Article

Forefoot Strikers Exhibit Lower Running-Induced Knee Loading than Rearfoot Strikers

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Abstract

Purpose: Knee pain and Achilles tendinopathies are the most common complaints among runners. The differences in the running mechanics may play an important role in the pathogenesis of lower limb overuse injuries. However, the effect of a runner's foot strike pattern on the ankle and especially on the knee loading is poorly understood. The purpose of this study was to examine whether runners using a forefoot strike pattern exhibit a different lower limb loading profile than runners who use rearfoot strike pattern. Methods: Nineteen female athletes with a natural forefoot strike (FFS) pattern and pair-matched women with rearfoot strike (RFS) pattern (n = 19) underwent 3-D running analysis at 4 m·s⁻¹. Joint angles and moments, patellofemoral contact force and stresses, and Achilles tendon forces were analyzed and compared between groups. Results: FFS demonstrated lower patellofemoral contact force and stress compared with heel strikers (4.3 ± 1.2 vs 5.1 ± 1.1 body weight, P = 0.029, and 11.1 ± 2.9 vs 13.0 ± 2.8 MPa, P = 0.04). In addition, knee frontal plane moment was lower in the FFS compared with heel strikers (1.49 ± 0.51 vs 1.97 ± 0.66 N·m·kg⁻¹, P =0.015). At the ankle level, FFS showed higher plantarflexor moment (3.12 ± 0.40 vs 2.54 ± 0.37 N·m·kg⁻¹; P = 0.001) and Achilles tendon force (6.3 ± 0.8 vs 5.1 ± 1.3 body weight; P = 0.002) compared with RFS. Conclusions: To our knowledge, this is the first study that shows differences in patellofemoral loading and knee frontal plane moment between FFS and RFS. FFS exhibit both lower patellofemoral stress and knee frontal plane moment than RFS, which may reduce the risk of running-related knee injuries. On the other hand, parallel increase in ankle plantarflexor and Achilles tendon loading may increase risk for ankle and foot injuries.

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... Warne et al. showed that a six-week combination program of gait retraining and minimalist shoes could reduce the loading rate and peak impact force by transforming the pattern of RFS to a nonrearfoot strike pattern [16,17]. Female natural FFS had lower extension moment, patellofemoral joint contact force, and patellofemoral stress than those in the RFS group [18]. Researchers transversely compared the biomechanical data between these two strike patterns [18] and the acute changes in their longitudinal posture to analyze their differences [19]. ...
... Female natural FFS had lower extension moment, patellofemoral joint contact force, and patellofemoral stress than those in the RFS group [18]. Researchers transversely compared the biomechanical data between these two strike patterns [18] and the acute changes in their longitudinal posture to analyze their differences [19]. Moreover, most studies of gait retraining have targeted runners with patellofemoral pain [20], ignoring the different running patterns such as greater hip adduction and internal rotation between runners with patellofemoral pain and healthy runners [21]. ...
... For the mechanical property of the patellofemoral joint, a significant decrease of 13.3% was observed in peak PFS in the EG. Similarly, Kulmala et al. [18] showed that the peak PFS of FFS decreased by 15% compared with that of RFS. In the EG, the peak knee extension moment was significantly reduced by 13.8% after the 12-week gait retraining. ...
Article
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Purpose: To explore the changes in knee sagittal angle and moment and patellofemoral joint (PFJ) force and stress before and after 12-week gait retraining. Methods: A total of 30 healthy male recreational runners were randomized into a control group (n = 15) who ran in their original strike pattern using minimalist shoes or experimental group (n = 15) who ran in a forefoot strike pattern using minimalist shoes during the 12-week gait retraining. The kinematic and kinetic data of the dominant leg of the participants during the 12 km/h running were collected by 3D motion capture systems and 3D force platforms. Besides, the biomechanical property of the PFJ was calculated on the basis of the joint force model and the regression equation of the contact area. Results: After the 12-week gait retraining, 78% of the rearfoot strikers turned into forefoot strikers. Peak knee extension moment and peak PFJ stress decreased by 13.8% and 13.3% without altering the running speed, respectively. Meanwhile, no changes in maximum knee flexion angle/extension moment and PFJ force/stress were observed for the control group. Conclusion: The 12-week gait retraining effectively reduced the PFJ stress, thereby providing a potential means of reducing the risk of patellofemoral pain syndrome while running.
... During running, the FSP determines that some muscles will be especially demanded. In this way, rearfoot strike pattern, under shod condition, shows higher demand of knee extensors [22] and midfoot or forefoot strike pattern, under barefoot condition, especially demands the ankle plantar flexors [23]. ...
... However, under shod condition a positive correlation of small magnitude between the CSA and thickness of the PT and Kvert and Kleg was found. Previous studies had demonstrated higher demand of the AT during barefoot running [23] and higher demand of the PT during shod condition [20,22]. Therefore, in light of these results, the major finding of this study was the specificity of the relationship between the morphologic characteristics of the connective tissue and the function the lower-limb stiffness. ...
... Our findings show that during shod running most of the runners show a rearfoot strike pattern, which is supported by previous research [21]. Runners with a rearfoot strike pattern have shown a higher flexion of the knee during the mid-stance phase [20] that causes a higher knee joint load compared to runners with a forefoot strike pattern [22]. As shown in the introduction section, the lower limb behaves like a spring during running [1,2]. ...
Article
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Background: The lower limb behaves like a spring compressing and decompressing during running, where lower-limb stiffness is one of the most influential factors. This prospective observational study is aimed at examining the relationship between the connective tissue morphology and lower-limb stiffness and investigating whether the barefoot/shod condition influences on such relationship. Methods: 14 male amateur runners (10-km time trial <50') were included. Data were recorded over one session, where participants ran 2 trials (i.e., barefoot and shod conditions) of 3 minutes at 12 km/h, where running spatiotemporal parameters and vertical (Kvert) and leg stiffness (Kleg) were obtained. Prior to testing trials, thickness and cross-sectional area (CSA) were recorded for Achilles (AT) and patellar tendons (PT) and plantar fascia (PF) with ultrasound. Results: Under barefoot condition, a positive correlation was found between Kleg and AT-thickness and CSA and PF-thickness; and between Kvert and AT-thickness and PF thickness. Under shod condition, a positive correlation was found between Kleg and PT-CSA and PT-thickness, and between Kvert and PT-CSA and PT-thickness. Conclusions: The results reveal a specificity of the relationship between the lower-limb stiffness and the morphology of the connective tissue. Greater tendon shows higher lower-limb stiffness when that tendon is specially demanded by the function.
... This approach permits to calculate net joint loading and also to estimate the internal force. For instance, the Achilles tendon force has been measured by implanting a transducer under local anaesthesia (Komi et al., 1987), but can be estimated by dividing the plantarflexion moment by the approximated Achilles tendon lever arm (Kulmala et al., 2013). As such, an analysis of external and internal loading becomes possible. ...
... study 8) to perform additional running trials on the ball of the foot. The method proposed by Kulmala et al. (2013) was used to estimate the Achilles tendon force for his habitual running style (i.e., pronounced rearfoot striking) and an instructed running style. Figure 23 shows the Achilles tendon force in the case when acutely changing from a habitual rearfoot strike to an instructed forefoot strike at approximately ~3.3 m/s. ...
... Figure 23 shows the Achilles tendon force in the case when acutely changing from a habitual rearfoot strike to an instructed forefoot strike at approximately ~3.3 m/s. The results are in line with the previous findings (Kulmala et al., 2013;Lieberman et al., 2010;Williams et al., 2000). These findings indicated a significantly lower vertical loading rate and greater loading of Achilles tendon when running with a forefoot strike pattern. ...
Thesis
Running is a gross-motor skill and a popular physical activity, though it comes with a risk of injury. Gait retraining is performed with the intent on managing the risk of running injury. The peak tibial acceleration may be linked with running injuries and is suitable as input for biofeedback. So far, retraining programs with the use of biofeedback on peak tibial acceleration have been bound to a treadmill. Therefore, the objective of this doctoral thesis was to evaluate the effectiveness of a novel music-based biofeedback system on peak tibial acceleration in the context of gait retraining in a training environment. This system is wearable and has lightweight sensors to attach to the lower leg. The sensor first records the tibial acceleration. Then, a processing unit detects the acceleration spike for direct auditory biofeedback. Studies 1 to 5 covered the measurement of peak tibial accelerations, the design of the music-based feedback, and the effectiveness evaluation of the biofeedback system for impact reduction in a training center. In study 1 the peak tibial acceleration of a group of distance runners was reliable in the same test and repeatable in a re-test. The peak tibial accelerations increased with running speed and were correlated with the maximum vertical loading rate of the ground reaction force, which is an impact characteristic derived in the biomechanics laboratory. The developed peak detection algorithm identified the peak tibial acceleration in real-time. The music-based feedback was developed in study 2. The music was superimposed with perceptible pink noise. The noise intensity could be linked to a biological parameter such as the peak acceleration tibial. The tempo of the music synchronized with the cadence of the runner to motivate the runner and allowed for a user-induced change in cadence in response to the biofeedback. Studies 3 to 5 examined the effectiveness of music-based biofeedback on the peak tibial peak in a training environment. We demonstrated that smaller peak values are achievable with the aid of the validated biofeedback system. In study 3, ten runners with high peak tibial acceleration were subjected to biofeedback on the momentary peak tibial acceleration. The group was able to reduce their peak tibial acceleration by 27% or 3 g in the biofeedback condition. Study 4 evaluated the initial learning effect within a single session at ~11.5 km/h. The main change in peak acceleration occurred after approximately 8 minutes of biofeedback. However, there was substantial between-subject variation in time which ranged from 4 to 1329 gait cycles. Study 5 confirmed the effectiveness of the biofeedback in a quasi-randomized study with control group. The experimental group received the biofeedback in a 3-week retraining program comprising of biofeedback faded in time. The control group received tempo-synchronized music as placebo. A running speed of approximately 10 km/h was maintained session after session via speed feedback. All runners completed the running program consisting of 6 sessions. The peak acceleration decreased by 26% or 3 g in the experimental group. The smaller peak values in studies 3-5 must have resulted from a movement alteration, although there was no significant change in running cadence at the group level. Studies 6 to 9 give insight into possible strategies for low(er) peak tibial acceleration in level running. In study 6, we discovered that peak tibial accelerations depend on the manner of heel striking. Specifically, a more pronounced heel landing was correlated with smaller axial (1D) and resultant (3D) peak tibial accelerations. The multicenter results of study 7 showed greater resultant peak acceleration in non-rearfoot strikes compared with heel strikes. This greater acceleration was due to an abrupt horizontal deceleration of the lower leg. In study 8, we described and compared the running mechanics of a successful long-distance runner with low (impact) load and a high load capacity. A pronounced heel strike in conjunction with long stance and short flight phases characterized a low-impact runner who successfully completed 100 marathons in 100 days. Study 9 documented adaptations post-biofeedback in a lab center. There was no clear relationship between the changes in peak tibial acceleration and in running cadence, which confirmed the results of the data captured in the training center. Casuistry showed visually detectable changes in the curve of the vertical ground reaction force. A runner with high peak tibial acceleration peaks changed to a more pronounced rearfoot strike or changed to a non-rearfoot strike pattern to reduce the axial peak tibial acceleration. These results suggest the existence of different distal strategies for impact reduction elicited by biofeedback. Our experiments opened the possibility of impact reduction with the use real-time auditory biofeedback that is perceptible and motivating. Two motor strategies were discovered to run with less peak tibial acceleration. We hope these findings offer encouragement for runners, coaches and clinicians who wish to target a form of low(er) impact running. The biofeedback system effectively modified the running form and has great ecological value due to the portable hardware and energy source for outdoor usage. User-oriented biofeedback systems should become available for the consumer and the patient if proven useful for respectively injury reduction and injury management. Overall, this doctoral thesis contributed to a better understanding of impact severity in distance running and its reduction in a gait retraining context with the use of real-time music-based biofeedback.
... 5,34 Taking a biomechanical model approach to injury, RRIs are caused by high loading relative to tissue strength. 33 Given that the foot is the first point of ground impact and has the potential to mediate the subsequent force applied to the body, 25,38 the relationship between foot strike technique (FST) and RRI has received significant attention within the scientific 11,25,53,66 and general running communities. 46 It has been speculated that for the majority of human evolutionary history, runners would have run barefoot or would have run in minimalist footwear with little or no cushioning (eg, sandals). ...
... Interest in the relationship between FST and injury has, at least in part, been guided by the research examining the relationship between FSP and loading. Some research has found RFSs result in higher magnitudes 38,47,62 and rates 38,57,69 of whole-body loading (via vertical ground reaction forces) and higher knee loading 25,38 in comparison with an FFS (or non-RFS). While loading forms a necessary component of training, resulting in homeostatic-positive responses and adaptations, 9,65 excessive cumulative load and a poor work-recovery ratio may result in maladaptation to training and an increased risk of injury. ...
... Interest in the relationship between FST and injury has, at least in part, been guided by the research examining the relationship between FSP and loading. Some research has found RFSs result in higher magnitudes 38,47,62 and rates 38,57,69 of whole-body loading (via vertical ground reaction forces) and higher knee loading 25,38 in comparison with an FFS (or non-RFS). While loading forms a necessary component of training, resulting in homeostatic-positive responses and adaptations, 9,65 excessive cumulative load and a poor work-recovery ratio may result in maladaptation to training and an increased risk of injury. ...
