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The habitual motion path theory predicts that humans tend to maintain their habitual motion path (HMP) during locomotion. The HMP is the path of least resistance of the joints defined by an individual’s musculoskeletal anatomy and passive tissue properties. Here we tested whether participants with higher HMP deviation and whether using footwear that increases HMP deviation during running show higher reductions of knee joint articular cartilage volume after 75 minutes of running. We quantified knee joint articular cartilage volumes before and after the run using a 3.0-Tesla MRI. We performed a 3D movement analysis of runners in order to quantify their HMP from a two-legged squat motion and the deviation from the HMP when running in different footwear conditions. We found significantly more cartilage volume reductions in the medial knee compartment and patella for participants with higher HMP deviation. We also found higher cartilage volume reductions on the medial tibia when runners wore a shoe that maximized their HMP deviation compared with the shoe that minmized their HMP deviation. Runners might benefit from reducing their HMP deviation and from selecting footwear by quantifying HMP deviation in order to minimize joint cartilage loading in sub-areas of the knee.
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SCIENTIFIC REPORTS | (2020) 10:1363 |
The habitual motion path theory:
Evidence from cartilage volume
reductions in the knee joint after
75 minutes of running
Steen Willwacher1*, Daniela Mählich1, Matthieu B. Trudeau2, Joseph Hamill3, Gillian Weir3,
Gert-Peter Brüggemann1 & Grischa Bratke4
The habitual motion path theory predicts that humans tend to maintain their habitual motion path
(HMP) during locomotion. The HMP is the path of least resistance of the joints dened by an individual’s 
musculoskeletal anatomy and passive tissue properties. Here we tested whether participants with
higher HMP deviation and whether using footwear that increases HMP deviation during running show
higher reductions of knee joint articular cartilage volume after 75 minutes of running. We quantied 
knee joint articular cartilage volumes before and after the run using a 3.0-Tesla MRI. We performed a 3D 
movement analysis of runners in order to quantify their HMP from a two-legged squat motion and the 
deviation from the HMP when running in dierent footwear conditions. We found signicantly more 
cartilage volume reductions in the medial knee compartment and patella for participants with higher
HMP deviation. We also found higher cartilage volume reductions on the medial tibia when runners
wore a shoe that maximized their HMP deviation compared with the shoe that minmized their HMP
deviation. Runners might benet from reducing their HMP deviation and from selecting footwear by 
quantifying HMP deviation in order to minimize joint cartilage loading in sub-areas of the knee.
Overuse injuries in distance running occur with gradual onset over time and result from the repetitive stress of
biological tissues and associated cumulative trauma1. e knee joint is the most common site for running-related
overuse injuries (RROIs)2. Nigg et al. have proposed that the neural control of running is tuned towards mini-
mizing mechanical stress of biological tissues, resulting in an optimal path of lower extremity joint movement for
each individual and every specic movement3. Recently, we proposed a redenition of this theory by assuming
that the neural control of running is tuned towards keeping the individual’s habitual joint motion path (HMP),
which we dene as the joints’ path of least resistance, and a function of an individual’s anatomy and passive tissue
mechanical properties4. As such, the HMP is the set of joint kinematics during motions which minimizes loading
of lower extremity joints relative to the loads during running. Examples for these relatively low loading motions
are walking, stair climbing, sitting down or standing up from a chair. Consequently, we have developed a simple
method to estimate the HMP for individuals from a basic half-squat movement4.
Running at typical distance running speeds requires greater force application to the ground in order to satisfy
the body weight support requirement during shorter ground contact times compared to walking5,6. erefore,
runners must generate amplied lower extremity joint moments when running in order to maintain the HMP
and to optimize the load distribution to regions that have been adapted to carry these loads. Based on the HMP
theory, deviating from the HMP leads to loading of less adapted structures of lower extremity joints, resulting in
a greater risk of sustaining a running-related overuse injury. From the same theoretical background, we proposed
that running footwear selection should account for the minimization of the deviation from the HMP4. Footwear
that does not fulll this task would lead to deviation from the HMP or additional muscle activity to keep the
HMP. Both of these consequences would result in greater loading of joint structures.
1Institute of Biomechanics and Orthopaedics, German Sport University, Cologne, Germany. 2Brooks Sports
Inc., Seattle, Washington, USA. 3Biomechanics Laboratory, University of Massachusetts, Amherst, MA, USA.
4Department of Diagnostic and Interventional Radiology, University of Cologne, Cologne, Germany. *email:
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e HMP theory was derived from the assumption that the neural control of running is adjusted to avoid
irreversible injuries such as osteoarthritis. ese optimization strategies might have also been essential for human
evolution7. While the HMP theory was developed from a sound theoretical background, it has only very rarely
been tested empirically4,810.
Measuring the loads imposed on cartilage structures in a running participant non-invasively in-vivo is not
feasible using current technology. Nonetheless, with high-resolution magnetic resonance imaging (MRI) one can
measure cartilage volumes before and aer a prolonged run1114. Cartilage volume may act as a surrogate variable
to indirectly quantify the loading imposed onto the cartilage15. Knee joint cartilage morphology has been related
to biomechanical loading characteristics of the knee during locomotion15.
erefore, the purpose of the present study was to test hypotheses derived from the HMP theory. Specically,
we hypothesized that knee joint cartilage loading, quantied via cartilage volume reductions aer 75 minutes of
running, would be lower in runners who maintained a lower HMP deviation during running compared to run-
ners who deviated more from their HMP. Further, we hypothesized that specic footwear that minimized HMP
deviation in a runner would also minimize cartilage volume reductions during prolonged running. Due to the
high prevalence of RROI at the knee2, we focused on the knee joint in this study.
