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Abstract

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.

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... After foot strike, the ground reaction force propagates through the subtalar joint, contributing to rearfoot eversion, a necessary function enabling foot pronation in order to aid in shock absorption, and help the foot form a rigid lever to prepare for push-off [7]. Increasing the step rate has been shown to decrease peak ground reaction forces and loading rates, which may require less energy absorption from the lower extremity musculature and joints [17][18][19][20][21]. Increasing step rate effectively draws the foot closer to the body center of mass at ground contact, reducing vertical oscillation of the center of mass, thereby reducing the energy absorbed by the lower limbs, and altering joint kinematics [20,21]. ...
... After foot strike, the ground reaction force propagates through the subtalar joint, contributing to rearfoot eversion, a necessary function enabling foot pronation in order to aid in shock absorption, and help the foot form a rigid lever to prepare for push-off [7]. Increasing the step rate has been shown to decrease peak ground reaction forces and loading rates, which may require less energy absorption from the lower extremity musculature and joints [17][18][19][20][21]. Increasing step rate effectively draws the foot closer to the body center of mass at ground contact, reducing vertical oscillation of the center of mass, thereby reducing the energy absorbed by the lower limbs, and altering joint kinematics [20,21]. For example, increasing step rate has been shown to decrease peak hip adduction [20,[22][23][24], peak knee abduction [25], and peak rearfoot eversion [2], all of which have been implicated in the development of specific RRIs [10,15,26]. ...
... Increasing the step rate has been shown to decrease peak ground reaction forces and loading rates, which may require less energy absorption from the lower extremity musculature and joints [17][18][19][20][21]. Increasing step rate effectively draws the foot closer to the body center of mass at ground contact, reducing vertical oscillation of the center of mass, thereby reducing the energy absorbed by the lower limbs, and altering joint kinematics [20,21]. For example, increasing step rate has been shown to decrease peak hip adduction [20,[22][23][24], peak knee abduction [25], and peak rearfoot eversion [2], all of which have been implicated in the development of specific RRIs [10,15,26]. ...
Article
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Relatively high frontal and transverse plane motion in the lower limbs during running have been thought to play a role in the development of some running-related injuries (RRIs). Increasing step rate has been shown to significantly alter lower limb kinematics and kinetics during running. The purpose of this study was to evaluate the effects of increasing step rate on rearfoot kinematics, and to confirm how ground reaction forces (GRFs) are adjusted with increased step rate. Twenty runners ran on a force instrumented treadmill while marker position data were collected under three conditions. Participants ran at their preferred pace and step rate, then +5% and +10% of their preferred step rate while being cued by a metronome for three minutes each. Sagittal and frontal plane angles for the rearfoot segment, tibial rotation, and GRFs were calculated during the stance phase of running. Significant decreases were observed in sagittal and frontal plane rearfoot angles, tibial rotation, vertical GRF, and anteroposterior GRF with increased step rate compared with the preferred step rate. Increasing step rate significantly decreased peak sagittal and frontal plane rearfoot and tibial rotation angles. These findings may have implications for some RRIs and gait retraining.
... 39 In brief, athletes walked for two minutes to acclimate to the treadmill and motion capture setup. For healthy baseline testing, athletes ran at standardized speeds of 2.68, 2.95, 3.35, 3.80, and 4.47 m/s (10,9,8,7, and 6 min/mile, respectively). Following ACLR, athletes underwent a standardized testing protocol which included running gait analyses performed at 4, 6, 8, and 12 months post-operatively. ...
... Whole-body kinematics were collected using 42 reflective markers placed on the body segments of each athlete, 23 of which were located on anatomical landmarks. 7 Markers were placed by the same researcher [MRSJ] for all data collections on all athletes. A static standing position was also recorded to establish joint centers and for model scaling. ...
... Biomechanical modeling and analyses have been described in detail. 7 Briefly, the body was modeled as a 14-segment articulated linkage and body segments were scaled using the athlete's height, mass, and segment lengths. 15 Joint angles were computed at each time step using a global optimization routine to minimize the weighted sum of squared differences between the measured and the model marker positions. ...
Article
Background Preinjury running biomechanics are an ideal comparator for quantifying recovery after anterior cruciate ligament (ACL) reconstruction (ACLR), allowing for assessments within the surgical and nonsurgical limbs. However, availability of preinjury running biomechanics is rare and has been reported in case studies only. Purpose/Hypothesis The purpose of this study was to determine if running biomechanics return to preinjury levels within the first year after ACLR among collegiate athletes. We hypothesized that (1) surgical knee biomechanics would be significantly reduced shortly after ACLR and would not return to preinjury levels by 12 months and (2) nonsurgical limb mechanics would change significantly from preinjury. Study Design Cohort study; Level of evidence, 2. Methods Thirteen Division I collegiate athletes were identified between 2015 and 2020 (6 female; mean ± SD age, 20.7 ± 1.3 years old) who had whole body kinematics and ground-reaction forces recorded during treadmill running (3.7 ± 0.6 m/s) before sustaining an ACL injury. Running analyses were repeated at 4, 6, 8, and 12 months (4M, 6M, 8M, 12M) after ACLR. Linear mixed effects models were used to assess differences in running biomechanics between post-ACLR time points and preinjury within each limb, reported as Tukey-adjusted P values. Results When compared with preinjury, the surgical limb displayed significant deficits at all postoperative assessments ( P values <.01; values reported as least squares mean difference [SE]): peak knee flexion angle (4M, 13.2° [1.4°]; 6M, 9.9° [1.4°]; 8M, 9.8° [1.4°]; 12M, 9.0° [1.5°]), peak knee extensor moment (N·m/kg; 4M, 1.32 [0.13]; 6M, 1.04 [0.13]; 8M, 1.04 [0.13]; 12M, 0.87 [0.15]; 38%-57% deficit), and rate of knee extensor moment (N·m/kg/s; 4M, 22.7 [2.4]; 6M, 17.9 [2.3]; 8M, 17.5 [2.4]; 12M, 16.1 [2.6]; 33%-46% deficit). No changes for these variables from preinjury ( P values >.88) were identified in the nonsurgical limb. Conclusion After ACLR, surgical limb knee running biomechanics were not restored to the preinjury state by 12M, while nonsurgical limb mechanics remained unchanged as compared with preinjury. Collegiate athletes after ACLR demonstrate substantial deficits in running mechanics as compared with preinjury that persist beyond the typical return-to-sport time frame. The nonsurgical knee appears to be a valid reference for recovery of the surgical knee mechanics during running, owing to the lack of change within the nonsurgical limb.
... The effectiveness of acute changes in running retraining programs based on transitions to FFS has previously been examined in laboratory protocols. 10,11,[13][14][15][16][17] Huang et al. 13 reported a reduction in impact loading by combining FFS and increase cadence. Moreover, Baggaley et al. 10 compared three components of real-time visual feedback during a single session which included: targeting a FFS using the footstrike angle (FSA), decreasing step length by 7.5% and decreasing vertical loading rate by 15%. ...
... In addition, several acute programs have determined that an increase of cadence between 10%-15% is associated with a decrease of impact forces, in combination with a transition to FFS, and a decrease in the step length and duration. [15][16][17] Therefore, changes in running patterns associated with FFS and increase of cadence, have both been shown to reduce impact attenuation after running retraining programs, which may reduce the risk of injury. 2,5,18 Despite the promising effects of acute laboratory-based running retraining programs, the use of sophisticated instruments, for example, force plates to provide real-time biofeedback, do not have good clinical utility due to availability and cost. ...
... Increases in running speed have been shown to be effective in reducing the prevalence of RFS. 7,26 The CAD group performed a retraining program based on an increase of 10% of their natural cadence at comfortable speed determined at baseline following the protocol suggested by previous studies, [15][16][17] and a digital metronome was used to provide auditory feedback. 12 The CAD group was asked to strike their feet to the beat of the metronome and, to control the comfortable speed, the retraining sessions were performed either on a treadmill or on a 400-meter running track (controlling the pace by GPS or lap time) both within the same sporting facilities. ...
Article
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The aim of this study was to compare the effects of two 10-week non-laboratory based running retraining programs on foot kinematics and spatiotemporal parameters in recreational runners. One hundred and three recreational runners (30 ± 7.2 years old, 39% females) were randomly assigned to either: a barefoot retraining group (BAR) with 3 sessions/week over 10 weeks, a cadence retraining group (CAD) who increased cadence by 10% again with 3 sessions/week over 10 weeks and a control group (CON) who did not perform any retraining. The footstrike pattern, footstrike angle (FSA) and spatial-temporal variables at comfortable and high speeds were measured using 2D/3D photogrammetry and a floor-based photocell system. A 3x2 ANOVA was used to compare between the groups and 2 time points. The FSA significantly reduced at the comfortable speed by 5.81° for BAR (p < 0.001; Cohen’s d = 0.749) and 4.81° for CAD (p = 0.002; Cohen’s d = 0.638), and at high speed by 6.54° for BAR (p < 0.001; Cohen’s d = 0.753) and by 4.71° for CAD (p = 0.001; Cohen’s d = 0.623). The cadence significantly increased by 2% in the CAD group (p = 0.015; Cohen’s d = 0.344) at comfortable speed and the BAR group showed a 1.7% increase at high speed. BAR and CAD retraining programs showed a moderate effect for reducing FSA and rearfoot prevalence, and a small effect for increasing cadence. Both offer low-cost and feasible tools for gait modification within recreational runners in clinical scenarios.
... Much research [8,[12][13][14] has shown that an increase in stride frequency (SF) can reduce the risk of injury for different reasons: on the one hand, knee flexion and plantar flexion increases in the stance phase as a consequence of resistive forces are reduced, the angular velocity of these joints increases, and hip stabilization during running is improved [8]. To favor the runner's performance, the increase has to be 10% more in SF [12,15,16]. ...
... Much research [8,[12][13][14] has shown that an increase in stride frequency (SF) can reduce the risk of injury for different reasons: on the one hand, knee flexion and plantar flexion increases in the stance phase as a consequence of resistive forces are reduced, the angular velocity of these joints increases, and hip stabilization during running is improved [8]. To favor the runner's performance, the increase has to be 10% more in SF [12,15,16]. ...
... It has been shown [13] that at the same speed, at a faster SF, the metatarsal is supported, while, during a slower SF, the forefoot and rearfoot are supported, increasing the risk of injury [8]. On the other hand, the knee, ankle, and hip joints absorb less mechanical energy [12] as the impact of the lower limbs against the ground is less [14]. In turn, there is less peak hip flexion and adduction when the loading response occurs. ...
Article
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The number of participants in popular races has increased in recent years, with most of them being amateurs. In addition, it has been observed that there is a high percentage of injuries among them, and some of these injuries may be related to a low stride frequency. The aim of this research was to check if a continuous running training program with a musical base improves the stride frequency of popular runners. For this purpose, the effect of a 6 week continuous running training program with the help of a musical track with a constant rhythm that was 10% higher than the preferred stride frequency of the subjects was analyzed and compared to a control group that performed the continuous running training without sound stimuli. Significant increases were found in the evolution of stride frequency in the experimental group between the pre- and post-test (p = 0.002). No significant changes were observed in the stride frequency of the control group. These results show that training with music feedback helps to improve stride frequency in recreational runners. Future research should study the evolution of the improvement obtained in time as it is unknown if the increase in stride rate has been integrated in the runner’s technique, making the improvement obtained permanent. Future research is needed to confirm these results by enlarging the sample and carrying out an exhaustive biomechanical study.
... Each joint's position and gro reaction force data were obtained using Qualisys's Qualisys Track Manager Program data processing. To remove the noise of the data, Butterworth second-order low-pas tering at 12 Hz was performed for the 3D position coordinate data [35]. The ground r tion force data were set at a power spectrum density (PSD) of 99% of the value of the off frequency [36]. ...
... Each joint's position and gro reaction force data were obtained using Qualisys's Qualisys Track Manager Program data processing. To remove the noise of the data, Butterworth second-order low-pas tering at 12 Hz was performed for the 3D position coordinate data [35]. The ground tion force data were set at a power spectrum density (PSD) of 99% of the value of the off frequency [36]. ...
... Each joint's position and ground reaction force data were obtained using Qualisys's Qualisys Track Manager Program for data processing. To remove the noise of the data, Butterworth second-order low-pass filtering at 12 Hz was performed for the 3D position coordinate data [35]. The ground reaction force data were set at a power spectrum density (PSD) of 99% of the value of the cut-off frequency [36]. ...
Article
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(1) Background: The objective of this study was to determine physical and biomechanical changes in age groups upon running. (2) Method: 75 male adults (20–80s) participated in the study. Bone mineral density and lower extremity joint strength were measured according to age-increase targeting. Based on age, correlations among running characteristics, impulse, impact force, maximum vertical ground reaction force, loading rate, lower extremity joint 3D range of motion, joint moment, and power upon running motion were calculated. (3) Result: Older runners tended to show lower bone mineral density, extremity maximum strength, stride time, and stride distance, with smaller RoM and joint power of ankle and knee joints in the sagittal plane, compared with younger subjects. However, there were no significant correlations between age and impact variables (i.e., impulse, impact force, peak GRF, and loading rate) during running. (4) Conclusion: Older runners tend to show weaker physical strength characteristics, such as bone mineral density and muscle strength and lower joint functionality of ankle and knee joints during running, compared with younger runners. Therefore, strengthening the lower extremity muscle and improving dynamic joint function, especially for ankle joints, can be helpful for injury prevention during running.
