Marathon Season Injuries: Part 2
In part 2 of this series on marathon running injuries we discuss achilles tendon and plantar fascia pain and dysfunction. The achilles tendon is the major tendon connecting the calf complex to the foot. It plays a vital role in the absorption and propulsion phase of all running tasks. The plantar fascia functions to maintain the integrity of the foot’s bony and musculature structure and transmits forces across the foot. Both achilles tendon and plantar fascia pain in distance running can be severe and debilitating and significantly reduce the ability of the runner to perform at their best.
So what causes the development of these running related injuries?
As we have discussed in previous articles these injuries are typically influenced by three key domains. They are training load (volumes and intensities), tissue characteristics (strength, range of motion, power and plyometric power) and bio-mechanics. Let’s explore how each of these areas may contribute to the development of injury.
Training load and intensity
There are some common threads when it comes to the development of PF and AT pain. The common factors that contribute to injuries in running are significant jumps in training volume (weekly volumes) and running speeds (km pace). Work by Nielsen et al 2014 highlights that changes of >30% from one week to the next in either factor is a strong contributor to the development of lower limb running injuries. The basic recommendation for this for anyone preparing for a major distance race is to make gradual progressions in their loads both volume and intensity, generally increases of 10-15% are tolerated reasonably well. However individualization is required for those increasing to very high volumes (>100km per week). This process is likely to take months to years to coordinate before they can achieve these very high training loads and tolerate them without difficulty.
Joint range and lower limb tissue biomotor abilities.
A lack of dorsiflexion range of motion (ability to bend ankle up towards the head) has been discussed as a contributing factor for the development of PF pain, McPoil eta al 2008, with Riddle et al 2003 suggesting risk reduced when patients had >10 degrees of passive dorsiflexion range. In discussions with a colleague working in elite cricket, a knee to wall marking of <12 cm has been suggested to increase the risk of lower limb injuries in fast bowlers. This statistic comes from unpublished internal data. However there appears to be an upper limit with Mahieu et al 2006 suggesting that too much dorsiflexion range may also be a contributor to achilles overuse injuries. In the section on biomechanics below we will show why this may be the case.
Calf and foot strength capabilities
Strength measures have been suggested to be associated with increased development of foot and achilles overload, Mahieu et al 2006. This suggests that increasing strength measures (force output) in the plantarflexors may be protective for the development of achilles and PF pain. Attention should be placed on strengthening both the gastrocnemius (crosses the knee, and therefore requires knee to be extended when performing heel raises) and the deeper calf and soleus (does not cross the knee and is strengthened with bent knee calf/heel raises).
Lower limb and leg stiffness, that is the ability to control the joints from flexing excessively under the weight of gravity when running is suggestive to be protective in lower leg overload injuries, Lorimer and Hume 2016. This suggests that loading such as plyometric training that is associated with training limb stiffness may be a protective factor for reducing lower limb overload in distance running, however further research is required to explore this at length for prescriptive recommendations on how much and how often to do this in injury reduction with different populations.
Work by Lorimer and Hume 2016 highlights that increased leg stiffness (landing without overflexing at the knee, hip and ankle) is protective for development of achilles injuries. This study highlighted that the surface that one is running on has an influence and that softer surfaces often require increased stiffness properties of the leg upon landing. If the runner is unable to create this firmer landing then the achilles is potentially overloaded to make up for the lack of surface stiffness. The reason this is the case is that it requires the achilles to have to absorb such ground reaction forces and cover greater range of motion as the ankle is placed into greater dorsiflexion during midstance (see picture), and this has been associated with increased injury risk of the achilles during running.
In summary we can see that both plantar fascia and achilles overuse injuries are associated with clear risk factors that when addressed are likely to provide ongoing reduction in the development of these injuries. Activities that increase the force output and stiffness capability of the ankle and leg, increase the dorsiflexion range (flexibility training, strasbourg sock) and retraining of landing stiffness and propulsion in running are likely to improve the injury symptoms or avoid them. If these items are in place, effort must be put towards planning training and gradually increasing the volume and speed (intensity) of the runs in preparation for any racing, including a marathon.