Subjects and materials. We recruited twelve participants (seven males and five females; height:
1.77 ± 0.08 m; body mass: 70.9 ± 9.9 kg; age: 29 ± 4 years) for this study which involved a unique multi-visit MRI-
based protocol. All participants were recreational runners and were injury free for at least one year before the
study. None of the participants had known injuries of the articular cartilage of the knee joint. e ethics commit-
tee of the University of Cologne, Cologne, Germany had approved the study protocol. All procedures were carried
out in compliance with the declaration of Helsinki. We obtained written informed consent from all participants.
We performed data collection sessions during 4 dierent days, both in a biomechanics laboratory (1 visit) and
in the MRI facilities of the University hospital (3 visits; at least one week between individual visits).
Running mechanics and habitual motion path determination. In the biomechanics laboratory, we
analyzed the 3D running kinematics and kinetics of the participants while running on a 3D force instrumented
treadmill (Treadmetrix, Park City, UT, USA) at the participants’ self-selected speed using three dierent footwear
conditions. e participants selected the running speed based on experience such that they would feel comforta-
ble keeping the speed for 75 minutes.
e three footwear conditions were: (1) a neutral running shoe (either Brooks Launch or Brooks Glycerin,
based on individual preference) with a homogeneous density ethyl vinyl acetate (EVA) midsole (Control) without
any modications; (2) a Brooks Launch shoe modied by inserting sti plastic tubes along the lateral part in the
midsole (shoe A); and (3) a Brooks Launch shoe modied by inserting sti plastic tubes along the medial part
in the midsole (shoe B) (see Fig.1). We created the custom footwear conditions 2 and 3 using the same baseline
shoe; i.e., when hardening one side of the midsole by inserting plastic tubes, the holes on the other side were le
empty which eectively reduced the midsole hardness on that side. is way, a medial post was created when
inserting tubes on the medial side and vice versa.
We measured runner kinematics using a twelve-camera optoelectronic 3D motion capture system (MX40,
Vicon Motion Systems, Oxford, UK). We used a ve-segment rigid body model of the pelvis and the right lower
extremity to determine 3D joint kinematics. e details of the model can be found in previous publications1618.
During the same lab visit, the subjects performed ten two leg half-squat movements in sock shoes, which
consisted in running socks that have been glued to standard sock liners made out of 5.5 mm EVA foam4,19, at
self-selected speed. e participants placed their feet hip width apart with their feet pointing forwards. From
these movements, we estimated the knee joint HMP of each participant while following our recently published
protocol19. In brief, this protocol quanties the frontal and transverse plane knee joint angles at a knee exion
angle of 40 degrees during the eccentric phase of the half-squat. With this approach there was only one HMP
baseline to compare against running in the dierent footwear conditions. Please refer to the Supplementary
Materials (Supplementary Fig.1) for a graphical illustration of the deviation quantication. Aer determining
the HMP baseline from the half-squat, the protocol determined these angles at the same critical exion angle dur-
ing the eccentric part of the contact phase in the running movement. By subtracting the knee non-sagittal plane
angles during the squat baseline from the knee angles obtained in the running movement, the HMP deviation
Figure 1. Experimental shoe conditions used in this study. We created a laterally posted condition by inserting
plastic tubes in the lateral border of the midsole (A) and a medially posted condition by inserting plastic tubes
along the medial border of the midsole. (B) e neutral shoe was a neutral running shoe (either Brooks Launch
or Brooks Glycerin) without any holes or tubes within the midsole (not shown).
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was quantied. Since transverse and frontal plane ranges of motion at the knee joint in running are dierent, we
determined the overall HMP deviation by using a weighted sum of frontal and transverse plane deviations using
the following formula:
DevDev 05 Dev, (1)
HMPTot HMPFront HMPTrans
where DevHMP-Tot is the total HMP deviation in the running movement, DevHMP-Front is the HMP deviation within
the frontal plane and DevHMP-Trans is the deviation within the transverse plane of motion.
MRI data collection during prolonged running. In the MRI facilities, we installed a treadmill directly
in front of the MR room in order to minimize the time between running and MRI measurements, and additional
loading to the knee. On dierent days, each participant ran 75 minutes at the same speed as during the biome-
chanical assessment in three dierent footwear conditions. e individual running sessions were completed in
randomized order within a time period of less than four weeks. Measurements were taken at the same time of the
day for all participants.
We performed knee MRI scans before (pre-run) and immediately after (post-run) each running bout.
Furthermore, we performed additional MRI scans of the calf muscles at 2.5, 5, 10, 15 and 45 minutes, which
were not related to the purposes of this study. ese scans interrupted the treadmill running by 3:40 minutes on
average. All participants completed a 30-minute rest phase before the pre-run scan which involved lying on the
MR table outside of the MRI scanner so that the participitants could be placed within the scanner without further
movement or loading of the knee. We took the pre-run MRI scan for the segmentation aer the acquisition of the
survey and anatomical proton-density weighted images which lasted another 15 minutes, which meant an overall
rest of 45 minutes before the pre-run scan Each participant entered the MRI scanner within ten seconds following
the 75-minute run. e start of the scan occurred less than a minute aer nishing the run. Given the short time
between the end of the run and the completion of the scan, we believe that the subjects’ cartilage recovery was
minimal, and therefore that we were able to capture eects from the prolonged run.