... Adopting a forefoot strike pattern has been shown to reduce impact loading (Cheung & Davis, 2011) and tibiofemoral joint loading (Bowersock et al., 2017). Increased step rate has been shown to reduce impact loading (Hafer et al., 2015) and to lower mechanical energy absorbed by the hip and knee joints (Heiderscheit et al., 2011). Running softer can lead to decreased impact loading (Crowell et al., 2010) and anterior trunk lean has been suggested as a gait modification to soften footfalls (Arendse et al., 2004). ...
... Each trial lasted 5 min, and participants rested for 5 min or longer if requested between trials. Visual biofeedback was presented to train forefoot strike pattern (with two blocks indicating baseline and forefoot strike patterns, and a dot fall in the block during stance phase indicating the current strike pattern), and anterior trunk lean (with two blocks indicating baseline and 10-degree increased trunk lean, and a dot fall in the block indicating the current trunk lean angle), and a digital audio metronome (Seiko sq70, Seiko, Singapore) was used to help participants match the increased step rate (Heiderscheit et al., 2011). At the start of the trial, participants were told to follow the visual feedback to land the dot in the desired block (forefoot strike or increased trunk lean), or match the step rate to the audio feedback. ...
... Step rate was calculated as the number of right foot steps recorded from the ground reaction force multiplied by two (Heiderscheit et al., 2011). A test facilitator monitored the modifications while standing next to the treadmill. ...
Article
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Impact loading has been associated with running-related injuries, and gait retraining has been suggested as a means of reducing impact loading and lowering the risk of injury. However, gait retraining can lead to increased perceived awkwardness and effort. The influence of specifically trained and self-selected running gait modifications on acute impact loading, perceived awkwardness and effort is currently unclear. Sixteen habitual rearfoot/midfoot runners performed forefoot strike pattern, increased step rate, anterior trunk lean and self-selected running gait modifications on an instrumented treadmill based on real-time biofeedback. Impact loading, perceived awkwardness and effort scores were compared among the four gait retraining conditions. Self-selected gait modification reduced vertical average loading rate (VALR) by 25.3%, vertical instantaneous loading rate (VILR) by 27.0%, vertical impact peak (VIP) by 16.8% as compared with baseline. Forefoot strike pattern reduced VALR, VILR and peak tibial acceleration. Increased step rate reduced VALR. Anterior trunk lean did not reduce any impact loading. Self-selected gait modification was perceived as less awkward and require less effort than the specifically trained gait modification (p < 0.05). These findings suggest that self-selected gait modification could be a more natural and less effortful strategy than specifically trained gait modification to reduce acute impact loading, while the clinical significance remains unknown.
... Variations in running technique result in differential mechanical loading of specific anatomical structures, which is believed to affect injury risk, efficiency and performance [40][41][42][43][44][45] . Folland et al. 46 found that running technique explained 39% of the variation in energy costs and 31% of the variation in performance across runners. ...
... SF, expressed in strides per minute (strides·min -1 ), describes the duration of a complete stride cycle (left and right step). SF consequently relates to many biomechanical aspects of running 40,41,43,45,49,[105][106][107][108][109][110][111][112][113][114] . Hence, SF has received considerable attention from both scientific and practical perspective. ...
... This recommendation is based on the observation that, for all running distances, elite runners seem to use a SF of at least 90 strides·min -1 . However, it is doubtful that this SF is optimal for every runner at every speed, as 90 strides·min -1 is substantially higher than most self-selected stride frequencies (SFself) and even higher than SFopt reported in literature 40 41,113 . Among runners injury prevalence rates as high as 79.3% have been reported 6 and changing running technique may be effective to reduce the injury risk. ...
Thesis
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The large-scale usage of smartphone applications and sports watches in running provides the potential to lower injury risk and improve performance. To achieve these common goals, contextual factors need to be taken into account to provide users with accurate and personal feedback. This thesis aims to develop methods to improve the quality of wearable feedback and its interpretation. Within the data process from parameter detection to feedback to the user, the are several ways to improve the quality of the feedback. The studies in this thesis demonstrate various possibilities. The thesis projects concern an improved algorithm for cycle detection; a method to cross-validate speed; an approach to determine an energetic optimal running technique; highlight the importance of individual differences; and a concise, yet comprehensive description of the full spectrum of running styles. It is concluded that to further improve the quality of wearable feedback, cross-validation, self-optimization, biomechanical dependencies, and individual differences should be considered as demonstrated in the thesis.
... These effects are consistent with a lower energy demand of locomotion and center of mass vertical excursion indicative of more economical treadmill running. [9][10][11] Reductions in the degree of knee flexion are also related to running performance improvements, 10,11 and a lower protrusion with the 30% splint had a positive contribution across all running stages. Small changes in running pattern have been reported when different occlusal splints were worn 12 and, consequently, when the vertical dimension of occlusion was increased. ...
... These effects are consistent with a lower energy demand of locomotion and center of mass vertical excursion indicative of more economical treadmill running. [9][10][11] Reductions in the degree of knee flexion are also related to running performance improvements, 10,11 and a lower protrusion with the 30% splint had a positive contribution across all running stages. Small changes in running pattern have been reported when different occlusal splints were worn 12 and, consequently, when the vertical dimension of occlusion was increased. ...
Article
Wearing an intraoral jaw-protruding splint could enhance respiratory function in clinical settings and eventually exercise performance. Purpose: The authors studied the acute effect of wearing a lower-jaw-forwarding splint at different protruding percentages (30% and 50%) across a wide range of running exercise intensities. Methods: A case study was undertaken with a highly trained and experienced 27-year-old female triathlete. She performed the same incremental intermittent treadmill running protocol on 3 occasions wearing 3 different intraoral devices (30% and 50% maximum range and a control device) to assess running physiological and kinematic variables. Results: Both the 30% and 50% protruding splints decreased oxygen uptake and carbon dioxide production (by 4%-12% and 1%-10%, respectively) and increased ventilation and respiratory frequency (by 7%-12% and 5%-16%, respectively) along the studied running intensities. Exercise energy expenditure (approximately 1%-14%) and cost (7.8, 7.4, and 8.0 J·kg-1·m-1 for 30%, 50%, and placebo devices, respectively) were also decreased when using the jaw-protruding splints. The triathlete's lower limbs' running pattern changed by wearing the forwarding splints, decreasing the contact time and stride length by approximately 4% and increasing the stride rate by approximately 4%. Conclusions: Wearing a jaw-protruding splint can have a positive biophysical effect on running-performance-related parameters.
... Thus, changes in step characteristics due to running-induced fatigue during the race may affect the running speed and alter performance. While performing to achieve a higher running speed, increasing SL required greater work of the limb joints than increasing SF [20]. In addition, the level of force production from the limb muscles decreased with fatigue development during running [17,18,21]. ...
... Maintaining muscle force production against the onset of fatigue during maximal voluntary endurance running is an important factor for successful race performance [18,22]. Maintaining SL, rather than SF, would require a higher level of force production from the limb muscles [20,31]. Moreover, Hanley et al. [32] reported that runners maintained the same joint angles and foot positioning at initial contact throughout the 5000-m race while SL and SF decreased. ...
Article
Full-text available
This study examined the relationship between step characteristics and race time in a 5000-m race. Twenty-one male Japanese endurance runners performed a 5000-m race. Step length, step frequency, contact time, and flight time of two gait cycles (i.e., four consecutive ground contacts) were measured every 400-m by using high-speed video image. Moreover, step length was normalized to body height to minimize the effect of body size. In addition to step characteristics on each lap, the averages of all laps and the per cent change from the first half to the second half were calculated. The average step frequency and step length normalized to body height correlated significantly with the 5000-m race time (r = −0.611, r = −0.575, respectively, p < 0.05 for both). Per cent changes in contact time and step length correlated significantly with the 5000-m race time (r = 0.514, r = −0.486, respectively, p < 0.05 for both). These findings suggest that, in addition to higher step frequency and step length normalized to body height, smaller changes in step length during a given race may be an important step characteristic to achieving superior race performance in endurance runners.
... 8.5 7.9 Heartrate (beats per minute) 152 ± 8.9 155 ± 9.6 151 ± 8. performance. Previous studies for example showed a decrease in peak braking forces and vertical ground reaction forces with an increase in cadence (Heiderscheit, Chumanov, Michalski, Wille, & Ryan, 2011;Napier et al., 2018a;Willy, Buchenic, et al., 2016). Since a high peak braking force is associated with a five-fold higher risk of an injury, a gait retraining program that can modify cadence might therefore reduce the peak braking force and hereby reduce the risk of injury (Napier et al., 2018a(Napier et al., , 2018b. ...
... This is in line with a study from Chan et al (Chan et al., 2018) where there were significantly more calf injuries in the gait-retraining intervention group compared to the control group. Increasing cadence results in an increased load on the calf muscles (Ahn, Brayton, Bhatia, & Martin, 2014;Nunns, House, Fallowfield, Allsopp, & Dixon, 2013) but lowers the load on almost all others structures of the lower extremity, which potentially can result in a reduced overall injury risk (Edwards et al., 2009;Heiderscheit et al., 2011;Lenhart et al., 2014;Lenhart et al., 2015;Lyght et al., 2016;Napier et al., 2018aNapier et al., , 2018bWellenkotter et al., 2014;Willy, Buchenic, et al., 2016). Nevertheless, follow-up studies should take into account drop-out of participants due to the possible higher load and damage on the calf muscles/Achilles tendon. ...
Article
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Running with music has been shown to acutely change cadence. However, it is unclear if the increased cadence remains long-term when running without music in an in-field situation. The aim of this 12-week study was to investigate the effect of a 4-week music running program on cadence, speed and heartrate during and after the music running program. Seven recreational runners with a cadence of <170 steps per minute were randomly assigned to a baseline and post-intervention period of different durations. During the intervention phase, the participants ran with a musical beat that was 7.5-10% higher than their mean cadence at the start of the study. Cadence, heartrate and running speed were measured twice a week during a 5-kilometer run with a watch, and were analyzed using randomization tests and visual data inspection. Two participants dropped-out due to shortage of time (n = 1) and an acute calf injury (n = 1). Cadence significantly increased during the intervention period (+8.5%), and remained elevated during the post-intervention period (+7.9% (p = .001)) in comparison with the baseline period. Heartrate and running speed did not significantly change during any period. This study among five participants shows that four weeks of running with a musical beat that is 7.5-10% higher than the preferred cadence may be an effective and feasible intervention to increase running cadence. Importantly, the increased cadence occurred without simultaneous increases in running speed and heartrate, hereby potentially reducing mechanical loading without increasing metabolic load.
... Decreased stride length has been associated with a reduction in impact forces and the active peak of the vertical GRF, as well as a decreased vertical loading rate of the GRF (Hobara et al., 2012). Additionally, decreasing stride length has been shown to reduce joint moments (Derrick et al., 1998;Heiderscheit et al., 2011;Thompson et al., 2014), impact accelerations (Smith et al., 1986;Hamill et al., 1995;Mercer et al., 2005), and leg stiffness (Farley and Gonzalez, 1996;Morin et al., 2007), which are factors that have been associated with increased risk of running-related overuse injuries. Clinically, evidence suggests that reducing stride length may reduce the incidence of tibial stress fractures (Ferber et al., 2002;Davis et al., 2004;Milner et al., 2006;Pohl et al., 2008) and plantar fasciitis (Pohl et al., 2009). ...
... In terms of stride length, previous research has shown that decreasing stride length, which may have resulted in a F/MFS pattern, decreases the impact peak (Hobara et al., 2012) and active peak magnitude of the vertical GRF (Morin et al., 2007;Heiderscheit et al., 2011;Thompson et al., 2014), as well as decreasing the vertical loading rate of the GRF (Hobara et al., 2012). Additionally research examining alterations in foot strike has shown that RFS pattern results in increased vertical loading rates (Almeida et al., 2015;Rice et al., 2016). ...
Article
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Modifying stride length and/or foot strike in running results in mechanical alterations associated with injury risk. Stride length and foot strike have often been treated as independent factors that affect running mechanics, but there is evidence to suggest that they may be coupled. The purpose of this study was to determine if foot strike and stride length are coupled in running, and if so, can these variables be independently manipulated? Additionally, we sought to determine how independently and simultaneously manipulating stride length and foot strike influenced running kinematics and kinetics. Fifteen individuals ran over ground with stride lengths +/– 10 % of their preferred stride length while adopting both a fore/mid foot strike and rear foot strike pattern, as well as running with their self-selected stride length and foot strike when the opposite variable was controlled. Three-dimensional motion capture and force plate data were captured synchronously during the manipulated stride length x foot strike trials. The results indicate that foot strike and stride length are coupled, with shorter stride lengths being associated with a F/MFS and longer stride lengths being associated with a RFS pattern. Impact peak magnitude was primarily dependent on foot strike, with a F/MFS pattern reducing the magnitude of the impact peak force regardless of stride length. Peak vertical and horizontal ground reaction forces were found to be primarily dependent on stride length, with longer stride lengths resulting in increased vertical and horizontal ground reaction forces, regardless of foot strike. It is difficult, but possible, to independently manipulate stride length and foot strike. Clinicians should be aware of the coupled changes in stride length and foot strike.
... During both running and cycling, these muscle groups control the movements of the knee and hip joints and the recruitment patterns of quadriceps and hamstring muscles increase with increasing exercise intensities (Camic et al., 2015). In this context, the occurrence of strength discrepancies during these testing modalities may affect all-out exercise performance (Heiderscheit et al., 2011). Rather than the mechanical properties of cycling and running techniques, the strength of the lower extremity muscles affects the exercise performance due to the recruitment of the lower extremity muscles in a manner that leads to muscular fatigue during strenuous activities (Millet et al., 2009). ...
