Page 106 - Journal of Special Operations Medicine - Spring 2016

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researchers and healthcare practitioners. They partici- responses and running biomechanics. Running in mini-
pated in a long process that involved identifying and malist shoes generally resulted in a lower physiological
discussing the characteristics of shoes of this type. The energy cost than did running in conventional shoes, in
5–8
definition they developed for a minimalist shoe was most studies. This is likely because many minimalist
“footwear providing minimal interference with the nat- shoes are lighter than conventional shoes. During run-
ural movement of the foot due to its high flexibility, low ning, the foot and the leg are accelerated and deceler-
heel to toe drop, weight and stack height, and the ab- ated during each gait cycle, and lighter shoes require less
sence of motion control and stability devices.” A “mini- muscular force to produce these changes in movement.
malist index” was developed to determine the degree of Less muscular force results in a lower energy cost. It
minimalism in the shoe. The minimalist index included is estimated that the energy cost of running increases
the following: shoe weight, stack height (height of the by about 0.7–1% for every 100g of additional shoe
shoe in the middle of the heel), heel to toe drop, amount weight. 9,10 Thus, the lighter the shoe, the lower is the
of stability/motion control technologies, and flexibility. energy cost of running.
Each of these characteristics was rated on a scale (0–5
points), with the final index expressed as a percentage of Other differences between these two types of shoes have
the total possible points. A separate study involving 85 to do with the mechanics of running. There are three
individuals who applied the minimalist index to a vari- major ways runners contact the ground; these are illus-
ety of running shoes found excellent agreement between trated in Figure 2. In the rearfoot strike, the foot is more
raters (interrater reliability 0.84–0.94). 3 dorsiflexed (pointed upward at the ankle), increasing
the loading requirement of the anterior tibial muscles
Some have subdivided minimalist shoes into at least two (front of the shin); contact is on the lateral (outside) part
4
broad categories: barefoot and cushioned. These are of the heel; and the knee is extended. The muscles of the
generally characterized by the amount of cushioning ma- thigh (vastus muscles) must absorb much of the force
terial between the foot and the ground and by the degree of impact using eccentric (lengthening) muscle contrac-
of drop (angle) from the heel to the toe. Barefoot-type tions. In a forefoot strike, the foot impacts the ground
shoes are little more than thin foot coverings offering on the front of the foot with a slight plantarflexion (foot
protection from running-surface hazards. The soles are extended at the ankle) and more knee flexion, thus mak-
very flexible and have no arch support, very little mate- ing the lower limb less rigid and more able to adapt the
rial between the foot and the ground, and no drop from foot to the landing surface. A midfoot strike pattern is
the heel to the toe. Cushioned shoes have more material intermediate between the rearfoot and forefoot, with the
between the foot and the ground, to provide some cush- heel and forefoot striking the ground almost simulta-
ioning. There is usually some degree of drop from the neously. Studies have suggested that 72–95% of people
heel to the toe but little or no arch support. Examples of who wear conventional shoes contact the ground with
the two types of minimalist shoes are shown in Figure 1. a rearfoot strike pattern. 11–14 Among runners who have
never before run in minimalist shoes, the proportion of
rearfoot strikes is highest in a conventional shoe, lower
Physiological/Biomechanical Differences: in cushioned minimalist shoe, and lowest in a barefoot
Minimalist Versus Conventional Running Shoes
minimalist shoe. 4,15 The majority of runners who have
Studies that have compared minimalist with conventional been using minimalist shoes for some time strike the
running shoes have found differences in physiological ground with a forefoot or midfoot strike pattern. 6,14
One study showed that 6 weeks after transitioning to
minimalist shoes, only 36% of runners were still using a
Figure 1 Examples of barefoot and cushioned minimalist
running shoes.
Figure 2 Joint functions for rearfoot, midfoot, and forefoot
strike patterns during running.

90 Journal of Special Operations Medicine Volume 16, Edition 1/Spring 2016