Differences and mechanisms
heel height and knee flexion angle during a
forward hopping task in collegiate females [22] .
They reported that increasing heel raises from
0 mm to 24 mm, significantly increased the
peak knee flexion angle. Moreover, a study by
Chambon et al. (2015) found that wearing shoes
with increasing pitch (0, 4 and 8 mm), reduced
ankle dorsiflexion and increased knee flexion
angle excursions compared to barefoot while
running over ground [23] , thereby indicating that
footwear pitch may be a factor driving changes
in peak KFM and/or the knee-GRF lever arm. relevant in explaining the increase in peak KFM
with footwear, these kinematic alterations are
still of relevance in the context of PFP given
that recent systematic reviews report kinematic
differences at the knee and ankle between
individuals with and without PFP whilst wearing
similar footwear styles [6, 34, 35] . Knowing that
stability and neutral footwear generally increase
knee and ankle kinematics associated with
the development of PFP [6, 34, 35] , shoes with a
lower pitch (i.e., < 5 mm) may be beneficial in an
adolescent cohort.
Contrary to these findings, a recent randomized
controlled trial by Malisoux et al. (2017) reported
the effect of 0, 6 and 10 mm pitch shoes on
lower limb kinematics over a period of 6 months
[31]
. Surprisingly, there was no between-shoe
differences for mid-stance knee flexion angle;
however, the flexion angle decreased in all
shoe conditions over the six-month period. It is
important to note that participants in Malisoux
et al. (2017) ran on an instrumented treadmill,
which can produce opposite kinematic effects to
over-ground running and, as such, may explain
their contradictory findings [31] . In support, the
aforementioned study by Chambon et al. (2015)
also found that running surface (i.e., over-
ground versus a treadmill) had the opposite
effect regarding the pitch of shoes and knee
kinematics [23] . Nonetheless, in the present study
footwear pitch likely caused an increase in peak
KFM via the knee-GRF lever arm, as our testing
was performed over-ground. Although the mechanism by which footwear
changed the knee-GRF lever arm was not
explored, running-related spatiotemporal
variables may be important to include in future
studies. Specifically, examining the association
between changes in stride length and knee-GRF
lever arm distance between footwear conditions
is suggested based on recent evidence
demonstrating footwear-related effects on
stride length and peak KFM [32, 36] . For example,
Sinclair and colleagues (2016) revealed that
stability shoes not only increased peak KFM, but
also increased stride length in comparison to
barefoot-inspired shoes [31] . While this suggests
that stride length could indeed be related to the
knee-GRF lever arm, which primarily dictates
peak KFM, further investigation is required.
Greater hip, knee and ankle flexion angles
at time of peak KFM in shoes compared to
barefoot were also found. Numerous other
studies support these findings in both stability
and/or neutral footwear [8, 20, 32, 33] . Although not
This study has a number of limitations. It
included a healthy adolescent/young adult
female cohort free of PFP; thus, no link can be
made between footwear-related peak KFM and
the risk of developing the condition. Further,
prospective research is required to determine
causality. In addition, only external moments
and kinematic predictors of a change in peak
KFM were included and there are likely other
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