... With this regard, it can be speculated that the contributions of the lower extremity muscles vary depending on the exercise mode regardless of the type of testing modality and hip muscles have great importance to maintain exercise performance at intense and constant exercise modalities compared to the incremental testing procedures. However, the results of another study showed that a simple 10% increase in running step rate while maintaining preferred running speed has been shown to reduce energy absorption at the hip during the loading response while these potentially beneficial alterations to hip mechanics during loading response was accompanied by increased activation of the hamstring and gluteal muscles during the late swing (Chumanov et al., 2012;Heiderscheit et al., 2011). Thus, despite a greater contribution by the hip muscles during either VO2max performance, further analyses are needed to understand the interactions between the VO2max performance and individual muscle performance responses considering the biomechanical differences between incremental and constant testing protocols. ...
Article
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Preliminary VO2max verification testing allows to examine the reproducibility of comparable tests in the same participants and helps to verify whether neuromuscular performance is associated with VO2max during different testing conditions. The main purpose of this study was to compare VO2max values obtained using a graded treadmill and cycling protocols and to verify whether the results are also reproducible during the constant time to exhaustion testing protocols. The second rationale of the study was to characterize the contributions of hip and knee muscle strength during four different testing conditions, and to determine how these quantities change when altering the modality of exercise for a given exercise intensity. A repeated measures study design was used. A total of 20 healthy male participants (21.20±2.17 years) underwent preliminary VO2max testing sessions on treadmill and cycling ergometers with 24-h intervals. Isokinetic strength performance of hip and knee muscles was tested at 60 o /sec angular velocity. A paired and independent-sample t-test was performed for inter-group and intra-group comparisons. Linear regression was applied to determine the percentage of variation in VO2max testing outputs during either testing modality explained by hip and knee muscle strength parameters. Lower extremity strength characteristics of hip and knee were symmetric between the dominant and non-dominant limb (p>0.05). VO2max and blood lactate concentration were significantly greater during constant testing protocols for either testing modalities (p<0.001). Hip muscle strength performance explained a greater variation in VO2max parameters during incremental (cycling r 2 = 0.25, running r 2 = 0.24) and constant (cycling r 2 = 0.35, running r 2 = 0.33) testing protocols for either testing modality compared to the contribution of knee muscle strength performance on VO2max parameters during incremental (cycling r 2 = 0.17, running r 2 = 0.17) and constant (cycling r 2 = 0.23, running r 2 = 0.18) testing protocols. The local muscular performance of the hip and knee muscles were strongly related with the changes in running and cycling mechanics and hip muscles had a greater contribution to the VO2max performance during constant protocols than knee muscles. In conclusion, the extent to which contribution of lower extremity muscles during VO2max testing relies more on the mode of the exercise rather than the type of the testing modality.
... Although we focused on examining the trajectory of CoM accelerations in cycling and running using accelerometry outside of the laboratory environment, other studies (Cejuela et al., 2007;Hausswirth et al., 2010;Weich et al., 2020) have examined gait mechanics relative to additional kinematic and kinetic parameters. For instance, an increase in running cadence has been reported to be accompanied by reductions in peak hip adduction angle, hip external adduction and internal rotation moments that influence the magnitude of CoM accelerations (Heiderscheit et al., 2012). An influence of this kind could suggest a deviation from an individual triathlete's accustomed running cadence. ...
... Aside from running cadence, another spatiotemporal strategy associated with an increase in running cadence is a shortened step length (Chapman et al., 2008;Schubert et al., 2014). A reduction in step length places the initial loading closer to the triathlete's CoM (Heiderscheit et al., 2012). This may be reflected by a lower magnitude of anteroposterior acceleration during running after cycling. ...
Article
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While the sport of short-distance (Sprint) triathlon provides an opportunity to research the effect of the center of mass (CoM) when cycling and running, much remains to be done. The literature has failed to consistently or adequately report how changes to hand position influence subsequent running as inferred by the magnitude of CoM acceleration. The demands of cycle training in a drops and aerodynamic position followed by running remain unquantified in Sprint Distance triathlon. Thus, far data collected indicate that the cycle to run transition (T2) is important for overall race success. While many age-groupers participate in Sprint Distance triathlon, the lack of T2 based research make comparisons between cycle hand position and ensuing running difficult. The motion of the human body when cycling and running in triathlon can be described by the motion of its CoM in a local coordinate system. Unobtrusive wearable sensors have proven to be an informative resource to monitor the magnitude of CoM accelerations in running. However, the extent to which they are used in cycling is unclear. Therefore, the aim of the present study was to analyse the temporal magnitudes of CoM acceleration when cycling position and cadence is changed and to analyse these effects on running after cycling. Ten recreational triathletes completed two 20 km cycling trials at varied cadence in a drops position (parts of the handlebars that curve outward, Cycle Drops) and an aerodynamic position (arms bent, forearms parallel to the ground, Cycle Aero ) immediately followed by a 5 km run at self-selected pace. Torso kinematics by way of CoM acceleration magnitude were captured in a typical training setting using a triaxial accelerometer. CoM acceleration was quantified in m/s ² and variability was measured by the coefficient of variation (CV) and root mean square (RMS). Results from Cycle Aero indicated that acceleration of the CoM in longitudinal (CV = 1%) and mediolateral directions (CV = 3%) was significantly reduced ( p < 0.001) compared to Cycle Drops . As for rate of perceived exertion (RPE), a significant difference was observed with triathletes reporting higher values in Cycle Aero alongside a greater CoM acceleration magnitude in the anteroposterior direction. The CoM varied significantly from Run Aero with less longitudinal (CV = 0.2, p < 0.001) and mediolateral acceleration observed (CV = 7.5%, p < 0.001) compared to Run Drops . Although greater longitudinal acceleration was observed in the initial 1 km epoch of Run Aero , triathletes then seemingly adjusted their CoM trajectory to record lower magnitudes until completion of the 5 km run, completing the run quicker compared to Run Drops (22.56 min ¹ ± 0.2, 23.34 min ¹ ± 0.5, p < 0.001, CV = 1.3%). Coaches may look to use triaxial accelerometers to monitor performance in both cycling and running after cycling.
... Las diferencias más pequeñas se encontraron en el tobillo, ya que está en el contacto más cercano con el suelo con respecto a la tercera ley de Newton. El impacto del tobillo está influenciado por el peso del atleta (Derrick, Dereu & McLean, 2002), la masa muscular y grasa de la extremidad inferior (Liu & Nigg, 2000), la superficie de impacto (Dixon, Collop & Batt, 2000), el tipo de calzado (Hardin, Van Den Bogert & Hamill, 2004), y el tiempo de vuelo entre pasos relacionados con la velocidad de zancada (Heiderscheit, Chumanov, Michalski, Wille & Ryan, 2011). En este estudio, solo el peso de los participantes (DE = 4.2 kg), la proporción de masa muscular y masa grasa en la extremidad inferior y el tiempo de vuelo pudieron influir en los resultados. ...
... Investigaciones previas evidenciaron la mayor carga en el tobillo por su proximidad al contacto con el suelo, disipándose la carga a través de las estructuras musculoesqueléticas en ascenso vertical por rodilla, región lumbar y espalda donde se registró la menor carga Gómez-Carmona, Bastida-Castillo, García-Rubio et al., 2019). Uno de los factores modificables es la velocidad de carrera que tiene un efecto directo en el patrón de desplazamiento con mayor tiempo de vuelo e impacto en el apoyo (Heiderscheit et al., 2011), que influye directamente en una mayor carga externa recibida tanto en tren inferior como superior Nedergaard et al., 2017). Finalmente, se encontró una amplia variabilidad intersujeto producida por diferente biomecánica de marcha y características antropométricas específicas (Cochrum et al., 2017). ...
Thesis
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La acelerometría es un método de cuantificación de la carga externa que está teniendo una aplicación exponencial gracias a su integración en dispositivos electrónicos para el análisis del rendimiento en deportes colectivos. La carga externa ha sido comúnmente cuantificada a través del desplazamiento (distancia y velocidad), no teniendo en cuenta su efecto a nivel neuromuscular. Por ello, el objetivo principal de la presente Tesis Doctoral es el análisis de la carga externa que soportan múltiples ubicaciones anatómicas de forma simultánea en los desplazamientos deportivos, específicamente en baloncesto. Para ello, se realiza una revisión sistemática detectando que diferentes aspectos técnicos requieren una evaluación previa al registro así como que los acelerómetros miden la aceleración del segmento al que están unidos. Para subsanar ambos aspectos, se realiza un análisis de la precisión y fiabilidad del sensor, se identifican los índices de carga y frecuencia de muestreo adecuados, así como se diseña y valida un protocolo de registro multi-ubicación y una batería de evaluaciones que representa los desplazamientos más comunes en los deportes de invasión. Finalmente, se realiza la evaluación multi-ubicación de la carga externa en test de laboratorio y test de campo para evaluar el efecto de la velocidad, sexo y tipo de desplazamiento, así como establecer perfiles de rendimiento individual. A partir de estos resultados, los entrenadores podrán identificar la carga externa específica de cada estructura musculoesquelética para diseñar programas individualizados de acondicionamiento físico, prevención de lesiones y recuperación adaptados a los grupos musculares con mayor carga externa. Accelerometry is a method for quantifying external load that is having an exponential application thanks to its integration in electronic performance and tracking systems in team sports. External load has been commonly quantified through displacement (distance and speed), not considering its effect at the neuromuscular level. Therefore, the main objective of this Doctoral Thesis is the analysis of the external load supported by multiple anatomical locations simultaneously in sports movements, specifically in basketball. To do this, a systematic review is carried out, detecting those different technical aspects that require an evaluation prior to registration, as well as that the accelerometers measure the acceleration of the segment to which they are attached. To correct both aspects, an analysis of the precision and reliability of the sensor was performed, the appropriate load index and sampling frequency were identified, as well as a multi-location registration protocol and a battery of evaluations that represent the most common displacements in invasion sports were designed and validated. Finally, the multi-location evaluation of the external load was performed in laboratory and field tests to evaluate the effect of speed, sex and type of movement, as well as to establish individual performance profiles. From these results, trainers will be able to identify the specific external load of each musculoskeletal structure to design individualized programs for physical conditioning, injury prevention and recovery adapted to the muscle groups with the highest external load.
... Altering stride frequency affects lower limb joint kinematics and kinetics, 4 but it remains hard to relate these changes in joint kinematics and kinetics to whole-body metabolic energy expenditure. Increasing stride frequency reduces peak vertical ground reaction force (GRF) and breaking impulse 5,6 and shortens the stance time but increases duty factor (i.e., stance time divided by stride time). 7 Power and work produced around the lower limb joints change with stride frequency. ...
... During stance, negative and positive work per stride decrease with increasing stride frequency for the ankle, knee, and hip joints. 5 Even when normalizing joint work to time, and thus accounting for the difference in number of strides per distance or time, average joint power in the ankle and knee is lower when increasing stride frequency whereas average positive hip joint power during swing greatly increases with increasing stride frequency. 7 These findings have led to the idea that the preferred or optimal stride frequency represents a trade-off between minimizing energy expenditure during stance without substantially reducing the available time to produce the necessary forces or excessively increasing the cost associated with leg swing. ...
Article
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While it is well recognized that the preferred stride frequency (PSF) in running closely corresponds to the metabolically optimal frequency, the underlying mechanisms are still unclear. Changes in joint kinematics when altering stride frequency will affect the muscle‐tendon unit lengths and potentially the efficiency of muscles crossing these joints. Here, we investigated how fascicle kinematics and forces of the triceps surae muscle, a highly energy consuming muscle, are affected when running at different stride frequencies. Twelve runners ran on a force measuring treadmill, adopting five different frequencies (PSF; PSF±8%; PSF±15%), while we measured joint kinematics, whole‐body energy expenditure, triceps surae muscle activity, and soleus (SOL; N = 10) and gastrocnemius medialis (GM; N = 12) fascicle kinematics. In addition, we used dynamic optimization to estimate SOL and GM muscle forces. We found that SOL and GM mean muscle fascicle length during stance followed an inverted U‐relationship with the longest fascicle lengths occurring at PSF. Fascicle lengths were shortest at frequencies lower than PSF. In addition, average SOL force was greater at PSF‐15% compared to PSF. Overall, our results suggest that reduced SOL and GM muscle fascicle lengths, associated with reduced muscle force potential, together with greater SOL force demand, contribute to the increased whole‐body energy expenditure when running at lower than PSF. At higher stride frequencies, triceps surae muscle kinematics and force production were less affected suggesting that increased energy expenditure is rather related to higher cost of leg swing and greater cost of force production.
... A secondary analysis was performed to assess footstrike pattern and stride frequency, variables known to change with footwear and affect the primary dependent variables, stiffness, 29,42,43 and vertical impact characteristics. 13,44 Strike index and sagittal plane ankle angle at initial contact were calculated to evaluate changes in the footstrike pattern. The strike index was calculated as the location of the center of pressure at initial contact relative to the length of the foot (rearfoot = 0%-33%; midfoot = 34%-66%; forefoot = 68%-100%). ...