We performed the multiple-slice MRIs on a 3.0 Tesla scanner (Ingenia, Philips N.V., Amsterdam, Netherlands)
with a 16-channel high resolution transmitting and receiving knee coil. We carefully positioned the participants
in a supine orientation while centering the knee joint center within the magnet and attached with the knee coil.
We used a 3D water selective (WATS) T1 gradient echo sequence (repetition time: 11 ms; echo time: 5.6 ms; ip
angle: 10°) with a eld of view of 160 × 160 × 90 mm and 180 partially overlapping slices (gap: 0.5 mm). e
size for the acquired voxels was set to 0.493 × 0.493 × 1 mm and 0.286 × 0.286 × 0.5 mm for the reconstruction
voxels. e eective scan duration was 5:27 minutes for the complete sequence while using parallel imaging for
faster image acquisition (SENSE factor 2).
We conducted segmentation of the total subchondral bone area (Piscoya et al., 2005) and the cartilage joint
surface area (AC) by manual segmentation on a section by section basis with a B-spline Snake algorithm (deform-
able contour) using custom soware (Chondrometrics GmbH, Ainring, Germany). We divided the knee joint
into seven anatomical regions14,20 (Fig.2A): patella (P), medial tibial compartment (MT), lateral tibial compart-
ment (LT), the medial (MF) and lateral (LF) femoral condyles, and medial and lateral central (weight bearing
area) femoral condyles (CMF and CLF). In these anatomical regions, we calculated the cartilage volume (VC)
from three-dimensional reconstructions. We normalized cartilage volumes to body mass and height, and quan-
tied dierences between pre and post run cartilage volumes. We expressed these cartilage volume reductions as
percentage dierences relative to the pre-run condition.
Statistical analysis. We applied one-tailed Wilcoxon rank sum tests to determine whether the relative car-
tilage volume reductions of the runners with the highest overall HMP deviation (n = 6) were higher than those
of the runners with the lowest HMP deviation (n = 6). To improve the robustness of this analysis, we averaged
cartilage volume reductions and HMP deviation values over all three footwear conditions. We further performed
comparisons between the footwear conditions with the highest and the lowest individual HMP deviation values
using dependent sample t-tests. In addition to these pairwise comparisons, we performed simple linear regression
analyses to identify potential relationships between HMP deviation and cartilage volume reductions. We set the
level of signicance for all tests to 0.05. We quantied eect sizes for between group and between footwear com-
parisons (Cohen’s d,21) using
, being the average and
being the sample variance of the group or footwear data. Eect sizes of 0.2
were considered as small, 0.5 as medium, and 0.8 as large21.
All statistical analyses were performed using Matlab soware (R2018b, Statistics and Machine Learning
Toolbox, e Mathworks, Natick, MA, USA).
e participants ran the 75-minute running trials at a constant speed of 2.78 ± 0.38 m/s. e fastest individual
performed the running trials at 3.33 m/s and the slowest at 2.31 m/s. We observed signicant reductions in car-
tilage volume in all knee joint sub areas aer the 75-minute run compared to the pre-run condition (Fig.2B–D).
Runners with greater overall HMP deviation values (n = 6, average over all footwear conditions: 12.5 ± 2.7°)
were characterized by greater cartilage volume losses in the MT (p = 0.047), MF (p = 0.033) and P (0.033)
sub-areas of the knee joint cartilage compared to runners with lower HMP deviation values (n = 6, average over
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SCIENTIFIC REPORTS | (2020) 10:1363 |
all footwear conditions: 6.2 ± 2.3°)(Fig .2B,C). ere were no signicant dierences between HMP deviation
groups with respect to body mass (p = 0.94; high deviators: 69.7 ± 8.6 kg, low deviators: 70.2 ± 14.9 kg) and
body height (p = 0.85; high deviators: 1.77 ± 0.07 m, low deviators: 1.78 ± 0.13 m). We did not nd a system-
atic dierence in self-reported physical activity levels between high and low HMP deviator groups. Further, we
found no signicant dierences in running speed between the two groups of runners (p = 0.38; high deviators:
2.71 ± 0.41 m/s, low deviators: 2.93 ± 0.42 m/s).
We identied a signicant relationship between overall HMP deviation and the amplitude of MT (R² = 0.43;
p = 0.031) and MF (R² = 0.35; p = 0.045) sub area cartilage volume reductions.
For each participant, we determined the shoe with the greatest overall HMP deviation and the shoe with the
least HMP deviation. ree, three and six runners had the greatest HMP deviation in the laterally posted, medi-
ally posted and neutral shoe conditions, respectively. Two, seven and three runners had the least deviation in the
laterally posted, medially posted and neutral shoe conditions, respectively.
