Running biomechanics, the influence of different footwear conditions

Athletes with overuse injuries of the ankle and foot regions are often
encountered in clinical practice.1,2 One of the common foot overuse injuries in
athletes and especially in runners is metatarsalgia.3,4 Metatarsalgia refers to
localized or generalized forefoot pain in the region of the metatarsal heads.5
The main cause of metatarsalgia in around 70% of the cases is related to
biomechanical factors and especially to an overload in forefoot region.6 A
treatment option is to reduce the plantar loading in the forefoot region.5,7
This treatment goal can be achieved with the use of a rocker profile in the toe
region of the shoe (toe-rocker shoe, figure 1-B).8 It is shown that this type
of shoe can reduce the pressure in forefoot region 12% to 55% in walking.9 In
addition, different changes in kinetics and kinematics of lower extremity have
been reported due to toe-rocker shoes; for instance a decrease in dorsal
flexion external moment of the ankle in the late stance during normal
walking.10 This biomechanical effect could be beneficial in Achilles
tendinopathy treatment.11 At this moment we perform a study to the effects of a
toe-rocker shoe during slow running in patients with Achilles tendinopathy.
This study has been approved by the METc of the UMCG (nr: NL34288.042.11)
While it has been shown that rocker shoes have effects on the biomechanics of
the lower extremity during walking, it is not clear whether the effects are
similar in more dynamic tasks like running. Since speed influences
biomechanical parameters such as plantar pressure pattern,12,13 lower extremity
muscle activity14,15, and the gait kinetics and kinematics,16,17,18 the
biomechanical efficacy of rocker shoes needs to be assessed in (fast) running
as well.
In recent years, barefoot running has become more popular around the world, and
thus more scientific attention has been paid to the barefoot running
biomechanics.19 Although not scientifically proven, it is believed that
barefoot running has the potential ability to reduce running injuries as
well.20 Reduction of vertical ground impact forces, increase in foot muscles
strength and increased activity of calf musculature in barefoot running are
believed to be among the biomechanical factors involved in injury prevention.20
However, the results are controversial. For instance, both increase and
decrease in vertical ground impact forces have been reported for barefoot
running.19,21,22,23 Furthermore, hardness and properties of shoe sole are
thought to be linked with comfort and rate of running injuries.24 Due to lack
of protection, barefoot runners are at risk of skin wounds, manufactures have
increased interest in so-called minimalist shoes (Figure 1-C). Minimalist shoes
with a thin midsole are believed to mimic barefoot running while providing a
layer of protection compared to barefoot running, and therefore can be used as
an alternative to barefoot running.19,22 It has been reported that minimalist
shoes have similar walking economy to barefoot condition.25 Consequently, it
can be hypothesized that economy of running with minimalist shoes is more
efficient than other shoe conditions such as standard running shoes (Figure
1-A) or rocker shoes. However, the knowledge regarding these aspects is still
scarce.
As a consequence, in this study the influence of different footwear conditions
on running biomechanics and economy will be assessed in one session using three
separate experimental parts.

Primary Objective:
Part 1: To investigate the running biomechanics of toe-rocker shoes versus
standard running shoes
Part 2: To investigate the running biomechanics of barefoot running in
comparison to minimalist and standard running shoes
Part 3: To investigate the running economy of minimalist shoes and toe-rocker
shoes in comparison to standard running shoes

Secondary Objective(s):
Part 1: To assess lower extremity kinetics, kinematics and also lower leg
muscular activity
in comparison to standard running shoes during running
Part2: To assess kinetics, kinematics and muscular activity of the lower
extremity of toe-rocker shoes in comparison to standard running shoe
Part 3: To assess some other physiological parameters (heart rate, respiratory
exchange rate), perceived excretion of running with 3 different shoe conditions
and the first impression of comfort of the different shoe types.

In one single session subjects will undergo three separate experimental parts.
The estimated time for each measurement is about 45 minutes (2-3 hours in
total). The location will be in the Sports Field Lab Groningen, School of
Sports Studies, Hanze University of Applied Sciences, Groningen. Each part
follows a cross-over design to account for order effects in comparing different
shoes. Participants are randomized to the different orders in running with
pairs of shoes.

All participants in the study will run inside the lab on a treadmill at
sub-maximal speed and over-ground at their normal comfortable speed.
The toe-rocker shoes are standardized and modified by orthopedic shoe
technicians. This adaptation is provided for different diagnoses in regular
patient care. No risk is expected for running trials. The runners don*t have a
direct benefit from this study.
Participation will be rewarded with a 20¤ shopping bon.