Article
The running footwear literature reports a conceptual disconnect between shoe cushioning and external impact loading: footwear or surfaces with greater cushioning tend to result in greater impact force characteristics during running. Increased impact loading with maximalist footwear may reflect an altered lower-extremity gait strategy to adjust for running in compliant footwear. The authors hypothesized that ankle and knee joint stiffness would change to maintain the effective vertical stiffness, as cushioning changed with minimalist, traditional, and maximalist footwear. Eleven participants ran on an instrumental treadmill (3.5 m·s-1) for a 5-minute familiarization in each footwear, plus an additional 110 seconds before data collection. Vertical, leg, ankle, and knee joint stiffness and vertical impact force characteristics were calculated. Mixed model with repeated measures tested differences between footwear conditions. Compared with traditional and maximalist, the minimalist shoes were associated with greater average instantaneous and average vertical loading rates (P < .050), greater vertical stiffness (P ≤ .010), and less change in leg length between initial contact and peak resultant ground reaction force (P < .050). No other differences in stiffness or impact variables were observed. The shoe cushioning paradox did not hold in this study due to a similar musculoskeletal strategy for running in traditional and maximalist footwear and running with a more rigid limb in minimalist footwear.
... In the lower limbs, the knee and the foot are the most commonly injured locations due to intrinsic factors such as biomechanical abnormalities and muscle functionality [4], or extrinsic factors such as poor running technique [5] or unsuitable running shoes [6]. Overall, the biomechanical effects associated with foot-strike pattern, such as anatomic alignment of lower limb structures [7], stride length or foot pronation, and the greater vertical ground reaction force load rate are thought to be important issues related to several overuse injuries [8,9]. The impact peak is associated with high rates of loading while running [10]. ...
Article
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Foot-strike and the associated load rate are factors related to overuse injuries in runners. The purpose of this study was to analyse structural and functional changes in runners using floating heel running shoes, compared with runners using conventional footwear. A randomised control trial was conducted. Twenty runners with overuse injuries were followed over a 12-week gait retraining programme using floating heel running shoes or their conventional footwear. Pain was measured with pressure pain thresholds (PPTs), structural changes were measured with ultrasonography, and severity and impact of injury was scored on the Oslo Sports Trauma Research Centre Overuse Injury Questionnaire (OSTRC-O). Statistical differences were found between groups after the intervention (p < 0.001), with a medium size effect SE = 0.8, and the floating heel running shoes group reached higher PPTs values. Participants using floating heel running shoes showed higher OSTRC-O scores than those using their conventional footwear (p < 0.05), with higher scores after the intervention (p < 0.05). A 12-week gait retraining programme using floating heel running shoes had positive effects on the injury recovery process when compared to the use of conventional footwear, with significant differences in terms of pain and impact on sports activity.
... A recent systematic review that investigated the influence of stride frequency on running mechanics found that an increased stride rate consistently resulted in decreased ground reaction force, impact shock and attenuation, and energy absorbed at the hip, knee, and ankle (Schubert et al., 2014). Runners who increased their step rate by 10% in response to a digital audio metronome had substantially reduced loading to the hip and knee joints (Heiderscheit et al., 2011), and increasing stride length by 10% decreases the probability of tibial stress fractures (Edwards et al., 2009). Additionally, increasing runners' step rate to 10% above their preferred step rate has demonstrated no significant increase in oxygen consumption or heart rate (Hamill et al., 1995). ...
Article
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Background: The purpose of this study was to evaluate the validity of the SHFT digital run coach on measurements of Landing Angle, Toe Off Angle, and ground contact time. Methods: Twenty-one participants wore two SHFT pods and ran on a treadmill for ten minutes at 5 mph and 1% incline. Three 30-second videos were taken while participants ran. For each video, landing angle, TOA, and ground contact time were measured at three time points using the Hudl Technique application. For each variable, the mean of nine measurements, three from each video, was taken. Results: A one-way repeated measures ANOVA revealed significant differences between SHFT and Hudl for landing angle, TOA, and ground contact time. Conclusion: Despite its claims to be the world's most intelligent virtual running coach, SHFT was not found to validly measure landing angle, TOA, and ground contact time. SHFT overestimated landing angle and underestimated TOA and ground contact time. Because of its inaccurate measurements, SHFT may give runners improper coaching tips, and the coaching aspect of SHFT needs to be investigated in future studies.
... The reduced plantarflexor moments, vertical GRFs, and vertical displacement in persons with ASD could be a by-product/mechanism of their decreased stride lengths and increased frequency (the inverse of stride length) [47,48]. In neurotypical adults, running at increased cadences results in reduced vertical GRFs and reduced vertical displacement [49,50]. ...
... While resistance training increases the load capacity of tissue, the strength gains do not typically improve the running biomechanics associated with injury risk (Willy and Davis, 2011). Several running retraining approaches have been suggested, such as increasing step rate or transitioning to a non-rearfoot strike, and the biomechanical effects of each are well-described in adults (Heiderscheit et al., 2011;Chumanov et al., 2012;Adams et al., 2018;Yong et al., 2018;Napier et al., 2019;Zimmermann and Bakker, 2019). Despite few clinical trials, the findings have been consistently positive in that appropriately applied running retraining improves patient-reported outcomes and injury recovery (Noehren et al., 2011;Willy et al., 2012;Helmhout et al., 2015). ...
Article
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Global participation in running continues to increase, especially amongst adolescents. Consequently, the number of running-related injuries (RRI) in adolescents is rising. Emerging evidence now suggests that overuse type injuries involving growing bone (e.g., bone stress injuries) and soft tissues (e.g., tendinopathies) predominate in adolescents that participate in running-related sports. Associations between running biomechanics and overuse injuries have been widely studied in adults, however, relatively little research has comparatively targeted running biomechanics in adolescents. Moreover, available literature on injury prevention and rehabilitation for adolescent runners is limited, and there is a tendency to generalize adult literature to adolescent populations despite pertinent considerations regarding growth-related changes unique to these athletes. This perspective article provides commentary and expert opinion surrounding the state of knowledge and future directions for research in adolescent running biomechanics, injury prevention and supplemental training.
... For instance, switching from rear-foot to mid-foot or fore-foot strike pattern induces a distal shift of mechanical loading from the knee to the ankle (11,41). Increasing the running step rate diminishes the negative work performed at the hip and knee joints (14) or decreasing the step length can decrease PFJ stress (42,43). Similarly, postural modifications such as forward trunk-leaning seem effective in reducing PFJ stress (10,32,33), because trunk orientation during walking (18) or running (1,2,32,33) also significantly redistributes the mechanical demands of lower-limb joints. ...
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.
... The reduced plantarflexor moments, vertical GRFs, and vertical displacement in persons with ASD could be a by-product/mechanism of their decreased stride lengths and increased frequency (the inverse of stride length) [47,48]. In neurotypical adults, running at increased cadences results in reduced vertical GRFs and reduced vertical displacement [49,50]. ...
Article
Research examining gait biomechanics of persons with autism spectrum disorder (ASD) has grown significantly in recent years and has demonstrated that persons with ASD walk at slower self-selected speeds and with shorter strides, wider step widths, and reduced lower extremity range of motion and moments compared to neurotypical controls. In contrast to walking, running has yet to be examined in persons with ASD. The purpose of this study was to examine lower extremity running biomechanics in adolescents (13-18-year-olds) with ASD and matched (age, sex, and body mass index) neurotypical controls. Three-dimensional kinematics and ground reaction forces (GRF) were recorded while participants ran at two matched speeds: self-selected speed of adolescents with ASD and at 3.0m/s. Sagittal and frontal plane lower extremity biomechanics and vertical GRFs were compared using two-way ANOVAs via statistical parametric mapping. Adolescents with ASD ran with reduced stride length at self-selected speed and reduced vertical displacement, loading-propulsion GRFs, propulsion plantarflexion moments, loading-propulsion hip abduction moments, and loading knee abduction moments at both speeds. Running at 3.0m/s increased sagittal plane hip and knee moments surrounding initial contact and frontal plane knee angles during mid stance and propulsion compared to self-selected speeds. Reduced contributions from primarily the ankle plantarflexion but also knee abduction and hip abduction moments likely reduced the vertical GRF and displacement. As differences favored reduced loading, youth with ASD can safely be encouraged to engage in running as a physical activity.
... This results in increased K vert of the spring mass system, a reduction in vertical displacement during the ground contact phase and less time taken for the system to bounce off the ground (Farley & Gonzalez, 1996). Likewise, Heiderscheit and colleagues (Heiderscheit et al., 2011) studied the effects of five different step frequencies on the hip, knee and ankle joint energy absorption, but neither shod running or foot-strike pattern were taken into account. Furthermore, endurance runners repeatedly manage the vertical ground reaction force impact (a collision force of about 1.5-3 times body weight) within the first 50 ms of the stance phase (Lieberman et al., 2010). ...
Article
This study aimed to determine the influence of footwear condition, foot-strike pattern and step frequency on running spatiotemporal parameters and lower-body stiffness during treadmill running. Thirty-one amateur endurance runners performed a two-session protocol (shod and barefoot). Each session consisted of two trials at 12 km · h −1 over 5 minutes altering step frequency every minute (150, 160, 170, 180 and 190 spm). First, participants were instructed to land with the heel first; after completion, the same protocol was repeated landing with the forefoot first. Repeated measures ANOVAs showed significant differences for footwear condition, foot-strike pattern and step frequency for each variable: percent contact time, percent flight time, vertical stiffness and leg stiffness (all p < 0.001). The results demonstrate greater estimated vertical and leg stiffness when running barefoot for both foot-strike patterns showing the largest values for barefoot+forefoot condition. Likewise, both vertical and leg stiffness became greater as step frequency increased. The proper manipulation of these variables facilitates our understanding of running performance and assist in training programmes design and injury management.
... For instance, transitioning the running landing technique from rearfoot to forefoot strike pattern shifts the mechanical loading from the knee to the ankle (Arendse et al., 2004;Bonacci et al., 2013;Goss & Gross, 2013;Williams, Green, & Wurzinger, 2012). Increasing the running step-rate results in reduced energy absorption by the hip and knee (Heiderscheit, Chumanov, Michalski, Wille, & Ryan, 2011), and decreasing the step length leads to lower patellofemoral joint stress (Willson, Ratcliff, Meardon, & Willy, 2015;Willson, Sharpee, Meardon, & Kernozek, 2014). Alternatively, an anterior trunk-lean during level running is proposed to manage pain and/or prevent injuries at the knee via shifting mechanical stress to the hip (Arendse et al., 2004;dos Santos, Nakagawa, Serrão, & Ferber, 2019;Goss & Gross, 2013;Huang et al., 2019;Teng & Powers, 2014, 2016. ...
Article
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This study aimed to investigate the role of trunk posture in running locomotion. Twelve recreational runners ran in the laboratory across even and uneven ground surface (expected 10 cm drop-step) with three trunk-lean angles from the vertical (self-selected, ∼15°; anterior, ∼25°; posterior, ∼0°) while 3D kinematic and kinetic data were collected using a 3D motion-capture-system and two embedded force-plates. Two-way repeated measures ANOVAs (α = 0.05) compared lower-limb joint mechanics (angles, moments, energy absorption and generation) and ground-reaction-force parameters (braking and propulsive impulse) between Step (level and drop) and Posture conditions. The Step-by-Posture interaction revealed decreased hip energy generation, and greater peak knee extension moment in the drop-step during running with posterior versus anterior trunk-lean. Furthermore, energy absorption across hip and ankle nearly doubled in the drop-step across all running conditions. The Step main effect revealed that the knee and ankle energy absorption, ankle energy generation, ground-reaction-force, and braking impulse significantly increased in the drop-step. The Posture main effect revealed that, compared with a self-selected trunk-lean, the knee’s energy absorption/generation, ankle’s energy generation and the braking impulse were either retained or attenuated when leaning the trunk anteriorly. The opposite effects occurred with a posterior trunk-lean. In conclusion, while the pronounced mechanical ankle stress in drop-steps is marginally affected by posture, changing the trunk-lean reorganizes the load distribution across the knee and hip joints. Leaning the trunk anteriorly in running shifts loading from the knee to the hip not only in level running but also when coping with ground-level changes.
... Second, gait retraining interventions may be a useful intervention, targeting many of the observed kinematic deficits. Specifically, increasing step rate has been shown to improve kinematics at the hip and pelvis, 43 reduce over-stride, 44 increase gluteal and calf muscle activation Kinematic Characteristics of Male Runners With a History of Recurrent Calf Muscle Strain Injury prior to foot contact 45 and reduce force requirements at the ankle joint. 46 Therefore, gait retraining may prove beneficial in the management of runners with recurrent CMSI through the restoration of mechanical deficits. ...
Article
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Background: Calf muscle strain injuries are a common running injury affecting male runners and are known to have high reoccurrence rates. Currently, limited evidence exists investigating factors associated with this injury with no previous study investigating the running kinematics of male runners with a history of repeat calf muscle strain injuries. Purpose: To investigate whether male runners with a history of repeat calf muscle strain injury demonstrate differences in stance phase running kinematics when compared to healthy controls. Study design: Case-control investigation. Level of evidence: 3b. Methods: Stance phase kinematics were compared between 15 male runners with a history of calf muscle strain injury and 15 male control participants during treadmill running at 3.2m/s. Independent t-tests were used to compare differences in stance phase kinematic parameters between groups and effect sizes were calculated using Cohen's d. Results: The group with a history of calf muscle strain injury demonstrated a significant 2.1⁰ and 3.1⁰ increase in contralateral pelvic drop and anterior pelvic tilt during mid stance. In addition, this group exhibited longer stance times and a more anterior tilted pelvis, flexed hip and a greater distance between the heel and centre of mass at initial contact. Large effect sizes, greater than 0.8, were observed for all differences. No significant differences were observed for ankle and knee joint kinematics between the groups. Conclusion: This is the first study to identify kinematic characteristics associated with recurrent calf muscle strain injury. While it is not possible to determine causality, the observed kinematic differences may contribute to recurrent nature of this injury. Specifically, it is possible that neuromuscular deficits of the hip and calf muscle complex may lead to increased strain on the calf complex. Rehabilitation interventions which focus on addressing pelvis and hip kinematics may reduce the demands placed upon the calf complex and could prove clinically effective.
