Running the Risk of Injury: Achilles Tendon Strain Prevention

The Achilles tendon strain is a perhaps one of the most common injuries found in long distance runners with its primary cause predominantly due to overuse. However, other causes include:

·         Increasing one’s physical activity levels too rapidly.

·         Insufficient pre-exercise stretching.

·         Over pronation, otherwise known as fallen arches or flat feet. The impact of each step in this condition causes the arch of the foot to collapse, therefore excessively stretching the Achilles tendon.

Such activities lead to an inflammation and tenderness of the tendon which is localised 2-6cm proximal of its insertion, a notion which is only exacerbated due to the fact blood supply to this region is limited. If left untreated degeneration and rupture of the Achilles tendon may result.

In this article, the focal prevention strategy for this hindrance to performance is the insertion of heel lifts, placed to the rear of the shoe. The use of heel lifts has previously been associated with a reduction in Achilles tendon injury¹, through the suggestion that they reduce peak ankle dorsiflexion that occurs during the midstance of running². This therefore causes a reduction in the stretch and strain experienced by the tendon.

The triceps surae is a muscle tendon complex consisting of the gastrocnemius and soleus muscles (see figure below), which together have the common insertion of the Achilles tendon at the calcaneus. This muscle-tendon complex crosses both the knee and ankle joints, thus its overall length is determined by alterations in ankle plantar- and dorsi-flexion as well as knee flexion and extension. However, this is dependent upon the type of muscle contraction and sporting activity being performed³. Previous literature states that the Achilles tendon contributes predominantly to the increased total length of the triceps surae directly following ground contact during running⁴, with surrounding muscle fibres providing a negligible contribution to movement⁵. Through this period of ground contact an eccentric muscle contraction occurs in order to control movements that follow impact, this is the point where Achilles tendon strain can arise.   

In the most recent study of its kind a statistically significant reduction in peak ankle dorsiflexion has been observed for increased heel lift conditions⁶, therefore providing biomechanical support to clinicians and practitioners that an increased heel lift leads to a reduction in Achilles tendon strain. It was found that a somewhat small heel lift of 7.5mm produced this significant effect on ankle dorsi flexion and that further increases to the magnitude of the heel lift could result in rear foot instability. We can therefore conclude that a relatively modest heel lift could be of benefit the long distance runners that engage in high volumes of training. However, the future direction of research regarding this topic should focus upon the biological make-up of the Achilles tendon. This will provide a greater understanding of how the tendon reacts to repetitive strain and its requirements for an enhanced recovery time.

References

1.   Grisogono V, 1989. Physiotherapy Treatment for Achilles Tendon Injuries. The Journal of the Chartered Society of Physiotherapy. 75, p. 562-572.
2.  Clement DB, Taunton JE & Smart GW, 1984. Achilles tendinitis and peritendinitis: etiology and treatment. American Journal of Sports Medicine. 12, p. 179-184.
3.    Bobbert et al, 1986. A model of the human triceps surae muscle-tendon complex applied to jumping. Journal of Biomechanics. 19, p. 887–898.
4.  Caldwell G.E, 1995. Tendon elasticity and relative length: Effects on the Hill two-component model. Journal of Applied Biomechanics. 11, p. 1-24.
5.   Van Ingen Schenau G.J, 1984. An alternative view of the concept of utilisation of elastic energy in human movement. Human Movement Science. 3, p. 301-336.
6.  Dixon S.J & Kerwin D.G, 1999. The influence of heel lift manipulation on sagittal plane kinematics in running. Journal of Applied Biomechanics. 15, p. 139-151.