muscle, bi‐acromial breath, arm span, and ape index were measured. General and specific strength were assessed through an arm jump test, a bench press test, and a hand and finger grip strength test in maximal and endurance conditions. All variables were combined into components via a principal component analysis (PCA) and the components used in a multiple regression analysis. The major finding of this study is that climbing ability is more related to specific rather than general strength. Only finger grip strength shows a higher level of initial strength between all samples while the arm jump test discriminates between climbers and non‐climbers. The PCA reveals three components, labeled as training, muscle, and anthropometry, which together explain 64.22% of the variance. The regression model indicates that trainable variables explained 46% of the total variance in climbing ability, whereas anthropometry and muscle characteristics explain fewer than 4%.     

Effect of exercise-induced muscle damage on endurance running performance in humans

Exercise-induced muscle damage (EIMD) is known to decrease muscle strength and power but its effect on endurance performance is unclear. Thirty moderately trained adult runners (24 men and six women) were randomly assigned to EIMD or control. The EIMD group jumped 100 times from a 35 cm bench, while controls did not perform any muscle-damaging exercise. Before and 48 h after treatment, subjects were tested on markers of EIMD, steady-state cardiorespiratory, metabolic and perceptual responses during a constant speed submaximal run; distance ran in 30 min on a treadmill. There were significant changes in muscle soreness, creatine kinase, and knee extensors strength (P<0.01). This EIMD significantly reduced self-paced time trial performance by 4% (P<0.01) because subjects reduced running speed (P=0.02), with no change in perceived exertion (P=0.31). No significant alterations in running economy and other physiological responses to submaximal running were found. However, there was a trend (P=0.08) for increased perceived exertion, which was correlated with decreased time trial performance (P<0.01). In conclusion, EIMD has a significant impact on endurance running performance in humans, and this effect seems to be mediated by alterations in the sense of effort.     

The effect of repeated periods of speed endurance training on performance,running economy,and muscle adaptations

The effect of repeated intense training interventions was investigated in eight trained male runners (maximum oxygen uptake [VO ₂‐max]: 59.3±3.2 mL/kg/min, mean±SD) who performed 10 speed endurance training (SET ; repeated 30‐seconds “all‐out” bouts) and 10 aerobic moderate‐intensity training sessions during two 40‐day periods (P1 and P2) separated by ~80 days of habitual training. Before and after both P1 and P2, subjects completed an incremental test to exhaustion to determine VO ₂‐max and a repeated running test at 90% vVO ₂‐max to exhaustion (RRT ) to determine short‐term endurance capacity. In addition, running economy (RE ) was measured at 60% vVO ₂‐max (11.9±0.5 km/h) and v10‐km (14.3±0.9 km/h), a 10‐km track‐running test was performed, and a biopsy from m. vastus lateralis was collected. 10‐km performance and VO ₂‐max (mL/min) were the same prior to P1 and P2, whereas RE was better (P <.05) before P2 than before P1. During P1 and P2, 10‐km performance (2.9% and 2.3%), VO ₂‐max (2.1% and 2.6%), and RE (1.9% and 1.8% at 60% vVO ₂‐max; 1.6% and 2.0% at v10‐km) improved (P <.05) to the same extent, respectively. Performance in RRT was 20% better (P <.05) after compared to before P2, with no change in P1. No changes in muscle expression of Na⁺,K⁺‐ATP ase α1, α2 and β1, NHE 1, SERCA 1 and SERCA 2, actin, and CaMKII were found during neither P1 nor P2. Thus, the present study demonstrates that a second period of intense training leads to improved short‐term performance and further improved RE , whereas 10‐km performance and VO ₂‐max improve to the same extent as during the first period.     

Analysis of ground reaction forces and muscle activity in individuals with anterior cruciate ligament reconstruction during different running strike patterns

BackgroundAnterior cruciate ligament reconstruction provides successful clinical outcomes. However, reconstruction cannot restore normative lower limb mechanics during running. While numerous studies have investigated running characteristics in individuals with anterior cruciate ligament reconstruction, no study has been compared foot strike patterns among them.Research questionIf ground reaction forces and lower extremity muscle activities in individuals with anterior cruciate ligament reconstruction and healthy control ones differ during three running strike patterns?MethodsIn this cross-sectional study, fourteen healthy adult males and fourteen adult males with anterior cruciate ligament reconstruction were recruited to participate. Surface electromyography of selected lower limb muscles and ground reaction forces were measured during three-strike patterns: rearfoot strike pattern, midfoot strike pattern, and forefoot strike pattern during barefoot running (∼ 3.3 m/s).ResultsThe results revealed that the strike patterns influenced the peak lateral ground reaction force (P < 0.001) and peak vertical impact ground reaction force (P = 0.002) during the stance phase of running for both groups. The strike pattern also influenced the tibialis anterior (P < 0.001) and vastus lateralis (P = 0.035) activities during the early stance phase for both groups. However, the vastus medialis (P = 0.030) presented reduced activity, and the biceps femoris (P = 0.039) presented increased activity in the anterior cruciate ligament reconstruction group. Tibialis anterior (P = 0.021), gastrocnemius medialis (P < 0.001) and vastus medialis (P < 0.001) presented lesser activity irrespective of strike patterns in the anterior cruciate ligament reconstruction group.SignificanceRunning with a forefoot strike pattern may be associated with lesser rearfoot eversion due to lower peak lateral ground reaction forces than running with a rearfoot strike pattern or midfoot strike pattern. Moreover, the altered muscle activities could contribute to the elevated risk of future joint injury in the anterior cruciate ligament reconstruction population.