Within the footwear conditions associated with the least overall HMP deviation (8.2 ± 5.9°; Fig.3) compared
to the shoes with the highest HMP deviation (10.6 ± 4.7°; Fig.3), we found signicantly lower cartilage volume
reductions in the MT sub-area (p = 0.004, Fig.2D). We identied a strong linear relationship between the dier-
ence between the two extreme footwear conditions in frontal plane deviation and the dierence between these
shoes in cartilage volume reductions in the CMF sub-area (R² = 0.58; p = 0.004).
e dierences in overall HMP deviation between the high and low HMP deviation groups were greater than
the dierences within subjects when comparing the highest and lowest deviation footwear condition (Fig.3).
e purpose of the present study was to test hypotheses derived from the HMP theory using cartilage volume
reductions as a variable for the indirect quantication of knee joint cartilage loading. We found greater carti-
lage volume reductions in the medial compartment of the knee in runners with greater deviation from their
HMP baseline compared to runners with lower deviation from their HMP baseline. erefore, we accept our rst
Figure 2. (A) Schematic drawing of cartilage sub-areas of interest in this study. (B) Individual response in
cartilage volumes to the 75-minutes running intervention. Individual data points are the average of the three
footwear conditions. Bold data points/lines indicate the mean values of the high and low deviation groups. In
each column the le value is the pre-run cartilage volume and the right value is the post-run cartilage volume. (C)
Relative post-run cartilage volume reductions between post-run and pre-run measurements (means – standard
deviations) between runners with high HMP deviation and runners with low HMP deviation in the dierent knee
joint sub-areas. * indicates a signicantly higher cartilage volume reduction in the High HMP deviation group
(p < 0.05). (D) Relative post-run cartilage volume reductions compared to pre-run (means – standard deviations)
between the footwear conditions with the highest and lowest overall HMP deviation. *Indicates a signicant
dierence between the two footwear conditions at a level of p < 0.05.
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hypothesis. Furthermore, we found signicantly less cartilage volume reduction in the MT sub-area when run-
ners wore footwear with the smallest amount of HMP deviation compared to footwear with the highest amount
of HMP deviation. erefore, we also accept our second hypothesis as it relates to the MT sub-area of the knee.
Cartilage volumes of the femur, tibia and patella cartilage in our study were consistent with previous literature
(e.g.11) and indicated a high variability of cartilage volume of the analyzed sample (Fig.2B). Previous studies also
reported reduced cartilage volumes aer running exercise of dierent durations and distances1113,22. Boocock
et al.11 identied a reduction of lateral tibial (5.7%), medial femoral (5.3%) and lateral femoral (4.0%) cartilage
volumes aer a 30-minute running trial. Aer a 5 km run, Kessler et al.22 reported a decrease in the patella (6.6%)
and tibial (3.6%) cartilage volumes. In general, the cartilage volume reductions reported in this study aer the
75-minute running bout agree with previous literature and 30-minutes loading scenarios1113,22.
e results of our study indicate that deviating from the habitual motion path was associated with increased
cartilage volume loss in some regions of the knee joint during a prolonged run. is suggests that deviating from
the habitual motion path may lead to greater loading on some regions of the knee joint. e greater cartilage
volume reductions in runners with greater HMP deviation might have occured because these runners might have
loaded cartilage sub-regions which may have been less adapted to mechanical loads given that, habitually, they
may be less loaded than other regions of the knee. Loading less adapted cartilage areas has been considered to be
a risk factor for the progression of overuse injuries such as knee osteoarthritis23. Consequently, monitoring the
habitual motion path during well controllable weight-bearing activities such as walking, stair climbing, squatting
or sitting down or up from a chair might be an interesting approach to prevent the fast progression of overuse
type injuries at the knee.
Furthermore, the development and selection of technological aids such as footwear should consider the HMP
of their users. e reduced cartilage volume reduction on the medial tibia across footwear conditions found in
this study support this idea, even though the eect sizes induced across footwear were smaller than the eect sizes
observed between runners of dierent HMP deviation patterns. However, the footwear conditions in this study
might not have been ideal for minimizing or maximizing HMP deviation for individual participants. It is inter-
esting to note that dierent shoe conditions minimized or maximized the HMP deviation in individual runners.
is highlights the idea that an individual approach is needed to inform footwear assignment for runners which
is based on the HMP theory. Future studies need to explore the eects of technological interventions including
footwear in greater detail, which might result in a better understanding of the determinants of HMP deviation in
running or other more demanding types of locomotion.
We determined the HMP basleline from a two-leg half squat motion as described in our previous protocol
paper4. We used this motion, because it is a common every day task, similar to e.g. sitting down on a chair.
Further, it requires relatively small force generation and can be well controlled by the participants. erefore, we
believe that it is likely that the HMP can be kept by the participants during the two-leg squat. Furthermore, pilot
studies inidicated a good reliability of the two-leg squat motion, e.g. in comparison to a one-leg squat motion,
which might have the benet of being more similar to the actual running motion. Future studies should attempt
to nd a method to quantify the individual HMP which includes several common knee-exion tasks which likely
Figure 3. Comparison of HMP deviation amplitudes between the high and low HMP deviation groups
(le) and the high and low HMP deviation footwear conditions (right). Each dot on the le part of the graph
represents a dierent runner, while each runner is represented by a dierent line in the right part of the graph.
Bold horizontal lines indicate the mean value of a group of runners (le part) or the mean value of the high and
low HMP deviation footwear conditions, respectively (right part). In the bottom part eects sizes (Cohen’s d)
for between group and between footwear comparisons are highlighted.
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SCIENTIFIC REPORTS | (2020) 10:1363 |
can be performed while staying within the HMP. is way, a more general and more robust quantication of the
HMP baseline might be obtained.