Article
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Background It has been suggested that foot strike technique (FST) at initial contact is related to running-related injuries (RRIs). Purpose To explore the relationship between FST and RRIs. Study Design Systematic review; Level of evidence, 3. Methods A systematic electronic search was performed using MEDLINE, PubMed, SPORTDiscus, Scopus, and Web of Science databases. Included were studies published in the English language that explored the relationship between FST and RRIs between January 1960 and November 2020. Results were extracted and collated. The Grading of Recommendations, Assessment, Development and Evaluation approach was applied to synthesize the quality of evidence. Results We reviewed 13 studies exploring the relationship between FST and RRIs. Of these, 6 studies reported FST categorically (foot strike pattern [FSP]), and 7 reported continuous measures (foot contact angle, ankle flexion angle, and strike index). Three of the 6 studies looking at categorical FSP found rearfoot strikers have a significantly greater retrospective injury rate than do non– rearfoot strikers, with 1 other study noting a greater risk associated with midfoot and forefoot strike. Regarding the continuous measures of FST, only 1 of the 7 studies reported a significant relationship with RRIs. Conclusion There was low evidence to suggest a relationship between FST (or its subcategories of categorical FSP and continuous measures) and RRIs. While two-thirds of the categorical studies found a relationship between FSP and RRIs, these studies were very low quality, with limitations such as retrospective study design, low participant numbers, and poor FSP assessment methods. More large-scale prospective studies are required.
... During even running (32,33), the reduction of PFJ stress because of forward trunk-leaning occurs without placing further mechanical stress on ankle plantar-flexors (32)(33)(34). This strategy differs to changing foot-strike pattern and step-rate in so much that the latter modifications shift biomechanical loading more distally (10,19,27), which may be associated with higher risks of ankle and foot injuries. The slope of running surface also influences PFJ stress . ...
... A recent study reported a greater reduction in peak PFJ stress when switching to a forefoot strike (;23%), or when increasing the step-rate (;12%), compared with forward trunk-leaning (;5%) during treadmill running (10). However, these modifications were associated with greater mechanical demands on the ankle and foot joints (10,19,27) without taking into consideration the impact of environmental demands. This is significant because most running is performed outdoors and is essentially challenged by uneven terrain. ...
Article
Although decline surfaces or a more upright trunk posture during running increase the patellofemoral joint (PFJ) contact force and stress, less is known about these kinetic parameters under simultaneous changes to the running posture and surface height. This study aimed to investigate the interaction between Step (10-cm drop-step and level step) and Posture (trunk angle from the vertical: self-selected, ∼15°; backward, ∼0°; forward, ∼25°) on PFJ kinetics (primary outcomes) and knee kinematics and kinetics as well as hip and ankle kinetics (secondary outcomes) in 12 runners at 3.5 ms-1. Two-way repeated measures analyses of variance (α = 0.05) revealed no step-related changes in peak PFJ kinetics across running postures; however, a decreased peak knee flexion angle and increased joint stiffness in the drop-step only during backward trunk-leaning. The Step main effect revealed significantly increased peak hip and ankle extension moments in the drop-step, signifying pronounced mechanical demands on these joints. The Posture main effect revealed significantly higher and lower PFJ kinetics during backward and forward trunk-leaning, respectively, when compared with the self-selected condition. Forward trunk-leaning yielded significantly lower peak knee extension moments and higher hip extension moments, whereas the opposite effects occurred with backward trunk-leaning. Overall, changes to the running posture, but not to the running surface height, influenced the PFJ kinetics. In line with the previously reported efficacy of forward trunk-leaning in mitigating PFJ stress while even or decline running, this technique, through a distal-to-proximal joint load redistribution, also seems effective during running on surfaces with height perturbations.
... Landing on the front of the foot has been proposed as less likely to lead to injury (Kulmala et al, 2013) as it reduces peak impact forces (Cavanagh and Lafortune, 1980;Lieberman et al, 2010). This is because the wider forefoot allows impact forces to be distributed over a larger area (Rooney and Derrick, 2013), although these forces are also reduced during heel-strike in appropriate footwear (Whittle, 1999). ...
... However, it is not conclusive that vertical loading forces are directly responsible for lower limb injury (Nigg, 1997), especially given the multiplanar and complicated movements involved in running. Furthermore, whereas rearfoot striking might be associated with certain injuries (e.g., at the knee), forefoot striking is associated with injury to other areas (e.g., ankle) (Kulmala et al, 2013). Higher loads to the gastrocnemius were found in forefoot striking (Shih, Lin and Shiang, 2013), and Stearne et al (2014) stated that forefoot striking thus might actually increase the risk of Achilles tendinopathy and triceps surae injury. ...
Chapter
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A knowledge of the biomechanics of running is invaluable when describing an athlete’s technique, explaining how they speed up or slow down, and understanding the external and internal forces that cause their movements. As the outward expression of movement, an athlete’s biomechanics translates their underlying physiological, nutritional and psychological processes into running motion, and those who are biomechanically “better” are often those who can manage this transfer more efficiently and economically while reducing injury risk. This chapter provides a brief review of the important aspects of the running stride and its various components, the effects of different footstrike patterns and fatigue on running technique, and how racing conditions such as wind, hills and underfoot surface affect an athlete’s biomechanics.
... It is well established that running with a NRFS compared to a RFS pattern redistributes the mechanical load associated with running from the knee to the ankle and calf musculature (Kulmala et al., 2013). For this reason, gait retraining FSP and to reduce impact loading have been suggested as interventions for patients with PFPS (Roper et al., 2016;Davis et al., 2020). ...
... Despite the success of our participants, clinicians implementing gait retraining should be aware of the possible risks of altering FSP. A NRFS exposes runners to greater injury risk in the ankle and foot (Kulmala et al., 2013;Chen et al., 2019). To mitigate injury risk in the current study we excluded individuals with previous foot fracture, included aspects of a commonly used gait retraining strengthening program for the feet and lower legs (Futrell et al., 2020) and implemented a gradual walk-to-run progression . ...
Article
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A rearfoot strike (RFS) pattern with increased average vertical loading rates (AVLR) while running has been associated with injury. This study evaluated the ability of an instrumented sock, which provides real-time foot strike and cadence audio biofeedback, to transition previously injured military service members from a RFS to a non-rearfoot strike (NRFS) running pattern. Nineteen RFS runners (10 males, 9 females) were instructed to wear the instrumented socks to facilitate a change in foot strike while completing an independent walk-to-run progression and lower extremity exercise program. Kinetic data were collected during treadmill running while foot strike was determined using video analysis at initial (T1), post-intervention (T2), and follow-up (T3) data collections. Nearly all runners (18/19) transitioned to a NRFS pattern following intervention (8 ± 2.4 weeks after the initial visit). Most participants (16/18) maintained the transition at follow-up (5 ± 0.8 weeks after the post-intervention visit). AVLR of the involved and uninvolved limb decreased 29% from initial [54.7 ± 13.2 bodyweights per sec (BW/s) and 55.1 ± 12.7 BW/s] to post-intervention (38.7 ± 10.1 BW/s and 38.9 ± 10.0 BW/s), respectively. This effect persisted 5-weeks later at follow-up, representing an overall 30% reduction on the involved limb and 24% reduction on the uninvolved limb. Cadence increased from the initial to the post-intervention time-point (p = 0.045); however, this effect did not persist at follow-up (p = 0.08). With technology provided feedback from instrumented socks, approximately 90% of participants transitioned to a NRFS pattern, decreased AVLR, reduced stance time and maintained these running adaptations 5-weeks later.
... Transitioning to a forefoot strike pattern shifts some of the demand of the knee extensors to the plantar flexors [30], effectively reducing the patellofemoral joint stress. This transition can also eliminate the impact transient of the vertical ground reaction force, thereby reducing the vertical load rate. ...
Article
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Purpose of review: Movement retraining in rehabilitation is the process by which a motor program is changed with the overall goal of reducing pain or injury risk. Movement retraining is an important component of interventions to address patellofemoral pain. The purpose of this paper is to review the methods and results of current retraining studies that are aimed at reducing symptoms of patellofemoral pain. Recent findings: The majority of studies reviewed demonstrated some improvement in patellofemoral pain symptoms and overall function. However, the degree of improvement as well as the persistence of improvement over time varied between studies. The greatest pain reduction and persistent changes were noted in those studies that incorporated a faded feedback design including between 8 and 18 sessions over 2-6 weeks, typically 3-4 sessions per week. Additionally, dosage in these studies increased to 30-45 min during later sessions, resulting in 177-196 total minutes of retraining. In contrast, pain reductions and persistence of changes were the least in studies where overall retraining volume was low and feedback was either absent or continual. Faulty movement patterns have been associated with patellofemoral pain. Studies have shown that strengthening alone does not alter these patterns, and that addressing the motor program is needed to effect these changes. Based upon the studies reviewed here, retraining faulty patterns, when present, appears to play a significant role in addressing patellofemoral pain. Therefore, movement retraining, while adhering to basic motor control principles, should be part of a therapist's intervention skillset when treating patients with PFP.
... The RFS lands with the dorsiflexed ankle, thereby exposing an impact peak of about 1.6 body weight (BW) during early stance and transmitting more axial vGRF to the knee [11]. Therefore, the RFS is demonstrated to be associated with patellofemoral disorders [12]. By contrast, the FFS lands with the plantar flexed ankle without the visible IP of GRF [10] accompanying the greater eccentric contraction in the triceps surae [13]. ...
Article
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Foot strike patterns influence the running efficiency and may be an injury risk. However, differences in the leg stiffness between runners with habitual forefoot (hFFS) and habitual rearfoot (hRFS) strike patterns remain unclear. This study aimed at determining the differences in the stiffness, associated loading rate, and kinematic performance between runners with hFFS and hRFS during running. Kinematic and kinetic data were collected amongst 39 runners with hFFS and 39 runners with hRFS running at speed of 3.3 m/s, leg stiffness (Kleg), and vertical stiffness (Kvert), and impact loads were calculated. Results found that runners with hFFS had greater Kleg (P = 0.010, Cohen's d = 0.60), greater peak vertical ground reaction force (vGRF) (P = 0.040, Cohen's d = 0.47), shorter contact time(t c ) (P < 0.001, Cohen's d = 0.85), and smaller maximum leg compression (ΔL) (P = 0.002, Cohen's d = 0.72) compared with their hRFS counterparts. Runners with hFFS had lower impact peak (IP) (P < 0.001, Cohen's d = 1.65), vertical average loading rate (VALR) (P < 0.001, Cohen's d = 1.20), and vertical instantaneous loading rate (VILR) (P < 0.001, Cohen's d = 1.14) compared with runners with hRFS. Runners with hFFS landed with a plantar flexed ankle, whereas runners with hRFS landed with a dorsiflexed ankle (P < 0.001, Cohen's d = 3.35). Runners with hFFS also exhibited more flexed hip (P = 0.020, Cohen's d = 0.61) and knee (P < 0.001, Cohen's d = 1.15) than runners with hRFS at initial contact. These results might indicate that runners with hFFS were associated with better running economy through the transmission of elastic energy.
... For runners who strike with a rear-foot strike pattern (RFS), the impact forces result in a distinct impact peak in the vertical ground reaction force (GRF)-time curve, which is often reduced or even eliminated in runners with a mid-foot (MFS) or fore-foot strike (FFS) pattern (Futrell et al., 2018;Lieberman et al., 2010). Furthermore, when runners switched from a RFS to a FFS, LR were reduced by over 50% (Samaan et al., 2014), and knee joint moments were reduced (Dorsey et al., 2000;Kulmala et al., 2013;Valenzuela et al., 2015). The results of these studies suggest that there is a relationship between LE loading patterns and foot-ground interactions. ...
Article
While running provides an accessible form of cardiovascular stimulus, many runners report lower extremity musculoskeletal injuries. Additionally, runners who develop overuse injuries, such as tibial stress fractures, also have higher loading rates (LR) and impact forces. Purpose Therefore, the purpose of this study was to investigate how uphill treadmill running at iso-efficient speeds (IES; a speed-incline combination having the same metabolic intensity as level running) influences impact LR, and peak vertical ground reaction forces (GRF). Methods Eleven collegiate distance runners completed 3 experimental running conditions (0%, 4%, and 8% treadmill inclination). During each running condition, the metabolic intensity was controlled by implementing an IES for each runner. Results All variables of interest were significantly reduced as treadmill incline increased (0% > 4% > 8%). Conclusion Incline running is more metabolically demanding compared to level running at the same speed. But, if speed is controlled to maintain metabolic output, runners could decrease LR and peak vertical GRF while achieving the same metabolic training stimulus as level running.
... In a previous study, the 3D GRF in the running and sidestep motions was estimated with a relative RMSE of 20% to 30% with a convolutional neural network (CNN) and data from an IMU attached to the sacrum [34]. The difference in the kinetics based on the change in the footstrike type during running is a GRF of 20% BW, knee adduction moment of 0.5 Nm/kg, and ankle plantar flexor moment of 0.6 Nm/kg [35]. Moreover, the risk of injury increased when the braking force exceeded 30% BW [36]. ...
Article
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Kinetics data such as ground reaction forces (GRFs) are commonly used as indicators for rehabilitation and sports performance; however, they are difficult to measure with convenient wearable devices. Therefore, researchers have attempted to estimate accurately unmeasured kinetics data with artificial neural networks (ANNs). Because the inputs to an ANN affect its performance, they must be carefully selected. The GRF and center of pressure (CoP) have a mechanical relationship with the center of mass (CoM) in the three dimensions (3D). This biomechanical characteristic can be used to establish an appropriate input and structure of an ANN. In this study, an ANN for estimating gait kinetics with a single inertial measurement unit (IMU) was designed; the kinematics of the IMU placed on the sacrum as a proxy for the CoM kinematics were applied based on the 3D spring mechanics. The walking data from 17 participants walking at various speeds were used to train and validate the ANN. The estimated 3D GRF, CoP trajectory, and joint torques of the lower limbs were reasonably accurate, with normalized root-mean-square errors (NRMSEs) of 6.7% to 15.6%, 8.2% to 20.0%, and 11.4% to 24.1%, respectively. This result implies that the biomechanical characteristics can be used to estimate the complete three-dimensional gait data with an ANN model and a single IMU.
... Sagittal plane ankle positioning can also have an effect on KJLs through the type of footfall strike adopted. Within running literature [71,72], it has been established that runners utilising a forefoot-strike pattern (i.e. plantarflexed) will generate significantly lower GRFs than rear-footfall pattern runners. ...
