2. Barefoot running allows the body to use the calf and other support muscles to a greater degree.
Rebuttal: Barefoot running forces the body to use the calf and other support muscles. This additional load could be a benefit while training, but why increase stress on the runner while racing or running as fast as possible in training?
Instead of relying on the shoe’s shock absorption characteristics to dissipate force, a barefoot runner is required to use muscular energy to support their body when it impacts the ground.
Barefoot forefoot runners enter the contact phase of their gait gently by using muscular force to slow their descent, starting at the ball of the foot. Cushioning the body entirely through its own structures is not free, however. It requires muscular power, mainly from the posterior tibial compartment. Running with external cushioning either from a shoe or a soft surface removes some of this burden because the heel is now able to contact the ground at a higher speed without getting injured. It removes the burden of eccentrically lowering the runner from initial forefoot contact through the lowest point of the stride. Supplying all the necessary cushioning puts massive additional stresses on the body compared to cushioned running, which could be one of the reasons why getting accustomed to barefoot running requires so much time.
These stresses certainly strengthen the body and might harden it to the demands of running barefoot or in shoes, but even after an acclimation period the body is still responsible for creating that cushioning for itself through muscular support of the foot. This costs energy.
Tucker wrote, “Running in shoes requires next to zero eccentric work in those (posterior tibial) muscles.” Eccentric work is a muscle exerting effort while being extended rather than contracting. This occurs, for example, in the calf muscles after contacting the ground while forefoot running. Eccentric muscle contractions are linked to muscular soreness and eventual breakdown.
Eliminating the eccentric work required by barefoot running relieves the runner of a burden. Habitually eliminating this stress can make a runner weak, but reducing the amount of eccentric contraction required by a runner might reduce his or her total muscular requirement and stress from a run. That sounds like a good thing on race day.
Training barefoot might have immense benefits to a runner’s strength and ability to withstand impact, but barefoot running on a hard surface might always be more metabolically expensive than running with external cushioning—either from a shoe or from soft ground—because runners must expend energy to cushion their body at foot strike.
The impact reduction from forefoot running could be an excellent way to reduce injuries caused by impact, but forgoing running shoes has other consequences, namely the elimination of energetically cheap cushioning that comes from shoes and perhaps an increased likelihood of injury to the tissues that provide this additional support.
Although this is speculative, perhaps barefoot runners select a true forefoot gait rather than a mid-foot gait because they need the additional cushioning that comes from softly landing on the forefoot. Shod runners with a similar stride might tend toward a mid-foot striking gait because the shoe is providing some of that additional cushioning for free.