While this study provides new evidence in support of the HMP theory, several limitations need to be con-
sidered when interpreting the results. Due to the extensive cost of MRI measurements used in this study, we
were only able to include twelve participants in the study. is low sample size was a limiting factor concerning
the statistical power of the study. Despite the low sample size, we found several signicant dierences between
subject groups and footwear conditions. However, future studies should try to replicate our ndings with a larger
sample size in order to further understand the eects of personalized footwear. Next, we used treadmill running
to induce running specic loading of the knee joint articular cartilage. e major amount of distance running is
performed over ground. erefore, replication of our results should also consider the use of over ground running,
even though the running conditions are much more dicult to standardize in this situation.
Furthermore, we only collected biomechanical data of runners in an non-fatigued state. During a 75 minutes
running bout, running mechanics can change because of running-induced fatigue17,24. erefore, future studies
should consider fatigue eects when quantifying HMP deviation during prolonged runs.
Finally, measuring knee joint kinematics in the frontal and transverse plane from skin mounted markers is
a challenging tasks and is prone to measurement errors, like e.g. so tissue, skin movement or knee cross-talk
artefacts2527. In particular, the so tissue artefact is dependent upon the muscle activation level and impact char-
acteristics of the movement. Even though we used a mathematical optimization of marker trajectory data in our
calculations of the orientation and position of the anatomical coordinate systems, such that the coordinates better
comply with rigid body assumptions10,28, of the thigh and shank. However, it is not unlikely that some of the HMP
deviations calculated were actually caused by measurement errors and not related to actual bone motion dier-
ences. Future studies should address this issue by using more precise measurement technologies like e.g. biplanar
In summary, we found evidence in support of the HMP theory. Runners with a higher deviation from the
HMP baseline showed signicantly greater cartilage volume reductions in several knee joint cartilage sub-regions.
Furthermore, the cartilage on the medial tibial compartment showed greater cartilage volume reductions when
participants were running in footwear that induced higher HMP deviation. ese results indirectly indicate
higher mechanical loading on potentially less adapted sub-regions of the knee joint cartilage when runners devi-
ate more from their HMP baseline.
Data availability
All underlying data is made available upon request by the corresponding author of this study.
Received: 10 July 2019; Accepted: 8 January 2020;
Published: xx xx xxxx
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is work was partly funded through a grant from Brooks Running Inc., Seattle, WA, USA. We are grateful to the
help of Katina Fischer, Stephan Dill and Markus Kurz during data collection.
Author contributions
e study was designed by S.W., M.B.T., G.P.B., J.H. and G.B. S.W. wrote the paper with substantial contribution
from M.B.T., G.P.B., J.H., G.W. and G.B. Experimental data were collected by D.M., G.B. and S.W. Biomechanical
model calculations were performed by S.W. and D.M. MRI analyses were performed by G.B. Statistical analyses
were performed by S.W.
Competing interests
e authors declare no competing interests.
Additional information
Supplementary information is available for this paper at
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... The magnitude of the joint motion may fluctuate, but the trajectory, or path, is stable. Alterations in footwear that resist or do not allow for skeletal movement along this path may increase tissue stress-either from a deviation from their pathway or from increased muscle activity to keep their individual habitual joint path-which in turn increases the risk of injury (Nigg, 2001;Enders et al., 2013;Willwacher et al., 2020). Originally called the Preferred Movement Path, this paradigm has since been updated and renamed the "habitual joint (motion) path, " adding that joint motion takes the path of least resistance due to an individual's anatomy and passive tissue properties (Trudeau et al., 2019). ...
... To our knowledge, no studies have directly tested the effect of matching footwear to minimize biomechanical variability and/or deviation from a specific motion path on running related injury. However, one study (Willwacher et al., 2020) suggested that increased time outside one's habitual motion path was associated with tissue-related changes in the knee joint. In this study of 12 healthy recreational runners, medial femur, medial tibia, and patella cartilage volume reductions were larger after 75 min of running in a shoe that increased a runner's deviation from their habitual joint path compared to one that reduced the deviation. ...
Full-text available
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.
... 21 It seems promising to integrate machine learning methods into these approaches, as the features that are unique to an individual (regardless of footwear) appear to vary widely between individuals ( Figure 5B). Subject-specific machine learning models could therefore be used to predict in which footwear design the movement patterns are most similar to a desired reference movement pattern (e.g., preferred movement path, 3,19,39 or habitual movement path 40,41 ). Machine learning models have the advantage that they can be trained on any number of multi-dimensional and time-continuous (biomechanical) variables and that no thresholds for low / high deviations need to be set for their predictions. ...
... It was speculated that the locomotor system aims to maintain this preferred movement path as it may be associated with reduced energy demands, lower joint and tissue loading, and / or lower risk of injury [10]. Potential implications have been investigated by a recent study [11] that showed that the loss in cartilage volume after a prolonged run could be reduced in runners who wore footwear that facilitated a runner's natural joint motion. Consequently, footwear constructions that do not support a preferred movement path may be harmful to the locomotor system and may potentially cause an increased energy / muscle activity demand, and / or an increased risk of injury. ...