Article
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Background Cutting actions are associated with non-contact ACL injuries in multidirectional sports due to the propensity to generate large multiplanar knee joint loads (KJLs) that have the capacity to increase ACL loading and strain. Numerous studies have investigated the biomechanical determinants of KJLs in cutting tasks. The aim of this systematic review was to comprehensively review the literature regarding biomechanical determinants of KJLs during cutting, in order to develop a cutting technical framework alongside training recommendations for practitioners regarding KJL mitigation. Methods Databases (SPORTDiscus, Web of Science and PubMed) were systematically searched using a combination of the following terms: “Biomechanical determinants”, or “Knee abduction moment”, or “Technical determinants”, or “Knee loading”, or “Knee loads”, or “Mechanical determinants”, or “ACL strain”, or “Knee adduction moment”, or “Anterior tibial shear”, or “Knee internal rotation moment”, or “Knee valgus moment” AND “Change of direction”, or “Cutting manoeuvre”, or “Run and cut”, or “Run-and-cut”, or “Sidestepping”, or “Side-stepping”, or “Shuttle run”. Inclusion criteria were as follows: studies examining a cutting task < 110° with a preceding approach run that examined biomechanical determinants of KJLs using three-dimensional motion analysis. Results The search returned 6404 possibly eligible articles, and 6 identified through other sources. Following duplicate removal, 4421 titles and abstracts were screened, leaving 246 full texts to be screened for inclusion. Twenty-three full texts were deemed eligible for inclusion and identified numerous determinants of KJLs; 11 trunk, 11 hip, 7 knee, 3 multiplanar KJLs, 5 foot/ankle and 7 identifying ground reaction forces (GRFs) as determinants of KJLs. Conclusion Using the framework developed from the results, cutting KJLs can be mitigated through the following: reducing lateral foot-plant distances, thus lowering hip abduction and orientating the foot closer to neutral with a mid-foot or forefoot placement strategy; minimising knee valgus and hip internal rotation angles and motion at initial contact (IC) and weight acceptance (WA); avoiding and limiting lateral trunk flexion and attempt to maintain an upright trunk position or trunk lean into the intended direction; and finally, reducing GRF magnitude during WA, potentially by attenuation through increased knee flexion and emphasising a greater proportion of braking during the penultimate foot contact (PFC).
... Moreover, another limitation of this research is that biomechanical variables were not controlled. For example, the AT load is up to 19 % higher for forefoot runners than rearfoot runners (Kulmala et al., 2013). Further research might investigate the association of AT dimensions and the incidence of running injuries, especially in non-rearfoot runners. ...
Conference Paper
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The aim of this study was to compare the dimensions of Achilles tendon, Achilles tendon moment arm and foot lever ratio between runners with tendinopathy and healthy control runners. We paired 12 runners diagnosed with baseline tendinopathy with 12 healthy control runners. The dimensions of Achilles tendon, Achilles tendon moment arm and foot lever ratio were measured using kinematic analysis and ultrasound imaging. Based on the parametric paired-samples T-Test, we compared the dependent variables measured on the affected lower limb. No differences were found between the groups for Achilles tendon length, Achilles tendon moment arm and foot lever ratio. Runners diagnosed with tendinopathy had thicker Achilles tendons than healthy control runners.
... These include (1) differences in the calculation of GRF variables, (2) criteria used to define injury, (3) underpowered studies (range, 6-16 participants), and (4) lack of controlling for foot strike pattern. Runners with different foot strike patterns are known to exhibit different joint mechanics and GRFs during running, 24,41 as well as associations between vertical load rates and injury. 16 Several studies have also identified a potential relationship between lower extremity stiffness during running and injury. ...
Article
Background: Inconsistent associations have been reported for impact-related ground reaction force variables and running injuries when grouping all injuries together. However, previous work has shown more consistent associations when focusing on specific injuries. Purpose: To compare ground reaction force variables between healthy and injured runners as a group and within specific common injuries. Study design: Controlled laboratory study. Methods: A total of 125 runners presenting with patellofemoral pain, tibial bone stress injury, plantar fasciitis, Achilles tendinopathy, or iliotibial band syndrome and 65 healthy controls completed an instrumented treadmill assessment at a self-selected speed. Impact-related ground reaction force variables included vertical average (VALR) and instantaneous (VILR) load rates, posterior and medial/lateral instantaneous load rates, and vertical stiffness at initial loading (VSIL). Mean comparisons were made between the general and specific injury and control groups (α = .05). Cutoff thresholds were established and evaluated using several criteria. Results: VALR (+17.5%; P < .01), VILR (+15.8%; P < .01), and VSIL (+19.7%; P < .01) were significantly higher in the overall injured versus control groups. For individual injuries, VALR, VILR, and VSIL were significantly higher for patellofemoral pain (+23.4%-26.4%; P < .01) and plantar fasciitis (+17.5%-29.0%; P < .01), as well as VSIL for Achilles tendinopathy (+29.4%; P < .01). Cutoff thresholds showed better diagnostic criteria for individual versus grouped injuries. Conclusion: Impact variables (VALR, VILR, and VSIL) were significantly higher when assessing the injured group as a whole. However, these findings were driven by specific injury groups, highlighting the importance of taking an injury-specific approach to biomechanical risk factors for running injury. Clinical relevance: These results suggest that practitioners may want to address impact loading in their treatment of injured runners, especially in those with patellofemoral pain and plantar fasciitis.
... Estudios como el de Salzler et al. (Salzler, Bluman, Noonan, Chiodo, & de Asla, 2012) y el de Kulmala et al. (Kulmala, Avela, Pasanen, & Parkkari, 2013) destacan que se podría producir un aumento en el riesgo de lesiones por sobreuso en el tobillo y musculatura del tríceps sural. ...
... Patellofemoral contact area is calculated as a function of knee flexion angle, and pfJS is calculated by dividing pfJRF by the contact area. This model has been used to estimate pfJRFs and pfJSs during walking (Brechter & Powers, 2002b), stair ascent and descent (Brechter & Powers, 2002a), running (Kulmala, Avela, Pasanen, & Parkkari, 2013;Willson, Ratcliff, Meardon, & Willy, 2015), and squatting (Salem & Powers, 2001;Wallace et al., 2002). However, it is subject to several limitations including not accounting for co-contraction at the knee, and deriving quadriceps effective lever arms and patellofemoral contact areas from cadaver studies using limited ranges of knee flexion. ...
Article
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Back squats are a common strengthening exercise for knee and hip musculature. However, repetitive loaded movements like backs squats result in high patellofemoral joint loading and therefore may contribute to the development of common overuse injuries. Thus, it is important to understand how changing parameters such as squat depth or load influences patellofemoral loading. This study investigated differences in patellofemoral loading when experienced female lifters squatted to three depths (above parallel, parallel, and below parallel) and with three loads (unloaded, 50%, and 85% of depth-specific one repetition maximums). Patellofemoral joint reaction forces (pfJRF) and stresses (pfJS) were calculated from biomechanical models incorporating knee extensor moments (KEM) and joint angles. Peak KEMs displayed a depth-by-load interaction such that within each depth, as load increased so did peak KEM. However, within each load, the effects of depth were different. Peak pfJRF also increased with load and was higher at below parallel than above or parallel depths. Peak pfJS also displayed a depth by load interaction, increasing with load within a given depth, and being greatest at the below parallel depths within a given load. If patellofemoral joint loading is a concern clinicians or coaches should carefully monitor the depth and load combinations being used.
... In particular, a protruding impact peak (Figure 1) is one of the features of vertical GRF that is indirectly related to injury risk while running. Protruding impact peak is often related to heel striking, which gained a lot of interest in research on running-related sport injuries (Kulmala et al. 2013;Knorz et al. 2017). ...
Article
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Protruding impact peak is one of the features of vertical ground reaction force (GRF) that is related to injury risk while running. The present research is dedicated to predicting GRF impact peak appearance by setting a binary classification problem. Kinematic data, namely a number of raw signals in the sagittal plane, collected by the Vicon motion capture system (Oxford Metrics Group, UK) were employed as predictors. Therefore, the input data for the predictive model are presented as a multi-channel time series. Deep learning techniques, namely five convolutional neural network (CNN) models were applied to the binary classification analysis, based on a Multi-Layer Perceptron (MLP) classifier, support vector machine (SVM), logistic regression, k-nearest neighbors (kNN), and random forest algorithms. SVM, logistic regression, and random forest classifiers demonstrated performances that do not statistically significantly differ. The best classification accuracy achieved is 81.09% ± 2.58%. Due to good performance of the models, this study serves as groundwork for further application of deep learning approaches to predicting kinetic information based on this kind of input data.
... These include (1) differences in the calculation of GRF variables, (2) criteria used to define injury, (3) underpowered studies (range, 6-16 participants), and (4) lack of controlling for foot strike pattern. Runners with different foot strike patterns are known to exhibit different joint mechanics and GRFs during running, 24,41 as well as associations between vertical load rates and injury. 16 Several studies have also identified a potential relationship between lower extremity stiffness during running and injury. ...
... However, although mechanically sound, using an increased plantarflexed foot strike as an isolated strategy may not be sufficient and functionally limiting. Over time this strategy may be dangerous for the body, possibly leading to injurious consequences (Wheat, 2005) such as patellofemoral pain (Kulmala et al., 2013). ...
Article
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Impact loading plays a key role in the pathophysiology of running-related injuries. Providing real-time feedback may be an effective strategy to reduce impact loading; however, it is currently unclear what an effective training method to help runners achieve a habitual low loading rate is. We subjected 20 healthy non-runners to a structured sequence of direct and indirect biofeedback designed to facilitate broader exploration of neuro-mechanical workspace for potential movement solutions (indirect feedback on cadence and foot-strike angle) and to refine and converge upon an optimal sub-set of that space to match the task goal (direct feedback on loading rate). While indirect biofeedback on foot-strike angle yielded a lower impact load than providing direct biofeedback on loading rate, compared to indirect biofeedback on foot-strike angle, providing direct feedback on loading rate statistically increased (+58%, p = 0.007) the range of goal-relevant solutions participants used to lower their impact loading. Results showed that structured feedback was effective in increasing the range of input parameters that match the task goal, hence expanding the size of goal-relevant solutions, which may benefit running performance under changing environmental constraints.
... The footwear described in a recent paper by Kulmala et al. would fall within this classification, since the model examined (Brooks Ghost 6) had a heel-toe drop of 12 mm. Nevertheless, these authors used a different term, "Conventional cushioned running shoes" [41]. Knapik (2009) reported that the terms "motion control", "stability" or "cushioned" shoes were applied interchangeably to 17 of the 19 shoes studied by the three entities consulted (store, manufacturer and magazine) [28]. ...
Article
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Objective: Our study aim is to identify and describe the definitions used for different types of running shoes. In addition, we highlight the existence of gaps in these concepts and propose possible new approaches. Methods: This review was undertaken in line with the guidelines proposed by Green et al., based on a literature search (until December 2019) of the PubMed, Web of Science, Scopus, SPORTDiscus and Google Scholar databases. A total of 23 papers met the inclusion criteria applied to identify the definition of running shoes. Results: Although there is a certain consensus on the characteristics of minimalist footwear, it is also described by other terms, such as barefoot-style or barefoot-simulating. Diverse terms are also used to describe other types of footwear, and in these cases, there is little or no consensus regarding their characteristics. Conclusions: The terms barefoot-simulated footwear, barefoot-style footwear, lightweight shoes and full minimalist shoes are all used to describe minimalist footwear. The expressions partial minimalist, uncushioned minimalist and transition shoes are used to describe footwear with non-consensual characteristics. Finally, labels such as shod shoes, standard cushioned running shoes, modern shoes, neutral protective running shoes, conventional, standardised, stability style or motion control shoes span a large group of footwear styles presenting different properties.
... We sought to address three fundamental issues. First, based on the reported effects of forefoot striking on the Achilles tendon 16,19 , we hypothesized that energy storage in the plantar flexor tendons is greater during forefoot striking compared to rearfoot striking. Second, based on differences in knee and ankle kinematics at foot contact between rearfoot and forefoot striking, we hypothesized that there are shorter plantar flexor fiber lengths and changes to the plantar flexor muscles' ability to generate peak active force. ...
Article
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Running is thought to be an efficient gait due, in part, to the behavior of the plantar flexor muscles and elastic energy storage in the Achilles tendon. Although plantar flexor muscle mechanics and Achilles tendon energy storage have been explored during rearfoot striking, they have not been fully characterized during forefoot striking. This study examined how plantar flexor muscle-tendon mechanics during running differs between rearfoot and forefoot striking. We used musculoskeletal simulations, driven by joint angles and electromyography recorded from runners using both rearfoot and forefoot striking running patterns, to characterize plantar flexor muscle-tendon mechanics. The simulations revealed that foot strike pattern affected the soleus and gastrocnemius differently. For the soleus, forefoot striking decreased tendon energy storage and fiber work done while the muscle fibers were shortening compared to rearfoot striking. For the gastrocnemius, forefoot striking increased muscle activation and fiber work done while the muscle fibers were lengthening compared to rearfoot striking. These changes in gastrocnemius mechanics suggest that runners planning to convert to forefoot striking might benefit from a progressive eccentric gastrocnemius strengthening program to avoid injury.
... It was noted that forefoot runners exhibit higher mechanical loading characteristics on ankle structures whereas rearfoot runners show a higher loading of the knee joint (7,13). One possible conclusion of this fact is that forefoot runners are more prone to ankle and foot injuries and rearfoot runners more prone to knee injuries (32). The injury patterns of the human foot may also differ as MFS/FFS running could possibly increase the risk for metatarsal, plantar, and submetatarsal skin injuries (42). ...
