To avoid injury and save energy when running, your knee biomechanics are just as important as your foot strike mechanics. Research shows that one of the best ways to improve your knee mechanics during running is by not wearing conventional running shoes because the thick shoe cushioning encourages knee extension at touchdown, causing the knee-joint to lock into a stiff position.
Any type of athletic footwear that feels barefoot will yield more efficient knee kinematics, such as greater knee flexion, during running. Likewise, if you really want to optimize your knee kinematics during running, you can try running barefoot as barefoot running was associated with better knee stability.
A well-known study by Perl et al. (2012) discovered that barefoot and pure minimalist shod runners were more economical based on knee kinematics than heel strike and forefoot runners who wore the standard running shoe (shod).
How To Improve Your Knee Biomechanics When Running
The barefoot and minimalist runners had a 9% reduction in knee excursion than the shod runners. By comparison, shod runners had excessive knee flexion during touchdown.
Although increased knee flexion helps absorb impact during running, too much knee flexion, exaggerated by shoe cushioning, slackens the Achilles tendon causing a reduction in elastic energy storage. Another economic burden is that increased knee flexion increases eccentric contractions of the quads in attempt to control knee flexion thereby rising muscle costs.
Isabel (2016) also noted that knee flexion at touchdown gives you extra fuel for running. Knee flexion at touchdown reduces the amount of knee flexion needed during the swing phase of running, therefore reducing the energy needed to flex the leg during swing (Royer and Martin, 2005). Knee flexion at touchdown saves on energy by lowering the leg’s moment of inertia, meaning that it becomes less difficult for the cyclic rotation of the legs to accelerate the body’s mass. What this all means is that slightly bending your knee when your foot strikes the ground during running, reduces the mechanical work of the leg, thereby saving energy.
Nevertheless, the results from the study were quite unexpected because past reports have strongly associated increased shoe cushioning with decreased knee flexion which amplified impact in runners. Nevertheless, too much or too less knee flexion seems to be an unintended consequence of the standard running shoe that has implications to both injury and performance.
Earlier work by McNitty-Gray et al.(1989) and Robbins and Hanna (1987) demonstrated that humans are more than capable of moderating impact dramatically through innate, reflexive behaviors, such as knee flexion, in response to hard surfaces. Their work also revealed that knee flexion modification is triggered by sensory input at the plantar surface.
The Take Home Message
In running, the customary approach to improve performance relies on shoe technology. However, the shoe cushioning-increased knee flexion link most likely is bad news for runners. In such a scenario, running barefoot or in pure minimalist footwear would mitigate hyper-knee flexion because the feet are able to capture more sensory input from the ground.
More From Run Forefoot:
Isabel, M. Is There an Economical Running Technique? A Review of Modiﬁable Biomechanical Factors Affecting Running Economy. Sports Med, 2016;47:793-807.
Perl et al. Effects of footwear and strike type on running economy. Med Sci Sports Exerc, 2012;44(7):1335-43.
McNitt-Gray JL, Yokoi T. The influence of surface characteristics on the impulse characteristics of drop landings. Proceedings of the 13′ Annual Meeting of the American Society of Biomechanics. Vermont: American Society of Biomechanics, 1989: 92-3.
Robbins SE, Hanna AM. Running related injury prevention through barefoot adaptations. Med Sci Sports Exer 1987; 19: 148-56.
Robbins SE, Hanna AM, Gouw GJ. Overload protection: avoidance response to heavy plantar surface loading. Med Sci Sports Exer 1988;20:85-92.
Robbins SE, Hanna AM, Gouw GJ. Running related injury prevention through innate impact moderating behaviour. Med Sci Sports Exer 1989;21:130-9.
Royer TD, Martin PE. Manipulations of leg mass and moment of inertia: effects on energy cost of walking. Med Sci Sports Exerc.
BSc Neurobiology; MSc Biomechanics candidate, ultra minimalist runner & founder of RunForefoot. I was a heel striker, always injured. I was inspired by the great Tirunesh Dibaba to try forefoot running. Now, I'm injury free. This is why I launched Run Forefoot, to advocate the health & performance benefits of forefoot running and to raise awareness on the dangers of heel striking, because the world needs to know.