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Studies on the paradigm of the preferred movement path are scarce, and as a result, many aspects of the paradigm remain elusive. It remains unknown, for instance, how muscle activity adapts when differences in joint kinematics, due to altered running conditions, are of low / high magnitudes. Therefore, the purpose of this work was to investigate changes in muscle activity of the lower extremities in runners with minimal (≤ 3°) or substantial (> 3°) mean absolute differences in the ankle and knee joint angle trajectories when subjected to different running footwear. Mean absolute differences in the integral of the muscle activity were quantified for the tibialis anterior (TA), peroneus longus (PL), gastrocnemius medialis (GM), soleus (SO), vastus lateralis (VL), and biceps femoris (BF) muscles during over ground running. In runners with minimal changes in 3D joint angle trajectories (≤ 3°), muscle activity was found to change drastically when comparing barefoot to shod running (TA: 35%; PL: 11%; GM: 17%; SO: 10%; VL: 27%; BF: 16%), and minimally when comparing shod to shod running (TA: 10%; PL: 9%; GM: 13%; SO: 8%; VL: 8%; BF: 12%). For runners who showed substantial changes in joint angle trajectories (> 3°), muscle activity changed drastically in barefoot to shod comparisons (TA: 39%; PL: 14%; GM: 16%; SO: 16%; VL: 25%; BF: 24%). It was concluded that a movement path can be maintained with small adaptations in muscle activation when running conditions are similar, while large adaptations in muscle activation are needed when running conditions are substantially different.
... Ausgehend vom originären Konzept in Bezug auf die Reduzierung der Stoßkräfte (Dämpfung) sowie die Skelettausrichtung (mediolaterale Stabilität) wird ein "Muskel-Tuning-Konzept" (basierend auf der Muskelvibration), ein Konzept zum "Präferierten Bewegungspfad" sowie zu einem sogenannten Kom-Abb. 6 [56][57][58]. ...
Sportorthopädie Sportorthopädie Seit der Einführung der ersten in-dustriell gefertigten Laufschuhe vor etwa 150 Jahren haben sich die drei primären funktionellen Anforderun-gen nicht verändert: Bei der Konzep-tion von Laufschuhen stehen nach wie vor Verletzungsprävention, Leis-tungsverbesserung und/oder Op-timierung des Komforts im Mittel-punkt. Ebenso wenig haben sich die Hauptbestandteile und somit der prinzipielle Aufbau eines Laufschuhs verändert. Dieser setzt sich aus zwei wesentlichen Komponenten zusam-men: dem Schaft und der Bodenein-heit, die aus Zwischensohle und Au-ßensohle besteht. Dennoch hat der Laufschuh nicht nur sein Aussehen gravierend verändert-auch seine Einsatzgebiete sind vielfältiger ge-worden, was wiederum in der Aus-prägung seiner funktionellen Eigen-schaften deutlich erkennbar ist. Der Artikel stellt neben aktuellen Lauf-schuhtrends auch neueste Material-entwicklungen und damit verbun-dene moderne Fertigungstechnolo-gien vor, deren Anwendung in der Orthopädie-Technik als sinnvoll er-achtet wird. Schlüsselwörter: Laufschuhe, Funkti-on, Konstruktion, Konzepte, Trends Since the introduction of the first industrially manufactured running shoe about 150 years ago, the three main functional requirements have remained the same: Preventing injuries , enhancing performance and/ or optimising comfort are the major goals when designing running footwear. The principle components and hence the structure of a running shoe have also changed very little. A running shoe consist of two main components, the upper and the bottom part, which consists of a midsole and an outsole. Nevertheless, not only has the appearance of running shoes changed considerably, they are now much more versatile, which their functional characteristics make clearly apparent. This article presents current trends in running footwear as well as the latest developments in materials and manufacturing that should be considered for possible application in orthopaedic technology.
Humans have the remarkable ability to run over variable terrains. During locomotion, however, humans are unstable in the mediolateral direction and this instability must be controlled actively—a goal that could be achieved in more ways than one. Walking research indicates that the subtalar joint absorbs energy in early stance and returns it in late stance, an attribute that is credited to the tibialis posterior muscle-tendon unit. The purpose of this study was to determine how humans (n = 11) adapt to mediolateral perturbations induced by custom-made 3D-printed “footwear” that either enhanced or reduced pronation of the subtalar joint (modeled as motion in 3 planes) while running (3 m/s). In all conditions, the subtalar joint absorbed energy (ie, negative mechanical work) in early stance followed by an immediate return of energy (ie, positive mechanical work) in late stance, demonstrating a “spring-like” behavior. These effects increased and decreased in footwear conditions that enhanced or reduced pronation ( P ≤ .05), respectively. Of the recorded muscles, the tibialis posterior ( P ≤ .05) appeared to actively change its activation in concert with the changes in joint energetics. We suggest that the “spring-like” behavior of the subtalar joint may be an inherent function that enables the lower limb to respond to mediolateral instabilities during running.
Full-text available
Fatigue alters rearfoot kinematics on an individual basis and may offer a means of functionally grouping runners. This proof of concept study aimed to determine whether fatigue related changes in rearfoot eversion could be used to functionally group runners. Sixteen male recreational runners had their frontal plane rearfoot kinematics recorded by a three-dimensional motion capture system before and after a 5km run. The magnitude of change in frontal plane rearfoot kinematics pre- to post-fatigue was calculated and K-means clustering used to identify functional groups based upon these changes. T-tests with statistical parametric mapping were used to compare fatigue related changes both within and between clusters. Two clusters or functional groups were evident within the data set. Nine participants were allocated to cluster 1 and displayed small and insignificant changes in frontal plane rearfoot motion post-fatigue. In contrast, the remaining seven participants were assigned to cluster 2 and displayed significant increases in rearfoot eversion between 3 and 84% of the stance phase post-fatigue. These findings prove the concept that fatigue related changes in rearfoot eversion can be used to functionally group participants. Additionally, the differing fatigue related changes reported by each group may alter the injury risk, training and footwear needs of each group. • Highlights • Fatigue related changes in frontal plane rearfoot motion can be used to functionally group individuals. • Cluster 1 display small and insignificant fatigue related changes, which suggests they can maintain their habitual movement pathway. • Cluster 2 displayed significant increases in rearfoot eversion for the majority of the stance phase, suggesting an inability to maintain their habitual movement pathway, which may increase injury risk.