Article
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The footstrike pattern of an athlete is understood as the way the foot touches the ground. Over the years, several definitions and techniques to classify and quantify footstrike patterns have been described. Therefore, this narrative review summarizes the existing classifications of footstrike patterns, gives suggestions for further use of these classifications, and provides a summary of the relationship between footstrike patterns and the occurrence of overuse injuries. Footstrike patterns are classified by using nominal (e.g. forefoot strike, midfoot strike, rearfoot strike) or continuous variables (e.g. footstrike angle). Possible assessments include visual, video-based, 3D-biomechanical, force plate-based or inertial measurement unit-based analysis. Scientists, coaches, and clinicians can choose between different methods to analyze footstrike patterns in runners. All approaches to classify footstrike patterns have advantages and limitations. In certain situations, it might be beneficial to combine these methods. Despite great efforts in analyzing footstrike patterns, relationships between footstrike patterns and running-related injuries are mostly unclear at present. Based on the current literature, causal links to overuse injuries, recommendations to change running technique, and other simplifications solely based on the footstrike pattern must be considered critically.
... Numerous cross-sectional studies have suggested that there may be distinct biomechanical differences between male and female runners (Almonroeder and Benson, 2017;Chumanov et al., 2008;Ferber et al., 2003;Hannigan et al., 2018;Phinyomark et al., 2015;Sinclair and Selfe, 2015;Vannatta and Kernozek, 2018;Willson et al., 2012;Willson et al., 2015) and recent evidence suggests that level of competition and weekly running mileage may also influence running biomechanics (Clermont et al., 2017;Clermont et al., 2019). There is a relatively large body of evidence that have reported distinctly different biomechanical features of running gait with changes in footstrike pattern (Almonroeder et al., 2013;Kernozek et al., 2016;Kernozek et al., 2018;Kulmala et al., 2013;Stearne et al., 2014;Vannatta et al., 2017;Vannatta and Kernozek, 2015). Additionally, footwear conditions may also affect biomechanical variables (Lewinson et al., 2016). ...
Article
Background: The role of biomechanical variables of running gait in the development of running related injury has not been clearly elucidated. Several systematic reviews have examined running biomechanics and its association with particular running related injuries. However, due to retrospective designs, inferences into the cause of these injuries are limited. Although prospective studies have been completed, no quantitative analysis pooling these results has been completed. Methods: A systematic review of MEDLINE, CINAHL, and PubMed was completed. Articles included used prospective study designs, human subjects currently completing a regular running program, and a minimum 12-week follow-up period. Excluded articles had no biomechanical data reported, participants who were beginning runners or military recruits, or had an intervention provided. Findings: Thirteen studies met these criteria. Pooled analyses were completed if two or more studies were available with samples that investigated the same sex and competition level. A qualitative synthesis was completed when pooled analysis was not possible. Five unique running samples were identified and allowed for pooled analyses of variables in mixed-sex collegiate runners and female recreational runners. Moderate evidence exists for increased hip adduction and reduced peak rearfoot eversion as risk factors for running related injury in female recreational runners. Variables differed in other samples of runners. Interpretation: A runner's sex and competition level may affect the relationship between biomechanical factors and the development of running related injury. Hip adduction and rearfoot eversion may be important factors related to running related injury in female recreational runners. Further investigation of biomechanical factors in running injury is warranted.
... 19 To date, however, only 1 study 20 suggested that novice runners who increased their weekly volume by more than 30% could be more prone to develop distance-based running injuries such as PFP than runners who changed their weekly running distance by less than 10%. This result may be due to the complexity of external load (influenced by, for example, speed, 21 hills, 22 foot-strike pattern, 23 and cadence 24 ) but may also be due to the difficulty of measuring maximum capacity, which may vary greatly among individuals and even among days in the same runner. As proposed by Wiese-Bjornstal, 25 the sport injury risk consists of a combination of biological, physical, psychological, and sociocultural factors. ...
Article
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Patellofemoral pain (PFP) is among the most common injuries in recreational runners. Current evidence does not identify alignment, muscle weakness, and patellar maltracking or a combination of these as causes of PFP. Rather than solely investigating biomechanics, we suggest a holistic approach to address the causes of PFP. Both external loads, such as changes in training parameters and biomechanics, and internal loads, such as sleep and psychological stress, should be considered. As for the management of runners with PFP, recent research suggested that various interventions can be considered to help symptoms, even if these interventions target biomechanical factors that may not have caused the injury in the first place. In this Current Concepts article, we describe how the latest evidence on education about training modifications, strengthening exercises, gait and footwear modifications, and psychosocial factors can be applied when treating runners with PFP. The importance of maintaining relative homeostasis between load and capacity will be emphasized. Recommendations for temporary or longer-term interventions will be discussed. A holistic, evidence-based approach should consist of a graded exposure to load, including movement, exercise, and running, while considering the capacity of the individual, including sleep and psychosocial factors. Cost, accessibility, and the personal preferences of patients should also be considered.
... The authors concluded that a forefoot strike pattern was generally associated with a greater vertical maximum peak force but significantly lower loading rates in the ankle, knee, and hip joints, which is in line with the lower flexion and compression of the lower limb observed for DF low than DF high . Similar studies were performed by other researchers and demonstrated that a forefoot strike pattern reduces knee loads whereas a rearfoot strike pattern reduces loads at the Achilles tendon [65][66][67] and ankle joint [68], again agreeing with less lower limb flexion for DF low than DF high . ...
Article
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The aim was to identify the differences in lower limb kinematics used by high (DF high) and low (DF low) duty factor (DF) runners, particularly their sagittal plane (hip, knee, and ankle) joint angles and pelvis and foot segment angles during stance. Fifty-nine runners were divided in two DF groups based on their mean DF measured across a range of speeds. Temporal characteristics and whole-body three-dimensional kinematics of the running step were recorded from treadmill runs at 8, 10, 12, 14, 16, and 18 km/h. Across speeds, DF high runners, which limit vertical displacement of the COM and promote forward propulsion, exhibited more lower limb flexion than DF low during the ground contact time and were rearfoot strikers. On the contrary, DF low runners used a more extended lower limb than DF high due to a stiffer leg and were midfoot and forefoot strikers. Therefore, two different lower limb kinematic mechanisms are involved in running and the one of an individual is reflected by the DF.
... This translates into a difference in the resulting C 20 values. The importance of this difference is that the meniscus bears a load that is several times the body weight (Mündermann et al. 2008;Kulmala et al. 2013), and therefore undergoes large strain deformation, which means the high strain response is important under physiological loading conditions. While the literature on the microstructure of porcine meniscus is limited, it has been reported to be roughly similar to human meniscus geometrically (Takroni et al. 2016) and in terms of anatomical structure, potential of healing, and weight (Dutton et al. 2010). ...
Article
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Constitutive modeling of the meniscus is critical in areas like knee surgery and tissue engineering. At low strain rates, the meniscus can be described using a hyperelastic model. Calibration of hyperelastic material models of the meniscus is challenging on many fronts due to material variability and friction. In this study, we present a framework to determine the hyperelastic material parameters of porcine meniscus (and similar soft tissues) using no-slip uniaxial compression experiments. Because of the nonhomogeneous deformation in the specimens, a finite element solution is required at each step of the iterative calibration process. We employ a Bayesian calibration approach to account for the inherent material variability and a Bayesian optimization approach to minimize the resulting cost function in the material parameter space. Cylindrical specimens of porcine meniscus from the anterior, middle and posterior regions are tested up to 30% compressive strain and the Yeoh form of hyperelastic strain energy density function is used to describe the material response. The results show that the Yeoh form is able to accurately describe the compressive response of porcine meniscus and that the Bayesian calibration and optimization approaches are able to calibrate the model in a computationally efficient manner while taking into account the inherent material variability. The results also show that the shear modulus or the initial stiffness is roughly uniform across the different areas of the meniscus, but there is significant spatial heterogeneity in the response at high strains. In particular, the middle region is considerably stiffer at high strains. This heterogeneity is important to consider in modeling the response of the meniscus for clinical applications.
... During running, different foot strike patterns may affect Achilles tendon force, knee loading, and the potential for Achilles tendon or knee injury [11]. Mechanical consequences from the shift from an RFS to MFS or FFS pattern are thought to minimize some risk factors associated with running-related injuries such as tibial stress injuries, plantar fasciitis, tibial stress fractures, and knee injuries [12]. Several studies compared the kinetic and kinematic properties and muscle activity of these various foot strike patterns during running [13,14]. ...
Article
Background Anterior 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 question If 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? Methods In 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). Results The 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. Significance Running 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.
... Thus, many shoe manufacturers have also begun to focus on barefoot running, in which Vibram Five Fingers, Nike Free and minimalist shod were produced and incorporated into the forefoot style [24,25]. It has been reported that forefoot runners exhibit increases in Achilles tendon force (ATF) and reductions in patellofemoral contact force (PTF) and pressure (PP) in comparison to individuals exhibiting a rearfoot strike pattern [26]. Numerous studies have verified that BF and minimalist BFIS were associated with increases in vertical loading rates, reduced knee extensor and increased ankle plantarflexion moments [24,27]. ...
Article
Objectives: Although overuse running injury risks for the ankle and knee are high, the effect of different shoe designs on Achilles tendon force (ATF) and Patellofemoral joint contact force (PTF) loading rates are unclear. Therefore, the primary objective of this study was to compare the ATF at the ankle and the PTF and Patellofe-moral joint stress force (PP) at the knee using different running shoe designs (forefoot shoes vs. normal shoes). Methods: Fourteen healthy recreational male runners were recruited to run over a force plate under two shoe conditions (forefoot shoes vs. normal shoes). Sagittal plane ankle and knee kinematics and ground reaction forces were simultaneously recorded. Ankle joint mechanics (ankle joint angle, velocity, moment and power) and the ATF were calculated. Knee joint mechanics (knee joint angle velocity, moment and power) and the PTF and PP were also calculated. Results: No significant differences were observed in the PTF, ankle plantarflexion angle, ankle dorsiflexion power, peak vertical active force, contact time and PTF between the two shoe conditions. Compared to wearing normal shoes, wearing the forefoot shoes demonstrated that the ankle dorsiflexion angle, knee flexion velocity, ankle dorsiflexion moment extension, knee extension moment, knee extension power, knee flex-ion power and the peak patellofemoral contact stress were significantly reduced. However, the ankle dorsiflexion velocity, ankle plantarflexion velocity, ankle plantarflexion moment and Achilles tendons force increased significantly. Conclusions: These findings suggest that wearing forefoot shoes significantly decreases the patellofemoral joint stress by reducing the moment of knee extension, however the shoes increased the ankle plantarflexion moment and ATF force. The forefoot shoes effectively reduced the load on the patellofemoral joint during the stance phase of running. However, it is not recommended for new and novice runners and patients with Achilles tendon injuries to wear forefoot shoes.
... On the other hand, past studies have suggested that the properties of the AT could be affected by running strike patterns [6,44,45]. The plantarflexion torque exerted to resist dorsiflexion torque during running with a forefoot strike pattern was larger than that exerted to resist dorsiflexion torque during running with a rearfoot strike pattern and is important for energy release and absorption by plantar flexors [46]. ...
Article
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The morphological and mechanical properties (e.g., stiffness, stress, and force) of the Achilles tendon (AT) are generally associated with its tendinosis and ruptures, particularly amongst runners. Interest in potential approaches to reduce or prevent the risk of AT injuries has grown exponentially as tendon mechanics have been efficiently improving. The following review aims to discuss the effect of different types of exercise on the AT properties. In this review article, we review literature showing the possibility to influence the mechanical properties of the AT from the perspective of acute exercise and long-term training interventions, and we discuss the reasons for inconsistent results. Finally, we review the role of the habitual state in the AT properties. The findings of the included studies suggest that physical exercise could efficiently improve the AT mechanical properties. In particular, relatively long-term and low-intensity eccentric training may be a useful adjunct to enhance the mechanical loading of the AT.
... It is likely that the increased quadriceps muscle forces and patellofemoral loading shown overall and in the female PFP group were mediated by the rearfoot strike pattern adopted in relation to control runners. Utilization of a rearfoot strike pattern places increased demands on the knee extensors [53], and patellofemoral stress is greater in rearfoot strikers [54]. From a clinical perspective, transitioning from a rearfoot strike pattern has been shown to attenuate patellofemoral joint loading and improve pain symptoms in male runners, although no such intervention has been undertaken in females [25]. ...
Article
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Patellofemoral pain (PFP) is a common atraumatic knee pathology in runners, with a complex multifactorial aetiology influenced by sex differences. This retrospective case–control study therefore aimed to evaluate lower limb kinetics and kinematics in symptomatic and control male and female runners using musculoskeletal simulation. Lower extremity biomechanics were assessed in 40 runners with PFP (15 females and 25 males) and 40 controls (15 females and 25 males), whilst running at a self-selected velocity. Lower extremity biomechanics were explored using a musculoskeletal simulation approach. Four intergroup comparisons—(1) overall PFP vs. control; (2) male PFP vs. male control; (3) female PFP vs. female control; and (4) male PFP vs. female PFP—were undertaken using linear mixed models. The overall (stress per mile: PFP = 1047.49 and control = 812.93) and female (peak stress: PFP = 13.07 KPa/BW and control = 10.82 KPa/BW) comparisons showed increased patellofemoral joint stress indices in PFP runners. A significantly lower strike index was also shown in PFP runners in the overall (PFP = 17.75% and control = 33.57%) and female analyses (PFP = 15.49% and control = 40.20%), revealing a midfoot strike in control, and a rearfoot pattern in PFP runners. Peak rearfoot eversion and contralateral pelvic drop range of motion (ROM) were shown to be greater in PFP runners in the overall (eversion: PFP = −8.15° and control = −15.09°/pelvic drop ROM: PFP = 3.64° and control = 1.88°), male (eversion: PFP = −8.05° and control = −14.69°/pelvic drop ROM: PFP = 3.16° and control = 1.77°) and female (eversion: PFP = 8.28° and control = −15.75°/pelvic drop ROM: PFP = 3.64° and control = 1.88°) PFP runners, whilst female PFP runners (11.30°) exhibited a significantly larger peak hip adduction compared to PFP males (7.62°). The findings from this investigation highlight biomechanical differences between control and PFP runners, as well as demonstrating distinctions in PFP presentation for many parameters between sexes, highlighting potential risk factors for PFP that may be addressed through focused intervention modalities, and also the need, where appropriate, for sex-specific targeted treatment approaches.