... 6 Whereas some scientific evidence suggested that external impact forces were associated with injury risk, 29,39 the influences of shoe cushioning on impact-force characteristics were inconsistent, 25,40,41 as opposed to, for example, running velocity 40 or step rate. 42 This does not exclude a role of shoe cushioning in injury risk, but the active mechanism is most likely not via external impact forces. ...
... In the analysis of foot pressure, it was necessary to analyze peak and maximal pressures separately. Peak force describes first peak in the gait cycle, as a result of initial contact, which is also known as braking force during running (Heiderscheit et al., 2011). Maximum pressure occurred typically during push off phase. ...
Article
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In ski mountaineering, equipment and its interaction with the exercising human plays an important role. The binding, as the crucial connection between boot and ski, must ensure safe fixation during downhill skiing and a free moving heel when walking uphill. Uphill, the binding offers the possibility to adopt the height of the heel (riser height) to personal preferences and the steepness of the ascent. This possible adjustment and its influence on various biomechanical parameters are the focus of this work. For this study, 19 male leisure ski mountaineers were tested on a treadmill, ascending at a fixed submaximal speed (3.9 ± 0.4 km·h−1) at 8, 16, and 24% gradient and with three heel riser heights, low (0 cm), medium (3.0 cm) and high (5.3 cm). The applied biomechanical measurement systems included a 3D motion capture system in sagittal plane, pressure insoles, a with strain gauges instrumented pole, spirometry and a comfort scale. Step length and step frequency were influenced by the riser height and the gradient (p ≤ 0.001). The high riser height decreased the step length by 5% compared to the low riser height over all tested gradients, while steps were 9.2% longer at the 24% gradient compared to the 8% gradient over all three riser heights. The high riser height revealed a force impulse of the pole 13% lower than using the low riser height (p < 0.001). Additionally, the high riser height reduced the range of motion of the knee joint and the ankle joint compared to the low riser height (p < 0.001). Therefore, advantageous settings can be derived, with the low riser height creating proper range of motion for ankle, knee and hip joint and higher propulsion via the pole at 8%, while higher riser heights like the medium setting do so at steeper gradients. These findings are in line with the conducted comfort scale. We would not recommend the highest riser height for the analyzed gradients in this study, but it might be an appropriate choice for higher gradients.
... The amount, frequency, and timing of vertical impact force are considered to be the key factors causing lower extremity running-related injuries [4][5][6]. Vertical impact force can be affected by a few factors, including running shoes, foot strike patterns, and spatiotemporal parameters such as step length and frequency [7][8][9][10][11]. Therefore, mitigating the factors associated Appl. ...
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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.
... El aumento de la cadencia entre un 5 y un 10% a la autoseleccionada genera una disminución en el stress de todas las estructuras anteriormente mencionadas siempre y cuando la velocidad de carrera permanezca sin modificaciones. 10,11 No se han observado déficits en el rendimiento y consumo de oxígeno a largo plazo en los corredores que han implementado este cambio, siempre y cuando los aumentos no excedan el 10%. No se ha determinado a la fecha el número óptimo de cadencia, sino que los beneficios se obtienen aumentando porcentualmente la frecuencia natural de paso de cada persona. ...
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Como todo submundo deportivo, el running evoluciona a medida que lo hace la tecnología de los elementos involucrados aunque hay ciertos mitos o leyendas que perduran y no conocen de ciencia, sino que se trasladan de boca en boca, de generación en generación de corredores como verdades absolutas. Lo primero que debemos entender es que un caso no hace a la regla pero, por otro lado, la regla no abarca todos los casos. Los que vamos en busca de la kinesiología basada en la evidencia, intentamos fundamentar todo lo que decimos con el mayor sustento científico posible. Sin embargo, los estudios pueden afirmar que algo funciona y también que algo no funciona. La clave aquí es que lo que está comprobado que funciona, no funciona para toda la población, y lo que está probado que no funciona va a funcionar en alguno. La evidencia en ciencias de la salud es cuestión de probabilidades, no de teoremas.
... 21 Increasing cadence by 10% above one's preferred cadence is commonly advocated given its greater effects on reducing sagittal plane knee joint moment magnitudes. 22 Biomechanical interventions may be useful for shifting forces to different body parts in Masters runners with running-related pain or injuries. However, given that running biomechanics and their relation with injuries may be sex or gender specific, 5 interventions could focus on a single sex or gender to control for differences. ...
Article
The objective of this study was to compare the immediate effects of modifications to footwear or cadence on lower limb biomechanics of female Masters runners. After analyzing habitual treadmill running biomechanics in 20 female runners (52.4 [8.3] y), we assessed the effects of 5 conditions: (1) barefoot running, (2) Merrell Vapor Glove, (3) Merrell Bare Access, (4) Brooks Pure Flow, and (5) increasing cadence by 10%. In comparison with habitual biomechanics, greater vertical loading rates of the ground reaction force were observed during running barefoot or with a Merrell Vapor Glove or Bare Access. There was high variability among participants as to changes in foot kinematics during the conditions. Running barefoot (−26.0%) and with a Merrell Vapor Glove (−12.5%) reduced sagittal plane knee moments, but increased sagittal plane ankle moments (both 6.1%). Increasing cadence by 10% resulted in a more modest decrease in knee flexion moments (−7.7%) without increasing peak external ankle dorsiflexion moments. When asked if they would prefer minimalist shoes or increasing cadence, 11 participants (55%) chose cadence and 9 (45%) chose footwear. Minimalist footwear decreased sagittal knee moments, but increased vertical loading rate and sagittal ankle moments. Increasing cadence may be useful to lower sagittal knee moments without increasing ankle moments.
... Eight successful trials from each participant were used for analysis. Marker trajectories and ground reaction forces were exported to Visual 3D (C-Motion, Inc., Rockville MD) where they were filtered using a 4th order, zero lag, low-pass Butterworth filter with a cut off frequency of 12 Hz [36] and 50 Hz [37], respectively. Stance phase was defined using filtered ground reaction forces based on when forces rose above and fell below a 20 N threshold. ...
Article
Background The presence of fatigue has been shown to modify running biomechanics. Throughout a run individuals become more fatigued, and the effectiveness of the musculoskeletal protective mechanism can diminish. Older adults are at an elevated risk for sustaining an overuse running related injury. This can be partially explained by changes in the musculoskeletal system and load attenuation. Research question The purpose was to compare post-fatigue running mechanics between older and younger runners. Methods Thirty runners (15 young, 15 older) between the ages of 18-65 participated in this study. All participants ran at least 15 miles/week. Running kinematics were captured using a 10-camera motion capture system while participants ran over a 10-m runway with force platforms collecting kinetic data under two conditions: C1: rested state at a controlled pace of 3.5 m/s (± 5%); C2: post-exertional protocol where pace was not controlled, rather it was monitored based on heartrate and RPE representative of somewhat-hard to hard intensity exercise. Prior to C2, participants underwent an exertional protocol that consisted of a maximal exercise test to induce fatigue and a required cool-down. A 2 (state of fatigue) x 2 (age) MANOVA was run to test for the effects of fatigue and age and their interactions. Results: No state of fatigue x age interaction was observed. A main effect of age for peak knee extension moment (Y > O; p = 0.01), maximum knee power (Y > O; p = 0.04), maximum hip power (O >Y; p =0.04), and peak vertical ground reaction force (Y > O; p = 0.007). Regardless of age, participants exhibited decreased knee ROM (p=0.007) and greater hip extension moment (p<0.001) in C2 compared to C1. Conclusion While different in knee and hip mechanics overall, the subtle differences observed demonstrate that older runners exhibit comparable gait adaptions post-fatigue to younger volume-matched runners.
... In our sample, runners that exhibited a reduction in stride length did not present an impact peak. Various authors [27,28] agree that shock attenuation changes only when stride length changes. We support that it is plausible that the association between an impact peak and stride length may vary due to leg geometry changes as stride length changes [27]. ...
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Running is a physical activity and the investigation of its biomechanical aspects is crucial both to avoid injuries and enhance performance. Recreational runners may be liable to increased stress over the body, particularly to lower limb joints. This study investigates the different running patterns of recreational runners by analyzing characteristics of the footwear impact peak, spatiotemporal, and kinematic parameters among those that present with a peak impact and those that do not, with a 3D markerless system. Thirty recreational runners were divided into two groups: impact peak group (IP) (n = 16) and no impact peak group (n = 14) (n-IP). Kinematic and spatiotemporal parameters showed a large Cohen’s d effect size between the groups. The mean hip flexion was IP 40.40° versus n-IP 32.30° (d = −0.82). Hip extension was IP 30.20° versus n-IP 27.70° (d = −0.58), and ankle dorsiflexion was IP 20.80°, versus n-IP 13.37° (d = −1.17). Stride length was IP 117.90 cm versus n-IP 105.50 cm (d = −0.84). Steps per minute was IP group 170 spm, versus n-IP 163 spm (d = −0.51). The heel-to-toe drop was mainly 10–12 mm for the IP group and 4–6 mm for the n-IP group. Recreational runners whose hip extension is around 40°, ankle dorsiflexion around 20°, and initial foot contact around 14°, may be predisposed to the presence of an impact peak.
... [31][32][33] And a runner's centre of mass excursion as well as peak vertical ground reaction force were observed to reduce when stride frequency was increased. 34,35 These studies demonstrate that longer strides for a given speed increase the risk of injury. Because injuries develop over time, horses that reduce their speed and stride length could be attempting to circumvent or reduce pain due to an undetected or impending injury. ...
Article
Background: Certain stride characteristics have been shown to affect changes in biomechanical factors that are associated with injuries in human athletes. Determining the relationship between stride characteristics and musculoskeletal injury (MSI) may be key in limiting injury occurrence in the racehorse. Objectives: This study aimed to determine whether changes in race day speed and stride characteristics over career race starts are associated with an increased risk of MSI in racehorses. Study design: Case-control study. Methods: Speed, stride length, and stride frequency data were obtained from the final 200 m sectional of n = 5,660 race starts by n = 584 horses (case n = 146, control n = 438). Multivariable joint models, combining longitudinal and survival (time to injury) analysis, were generated. Coefficients and their 95% confidence intervals (CI) are presented. Results: The risk of MSI increased by 1.18 (95% CI 1.09, 1.28; P < 0.001) for each 0.1 m/s decrease in speed and by 1.11 (95% CI 1.02, 1.21; P = 0.01) for each 10 cm decrease in stride length over time (career race starts). A more marked rate of decline in speed and stride length was observed approximately 6 races prior to injury. Risk of MSI was highest early in the horse's racing career. Main limitations: Only final sectional stride characteristics were assessed in the model. The model did not account for time between race starts. Conclusions: Decreasing speed and stride length over multiple races is associated with MSI in racehorses. Monitoring stride characteristics over time may be beneficial for the early detection of MSI.
... Changes in cadence result in changes in joint kinematics, with the knee most involved through an increase in flexion at initial contact, with an accompanying increase in ankle plantarflexion (Heiderscheit et al., 2011) and a decrease in shank angle at initial contact (Preece et al., 2019). These joint positions are associated with forefoot or midfoot striking, which is the predominant footstrike pattern amongst middle-distance runners (Hayes and Caplan, 2012), and is similarly found amongst the world's best male 10,000 m runners (Hanley et al., 2021b), possibly because of a potential association with better running economy (Santos-Concejero et al., 2014). ...
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The 800 m race challenges the aerobic and anaerobic energy systems, and athletes adopt a technique that allows for running efficiency as well as sprinting speeds. The aim of this novel study was to compare important kinematic variables between the two laps of the 2017 IAAF World Championships women's final. Video data (150 Hz) were collected of all eight finalists on both laps at a distance approximately 50 m from the finish line along the home straight. Running speed, step length, cadence, temporal variables, sagittal plane joint angles, and shank angle at initial contact were measured. Running speed was faster on lap 2 (p = 0.008) because of large increases in cadence (p = 0.012). These higher cadences resulted in large decreases in contact times (p = 0.031) and in flight times (p = 0.016) on lap 2. Greater knee flexion and ankle plantarflexion (p ≤ 0.039) at initial contact on lap 2 seemed partly responsible for shorter swing times (p = 0.016), and which accompanied a decrease in shank angle at initial contact from lap 1 (7 •) to a more vertical position on lap 2 (4 •) (p = 0.008). Coaches should note that the need for higher cadence, horizontal impulse production during shorter contact times, and the adoption of forefoot striking require strength and neural system training to allow for athletes to increase cadence during the sprint finish. Increasing cadence (and not step length) was the driving factor for faster finishing speeds in the women's 800 m.
... In terms of performance, while overstriding is common among untrained and infrequent runners, more skilled and faster distance runners are often observed to avoid overstriding (Folland et al., 2017;Preece et al., 2019;Trowell et al., 2019), possibly because it negatively affects running economy. In particular, overstriding has been shown to generate especially large braking forces, the posteriorly directed forces in the horizontal plane that slow the body down during running (Heiderscheit et al., 2011;Lieberman et al., 2015b;Napier et al., 2019;Wille et al. 2014). To counter these larger braking forces and maintain a steady running speed, overstriding is expected to require leg and thigh muscles to generate larger forces to propel the body forward, thus costing more energy (Chang & Kram, 1999). ...