Objective Running is among the most popular recreational activities; nonetheless, the acute post-race changes of cartilage or meniscus have rarely been determined. The current study aimed to review the acute changes in knee cartilage and meniscus among habituate runners following long-distance running detected by using quantitative magnetic resonance imaging (MRI).Materials and methodsSystematic literature search was performed on those dominate clinical databases which including MEDLINE, Cochrane, Embase, ScienceDirect, and Web of Science. Included studies should be conducted on healthy marathon runners, and the participants should be examined before and after running by using MRI. Intervention studies were excluded.ResultsA total number of 14 studies were finally included in this review which all examined the cartilage or meniscus by using MRI functional sequences. Among them, six studies quantitatively measured the changes regarding volume of the knee cartilage or/and meniscus. Five studies found that the volume would decrease initially after running. Ten studies reported T2 (T2*) would decrease after running and returned to the baseline in a short term, while T1ρ may remain increased in months. Five studies measured subareas for T2 (T2*) value, and found that the superficial and medial subarea changed more vastly than other regions after running.Conclusion Runners experience transient changes in the volume and signals of knee cartilage and meniscus after long-distance running. A liquid exchange and material interaction in cartilage and meniscus was observed after running. Superficial and medial areas of knee cartilage and meniscus might be more susceptible to mechanical loading.
This study presents vector coding technique applied to angle-angle joint diagrams to quantify modification of normal gait pattern due to increased knee joint stiffness. Subject specific in-verse kinematic analysis was performed during normal gait (NG), stiff knee gait (SKG) and slow running (SR). Case study relates to a healthy 40-year-old male subject weighing 70 kg and 1.86 m tall. Reflective adhesive marks were placed at skin surface of lower limbs selected anatomical points. Images of reflective marks during experimental tests at NG, SKG and SR were captured using camera system. AnyGait software was used for inverse kinematic to ob-tain lower limb joint angles. Flexion-extension angle-angle diagrams were plotted for the hip, knee, ankle joints and vector coding applied. Results of non-invasive and autonomous vector coding made it possible to objectify and quantify subtle undetectable changes using direct ob-servation of lower limb joint movement at SKG and SR in relation to NG.
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The current literature on footwear cushioning and pronation has suggested that there may not be a relationship between chronic injury risk and these parameters based on mixed findings and lack of evidence of an association with prospective injury rates. Since footwear has been designed and developed based on cushioning and pronation, we suggest that we have possibly been on a misguided path in footwear design for the last few decades. Current thought thus implies that a new method of footwear prescription is necessary if we are to guide runners toward appropriate footwear that accommodates their individual biomechanical patterns during running. Based on a series of studies investigating the response of the leg to movement and loading patterns, we developed a novel paradigm based on Nigg’s ‘preferred movement path’. The assumptions of the ‘preferred motion path’ were modified in the new method and refined as the ‘habitual motion path’. We focused on knee motion in addition to foot and ankle motion since the greatest number of injuries to runners is at the knee. We utilized a kinematic method for developing a calculation to determine the deviation of a runner’s joint motion path during running from their habitual motion path. We used this deviation as an index for the individual prescription of an appropriate running shoe. While this new method matches a runner based only on their biomechanics, there are other factors that need to be considered. For example, in footwear selection, the individual’s training and injury history in addition to the experience that the runner is seeking from their run must also be considered.
The effect of maximal isolated muscle and cardiovascular fatigue on lower extremity biomechanics during running has been investigated extensively. However, the majority of runners do not run to exhaustion regularly. Consequently, research and industry are interested in biomechanical changes over the course of a typical prolonged run and how footwear technology may affect them. This study investigated the influence of neutral and stability footwear worn during a 42-minute prolonged treadmill run on lower extremity biomechanics. Fourteen male rearfoot runners completed two prolonged running sessions where they ran for 21 minutes on a force instrumented treadmill in a neutral shoe (baseline run). Participants then changed into another neutral shoe of the exact same construction but a different color or into a stability shoe and ran for a further 21 minutes (intervention run). Three-dimensional kinematics and kinetics were measured at the beginning and end of each 21-minute running period. Main effects for time were observed at the hip, knee, and ankle during both the baseline and intervention runs. Particularly, increased knee flexion and rearfoot eversion observed during mid-stance may exhibit a strategy to reduce the effective mass and minimize joint loads applied to the foot and knee. No main effects for footwear condition were found in lower extremity biomechanics. However, individual responses to the neutral and stability shoe conditions were observed. Running shoe design should: (1) focus on both acute and prolonged changes in lower extremity biomechanics at the individual level, and (2) further investigate the use of materials/architecture that allow runners to stay within their initial (baseline) preferred motion path and/or provide greater support when preferred motion path changes throughout a prolonged run.