... The higher FSI in the MFS group results in distinct distributions of the muscular output in the lower extremities between RFS and MFS runners [i.e., higher moments at the ankle and lower moments at the knee joint for MFS (Kulmala et al., 2013;Kuhman et al., 2016)], and leads to improvements in the cost coefficient (Ekizos et al., 2018). However, the improved cost coefficient due to the higher FSI in MFS did not improve running economy because of the lower contact time and thus greater rate of ground reaction force development (Ekizos et al., 2018). ...
Article
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In this paper we examined how runners with different initial foot strike pattern (FSP) develop their pattern over increasing speeds. The foot strike index (FSI) of 47 runners [66% initially rearfoot strikers (RFS)] was measured in six speeds (2.5–5.0 ms ⁻¹ ), with the hypotheses that the FSI would increase (i.e., move toward the fore of the foot) in RFS strikers, but remain similar in mid- or forefoot strikers (MFS) runners. The majority of runners (77%) maintained their original FSP by increasing speed. However, we detected a significant (16.8%) decrease in the FSI in the MFS group as a function of running speed, showing changes in the running strategy, despite the absence of a shift from one FSP to another. Further, while both groups showed a decrease in contact times, we found a group by speed interaction ( p < 0.001) and specifically that this decrease was lower in the MFS group with increasing running speeds. This could have implications in the metabolic energy consumption for MFS-runners, typically measured at low speeds for the assessment of running economy.
... According to the traditional view, the cushioning structure of running shoes allows for more material deformation and lowers the impact force, thereby playing an important role in protection of the lower extremities during running. Another view is that running shoes with large drops would promote a rearfoot strike pattern that increases the impact force [26]. Several studies have shown mixed results for the effect of the drop of running shoes on the vertical impact force and the vertical loading rate [5,8,[13][14][15]27]. ...
Article
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The heel-to-toe drop of running shoes is a key parameter influencing lower extremity kinematics during running. Previous studies testing running shoes with lower or larger drops generally used minimalist or maximalist shoes, where the factors outside of the drop may lead to the observed changes in running biomechanics. Therefore, our aim was to compare the strike patterns, impact force, and lower extremity biomechanics when running in shoes that varied only in their drops. Eighteen habitual rearfoot strikers performed trials wearing running shoes with four drop conditions: 15 mm, 10 mm, 5 mm, and without a drop. Three-dimensional (3D) tracks of the reflective markers and impact force were synchronously collected using a video graphic acquisition system and two force plates. The biomechanical parameters were compared among the four drop conditions using one-way ANOVA of repeated measures. A greater foot inclination angle (p = 0.001, ηp2 = 0.36) at initial contact and a lower vertical loading rate (p = 0.002, ηp2 = 0.32) during the standing phase were found when running in shoes with large drops compared with running in shoes without a drop. Running in shoes with large drops, as opposed to without, significantly increased the peak knee extension moment (p = 0.002, ηp2 = 0.27), but decreased the peak ankle eversion moment (p = 0.001, ηp2 = 0.35). These findings suggest that the heel-to-toe drop of running shoes significantly influences the running pattern and the loading on lower extremity joints. Running shoes with large drops may be disadvantageous for runners with knee weakness and advantageous for runners with ankle weakness.
... Running with a NRF strike has been shown to elicit increased plantarflexor muscle activity and may cause higher plantarflexor moments and Achilles tendon strain compared with a RF strike pattern [12,[23][24][25]. It is possible the increased demand of plantarflexors of the lower limb with NRF strike running could lead to fatigue of these muscles, which some authors have postulated could be a reason for runners' inability to maintain a NRF strike pattern for an entire run or race [21,26]. ...
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1) Background: Research into foot strike patterns (FSP) has increased due to its potential influence on performance and injury reduction. The purpose of this study was to evaluate changes in FSP throughout a maximal 800-m run using a conformable inertial measurement unit attached to the foot.; (2) Methods: Twenty-one subjects (14 female, 7 male; 23.86 ± 4.25 yrs) completed a maximal 800-m run while foot strike characteristics were continually assessed. Two measures were assessed across 100-m intervals: the percentage of rearfoot strikes (FSP%RF), and foot strike angle (FSA). The level of significance was set to p ≤ 0.05.; (3) Results: There were no differences in FSP%RF throughout the run. Significant differences were seen between curve and straight intervals for FSAAVE (F [1, 20] = 18.663, p < 0.001, ηp 2 = 0.483).; (4) Conclusions: Participants displayed decreased FSA, likely indicating increased plantarflexion, on the curve compared to straight intervals. The analyses of continuous variables, such as FSA, allow for the detection of subtle changes in foot strike characteristics, which is not possible with discrete classifiers, such as FSP%RF.
... NRFS runners are exposed to higher injury risk in the ankle and foot because of the shift in loading that takes place from the knee and hip joints to the lower leg and foot. 60,61 Participants in this study reported no injuries during the intervention and remained injury-free 6 months after enrollment. This finding is of importance considering that previous injury is a risk factor for future RRI, 62 and up to 56% of runners who sustain a RRI have been observed to sustain a second injury within a 24-month period. ...
Article
Introduction: Running-related musculoskeletal injury (RRI) among U.S. military service members continues to negatively impact force readiness. There is a paucity of evidence supporting the use of RRI interventions, such as gait retraining, in military populations. Gait retraining has demonstrated effectiveness in altering running biomechanics and reducing running load. The purpose of this pilot study was to investigate the clinical effect of a gait retraining intervention on a military cadet population recovering from a lower-extremity RRI. Materials and methods: The study design is a pilot study. Before study initiation, institutional approval was granted by the Keller Army Community Hospital Office of Human Research Protections. Nine rearfoot strike (RFS) runners recovering from a lower-extremity RRI at the U.S. Military Academy were prospectively enrolled and completed a gait retraining intervention. Participants followed-up with their assigned medical provider 6 times over 10 weeks for a clinical evaluation and running gait retraining. Gait retraining was provided utilizing verbal, visual, and audio feedback to facilitate a change in running foot strike pattern from RFS to non-rearfoot strike (NRFS) and increase preferred running step rate. At pre-intervention and post-intervention running ground reaction forces (GRF) [average vertical loading rate (AVLR), peak vertical GRF], kinematic (foot strike pattern) and temporospatial (step rate, contact time) data were collected. Participants self-reported their level of function via the Single Assessment Numeric Evaluation, Patient-Specific Functional Scale, and total weekly running minutes. Paired samples t-tests and Wilcoxon signed rank tests were used to compare pre- and post-intervention measures of interest. Values of P < .05 were considered statistically significant. Results: Nine patients completed the 10-week intervention (age, 20.3 ± 2.2 years; height, 170.7 ± 13.8 cm; mass, 71.7 ± 14.9 kg; duration of injury symptoms, 192.4 ± 345.5 days; running speed, 2.8 ± 0.38 m/s). All nine runners (100%) transitioned from RFS to NRFS. Left AVLR significantly decreased from 60.3 ± 17.0 bodyweight per second (BW/s) before intervention to 25.9 ± 9.1 BW/s after intervention (P = 0.008; effect size (d) = 2.5). Right AVLR significantly decreased from 60.5 ± 15.7 BW/s to 32.3 ± 12.5 BW/s (P < .001; d = 2.0). Similarly, step rate increased from 169.9 ± 10.0 steps per minute (steps/min) before intervention to 180.5 ± 6.5 steps/min following intervention (P = .005; d = 1.3). Single Assessment Numeric Evaluation scores improved significantly from 75 ± 23 to 100 ± 8 (P = .008; d = 1.5) and Patient-Specific Functional Scale values significantly improved from 6 ± 2.3 to 9.5 ± 1.6 (P = .007; d = 1.8) after intervention. Peak vertical GRF (left, P = .127, d = 0.42; right, P = .052, d = 0.53), contact time (left, P = 0.127, d = 0.42; right, P = 0.052, d = 0.53), and total weekly continuous running minutes (P = 0.095, d = 0.80) remained unchanged at post-intervention. All 9 patients remained injury free upon a 6-month medical record review. Conclusions: In 9 military service members with a RRI, a 10-week NRFS gait retraining intervention was effective in improving running mechanics and measures of function. Patients remained injury-free 6 months following enrollment. The outcomes of this pilot study suggest that individuals recovering from certain lower-extremity RRIs may benefit from transitioning to an NRFS running pattern.
... For example, reduced knee flexion and ankle dorsiflexion were observed in the stance phase of FFS running. [7][8][9] In addition, a greater negative ankle joint moment was generated in the first half of the stance phase of FFS running, rather than RFS running. 10 In the first half of the stance phase, while running, the muscle-tendon units (MTU) of the ankle plantar flexors are lengthened, whereas they are shortened in the second half of the stance phase. ...
Article
The present study aimed to clarify the effect of the foot strike pattern on muscle–tendon behavior and kinetics of the gastrocnemius medialis during treadmill running. Seven male participants ran with 2 different foot strike patterns (forefoot strike [FFS] and rearfoot strike [RFS]), with a step frequency of 2.50 Hz and at a speed of 2.38 m/s for 45 seconds on a treadmill with an instrumented force platform. The fascicle behavior of gastrocnemius medialis was captured using a B-mode ultrasound system with a sampling rate of 75 Hz, and the mechanical work done and power exerted by the fascicle and tendon were calculated. At the initial contact, the fascicle length was significantly shorter in the FFS than in the RFS ( P = .001). However, the fascicular velocity did not differ between strike patterns. Higher tendon stretch and recoil were observed in the FFS ( P < .001 and P = .017, respectively) compared with the RFS. The fascicle in the positive phase performed the same mechanical work in both the FFS and RFS; however, the fascicle in the negative phase performed significantly greater work in the FFS than in the RFS ( P = .001). RFS may be advantageous for requiring less muscular work and elastic energy in the series elastic element compared with the FFS.
... In line with this finding, previous studies have reported reduced peak GRF values during barefoot in [38,39]. The characteristics of the vertical GRF during the first half of running gait depend upon the initial condition of the lower limb joints at touchdown [40]. During barefoot running, the ankle is in a more plantar-flexed position before initial contact and the knee becomes significantly more flexed before initial contact [8]. ...
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Purpose: The current study aimed to evaluate the effects of barefoot and shod running with two different styles on ground reaction force-frequency content in recreational runners with low arched feet. Methods: The statistical sample of this research was 13 males with Pronated Feet (PF) (Mean±SD age: 26.2±2.8 y; height: 176.1±8.4 cm; weight: 78.3±14.3 kg). A force plate (Bertec, USA) with a sample rate of 1000 Hz was used to record the reaction forces under each foot. Three test conditions in our study included shod running with rearfoot, midfoot, and forefoot patterns. Repeated-measures Analysis of Variance (ANOVA) was used for analyzing the data. Results: During forefoot running, the research subjects attained 10% higher GRF values in vertical direction, compared with rearfoot running (P˂0.001, d=2.133). Forefoot running decreased the peak vertical GRF, compared to rearfoot running (by 12%, P=0.01, d=0.826). Barefoot running decreased the peak vertical GRF, compared to shod running (by 6%, P=0.027, d=1.143). The collected results revealed a significantly lower FyMed (P<0.02, d=1.11, 14%), Fy99.5% (P<0.02, d=0.11, 8%), and greater FyNe (P<0.02, d=0.72, 10%), Fz99.5% (P<0.01, d=4.30, 124%), and FzNe (P<0.01, d=1.65, 44%) when running with rearfoot strike pattern, compared with forefoot strike pattern. Conclusion: The study subjects with pronated feet experienced greater GRF values during forefoot running than rearfoot; such data may imply an increased risk of running injuries. Therefore, forefoot running is not recommended for runners with pronated feet.
Article
Objectives To evaluate short-term effects of a four-week gait retraining program using visual feedback on trunk flexion angle, patellofemoral joint (PFJ) stress, lower extremity biomechanics and motor skill automaticity. Design Longitudinal interventional study. Settings University research laboratory. Participants Twelve asymptomatic recreational runners (seven male and five female). Main outcome measures Trunk kinematics as well as lower extremity kinematics and kinetics were assessed prior to training at week 1 (baseline) and week 2, 3, 4 and 8 (retention). PFJ stress was computed using a sagittal plane model. A dual-task procedure was performed to examine automaticity. Results At week 8, runners demonstrated 10.1° increase in trunk flexion angle (p < .001) and 17.8% reduction in peak PFJ stress (p < .001) compared to baseline. This is associated with a 16.8% decrease in knee extensor moment and less than 2.5° change in knee flexion angle. Participants also showed 33.3% increase in peak hip extensor moment and small reduction in peak ankle plantar flexor moment. Lastly, runners demonstrated automaticity of the modified skill with a dual-task cost of less than 3%. Conclusion The gait retraining program is effective to elicit short term changes in trunk position, PFJ stress, and automaticity of the new motor skill.
Chapter
Although people have been running since the beginning of time, running shoes are relatively recent and their development and availability have significantly increased during the last 50 years. Running footwear was and is still designed to first protect the runner’s feet and musculoskeletal apparatus. However, there is actually a paradigm shift with the release of advanced footwear technology aiming at improving running performance. Simultaneously, barefoot running or running with shoes offering minimal cushioning became increasingly popular. These two opposite trends raise a lot of questions: some of them unanswered, regarding their respective benefits and the risks for elite and recreational runners. This chapter describes the different types and structures of shoes used for running in and out of the stadium and addresses the performance and safety issues of these footwears.