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Research among non-industrial societies suggests that body kinematics adopted during running vary between groups according to the cultural importance of running. Among groups in which running is common and an important part of cultural identity, runners tend to adopt what exercise scientists and coaches consider to be good technique for avoiding injury and maximizing performance. In contrast, among groups in which running is not particularly culturally important, people tend to adopt suboptimal technique. This paper begins by describing key elements of good running technique, including landing with a forefoot or midfoot strike pattern and leg oriented roughly vertically. Next, we review evidence from non-industrial societies that cultural attitudes about running associate with variation in running techniques. Then, we present new data from Tsimane forager-horticulturalists in Bolivia. Our findings suggest that running is neither a common activity among the Tsimane nor is it considered an important part of cultural identity. We also demonstrate that when Tsimane do run, they tend to use suboptimal technique, specifically landing with a rearfoot strike pattern and leg protracted ahead of the knee (called overstriding). Finally, we discuss processes by which culture might influence variation in running techniques among non-industrial societies, including self-optimization and social learning.
... Although peak VGRF, VGRF impulse, and COM vertical excursion each demonstrated univariable associations, these variables are strongly associated with each other and step rate. 28,29 Inclusion of step rate in the final model indicates it is the stronger risk factor for BSI and likely captures changes associated with other biomechanical measures and BSI risk. This may explain the lack of significance identified among GRF variables. ...
Article
Objectives To determine if running biomechanics and bone mineral density (BMD) were independently associated with bone stress injury (BSI) in a cohort of National Collegiate Athletic Association Division I cross country runners. Methods This was a prospective, observational study of 54 healthy collegiate cross country runners over three consecutive seasons. Whole body kinematics, ground reaction forces (GRFs) and BMD measures were collected during the preseason over 3 years via motion capture on an instrumented treadmill and total body densitometer scans. All medically diagnosed BSIs up to 12 months following preseason data collection were recorded. Generalised estimating equations were used to identify independent risk factors of BSI. Results Univariably, step rate, centre of mass vertical excursion, peak vertical GRF and vertical GRF impulse were associated with BSI incidence. After adjusting for history of BSI and sex in a multivariable model, a higher step rate was independently associated with a decreased risk of BSI. BSI risk decreased by 5% (relative risk (RR): 0.95; 95% CI 0.91 to 0.98) with each one step/min increase in step rate. BMD z-score was not a statistically significant risk predictor in the final multivariable model (RR: 0.93, 95% CI 0.85 to 1.03). No other biomechanical variables were found to be associated with BSI risk. Conclusion Low step rate is an important risk factor for BSI among collegiate cross country runners and should be considered when developing comprehensive programmes to mitigate BSI risk in distance runners.
... Step rate modification has also been reported as a successful means to reduce anterior knee pain during running [39,40] and has also demonstrated efficacy in reducing symptoms after four weeks of training in runners with PFP. Similar studies investigating the use of strike pattern and step rate modification has shown reductions in both PFJS and PFP symptoms up to six months. ...
Article
Background Structure-specific loading is being increasingly recognized as playing a role in running related injuries. The use of interventions targeted at reducing patellofemoral joint loads have shown effectiveness in reducing symptoms of patellofemoral pain. Use of bodyweight support (BWS) has the potential to reduce loading on the patellofemoral joint during running to augment rehabilitation efforts. Research Question How is patellofemoral joint loading different when using a harness-based BWS system during running? Methods Twenty-five healthy females free from lower extremity injury were included. Participants completed four running trials on an instrumented treadmill with varying amounts of BWS using a commercially available harness system. Kinematic data from a 3D motion capture system and kinetic data from the treadmill were combined in a computer model to estimate measures of patellofemoral joint loading, knee kinematics, ground reaction force, and stride frequency. Results Peak patellofemoral joint stress and time-integral were reduced when running under BWS conditions compared to control conditions. Incremental decreases in patellofemoral loading were not observed with incremental increases in BWS. Peak knee flexion angle was reduced in all BWS conditions compared to control but was not different between BWS conditions. Knee flexion excursion was reduced in only the high BWS condition. Peak ground reaction force and stride frequency incrementally decreased with increased amounts of BWS. Significance Harness-based BWS systems may provide a simple means to reduce patellofemoral joint loading to assist in rehabilitation efforts, such as addressing patellofemoral pain.
... However, these wearable devices do not provide sufficient data to calculate joint kinetics. Foot strike pattern, foot inclination angle (the angle between the foot and the horizontal in the sagittal plane), step rate, and stride length are considered kinematic correlates to ground reaction or joint forces (Heiderscheit et al., 2011;Lenhart et al., 2014a,b;Wille et al., 2014;Souza, 2016). Runners who rearfoot strike tend to have low step rates, use longer steps, and run with higher magnitudes of peak vertical ground reaction force, loading rates, peak braking forces, and potentially larger lower extremity joint forces than non-rearfoot strikers. ...
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Many runners seek health professional advice regarding footwear recommendations to reduce injury risk. Unfortunately, many clinicians, as well as runners, have ideas about how to select running footwear that are not scientifically supported. This is likely because much of the research on running footwear has not been highly accessible outside of the technical footwear research circle. Therefore, the purpose of this narrative review is to update clinical readers on the state of the science for assessing runners and recommending running footwear that facilitate the goals of the runner. We begin with a review of basic footwear construction and the features thought to influence biomechanics relevant to the running medicine practitioner. Subsequently, we review the four main paradigms that have driven footwear design and recommendation with respect to injury risk reduction: Pronation Control, Impact Force Modification, Habitual Joint (Motion) Path, and Comfort Filter. We find that evidence in support of any paradigm is generally limited. In the absence of a clearly supported paradigm, we propose that in general clinicians should recommend footwear that is lightweight, comfortable, and has minimal pronation control technology. We further encourage clinicians to arm themselves with the basic understanding of the known effects of specific footwear features on biomechanics in order to better recommend footwear on a patient-by-patient basis.
... In a study in 2011 by Heiderscheit et al., a 5% increase in cadence resulted in decreased vertical excursion of COM and braking impulse. 22 Furthermore, a 10% increase in step frequency resulted in decreased vGRF at the hip and knee, peak hip adduction angle, and peak hip adduction and internal rotation moments. ...
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The purpose of the article is to present an updated literature review, as well as describe our approach to rehabilitation and return to sports following hip arthroscopy for femoroacetabular impingement (FAI) with labral repair. A literature review was performed to identify articles published within the last 10 years that were focused on this topic. Relevant articles were reviewed, and reference lists were searched to identify additional articles. Findings were summarized for rehabilitation phases and return-to-sports assessment. Additionally, advanced rehabilitation topics are reviewed. Several systematic reviews and individual case series were identified. There is relative uniformity concerning the use of a four-phase approach for rehabilitation. However, there is inconsistency in terms of timing and criteria for ultimate return to sport. Advanced rehabilitation topics were reviewed, and description of their relevance at various rehabilitation phases was provided. A four-phase approach to rehabilitation following hip arthroscopy for FAI is widely used with general uniformity, although the timing and level of detail concerning assessment and readiness for return to sport are variable. Advanced rehabilitation techniques may be used in select patients returning to high-level activities.
Article
Insertional Achilles tendinopathy (IAT) is a degenerative process at the insertion of the Achilles tendon onto the calcaneus. Many possible reasons for why this condition develops exist, and is likely due to a combination of factors, but an abnormal, bony prominence at the posterior-superior aspect of the calcaneus, known as a Haglund's deformity, may play a role in the development of IAT. This exostosis may cause increased compressive forces and irritation of the tendon at the calcaneal insertion, leading to pain and degenerative changes within the tendon. Non-operative treatments, including activity modification, eccentric exercise training, extracorporeal shock wave therapy, shoe wear modifications and orthotic inserts, and injection therapies, are the first line of treatment, but have shown varying levels of success in treating IAT. Operative treatments may be indicated after 3-6 months of failed non-operative treatment. In the case of IAT with Haglund's deformity, we describe the procedure of removing the exostosis, debriding the tendon, and reattaching the tendon to the calcaneus, with the use of the flexor hallucis longus tendon, when indicated. Return to sport timeline may be dependent upon severity of tendon damage pre-injury, but care should be taken to monitor load and pain management in a return to run progression program.
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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.
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Background: There is a scarcity of evidence describing how physical therapists use data from clinical examinations to inform the treatment of runners with knee pain. Objective: Our purpose was to examine the between physical therapist agreement on the selection of perceived impairments in runners with knee pain. Methods: Twelve physical therapists reviewed two cases of runners with knee pain. The cases included clinical subjective information, objective data, and review of videos of each participant running. Each rater selected up to three perceived impairments (from a list of eight) that each physical therapist would address at the next physical therapy session. Percent agreement was calculated to determine the between rater agreement on each individual perceived impairment selection and Fleiss Kappa was calculated for each unique combination of three perceived impair�ments per case. Results: Twelve raters with 51 (18–156) months of clinical experience participated. Percent agree�ment ranged from 8%-100% for both cases for individual impairments. When assessing the unique combination of three impairments selected, inter-rater agreement was less than what is expected due to chance alone (κ = −0.09, p = .92; κ = −0.09, p = .98) for both cases. Conclusion: The 12 physical therapists demonstrated poor to excellent levels of agreement when selecting an individual perceived impairment. Agreement was worse than chance when selecting a combination of three unique impairments.
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Background Increasing cadence in running has been advocated as a means to improve performance and reduce impact forces. Although acoustic pacing can be used for this purpose, it might by itself lead to an increased impact force, which would counteract the decrease in impact force that is being pursued by increasing the cadence with acoustic pacing and thus have a counterproductive effect. Research question What are the effects of acoustic pacing and cadence on peak impact force and loading rate during running? Methods Unpublished data from a previous study, in which 16 participants ran on an instrumented treadmill with various forms of acoustic pacing, were analyzed to address the research question. Peak impact force and loading rate while running with and without pacing, at three different cadences were extracted from the ground reaction force data and compared statistically between these two main conditions. In addition, we compared step-based and stride-based pacing, and paced and unpaced steps within stride-based pacing conditions. Results As expected, increasing the cadence was accompanied by a significant reduction in peak impact force and instantaneous vertical loading rate, whereas acoustic pacing had no significant effect on the impact forces compared to unpaced running with similar cadence, both before and after pacing. There were also no significant differences in this regard between step- and stride-based pacing. Significance Acoustic pacing does not adversely affect impact force when used to increase cadence in running with the aim of reducing the impact force and can thus be used for this purpose without introducing a counterproductive effect.
Running after childbirth, specifically how or when to return, is a hot topic in the field of physical therapy and on social media; however, there are significant gaps in the literature supporting when and how to safely initiate running postpartum. During pregnancy and following childbirth (both vaginal and cesarean), the body undergoes changes that may impact strength, neuromuscular control, endurance, and the ability to withstand the high-impact forces and repetitive nature of running. Many mothers experience new or worsened symptoms of musculoskeletal or pelvic floor dysfunction following pregnancy and childbirth and require physical therapy to normalize function. After most major injuries, it is common to participate in formalized rehabilitation; however, this is not the norm for athletes returning to running postchildbirth. Because of lack of evidence, many runners and clinicians struggle to develop appropriate rehabilitation progressions for return to running after childbirth. Pelvic and sports physical therapists must understand biomechanical features of running gait and safely progress strength, endurance, and neuromuscular control of the kinetic chain when guiding a runner back to running. This clinical commentary builds on existing guidelines, research, and expert opinion to propose a 4-phase rehabilitation framework to help runners initiate and progress running after childbirth. The result is an in-depth exercise prescription (intensity, frequency, type), examples of exercises (hip, abdominal, pelvic floor, and foot), running progression, and progression goals to prepare runners for symptom-free running after childbirth (see Video, Supplemental Digital Content 1, available at: http://links.lww.com/JWHPT/A58, where authors provide more insight on this return to running framework).
Article
Bone stress injuries (BSI) are overuse injuries that commonly occur in runners. BSI risk is multifactorial and not well understood. Unsupervised machine learning approaches can potentially elucidate risk factors for BSI by looking for groups of similar runners within a population that differ in BSI incidence. Here, a hierarchical clustering approach is used to identify groups of collegiate cross country runners (32 females, 21 males) based on healthy pre-season running (4.47 m/s) gait data which were aggregated and dimensionally reduced by principal component analysis. Five distinct groups were identified using the cluster tree. Visual inspection revealed clear differences between groups in kinematics and kinetics, and linear mixed effects models showed between-group differences in metrics potentially related to BSI risk. The groups also differed in BSI incidence during the subsequent academic year (Rand index = 0.49; adjusted Rand index = -0.02). Groups ranged from those including runners spending less time contacting the ground and generating higher peak ground reaction forces and joint moments to those including runners spending more time on the ground with lower loads. The former groups showed higher BSI incidence, indicating that short stance phases and high peak loads may be risk factors for BSI. Since ground contact duration may itself account for differences in peak loading metrics, we hypothesize that the percentage of time a runner is in contact with the ground may be a useful metric to include in machine learning models for predicting BSI risk.
Article
Patellofemoral pain syndrome: a literature review Patellofemoral pain (PFP) is one of the most common diagnoses of anterior knee pain, particularly among the physically active population. Symptoms mainly occur during load on the patellofemoral joint or in prolonged sitting. The etiology of PFP is complex, with multiple factors, such as overload and structural malalignment contributing to the development of the complaints, creating an imbalance of forces that stabilize the patella. The heterogeneity in the literature and the lack of evidence-based clinical guidelines reflect the challenge in the management of PFP. International consensus proposes multimodal intervention including exercise therapy targeting knee and hip strengthening. The aim of this article is to present the current literature in a comprehensive and unambiguous way and to provide both primary and secondary care providers with sufficient tools to work with this pathology in a more targeted way.