Purpose: To investigate the joint-specific contributions to the total lower extremity joint work during a prolonged fatiguing run. Methods: Recreational long-distance runners (RR; n = 13) and competitive long-distance runners (CR; n = 12) performed a 10-km treadmill run with near maximal effort. A three-dimensional motion capture system synchronized with a force instrumented treadmill was used to calculate joint kinetics and kinematics of the lower extremity in the sagittal plane during the stance phase at 13 distance points over the 10-km run. Results: A significant (P < 0.05) decrease of positive ankle joint work as well as an increase of positive knee and hip joint work was found. These findings were associated with a redistribution of the individual contributions to total lower extremity work away from the ankle towards the knee and hip joint which was more distinctive in the RR group than in the CR group. This redistribution was accomplished by significant (P < 0.05) reductions of the external ground-reaction force (GRF) lever arm and joint torque at the ankle and by the significant (P < 0.05) increase of the external GRF lever arm and joint torque at the knee and hip. Conclusion: The redistribution of joint work from the ankle to more proximal joints might be a biomechanical mechanism that could partly explain the decreased running economy in a prolonged fatiguing run. This might be because muscle-tendon units crossing proximal joints are less equipped for energy storage and return compared to ankle plantar flexors and require greater muscle volume activation for a given force. In order to improve running performance, long-distance runners may benefit from an exercise-induced enhancement of ankle plantar flexor muscle-tendon unit capacities.
The free moment is considered an important variable during running in lower extremity transverse plane loading of the support leg. The effect of current footwear technology on free moment application has not been widely studied despite evidence that greater free moment amplitudes may be related to common lower extremity overuse injuries. Therefore, the purpose of this study was to determine the effect of current running shoe types on the free moment application in running and to identify which design features specifically influence free moment waveforms. The free moments and lower extremity kinematics of 103 recreational runners were collected when running at 3.5 m/s using force plates embedded in the ground. Six conditions were analysed, ranging from minimalistic to motion-control footwear. Runners were classified into three groups of different free moment pattern using functional principal component and cluster analysis techniques. The results revealed that the free moment application can be affected by footwear technologies used in modern running shoes. Nonetheless, the free moment application was influenced to a greater extent by the overall running technique highlighted by the greater effect sizes for pattern membership compared to footwear effects. Footwear may affect the free moment application as a function of its torsional flexibility and to a lesser extent by means of motion-control features. Future studies should address the effect of footwear design features (such as shoe-mass and traction) on free moment application in greater detail to improve the running style with respect to injury prevention and performance enhancement.
Objective: To quantify the magnitude of global rearfoot motion, in particular, rearfoot adduction and to investigate its relationship to tibial rotation. Design: One hundred and four participants ran barefoot on an Ethylene Vinyl Acetate (EVA) foam. Global range of motion values for the shank, rearfoot and medial metatarsal segment as well as foot motion within the transverse plane were determined using an optoelectric motion capture system. Relationships between parameters were assessed using partial correlation analysis. Results: Global rearfoot adduction amounts to 6.1° (±2.7). Furthermore global rearfoot adduction and rearfoot eversion were significantly related to internal tibial rotation (partial correlation: r=0.37, p<0.001 and r=-0.24, p=0.015, respectively). Furthermore, a strong relationship between rearfoot adduction and transverse within foot motion (r=-0.65, p<0.001) was found. Conclusion: Next to rearfoot eversion, rearfoot adduction may be also important to the understanding of ankle joint coupling. Controlling rearfoot adduction and transverse within foot motion may be a mechanism to control excessive tibial rotation.
Longitudinal bending stiffness (LBS) of footwear has been shown to affect performance in jumping and sprinting tasks. A detailed description of the mechanisms underlying these performance alterations is lacking in the literature at the moment. Therefore, the purpose of this study is to describe why performance in a linear acceleration task is affected by LBS. Fifteen male athletes were analysed using full-body motion analysis combined with ground reaction force (GRF) measurements during the first step of a full effort 5 m sprint in a low stiffness baseline (BL), medium stiffness (MS) and high stiffness (HS) condition. A significant reduction in acceleration performance (−6.3%) was found in the HS condition compared to BL. Changes in acceleration performance in MS and HS were related to altered contact times, ground force application and overall body orientation, but not to alterations in energy absorption at the metatarsal phalangeal (MTP) joint. A gearing function of LBS was evident from increased MTP and ankle joint GRF lever arms, which might offer a potential to improve the effectiveness of horizontal force application. Nonetheless, athletes in this study were not using this potential to improve acceleration performance, possibly due to missing strength capacities. The results of this study indicate that high LBS might lead to reduced acceleration performance in athletes lacking the capacities to make use of the gearing function of footwear LBS. Footwear studies need to address the interrelationship between LBS, individual strength capacities, average ground force application and its effectiveness during acceleration tasks in the future.
In the past 100 years, running shoes experienced dramatic changes. The question then arises whether or not running shoes (or sport shoes in general) influence the frequency of running injuries at all. This paper addresses five aspects related to running injuries and shoe selection, including (1) the changes in running injuries over the past 40 years, (2) the relationship between sport shoes, sport inserts and running injuries, (3) previously researched mechanisms of injury related to footwear and two new paradigms for injury prevention including (4) the 'preferred movement path' and (5) the 'comfort filter'. Specifically, the data regarding the relationship between impact characteristics and ankle pronation to the risk of developing a running-related injury is reviewed. Based on the lack of conclusive evidence for these two variables, which were once thought to be the prime predictors of running injuries, two new paradigms are suggested to elucidate the association between footwear and injury. These two paradigms, 'the preferred movement path' and 'the comfort filter', suggest that a runner intuitively selects a comfortable product using their own comfort filter that allows them to remain in the preferred movement path. This may automatically reduce the injury risk and may explain why there does not seem to be a secular trend in running injury rates. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to