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Background The literature on the reliability of qualitative and quantitative measures for running video analysis in the adolescent population is limited. Reliability of 2-dimensional (2D) video analysis has been reported in adult runners, but these findings may not apply to youth runners. Purpose We sought to determine the intra-rater and inter-rater reliability of sagittal and frontal plane kinematics using 2D video analysis in healthy adolescent runners. Methods High-definition (1080p) videos were recorded of 10 healthy runners between 14 and 18 years old running on a treadmill at self-selected speed with markers attached to the cervical spine, pelvis, and lower extremities. Kinematic variables in the sagittal and frontal planes were measured using Dartfish Motion Analysis Software by 3 raters (2 sports medicine physical therapists and a research assistant). Intra- and inter-rater reliability were calculated using intraclass correlation coefficients (ICCs). Results Of the 10 runners, 4 (40%) were male and the mean age was 16 ± 1.5 years. The intra-rater ICC for all kinematic variables ranged from 0.574 to 0.999 for the experienced physical therapist, and 0.367 to 0.973 for the inexperienced research assistant. The inter-rater ICC for all raters ranged from −0.01 to 0.941. Eleven kinematic variables showed substantial agreement and 4 showed almost perfect agreement. Step width and foot progression showed fair and poor agreement, respectively. Conclusions Running analysis using 2D video can be performed reliably in adolescents on all kinematic variables except for step width and foot progression. Inexperienced raters can be properly trained in the video analysis of running kinematics to consistently assess the same runner.
Chapter
Anterior knee pain, also known as patellofemoral pain (PFP), affects approximately 22% of the general population, with increased prevalence in the adolescent community, as high as 28% [1]. It is twice as common among females (29.2%) than males (15.5%) [1]. The predominant demographics for PFP includes adolescents, young active adults, military recruits, and elite athletes particularly runners, cyclists, and basketball players [2–5].
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Background Traditional running shoes with heel-to-toe drops is thought to be a contributor to increased patellofemoral joint stress, which is proposed as a mechanism of patellofemoral pain. Research question: Is there an increase in patellofemoral joint stress when running in shoes with drops compared to running in shoes without a drop? Methods Lower limbs kinematics and ground reaction force were collected from eighteen healthy runners during over-ground running in shoes with 15 mm, 10 mm, 5 mm drops, and without a drop. Patellofemoral joint force and stress were calculated from the kinematic and kinetic data using a biomechanical model of the patellofemoral joint. Results The peak patellofemoral joint stress was increased by more than 15% when running in shoes with 15 mm and 10 mm drops compared to running in shoes without a drop (p = 0.003, p = 0.001). The knee flexion angle was significantly increased when running in shoes with 15 mm, 10 mm and 5 mm drops (p = 0.014, p = 0.003, p = 0.002), the knee extension moment (p = 0.009, p = 0.002) and patellofemoral joint force (p = 0.003, p = 0.001) were increased when running in shoes with 15 mm and 10 mm drops, compared to running in shoes without a drop. Significance Compared to running in shoes without a drop, running in shoes with > 5 mm drops increase the peak patellofemoral joint stress significantly, which is mainly due to the increased knee extension moment.
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Background: An estimated 56% of recreational runners sustain a running-related injury related to the high impact forces in running. Increasing step frequency (cadence) while maintaining a consistent speed has been shown to be an effective way to lower impact forces which may reduce injury risk. Purpose: To examine effects of increased cadence on peak impact force during running in an outdoor setting. It was hypothesized that as cadence increases, peak force would decrease. Study design: Repeated measures, quasi-experimental. Methods: Peak force and cadence measurements were collected from 15 recreational runners (8 females, 7 males) during two 2.4-mile outdoor runs. Peak force was measured using an insole-based load measuring device. Baseline session run was completed at participant's naturally preferred cadence and cadence session run was completed at a cadence targeted to be 10% greater than baseline. Pace was monitored with a GPS watch. Cadence was cued by an auditory metronome and measured with both GPS watch and insoles. Repeated-measures ANOVA's examined the differences in average peak force, GPS-reported cadence, and insole-reported cadence between mile 1 and mile 2, and across the two cadence conditions. Results: Cadence differences of 7.3% were observed between baseline and cadence sessions (p<0.001). A concurrent decrease in average peak force of 5.6% was demonstrated during the cadence run (p<0.05). Average cadences measured by GPS watch and insoles were found to be the same at both baseline (p=0.096) and during cadence (p=0.352) sessions. Conclusion: Increasing cadence by an average of 7% in an outdoor setting resulted in a decrease in peak force at two different time points during a 2.4-mile run. Furthermore, using a metronome for in-field cadence manipulation led to a change in cadence. This suggests that a metronome may be an effective tool to manipulate cadence for the purpose of decreasing peak impact force in an outdoor setting. Level of evidence: 3b.
Article
Objective: To systematically review and synthesise patellofemoral joint reaction force (PFJRF) in healthy individuals and those with patellofemoral pain and osteoarthritis (OA), during everyday activities, therapeutic exercises and with physical interventions (eg, foot orthotics, footwear, taping, bracing). Design: A systematic review with meta-analysis. Data sources: Medline, Embase, Scopus, CINAHL, SportDiscus and Cochrane Library databases were searched. Eligibility criteria: Observational and interventional studies reporting PFJRF during everyday activities, therapeutic exercises, and physical interventions. Results: In healthy individuals, the weighted average of mean (±SD) peak PFJRF for everyday activities were: walking 0.9±0.4 body weight (BW), stair ascent 3.2±0.7 BW, stair descent 2.8±0.5 BW and running 5.2±1.2 BW. In those with patellofemoral pain, peak PFJRF were: walking 0.8±0.2 BW, stair ascent 2.5±0.5 BW, stair descent 2.6±0.5 BW, running 4.1±0.9 BW. Only single studies reported peak PFJRF during everyday activities in individuals with patellofemoral OA/articular cartilage defects (walking 1.3±0.5 BW, stair ascent 1.6±0.4 BW, stair descent 1.0±0.5 BW). The PFJRF was reported for many different exercises and physical interventions; however, considerable variability precluded any pooled estimates. Summary: Everyday activities and exercises involving larger knee flexion (eg, squatting) expose the patellofemoral joint to higher PFJRF than those involving smaller knee flexion (eg, walking). There were no discernable differences in peak PFJRF during everyday activities between healthy individuals and those with patellofemoral pain/OA. The information on PFJRF may be used to select appropriate variations of exercises and physical interventions.
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Content Distance running is one of the most popular physical activities, and running-related injuries (RRIs) are also common. Foot strike patterns have been suggested to affect biomechanical variables related to RRI risks. Objective To determine the effects of foot strike techniques on running biomechanics. Data Sources The databases of Web of Science, PubMed, EMBASE, and EBSCO were searched from database inception through November 2018. Study Selection The initial electronic search found 723 studies. Of these, 26 studies with a total of 472 participants were eligible for inclusion in this meta-analysis. Study Design Systematic review and meta-analysis. Level of Evidence Level 4. Data Extraction Means, standard deviations, and sample sizes were extracted from the eligible studies, and the standard mean differences (SMDs) were obtained for biomechanical variables between forefoot strike (FFS) and rearfoot strike (RFS) groups using a random-effects model. Results FFS showed significantly smaller magnitude (SMD, −1.84; 95% CI, −2.29 to −1.38; P < 0.001) and loading rate (mean: SMD, −2.1; 95% CI, −3.18 to −1.01; P < 0.001; peak: SMD, −1.77; 95% CI, −2.21 to −1.33; P < 0.001) of impact force, ankle stiffness (SMD, −1.69; 95% CI, −2.46 to −0.92; P < 0.001), knee extension moment (SMD, −0.64; 95% CI, −0.98 to −0.3; P < 0.001), knee eccentric power (SMD, −2.03; 95% CI, −2.51 to −1.54; P < 0.001), knee negative work (SMD, −1.56; 95% CI, −2.11 to −1.00; P < 0.001), and patellofemoral joint stress (peak: SMD, −0.71; 95% CI, −1.28 to −0.14; P = 0.01; integral: SMD, −0.63; 95% CI, −1.11 to −0.15; P = 0.01) compared with RFS. However, FFS significantly increased ankle plantarflexion moment (SMD, 1.31; 95% CI, 0.66 to 1.96; P < 0.001), eccentric power (SMD, 1.63; 95% CI, 1.18 to 2.08; P < 0.001), negative work (SMD, 2.60; 95% CI, 1.02 to 4.18; P = 0.001), and axial contact force (SMD, 1.26; 95% CI, 0.93 to 1.6; P < 0.001) compared with RFS. Conclusion Running with RFS imposed higher biomechanical loads on overall ground impact and knee and patellofemoral joints, whereas FFS imposed higher biomechanical loads on the ankle joint and Achilles tendon. The modification of strike techniques may affect the specific biomechanical loads experienced on relevant structures or tissues during running.
Article
Over the last 50 years, the development of running shoes has been mainly focused on improving the protection and comfort of the runner and her/his foot. Although there have been tentative attempts by companies to make shoes a tool for improving athletic performance, this goal has only recently been achieved. Indeed, the year 2016 was a real turning point when Nike launched its first shoe benefiting from the advanced footwear technology. Advanced footwear technology mostly consists of an increased sole thickness, a curved and stiff plate embedded or below the shoe midsole, and an outsole with a marked concave shape. This innovation turned to a game changer in the world of distances running performance. Indeed, between 2016 and 2019, many male and female runners broke personal best times, national records, area, and world records in distance from 5 km to the marathon. The present article aimed at describing the magnitude of these performance enhancements in distance running as well as and the possible underlying performance-enhancement mechanisms associated with the advanced footwear technology. It also reviewed the existing literature on the safety aspects of "classical" construction shoes and advanced footwear technology shoes. It concluded on a possible shoe mechanical tests-based protocol to maintain fair distance running competitions while not totally preventing manufacturers to innovate, and some thoughts on the nature and goals of further studies to be conducted to assess the safety (macro- and micro-traumatic) of advanced footwear technology in both elite and recreational runner populations.
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Background Although it is assumed that the presence of patellofemoral pain (PFP) may result in compensatory behaviors that can alter trunk kinematics and lower limb mechanics, the influence of the exacerbation of patellofemoral pain on trunk kinematics and lower limb mechanics during stair negotiation has not been established. Research question Does the exacerbation of PFP symptoms lead to altered trunk kinematics and lower limb mechanics during stair negotiation? Methods Three-dimensional kinematics and kinetics were obtained from 45 women with PFP during stair descent and ascent. Data were obtained before and after a pain exacerbation protocol. The variables of interest were peak trunk, hip, and knee flexion, and ankle dorsiflexion; peak hip, and knee extensor, and ankle plantarflexor moments. Paired t-tests were used to compare the variables of interest before and after pain exacerbation. Results Following pain exacerbation, there was a decrease in peak knee extensor moment during stair descent (Effect size = −0.68; p = 0.01) and stair ascent (Effect size = −0.56; p = 0.02); as well as in peak ankle dorsiflexion during stair descent (Effect size = −0.33; p = 0.01) and stair ascent (Effect size = −0.30; p = 0.01). An increase in ankle plantarflexor moment during stair descent (Effect size = 0.79; p < 0.01) and stair ascent (Effect size = 0.89; p < 0.01) was also observed. No significant differences were observed for peak trunk, hip, and knee flexion or hip extensor moment (p > 0.05). Significance Our findings show compensatory strategies used by people with PFP in response to symptoms exacerbation that may have a negative impact on knee and ankle mechanics. Our findings also suggest that people with PFP do not seem to change their trunk, hip, and knee flexion or hip extensor moment during stair negotiation in response to symptom exacerbation.
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Runners were classified using their duty factor (DF) and using their foot-strike pattern (FSP; rearfoot, midfoot, or forefoot strikers), determined from their foot-strike angle (FSA). High and low DF runners showed different FSPs but DF was assumed to not only reflect what happens at initial contact with the ground (more global than FSP/FSA). Hence, FSP and DF groups should not necessarily be constituted by the same runners. However, the relation between FSP and DF groups has never been investigated, leading to the aim of this study. One hundred runners ran at 9, 11, and 13 km/h. Force data (1000 Hz) and whole-body kinematics (200 Hz) were acquired by an instrumented treadmill and optoelectronic system and were used to classify runners according to their FSA and DF. Weak correlations were obtained between FSA and DF values and a sensitivity of 50% was reported between FSP and DF groups, i.e., only one in two runners was attributed to the DF group supposedly corresponding to the FSP group. Therefore, ‘local’ FSP/FSA and DF do not represent similar running pattern information when investigated at the individual level and DF should be preferred to FSP/FSA when evaluating the global running pattern of a runner.
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In this review of patellofemoral joint forces as they might apply to implant design, methodologies for estimating forces on the patella and estimates of the forces, as reported in the literature, are summarized. Two methodologies exist for studying joint loads; one that measures kinematics in-vivo and uses analysis to estimate the joint loads and another that measures ground reaction forces and uses analysis to estimate the joint loads. In both these analyses many assumptions are required with varying degrees of uncertainty; here, those assumptions are examined with data from the published literature. The topics covered include: relationships between quadriceps forces and patellofemoral forces or patella ligament forces, relationships between knee joint moments and quadriceps forces, knee joint moments in various gaits, relationships between patellofemoral forces and lateral subluxation forces, and relationships between patella forces and inferior-superior forces. In many cases, there is little data on patella forces during normal activities, in other cases, there are some discrepancies in reported patella forces, i.e. during squat.
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Humans have engaged in endurance running for millions of years, but the modern running shoe was not invented until the 1970s. For most of human evolutionary history, runners were either barefoot or wore minimal footwear such as sandals or moccasins with smaller heels and little cushioning relative to modern running shoes. We wondered how runners coped with the impact caused by the foot colliding with the ground before the invention of the modern shoe. Here we show that habitually barefoot endurance runners often land on the fore-foot (fore-foot strike) before bringing down the heel, but they sometimes land with a flat foot (mid-foot strike) or, less often, on the heel (rear-foot strike). In contrast, habitually shod runners mostly rear-foot strike, facilitated by the elevated and cushioned heel of the modern running shoe. Kinematic and kinetic analyses show that even on hard surfaces, barefoot runners who fore-foot strike generate smaller collision forces than shod rear-foot strikers. This difference results primarily from a more plantarflexed foot at landing and more ankle compliance during impact, decreasing the effective mass of the body that collides with the ground. Fore-foot- and mid-foot-strike gaits were probably more common when humans ran barefoot or in minimal shoes, and may protect the feet and lower limbs from some of the impact-related injuries now experienced by a high percentage of runners.