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Modern footwear has changed in its role over the years from providing protection to controlling foot motion and stabilisation. However, Running Related Injuries (RRIs) continue to increase despite technological innovations in fabrication and design. As we evolve in our understanding of barefoot running, examining this pattern of running is worth giving attention to. Barefoot running changes the foot strike pattern to forefoot strike with reduction in stride length and impact loading. Also, barefoot form of running provides a greater proprioceptive challenge to plantar surface of the foot and increased energy conservation at the arches. The advent of new footwear trend in form of minimalist shoe is slowly gaining attention but it is presumptive to appreciate its benefits over barefoot running. The purpose of this review was to study the evidence regarding differences between shod and barefoot mechanics and how different footwear affords mechanical changes between them. Future directions on barefoot running mechanics and its progression are also suggested.
Article
Trunk flexion is an understudied biomechanical variable that potentially influences running performance and susceptibility to injury. We present and test a theoretical model relating trunk flexion angle to stride parameters, joint moments and ground reaction forces that have been implicated in repetitive stress injuries. Twenty-three participants (12 male, 11 female) ran at preferred trunk flexion and three more flexed trunk positions (moderate, intermediate and high) on a custom built Bertec™ instrumented treadmill while kinematic and kinetic data were simultaneously captured. Markers adhered to bony landmarks tracked the movement of the trunk and lower limb. Stride parameters, moments of force and ground reaction force were calculated using Visual 3D (C-Motion ©) software. From preferred to high trunk flexion, stride length decreased 6% (P < 0.001) and stride frequency increased 7% (P < 0.001). Extensor moments at the hip increased 70% (P < 0.001), but knee extensor (P < 0.001) and ankle plantarflexor moments (P < 0.001) decreased 22% and 14%, respectively. Greater trunk flexion increased rate of loading by 29% (P < 0.01) and vertical ground reaction force impact transients by 20% (P < 0.01). Trunk flexion angle during running has significant effects on stride kinematics, lower extremity joint moments and ground reaction force and should be further investigated in relation to running performance and repetitive stress injuries.
Article
Introduction: Loading rate (LR), the slope of the vertical ground reaction force (vGRF), is commonly used to assess running-related injury risk. However, the relationship between LR and running-related injuries, including bone stress injuries (BSI), is unclear. Inconsistent findings may result from the numerous LR calculation methods that exist and their application across different running speeds. Purpose: Assess the influence of calculation method and running speed on LR values and determine the association of LR during healthy running with subsequent injury. Methods: Healthy preseason running data and subsequent injury records from Division I cross country athletes (n = 79) over four seasons (2015-2019) at 2.68 m/s, preferred training pace, and 4.47 m/s were collected. LR at each speed was calculated four ways: 1) maximum and 2) average slope from 20-80% of vGRF magnitude at impact peak (IP), 3) average slope from initial contact to IP, and 4) average slope from 3-12% of stance time. Linear mixed effects models and generalized estimation equations were used to assess LR associations. Results: LR values differed depending on speed and calculation method (p-value <0.001). The maximum slope from 20-80% of the vGRF at 4.47 m/s produced the highest LR estimate and the average slope from initial contact to IP at 2.68 m/s produced the lowest. Sixty-four injuries (20 BSI) were observed. No significant association was found between LR and all injuries or BSI across any calculation method (p-values ≥0.13). Conclusions: Calculation method and running speed result in significantly different LR values. Regardless of calculation method, no association between LR and subsequent injury was identified. Thus, healthy baseline LR may not be useful to prospectively assess running-related injury risk.
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Single-subject with repeated measures. To determine if runners can use real-time visual feedback from an accelerometer to achieve immediate reductions in tibial acceleration and vertical-force loading rates. Stress fractures are a common injury among runners. Previous studies suggest that runners with higher than normal tibial acceleration and vertical-force loading rates are at increased risk for tibial stress fractures. If these runners can be trained to reduce the loading on their lower extremities, it may reduce their risk of stress fractures. Five subjects participated in this study. All subjects ran on a treadmill, instrumented with force transducers, during a single 30-minute session that was divided into warm-up, feedback, no-feedback, and cool-down periods. During running, the subjects also wore an accelerometer taped to their distal right tibia. Peak positive acceleration of the tibia, vertical force impact peak, and average and instantaneous vertical-force loading rates were assessed at the end of the warm-up, feedback, and no-feedback periods. Single-subject analysis revealed that 4 of the 5 subjects had significant reductions in their peak positive acceleration at the end of the no-feedback period compared to the warm-up. In addition, all of the subjects had significant decreases in impact peak and vertical ground reaction force loading rates at the end of the no-feedback period. In a single session of training with real-time visual feedback, it appears that most runners can reduce the types of lower extremity loading associated with stress fractures. This may lead to training programs that reduce the risk of stress fractures for runners.
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Cross-sectional experimental laboratory study. To examine differences in running mechanics between runners who had previously sustained iliotibial band syndrome (ITBS) and runners with no knee-related running injuries. ITBS is the second leading cause of knee pain in runners and the most common cause of lateral knee pain. Despite its prevalence, few biomechanical studies have been conducted to better understand its aetiology. Because the iliotibial band has both femoral and tibial attachments, it is possible that atypical hip and foot mechanics could result in the development of ITBS. The running mechanics of 35 females who had previously sustained ITBS were compared to 35 healthy age-matched and running distance-matched healthy females. Comparisons of hip, knee, and ankle 3-dimensional kinematics and internal moments during the stance phase of running gait were measured. The ITBS group exhibited significantly greater peak rearfoot invertor moment, peak knee internal rotation angle, and peak hip adduction angle compared to controls. No significant differences in peak rearfoot eversion angle, peak knee flexion angle, peak knee external rotator moment, or peak hip abductor moments were observed between groups. Females with a previous history of ITBS demonstrate a kinematic profile that is suggestive of increased stress on the iliotibial band. These results were generally similar to those reported for a prospective study conducted within the same laboratory environment.
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In this study, we assessed how ungraded jogging and graded walking at the same rating of perceived exertion (RPE) affect heart rate and oxygen consumption ([Vdot]O(2)). Twenty untrained participants completed a treadmill test to determine peak [Vdot]O(2) (mean = 40.3 +/- 6.3 ml . kg(-1) . min(-1)). Participants completed separate 30-min trials of moderate exercise (RPE of 13 on the Borg 6-20 scale) in random order on the treadmill: graded walking and ungraded jogging. Treadmill speed or grade was adjusted throughout the trial by the experimenter based on participant responses to maintain an RPE of 13. The jogging trial produced a significantly higher heart rate (161 +/- 18 vs. 142 +/- 24 beats . min(-1)) and [Vdot]O(2) (7.4 +/- 1.8 vs. 5.8 +/- 1.5 METs) (P < 0.01) than the walking trial. Treadmill grade decreased significantly during the walking trial (11.1 +/- 2.3% to 10.0 +/- 2.2%; P < 0.01), but treadmill speed did not change significantly during the jogging trial (5.2 +/- 1.0 miles . h(-1) to 5.0 +/- 0.9 miles . h(-1)) (P > 0.05), in an effort to maintain constant RPE. These findings provide evidence that similar perceptions of effort during graded walking and ungraded jogging do not produce similar cardiovascular and metabolic responses. The results indicate that, for a given prescribed perceived effort, jogging provides a greater stimulus for fitness benefits and caloric expenditure.
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Controlled laboratory study using a cross-sectional design. To determine whether females with patellofemoral pain (PFP) demonstrate differences in hip kinematics, hip muscle strength, and hip muscle activation patterns when compared to pain-free controls. It has been proposed that abnormal hip kinematics may contribute to the development of PFP. However, research linking hip function to PFP remains limited. Twenty-one females with PFP and 20 pain-free controls participated in this study. Hip kinematics and activity level of hip musculature were obtained during running, a drop jump, and a step-down maneuver. Isometric hip muscle torque production was quantified using a multimodal dynamometer. Group differences were assessed across tasks using mixed-design 2-way analyses of variance and independent t tests. When averaged across all 3 activities, females with PFP demonstrated greater peak hip internal rotation compared to the control group (mean +/- SD, 7.6 degrees +/- 7.0 degrees versus 1.2 degrees +/- 3.8 degrees; P<.05). The individuals in the PFP group also exhibited diminished hip torque production compared to the control group (14% less hip abductor strength and 17% less hip extensor strength). Significantly greater gluteus maximus recruitment was observed for individuals in the PFP group during running and the step-down task. The increased peak hip internal rotation motion observed for females in the PFP group was accompanied by decreased hip muscle strength. The increased activation of the gluteus maximus in individuals with PFP suggests that these subjects were attempting to recruit a weakened muscle, perhaps in an effort to stabilize the hip joint. Our results support the proposed link between abnormal hip function and PFP.
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We have developed a model of the human lower extremity to study how surgical changes in musculoskeletal geometry and musculotendon parameters affect muscle force and its moment about the joints. The lines of action of 43 musculotendon actuators were defined based on their anatomical relationships to three-dimensional bone surface representations. A model for each actuator was formulated to compute its isometric force-length relation. The kinematics of the lower extremity were defined by modeling the hip, knee, ankle, subtalar, and metatarsophalangeal joints. Thus, the force and joint moment that each musculotendon actuator develops can be computed for any body position. The joint moments calculated with the model compare well with experimentally measured isometric joint moments. We developed a graphical interface to the model that allows the user to visualize the musculoskeletal geometry and to manipulate the model parameters to study the biomechanical consequences of orthopaedic surgical procedures. For example, tendon transfer and lengthening procedures can be simulated by adjusting the model parameters according to various surgical techniques. Results of the simulated surgeries can be analyzed quickly in terms of postsurgery muscle forces and other biomechanical variables. Just as interactive graphics have enhanced engineering design and analysis, we have found that graphics-based musculoskeletal models are effective tools for designing and analyzing surgical procedures.
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To provide an extensive and up to date database for specific running related injuries, across the sexes, as seen at a primary care sports medicine facility, and to assess the relative risk for individual injuries based on investigation of selected risk factors. Patient data were recorded by doctors at the Allan McGavin Sports Medicine Centre over a two year period. They included assessment of anthropometric, training, and biomechanical information. A model was constructed (with odds ratios and their 95% confidence intervals) of possible contributing factors using a dependent variable of runners with a specific injury and comparing them with a control group of runners who experienced a different injury. Variables included in the model were: height, weight, body mass index, age, activity history, weekly activity, history of injury, and calibre of runner. Most of the study group were women (54%). Some injuries occurred with a significantly higher frequency in one sex. Being less than 34 years old was reported as a risk factor across the sexes for patellofemoral pain syndrome, and in men for iliotibial band friction syndrome, patellar tendinopathy, and tibial stress syndrome. Being active for less than 8.5 years was positively associated with injury in both sexes for tibial stress syndrome; and women with a body mass index less than 21 kg/m(2) were at a significantly higher risk for tibial stress fractures and spinal injuries. Patellofemoral pain syndrome was the most common injury, followed by iliotibial band friction syndrome, plantar fasciitis, meniscal injuries of the knee, and tibial stress syndrome. Although various risk factors were shown to be positively associated with a risk for, or protection from, specific injuries, future research should include a non-injured control group and a more precise measure of weekly running distance and running experience to validate these results.
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The literature related to Borg's ratings of perceived exertion (RPE) scale has revealed inconsistencies about the strength of the relationship between ratings of perceived exertion and various physiological criterion measures, such as heart rate, blood lactate concentration, percent maximal oxygen uptake (%VO2max), oxygen uptake (VO2), ventilation and respiration rate. Using sex of participants, fitness, type of RPE scale used, type of exercise, exercise protocol, RPE mode and study quality, we undertook a meta-analysis to determine the strength of the relationship between RPE scores and the six aforementioned physiological measures. The weighted mean validity coefficients were 0.62 for heart rate, 0.57 for blood lactate, 0.64 for %VO2max 0.63 for VO2, 0.61 for ventilation and 0.72 for respiration rate. Analysis of moderator variables revealed that the following study features could account for the variation of results across studies: heart rate--fitness, type of exercise, protocol and RPE mode; blood lactate concentration--sex, RPE scale; VO2--sex, exercise type, RPE mode; ventilation--sex, RPE mode; respiration rate--exercise protocol, RPE mode. The highest correlations between ratings of perceived exertion and the various physiological criterion measures were found in the following conditions: when male participants (whose VO2 or ventilation was measured) were required to maximally exert themselves (measuring %VO2max or ventilation); when the exercise task was unusual [e.g. when participants were swimming, which is less common than walking or running (when heart rate, %VO2max and VO2 are measured)]; or when the 15-point RPE scale (measuring blood lactate concentration) was used. These findings suggest that although Borg's RPE scale has been shown to be a valid measure of exercise intensity, its validity may not be as high as previously thought (r = 0.80-0.90), except under certain conditions.
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In this study, we examined the consequences of a global alteration in running technique on running kinematics and running economy in triathletes. Sixteen sub-elite triathletes were pre and post tested for running economy and running kinematics at 215 and 250 m.min-1. The members of the treatment group (n=8) were exposed to 12 weeks of instruction in the "pose method" of running, while the members of the control group (n=8) maintained their usual running technique. After the treatment period, the experimental group demonstrated a significant decrease in mean stride length (from 137.25+/-7.63 cm to 129.19+/-7.43 cm; P<0.05), a post-treatment difference in vertical oscillation compared with the control group (6.92+/-1.00 vs. 8.44+/-1.00 cm; P<0.05) and a mean increase in submaximal absolute oxygen cost (from 3.28+/-0.36 l.min-1 to 3.53+/-0.43 l.min-1; P<0.01). The control group exhibited no significant changes in either running kinematics or oxygen cost. The global change in running mechanics associated with 12 weeks of instruction in the pose method resulted in a decrease in stride length, a reduced vertical oscillation in comparison with the control group and a decrease of running economy in triathletes.
