Biomechanical assessments for runners with midportion Achilles Tendinopathy issues

With an injury rate of 2.35 per 1000 in the adult population (de Jonge et all, 2011), the Achilles tendon is one of the most commonly injured tendons, especially in athletes involved in running and jumping sports/activities (Kvist, 1994) (Wilson, 2005)

As per studies, the loading on the Achilles tendon during running increases to 12 times the body weight. This is much higher as compared to walking (upto 3.5 times body weight), or cycling (close to body weight) (Komi, et al., 1992). Such loading rates when combined with improper running biomechanics can be detrimental to Midportion Achilles Tendinopathy issues in runners.

A gait analysis, whether observational or through a video based system, is an excellent way to identify any biomechanical faults in the runner. A biomechanical fault can be as a result of either a physical limitation in the body or a technical error in the running form.  

In this blog, we will discuss various biomechanical faults that are associate with excessive loading on the Achilles tendon.

FOOT STRIKE PATTERN

Running with a rear footstrike pattern is considered to load the Achilles tendon less than running with a forefoot-strike pattern (Komi, et al., 1992). As per recent studies, running with a midfoot- or forefoot-strike pattern, as opposed to a rearfoot-strike pattern, added an additional load of 48 times body weight for each mile (1.6 km) run. (Almonroeder, et al., 2013)

ASSESSMENT OF FOOT STRIKE PATTERN

Foot strike pattern can be determined by measuring the foot inclination angle.

The foot inclination angle is the angle between the running surface and the

sole of the runner’s shoe and allows for the determination of foot-strike 

pattern.

Heel strike

(Landing on the posterior aspect of their heel)

Rearfoot strike 

(Landing on the anterior aspect of the heel, with FIA <10 degrees)

Midfoot strike

(Rearfoot & forefoot making contact nearly simultaneously, with FIA near 0°)

Forefoot strike

(Forefoot landing with FIA <0 degrees)

Within the context of return to sport, to control for overall loading, a runner 

who runs with a forefoot-strike pattern would not be allowed to run as far as

a runner with a rearfoot-strike pattern. (SILBERNAGEL & CROSSLEY, 2015)

OVERSTRIDING

Overstriding can be picked up when reviewing the video taken in the sagittal 

plane. The term simply means that the runner is landing excessively ahead 

of the center of mass of the body (COM can be approximated at the center 

of the pelvis). Doing this often increases the stride length of the runner, 

OVERPRONATION

Recent studies have linked excessive subtalar eversion with excessive Midportion Achilles Tendinopathy. In a study comparing running mechanics of runners with Achilles Mid-Portion Tendinopathy with healthy runners, The Achilles Tendinopathy Group displayed significantly greater sub-talar joint eversion displacement during mid-stance of the running gait.  (Ryan M, 2009)
Exercise programs for arch strengthening etc along with foot orthotics can be helpful in reducing excessive calcaneal eversion and reducing the load on Achilles tendon loading.hence the name ‘overstriding’. (Souza, 2016 )

Subtalar eversion can be assessed by measuring the rearfoot angle in the 

posterior view. Rearfoot angle is defined by the midline of the heel relative to

the midline of the lower leg.