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To test the hypothesis that dynamic load at baseline can predict radiographic disease progression in patients with medial compartment knee osteoarthritis (OA). During 1991-93 baseline data were collected by assessment of pain, radiography, and gait analysis in 106 patients referred to hospital with medial compartment knee OA. At the six year follow up, 74 patients were again examined to assess radiographic changes. Radiographic disease progression was defined as more than one grade narrowing of minimum joint space of the medial compartment. In the 32 patients showing disease progression, pain was more severe and adduction moment was higher at baseline than in those without disease progression (n=42). Joint space narrowing of the medial compartment during the six year period correlated significantly with the adduction moment at entry. Adduction moment correlated significantly with mechanical axis (varus alignment) and negatively with joint space width and pain score. Logistic regression analysis showed that the risk of progression of knee OA increased 6.46 times with a 1% increase in adduction moment. The results suggest that the baseline adduction moment of the knee, which reflects the dynamic load on the medial compartment, can predict radiographic OA progression at the six year follow up in patients with medial compartment knee OA.
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In order to further compare shod versus barefoot running, 35 subjects ran two bouts of 4 minutes at 3.33 m x s(-1) on a treadmill dynamometer. Parameters were measured on about 60 consecutive steps. Barefoot showed mainly lower contact and flight time (p < 0.05), lower passive peak (1.48 versus 1.70 body weight, p < 0.05), higher braking and pushing impulses (p < 0.05), and higher pre-activation of triceps surae muscles (p < 0.05) than shod. It was concluded that when performed on a sufficient number of steps, barefoot running leads to a reduction of impact peak in order to reduce the high mechanical stress occurring during repetitive steps. This neural-mechanical adaptation could also enhance the storage and restitution of elastic energy at ankle extensors level.
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To determine whether the current practice of prescribing distance running shoes featuring elevated cushioned heels and pronation control systems tailored to the individual's foot type is evidence-based. MEDLINE (1950-May 2007), CINAHL (1982-May 2007), EMBASE (1980-May 2007), PsychInfo (1806-May 2007), Cochrane Database of Systematic Reviews (2(nd) Quarter 2007), Cochrane Central Register of Controlled trials (2(nd) Quarter 2007), SPORTSDiscus (1985-May 2007) and AMED (1985-May 2007). Review English language articles were identified via keyword and medical subject headings (MeSH) searches of the above electronic databases. With these searches and the subsequent review process, controlled trials or systematic reviews were sought in which the study population included adult recreational or competitive distance runners, the exposure was distance running, the intervention evaluated was a running shoe with an elevated cushioned heel and pronation control systems individualised to the wearer's foot type, and the outcome measures included either running injury rates, distance running performance, osteoarthritis risk, physical activity levels, or overall health and wellbeing. The quality of these studies and their findings were then evaluated. No original research that met the study criteria was identified either directly or via the findings of the six systematic reviews identified. The prescription of this shoe type to distance runners is not evidence-based.
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Runners are sometimes advised to alter their strike pattern as a means of increasing performance or in response to injury. The purpose of this study was to compare lower extremity mechanics of rearfoot strikers (RFS), who were instructed to run with a forefoot strike pattern (CFFS) to those of a preferred forefoot striker (FFS). Three-dimensional mechanics of 9 FFS and 9 CFFS were evaluated. Peak values for most kinematic and kinetic variables and all patterns of movement were not found to be statistically different between CFFS and FFS. Only peak vertical ground reaction force and peak ankle plantarflexion moment were found to be significantly lower (p ≤ .05) in the CFFS group. This suggests that RFS are able to assume a FFS pattern with very little practice that is very similar to that of a preferred FFS. The impact of changing one's strike pattern on injury risk and running performance needs further study.
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Running is one of the most popular leisure sports activities. Next to its beneficial health effects, negative side effects in terms of sports injuries should also be recognised. Given the limitations of the studies it appears that for the average recreational runner, who is steadily training and who participates in a long distance run every now and then, the overall yearly incidence rate for running injuries varies between 37 and 56%. Depending on the specificity of the group of runners concerned (competitive athletes; average recreational joggers; boys and girls) and on different circumstances these rates vary. If incidence is calculated according to exposure of running time the incidence reported in the literature varies from 2.5 to 12.1 injuries per 1000 hours of running. Most running injuries are lower extremity injuries, with a predominance for the knee. About 50 to 75% of all running injuries appear to be overuse injuries due to the constant repetition of the same movement. Recurrence of running injuries is reported in 20 to 70% of the cases. From the epidemiological studies it can be concluded that running injuries lead to a reduction of training or training cessation in about 30 to 90% of all injuries, about 20 to 70% of all injuries lead to medical consultation or medical treatment and 0 to 5% result in absence from work. Aetiological factors associated with running injuries include previous injury, lack of running experience, running to compete and excessive weekly running distance. The association between running injuries and factors such as warm-up and stretching exercises, body height, malalignment, muscular imbalance, restricted range of motion, running frequency, level of performance, stability of running pattern, shoes and inshoe orthoses and running on 1 side of the road remains unclear or is backed by contradicting or scarce research findings. Significantly not associated with running injuries seem age, gender, body mass index, running hills, running on hard surfaces, participation in other sports, time of the year and time of the day. The prevention of sports injuries should focus on changes of behaviour by health education. Health education on running injuries should primarily focus on the importance of complete rehabilitation and the early recognition of symptoms of overuse, and on the provision of training guidelines.
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Abstract Barefoot running, which was how people ran for millions of years, provides an opportunity to study how natural selection adapted the human body to run. Because humans evolved to run barefoot , a barefoot running style that minimizes impact peaks and ...
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Impact forces have been associated with the development of musculoskeletal injuries. However, results of epidemiologic studies that assess the association between impact loading and the development of acute or chronic injuries do not support this notion. There is agreement that excessive impact force may produce damage to the human musculoskeletal system and that there is a window of loading in which biologic tissue reacts positively to the applied impact load. However, it seems that the impact forces and stresses acting on cartilage, bones, ligaments, and tendons during running are typically within an acceptable range. Running on soft or hard surface materials creates different feelings of comfort. A muscle-tuning model suggests that muscles in general attempt to avoid vibrations using a tuning strategy to establish a critically damped mechanical system. Thus, the different feeling may manifest itself in the form of changed comfort or performance, a concept that is certainly not in agreement with the previous paradigm of impact forces and cushioning. (C) Lippincott-Raven Publishers.
Article
Patellofemoral pain (PFP) has often been attributed to abnormal hip and knee mechanics in females. To date, there have been few investigations of the hip and knee mechanics of males with PFP. The purpose of this study was to compare the lower extremity mechanics and alignment of male runners with PFP with healthy male runners and female runners with PFP. We hypothesized that males with PFP would move with greater varus knee mechanics compared with male controls and compared with females with PFP. Furthermore, it was hypothesized that males with PFP would demonstrate greater varus alignment. A gait and single-leg squat analysis was conducted on each group (18 runners per group). Measurement of each runner's tibial mechanical axis was also recorded. Motion data were processed using Visual 3D (C-Motion, Bethesda, MD). ANOVAs were used to analyze the data. Males with PFP ran and squatted in greater peak knee adduction and demonstrated greater peak knee external adduction moment compared with healthy male controls. In addition, males with PFP ran and squatted with less peak hip adduction and greater peak knee adduction compared with females with PFP. The static measure of mechanical axis of the tibial was not different between groups. However, a post hoc analysis revealed that males with PFP ran with greater peak tibial segmental adduction. Males with PFP demonstrated different mechanics during running and during a single-leg squat compared with females with PFP and with healthy males. Based upon the results of this study, therapies for PFP may need to be sex specific.
Article
Although wearing high-heeled shoes has long been considered a risk factor for the development for patellofemoral pain (PFP) in women, patellofemoral joint kinetics during high-heeled gait has not been examined. The purpose of this study was to determine if heel height increases patellofemoral joint loading during walking. Eleven healthy women (mean age 25.0±3.1 yrs) participated. Lower extremity kinematics and kinetics were obtained under 3 different shoe conditions: low heel (1.27 cm), medium heel (6.35 cm), and high heel (9.53 cm). Patellofemoral joint stress was estimated using a previously described biomechanical model. Model outputs included patellofemoral joint reaction force, patellofemoral joint stress and utilized contact area as a function of the gait cycle. One-way ANOVAs with repeated measures were used to compare the model outputs and knee joint angles among the 3 shoe conditions. Peak patellofemoral joint stress was found to increase significantly (p=0.002) with increasing heel height (low heel: 1.9±0.7 MPa, medium heel: 2.6±1.2 MPa, and high heel: 3.6±1.5 MPa). The increased patellofemoral joint stress was mainly driven by an increase in joint reaction force owing to higher knee extensor moments and knee flexion angles. Our findings support the premise that wearing high-heeled shoes may be a contributing factor with respect to the development of PFP.
Article
Barefoot running, which was how people ran for millions of years, provides an opportunity to study how natural selection adapted the human body to run. Because humans evolved to run barefoot, a barefoot running style that minimizes impact peaks and provides increased proprioception and foot strength, is hypothesized to help avoid injury, regardless of whether one is wearing shoes.
Article
This study tests if running economy differs in minimal shoes versus standard running shoes with cushioned elevated heels and arch supports and in forefoot versus rearfoot strike gaits. We measured the cost of transport (mL O(2)·kg(-1)·m(-1)) in subjects who habitually run in minimal shoes or barefoot while they were running at 3.0 m·s(-1) on a treadmill during forefoot and rearfoot striking while wearing minimal and standard shoes, controlling for shoe mass and stride frequency. Force and kinematic data were collected when subjects were shod and barefoot to quantify differences in knee flexion, arch strain, plantar flexor force production, and Achilles tendon-triceps surae strain. After controlling for stride frequency and shoe mass, runners were 2.41% more economical in the minimal-shoe condition when forefoot striking and 3.32% more economical in the minimal-shoe condition when rearfoot striking (P < 0.05). In contrast, forefoot and rearfoot striking did not differ significantly in cost for either minimal- or standard-shoe running. Arch strain was not measured in the shod condition but was significantly greater during forefoot than rearfoot striking when barefoot. Plantar flexor force output was significantly higher in forefoot than in rearfoot striking and in barefoot than in shod running. Achilles tendon-triceps surae strain and knee flexion were also lower in barefoot than in standard-shoe running. Minimally shod runners are modestly but significantly more economical than traditionally shod runners regardless of strike type, after controlling for shoe mass and stride frequency. The likely cause of this difference is more elastic energy storage and release in the lower extremity during minimal-shoe running.
Article
This retrospective study tests if runners who habitually forefoot strike have different rates of injury than runners who habitually rearfoot strike. We measured the strike characteristics of middle- and long-distance runners from a collegiate cross-country team and quantified their history of injury, including the incidence and rate of specific injuries, the severity of each injury, and the rate of mild, moderate, and severe injuries per mile run. Of the 52 runners studied, 36 (69%) primarily used a rearfoot strike and 16 (31%) primarily used a forefoot strike. Approximately 74% of runners experienced a moderate or severe injury each year, but those who habitually rearfoot strike had approximately twice the rate of repetitive stress injuries than individuals who habitually forefoot strike. Traumatic injury rates were not significantly different between the two groups. A generalized linear model showed that strike type, sex, race distance, and average miles per week each correlate significantly (P < 0.01) with repetitive injury rates. Competitive cross-country runners on a college team incur high injury rates, but runners who habitually rearfoot strike have significantly higher rates of repetitive stress injury than those who mostly forefoot strike. This study does not test the causal bases for this general difference. One hypothesis, which requires further research, is that the absence of a marked impact peak in the ground reaction force during a forefoot strike compared with a rearfoot strike may contribute to lower rates of injuries in habitual forefoot strikers.
Article
Footstrike patterns during running can be classified discretely into a rearfoot strike, midfoot strike and forefoot strike by visual observation. However, the footstrike pattern can also be classified on a continuum, ranging from 0% to 100% (extreme rearfoot to extreme forefoot) using the strike index, a measure requiring force plate data. When force data are not available, an alternative method to quantify the strike pattern must be used. The purpose of this paper was to quantify the continuum of foot strike patterns using an easily attainable kinematic measure, and compare it to the strike index measure. Force and kinematic data from twenty subjects were collected as they ran across an embedded force plate. Strike index and the footstrike angle were identified for the four running conditions of rearfoot strike, midfoot strike and forefoot strike, as well as barefoot. The footstrike angle was calculated as the angle of the foot with respect to the ground in the sagittal plane. Results indicated that the footstrike angle was significantly correlated with strike index. The linear regression model suggested that strike index can be accurately estimated, in both barefoot and shod conditions, in the absence of force data.
Article
Background Although the benefits of running are well known, 19–79% of the runners get injured every year. Many risk factors are associated with the aetiology of running-related injuries, but still there is no consensus on the exact cause of running injuries. Kinetic variables, such as impact peak force, active peak force and the impact loading rate are scarcely studied in novice runners. Studies on the aetiology of stress fractures of the tibia showed conflicting results between kinetic factors and the development of stress fractures of the tibia. Objective To examine the effects of running kinetics on the incidence of running related injuries in novice recreational runners. Design Prospective cohort study. Kinetic variables were acquired from an instrumented treadmill with three force measuring transducers. Female participants ran at 2.2 m/s and 2.5 m/s and male participants at 2.5 m/s and 2.78 m/s. At each velocity the vertical ground reaction forces were measured, from which the kinetic variables were calculated. Setting Novice recreational runners. Participants 98 male and 100 novice female runners, mean age 39.8 years and a body mass index of 25.4 were included in the study and were followed for 9 weeks during the training program. Intervention The occurrence of a running related injury in a 9 week training program. Main outcome measurement A running related injury. Results The incidence of running related injuries was 20.4%. Injured runners showed higher values on the active force peak (2.24 BW vs 2.11 BW) and higher values on the loading rate (92.5 BW/s vs 86.4 BW/s) compared to the non-injured runners. These differences however were not significant. Conclusion This study showed no significant differences in kinetic variables between injured and non-injured novice recreational runners during a 9 week training program.