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This article outlines the practical management of iliotibial band friction syndrome (ITBFS) in running athletes. ITBFS is the most common cause of lateral knee pain in runners and is related to repetitive friction of the iliotibial band sliding over the lateral femoral epicondyle. Runners predisposed to this injury are typically in a phase of over training and often have underlying weakness of the hip abductor muscles. The diagnosis of ITBFS is clinical and is based on a thorough patient history and physical exam. In the acute phase, treatment includes activity modification, ice, nonsteroidal anti-inflammatory medication, and corticosteroid injection in cases of severe pain or swelling. During the subacute phase emphasis is on stretching of the iliotibial band and soft tissue therapy for any myofascial restrictions. The recovery phase focuses on a series of exercises to improve hip abductor strength and integrated movement patterns. The final return to running phase is begun with an every other day program, starting with easy sprints and avoidance of hill training with a gradual increase in frequency and intensity. In rare refractory cases that do not respond to conservative treatment, surgery can be considered.
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The purpose of this study was to present a systematic overview of published reports on the incidence and associated potential risk factors of lower extremity running injuries in long distance runners. An electronic database search was conducted using the PubMed-Medline database. Two observers independently assessed the quality of the studies and a best evidence synthesis was used to summarise the results. The incidence of lower extremity running injuries ranged from 19.4% to 79.3%. The predominant site of these injuries was the knee. There was strong evidence that a long training distance per week in male runners and a history of previous injuries were risk factors for injuries, and that an increase in training distance per week was a protective factor for knee injuries.
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The higher oxygen consumption reported when shod running is compared to barefoot running has been attributed to the additional mass of the shoe. However, it has been reported that wearing shoes also modified the running pattern. The aim of this study was to distinguish the mass and shoe effects on the mechanics and energetics when shod running. Twelve trained subjects ran on a 3-D treadmill ergometer at 3.61 m . s (-1) in six conditions: barefoot, using ultra thin diving socks unloaded, loaded with 150 g, loaded with 350 g, and two shoe conditions, one weighing 150 g and another 350 g. The results show that there was a significant mass effect but no shoe effect for oxygen consumption. Stride frequency, anterior-posterior impulse, vertical stiffness, leg stiffness, and mechanical work were significantly higher in barefoot condition compared to shod. Net efficiency, which has metabolic and mechanical components, decreased in the shod condition. The mechanical modifications of running showed that the main role of the shoe was to attenuate the foot-ground impact by adding damping material. However, these changes may lead to a decrease of the storage and restitution of elastic energy capacity which could explain the lower net efficiency reported in shod running.
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To determine the effect of modern-day running shoes on lower extremity joint torques during running. Two-condition experimental comparison. A 3-dimensional motion analysis laboratory. A total of 68 healthy young adult runners (37 women) who typically run in running shoes. All subjects ran barefoot and in the same type of stability running footwear at a controlled running speed. Three-dimensional motion capture data were collected in synchrony with ground reaction force data from an instrumented treadmill for each of the 2 conditions. Peak 3-dimensional external joint torques at the hip, knee, and ankle as calculated through a full inverse dynamic model. Increased joint torques at the hip, knee, and ankle were observed with running shoes compared with running barefoot. Disproportionately large increases were observed in the hip internal rotation torque and in the knee flexion and knee varus torques. An average 54% increase in the hip internal rotation torque, a 36% increase in knee flexion torque, and a 38% increase in knee varus torque were measured when running in running shoes compared with barefoot. The findings at the knee suggest relatively greater pressures at anatomical sites that are typically more prone to knee osteoarthritis, the medial and patellofemoral compartments. It is important to note the limitations of these findings and of current 3-dimensional gait analysis in general, that only resultant joint torques were assessed. It is unknown to what extent actual joint contact forces could be affected by compliance that a shoe might provide, a potentially valuable design characteristic that may offset the observed increases in joint torques.
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The fatigue life of bone is inversely related to strain magnitude. Decreasing stride length is a potential mechanism of strain reduction during running. If stride length is decreased, the number of loading cycles will increase for a given mileage. It is unclear if increased loading cycles are detrimental to skeletal health despite reductions in strain. To determine the effects of stride length and running mileage on the probability of tibial stress fracture. Ten male subjects ran overground at their preferred running velocity during two conditions: preferred stride length and 10% reduction in preferred stride length. Force platform and kinematic data were collected concurrently. A combination of experimental and musculoskeletal modeling techniques was used to determine joint contact forces acting on the distal tibia. Peak instantaneous joint contact forces served as inputs to a finite element model to estimate tibial strains during stance. Stress fracture probability for stride length conditions and three running mileages (3, 5, and 7 miles x d(-1)) were determined using a probabilistic model of bone damage, repair, and adaptation. Differences in stress fracture probability were compared between conditions using a 2 x 3 repeated-measures ANOVA. The main effects of stride length (P = 0.017) and running mileage (P = 0.001) were significant. Reducing stride length decreased the probability of stress fracture by 3% to 6%. Increasing running mileage increased the probability of stress fracture by 4% to 10%. Results suggest that strain magnitude plays a more important role in stress fracture development than the total number of loading cycles. Runners wishing to decrease their probability for tibial stress fracture may benefit from a 10% reduction in stride length.
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To examine the influence of the frequency of measurement on the rating of perceived exertion (RPE) during sub-maximal exercise. On two occasions participants performed 35 min sub-maximal treadmill exercise at the same running speed. In both runs RPE was measured after 5 min. Thereafter, RPE was measured at either 10-min intervals (RPE10 min), or 60-s intervals (RPE60 s) with the order of conditions controlled using a counter-balanced, cross-over design. The heart rate, VO(2) and RER were measured throughout each experimental trial. Significant differences in RPE between RPE60 s and RPE10 min were evident at 15, 25 and 35 min of exercise. No differences were evident between conditions in heart rate, VO(2) or RER. Differences in RPE between RPE60 s and RPE10 min indicate that the perception of exertion may be influenced by the act of measurement. The elevated RPE in RPE60 s may have been induced by an increased associative attentional focus.
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The first aim of this study was to assess how changes in the mechanical characteristics of the foot/shoe-ground interface affect spatio-temporal variables, ground pressure distribution, sagittal plane kinematics, and running economy in 8 experienced barefoot runners. The second aim was to assess if a special lightweight shoe (Vibram Fivefingers) was effective in mimic the experience of barefoot running. By using an instrumented treadmill, barefoot running, running with the Fivefingers, and running with standard running shoe were compared, analyzing a large numbers of consecutive steps. Foot/shoe-ground interface pressure distribution, lower limb kinematics, V.O(2) and heart rate data were simultaneously collected. Compared to the standard shod condition when running barefoot the athletes landed in more plantarflexion at the ankle. This caused reduced impact forces and changes in stride kinematics. In particular, significantly shorter stride length and contact times and higher stride frequency were observed (P<0.05). Compared to standard shod condition, V.O(2) and peak impact forces were significantly lower with Fivefingers (P<0.05) and much closer to barefoot running. Lower limb kinematics with Fivefingers was similar to barefoot running with a foot position which was significantly more plantarflexed than in control shoe (P<0.05). The data of this study support the assumption that changes in the foot-ground interface led to changes in running pattern in a group of experienced barefoot runners. The Fivefingers model seems to be effective in imitating the barefoot conditions while providing a small amount of protection.
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Movement and muscle activity of the hip have been shown to affect movement of the lower extremity, and been related to injury. The purpose of this study was to determine if increased hip strength affects lower extremity mechanics during running. Within subject, repeated measures design. Fifteen healthy women volunteered. Hip abduction and external rotation strength were measured using a hand-held dynamometer. Three-dimensional biomechanical data of the lower extremity were collected during running using a high-speed motion capture system. Measurements were made before, at the mid-point, and after a 6-week strengthening program using closed-chain hip rotation exercises. Joint range of motion (rearfoot eversion, knee abduction, hip adduction, and internal rotation), eversion velocity, eversion angle at heel strike, and peak joint moments (rearfoot inversion, knee abduction, hip abduction, and external rotation) were analyzed using repeated measures analysis of variance (P <or= 0.05). The independent variable was time (pre-, week 3, and week 6). A separate analysis of variance was conducted with the dependent variables of peak hip abduction and external rotation strength. Hip abduction (P=0.009) and external rotation strength (P<0.0005) increased by 13% and 23%, respectively. Eversion range of motion decreased (P=0.05), hip adduction range of motion increased (P=0.05), and a trend of decreased hip internal rotation range of motion (P=0.08) were found. Rearfoot inversion moment (P=0.02) and knee abduction moment (P=0.05) decreased by 57% and 10%, respectively. The hip abductors and external rotators were strengthened, leading to an alteration of lower extremity joint loading which may reduce injury risk. These exercises could be used in the rehabilitation, or prevention, of lower extremity injuries.
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A computer model of 23 knees was obtained by embedding, slicing and digitizing the bone outlines and ligament co-ordinates. Using co-ordinate transformations, various three-dimensional motions were imposed on the knees, and calculations made of femoral-tibial contact error, contact point locations and ligament lengths. Significant deviations in these parameters were noted for abnormal motions including the elimination of internal-external rotation and a-p displacement and the misplacement of a hinge producing correct motion. The resulting mismatch could result in shear in soft tissues, cuff-to-skin slippage and inaccurate ligament length patterns.
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An important determinant of the mechanics of running is the effective vertical stiffness of the body. This stiffness increases with running speed. At any one speed, the stiffness may be reduced in a controlled fashion by running with the knees bent more than usual. In a series of experiments, subjects ran in both normal and flexed postures on a treadmill. In other experiments, they ran down a runway and over a force platform. Results show that running with the knees bent reduces the effective vertical stiffness and diminishes the transmission of mechanical shock from the foot to the skull but requires an increase of as much as 50% in the rate of O2 consumption. A new dimensionless parameter (u omega 0/g) is introduced to distinguish between hard and soft running modes. Here, omega 0 is the natural frequency of a mass-spring system representing the body, g is gravity, and u is the vertical landing velocity. In normal running, this parameter is near unity, but in deep-flexed running, where the aerial phase of the stride cycle almost disappears, u omega 0/g approaches zero.
Article
The purpose of this study was to determine the effects of systematic changes in stride rate and length at a given running speed on the peak shank deceleration (PSD) experienced during ground contact. Data were collected from 10 well-trained subjects as they ran on a treadmill at a pace of 3.8 m s-1 (7-min mile-1). Shank deceleration was measured by a lightweight accelerometer which was tightly attached over the distal medial tibia. High-speed films (200 Hz) were taken from a side view to quantify modifications in sagittal plane movement which might have accompanied the stride rate changes. Five stride rate conditions were randomly presented - 10% slower, 5% slower, normal, 5% faster and 10% faster. Average PSD was computed from 10 steps during each condition and testing was repeated on three different occasions. For each session, PSD observed for each condition was normalized to that observed at the normal stride rate in order to minimize the effects of variations in attachment of the accelerometer between and within subjects. The normalized PSD results at each stride rate tested were - normal = 1.0, 10% slower = 1.09, 5% slower = 1.03, 5% faster = 0.96 and 10% faster = 0.91. Significant differences were found between all these means except normal and 5% slower. The kinematic analysis revealed non-significant results for hip, knee and ankle joint angles at touchdown for the various stride rates. Application of the findings to existing analytical models indicated that, for a given running speed, peak impact forces in the ankle and knee joints decreased as stride rate increased.
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Ten recreational runners (mean VO2max 64.7 ml . kg-1 . min-1) underwent a 5-d acclimation period to treadmill running at a 7 min . mile-1 pace (3.83 m . s-1) for 30 min each day. During these runs their freely chosen stride lengths were determined and expressed as a percentage of leg length (%LL). On two subsequent testing days stride length was systematically varied over a range of +/- 20% LL about the freely chosen value. O2 uptake was determined by the Douglas Bag method. All subjects exhibited a stride length of which O2 uptake was minimized, although the individual profiles varied considerably. The mean increases in VO2 were 2.6 and 3.4 ml . kg-1 . min-1 at the short- and long-stride length extremes, respectively. During unrestricted running deviations from optimal stride length caused a mean increase in VO2 of 0.2 ml . kg-1 . min-1. The relatively efficient running patterns used by the subjects during unrestricted running indicate either an adaption to the chosen stride length through training or a successful process of energy optimization.
Article
When humans and other mammals run, the body's complex system of muscle, tendon and ligament springs behaves like a single linear spring ('leg spring'). A simple spring-mass model, consisting of a single linear leg spring and a mass equivalent to the animal's mass, has been shown to describe the mechanics of running remarkably well. Force platform measurements from running animals, including humans, have shown that the stiffness of the leg spring remains nearly the same at all speeds and that the spring-mass system is adjusted for higher speeds by increasing the angle swept by the leg spring. The goal of the present study is to determine the relative importance of changes to the leg spring stiffness and the angle swept by the leg spring when humans alter their stride frequency at a given running speed. Human subjects ran on treadmill-mounted force platform at 2.5ms-1 while using a range of stride frequencies from 26% below to 36% above the preferred stride frequency. Force platform measurements revealed that the stiffness of the leg spring increased by 2.3-fold from 7.0 to 16.3 kNm-1 between the lowest and highest stride frequencies. The angle swept by the leg spring decreased at higher stride frequencies, partially offsetting the effect of the increased leg spring stiffness on the mechanical behavior of the spring-mass system. We conclude that the most important adjustment to the body