Article
A greater Q-angle has been suggested as a risk factor for Patellofemoral Pain Syndrome. Greater frontal plane knee moment and impulse have been found to play a functional role in the onset of Patellofemoral Pain Syndrome in a running population. Therefore, the purpose of this investigation was to determine the relationship between Q-angle and the magnitude of knee abduction moment and impulse during running. Q-angle was statically measured, using a goniometer from three markers on the anterior superior iliac spine, the midpoint of the patella and the tibial tuberosity. Thirty-one recreational runners (21 males and 10 females) performed 8-10 trials running at 4m/s (SD 0.2) on a 30m-runway. Absolute and normalized knee moment and impulse were calculated and correlated with Q-angle. Negative correlations between Q-angle and the magnitude of peak knee abduction moment (R²=0.2444, R=-0.4944, P=0.005) and impulse (R²=0.2563, R=-0.5063, P=0.004) were found. Additionally, negative correlations between Q-angle and the magnitude of weight normalized knee abduction moment (R²=0.1842, R=-0.4292, P=0.016) and impulse (R²=0.2304, R=-0.4801, P=0.006) were found. The findings indicate that greater Q-angle, which is actually associated with decreased frontal plane knee abduction moment and impulse during running, may not be a risk factor of Patellofemoral Pain Syndrome.
Article
It is hypothesized that patients with patellofemoral pain syndrome (PFPS) have hip and core muscle weakness leading to dynamic malalignment of the lower extremity. Thus, hip strengthening is a common PFPS treatment approach. To determine changes in hip strength, core endurance, lower extremity biomechanics, and patient outcomes after proximally focused rehabilitation for PFPS patients. Case series; Level of evidence, 4. Nineteen women (age, 22.68 ± 7.19 years; height, 1.64 ± 0.07 m; mass, 60.2 ± 7.35 kg) with PFPS participated in an 8-week program to strengthen the hip and core muscles and improve dynamic malalignment. Paired t tests were used to compare the dependent variables between prerehabilitation and postrehabilitation. The dependent variables were pain; functional ability; isometric hip abduction and external rotation strength; anterior, lateral, and posterior core endurance; joint range of motion (ROM; rearfoot eversion, knee abduction and internal rotation, and hip adduction and internal rotation); and peak internal joint moments (rearfoot inversion, knee abduction, and hip abduction and external rotation) during the stance phase of running. Significant improvements in pain, functional ability, lateral core endurance, hip abduction, and hip external rotation strength were observed. There was also a significant reduction in the knee abduction moment during running, although there were no significant changes in joint ROM. An 8-week rehabilitation program focusing on strengthening and improving neuromuscular control of the hip and core musculature produces positive patient outcomes, improves hip and core muscle strength, and reduces the knee abduction moment, which is associated with developing PFPS.
Article
lower-limb stress fracture is one of the most common types of running injuries. There have been several studies focusing on the association between stress fractures and biomechanical factors. In the current study, the ground reaction force and loading rate are examined. There is disagreement in the literature about whether the history of stress fractures is associated with ground reaction forces (either higher or lower than control), or with loading rates. a systematic review of the literature was conducted on the relationship between the history of tibial and/or metatarsal stress fracture and the magnitude of the ground reaction force and loading rate. Fixed-effect meta-analysis techniques were applied to determine whether or not the ground reaction force and/or loading rate are different between the stress fracture and control groups. thirteen articles were identified through a systematic search of the literature. About 54% of these articles reported significantly different vertical ground reaction force and/or loading rate between the stress fracture and control groups. Other studies (~46%) did not observe any significant difference between the two groups. Meta-analysis results showed no significant differences between the ground reaction force of the lower-limb stress fracture and control groups (P>0.05). However, significant differences were observed for the average and instantaneous vertical loading rates (P<0.05). the currently available data does not support the hypothesis that there is a significant difference between the ground reaction force of subjects experiencing lower-limb stress fracture and control groups. Instead, the vertical loading rate was found to be significantly different between the two groups.
Article
the objective of this study was to characterize the biomechanical effects of step rate modification during running on the hip, knee, and ankle joints so as to evaluate a potential strategy to reduce lower extremity loading and risk for injury. three-dimensional kinematics and kinetics were recorded from 45 healthy recreational runners during treadmill running at constant speed under various step rate conditions (preferred, ± 5%, and ± 10%). We tested our primary hypothesis that a reduction in energy absorption by the lower extremity joints during the loading response would occur, primarily at the knee, when step rate was increased. less mechanical energy was absorbed at the knee (P < 0.01) during the +5% and +10% step rate conditions, whereas the hip (P < 0.01) absorbed less energy during the +10% condition only. All joints displayed substantially (P < 0.01) more energy absorption when preferred step rate was reduced by 10%. Step length (P < 0.01), center of mass vertical excursion (P < 0.01), braking impulse (P < 0.01), and peak knee flexion angle (P < 0.01) were observed to decrease with increasing step rate. When step rate was increased 10% above preferred, peak hip adduction angle (P < 0.01) and peak hip adduction (P < 0.01) and internal rotation (P < 0.01) moments were found to decrease. we conclude that subtle increases in step rate can substantially reduce the loading to the hip and knee joints during running and may prove beneficial in the prevention and treatment of common running-related injuries.
Article
Hip strength assessment plays an important role in the clinical examination of the hip and groin region. The primary aim of this study was to examine the absolute test-retest measurement variation concerning standardized strength assessments of hip abduction (ABD), adduction (ADD), external rotation (ER), internal rotation (IR), flexion (FLEX) and extension (EXT) using a hand-held dynamometer. Nine subjects (five males, four females), physically active for at least 2.5 h a week, were included. Twelve standardized isometric strength tests were performed twice with a 1-week interval in between by the same examiner. The test order was randomized to avoid systematic bias. Measurement variation between sessions was 3-12%. When the maximum value of four measurements was used, test-retest measurement variation was below 10% in 11 of the 12 individual hip strength tests and below 5% in five of the 12 tests. No systematic differences were present. Standardized strength assessment procedures of hip ABD, ER, IR, FLEX, with test-retest measurement variation below 5%, hip ADD below 6% and hip EXT below 8%, make it possible to determine even small changes in hip strength at the individual level.
Article
The mechanical axis alignment of the lower extremity is typically measured from frontal plane radiographs of the entire lower extremity during double support standing. The purpose of this study was to test the hypothesis that the mechanical axis alignment can be predicted from skin markers on anatomical landmarks and anthropometric measurements and a stereophotogrammetric system based on significant correlation with the mechanical axis alignment measured from standing radiographs. Mechanical axis alignment was measured using full-limb radiographs for both knees of 62 patients with bilateral medial compartment knee osteoarthritis (OA). Mechanical axis alignment was also measured using a stereophotogrammetric system with markers on anatomical landmarks and anthropometric measurements to determine joint centers. The mechanical axis alignment from position capture correlated with that from radiographs (R(2)=0.544; P<0.001). This relationship did not depend on age, gender, BMI, or OA severity. A small but significant difference in the mechanical axis alignment between the two methods was observed (radiograph: 2.6 varus; position capture: 3.8 varus; P=0.001). Associations between mechanical axis alignment and OA severity were found for both methods (radiographic: R(2)=0.563; position capture: R(2)=0.807). The proposed method allows the measurement of the mechanical axis alignment without exposure to radiation. This method enables the establishment of the relationship between lower limb alignment and functional variables such as dynamic joint loading in degenerative joint disease and joint injury even in populations who typically do not undergo radiographic examination.
Article
Running is one of the most popular leisure sports activities. Next to its beneficial health effects, negative side effects in terms of sports injuries should also be recognised. Given the limitations of the studies it appears that for the average recreational runner, who is steadily training and who participates in a long distance run every now and then, the overall yearly incidence rate for running injuries varies between 37 and 56%. Depending on the specificity of the group of runners concerned (competitive athletes; average recreational joggers; boys and girls) and on different circumstances these rates vary. If incidence is calculated according to exposure of running time the incidence reported in the literature varies from 2.5 to 12.1 injuries per 1000 hours of running. Most running injuries are lower extremity injuries, with a predominance for the knee. About 50 to 75% of all running injuries appear to be overuse injuries due to the constant repetition of the same movement. Recurrence of running injuries is reported in 20 to 70% of the cases. From the epidemiological studies it can be concluded that running injuries lead to a reduction of training or training cessation in about 30 to 90% of all injuries, about 20 to 70% of all injuries lead to medical consultation or medical treatment and 0 to 5% result in absence from work. Aetiological factors associated with running injuries include previous injury, lack of running experience, running to compete and excessive weekly running distance. The association between running injuries and factors such as warm-up and stretching exercises, body height, malalignment, muscular imbalance, restricted range of motion, running frequency, level of performance, stability of running pattern, shoes and inshoe orthoses and running on 1 side of the road remains unclear or is backed by contradicting or scarce research findings. Significantly not associated with running injuries seem age, gender, body mass index, running hills, running on hard surfaces, participation in other sports, time of the year and time of the day. The prevention of sports injuries should focus on changes of behaviour by health education. Health education on running injuries should primarily focus on the importance of complete rehabilitation and the early recognition of symptoms of overuse, and on the provision of training guidelines.
Article
The gait of normal subjects and patients with varus deformities at the knee was studied by analyzing the interaction between the dynamic (muscular) and passive (ligamentous) restraints affecting lateral stability of the knee. A statistically determinant model predicted that the midstance-phase adducting moment during normal gait would cause lateral knee joint opening if either antagonistic muscle force and/or pretension in the lateral soft tissues were not present at the knee. The patient group tended to compensate for a high midstance-phase adducting moment by walking with a style of gait that demanded more muscle force (greater flexion-extension moments). This walking style reduced the chance of lateral joint opening. It can be speculated that this style of gait would help to maintain equilibrium at the knee. The higher muscle force would aid in resisting the adducting moment, keeping the joint closed laterally and thus increasing the stability of the knee.
Article
A mathematical model of the patellofemoral joint taking into account movements and forces in the sagittal plane is described. The system parameters of the model are the locations of the attachments of the quadriceps muscle and the patellar ligament, the length of the patellar ligament, the dimensions of the patella and the geometry of the articulating surfaces. They were obtained from ten autopsy knees. The model enables calculation of the relative position of the patella, patellar ligament and quadriceps tendon, the location of the patellofemoral contact point and the magnitude of the patellofemoral compression force and the force in the patellar ligament as a function of the location of the tibial tuberosity at different flexion-extension angles of the knee. The model is validated by comparing model data with experimentally determined data.
Article
Lateral view radiographs of ten autopsy knees were used to determine the orientation of the patellar ligament, patella and quadriceps tendon relative to tibia and femur at different flexion-extension angles (0-120 degrees) of the knee. The results show a linear relationship between the angle of flexion and the movement of the patellar ligament relative to the tibia and of the movement of the patella relative to tibia and femur. There is a non-linear relationship between angle of flexion and the movement of the quadriceps tendon relative to the patellar ligament, patella and femur. The angular changes between patella and patellar ligament are negligible. The complicated movements of the distal part of the quadriceps femoris muscle may significantly influence biomechanical parameters such as the forces acting at the patella and tibial tuberosity.
Article
Ground reaction forces and center of pressure (C of P) patterns were studied in 17 subjects running at 4.5 ms−1. The subjects were classified as rearfoot or midfoot strikers according to the location of the C of P at the time of first contact between foot and ground. The C of P path in the rearfoot group showed a continuous anterior movement during support while the C of P in most of the midfoot group migrated posteriorly during the first 20 ms of the support phase. Variability in both groups was most marked during early support. The mean peak to peak force components were 3 BW, 1 BW and 0.3 BW in the vertical, anteroposterior and mediolateral directions respectively. Consistent differences between groups were noted in all three components, but individual differences within a given group were also considerable. The C of P patterns are presented in conjunction with ground reaction force data, and the implications of the results in the areas of running mechanics, shoe design and sports injury are discussed.
Article
Proper assessment of the subtalar joint is critical for foot and ankle evaluation. Yet, reliability of open kinetic chain goniometric measurements of the subtalar joint has been poor. Two alternative techniques, navicular height and calcaneal position with an inclinometer, have been reported in the literature but lack reliability assessment. The purpose of this study was to determine the intertester and intratester reliability of navicular height and calcaneal position using an inclinometer. Thirty healthy, volunteer subjects (22 females, age 24 +/- 3.6 years; eight males, age 25 +/- 5.1 years) participated in this study. Two testers performed repeated measures on both feet of each subject (N = 60) during two testing sessions. Testers determined the 1) subtalar neutral position, 2) resting position, and 3) difference between these two measurements using an inclinometer for calcaneal position and navicular height. Intratester and intertester reliabilities (ICC 2, 1), standard errors of measurement, and 95% confidence intervals were determined. Intertester and intratester reliability for calcaneal position ranged from .68 to .91 for all measurements. Intertester and intratester reliability for navicular height ranged from .73 to .96 for all measurements. We conclude that these weight-bearing measurement techniques are reliable and acceptable for clinical and research purposes as measured. In addition, we hypothesize that these measurement techniques are simpler than previously described open kinetic chain methods.
Article
The measure of navicular drop has been used as an indicator of pronation at the foot. It is defined as the distance the navicular tuberosity moves in standing, as the subtalar joint is allowed to move from its neutral position to a relaxed position. The purposes of this study were to test the reliability of a method to measure navicular drop and to assess the relationships among measures of forefoot to rearfoot position, subtalar joint neutral position, and navicular drop. The results support traditional biomechanical theory but indicate that other factors contribute significantly to navicular drop.
Article
Objective. To compare the effects of axial loading, and anatomically based multi-plane loading of the extensor mechanism on the patellofemoral joint. Design. Repeated measures design using an in-vitro cadaver model. Background. Since