On many occasions we have discussed sprinting and hamstring injuries in this blog. I know its definitely an interest area of ours, so I hope you will indulge us in discussing further studies that are opening up ideas in the area. These include factors that may be contributing to hamstring injuries in sport that had previously not been identified. 

To put some background on this study, the group of researchers which is made up of teams in Japan, France and Finland. These respective researchers have been investigating sprinting, injuries and performance factors for more than a decade and it appears they are slowly closing some knowledge gaps on areas relating to performance, injury development, assessment and interventions for future performance. They have previously identified that the ability to push yourself horizontally during the acceleration of sprint is correlated with achieving higher tops speeds. Further to this they have shown that you can use basic methods to assess the force velocity profile of sprints and develop an understanding of how much horizontal force decrement you have. What this means the rate at which you are getting faster either is steady, drops quickly or drops gradually. With those dropping quickly losing horizontal force production properties sooner than others. 

Why is this important for hamstring injury?

Research that has built on this knowledge has shown that athletes with prior history of hamstring injury had greater reductions in horizontal force production under the fatigue of repeated sprints, Lord, Blazevich et al 2019. So the group across the three countries, Japan, France and Finland decided to measure the horizontal force production capabilities during sprint assessments in Soccer players (284 in total) at the start of the season and then up to 8 times during the season. 

So what did they find?

The results suggest the initial measure of horizontal force production during sprints before the season was not able to provide any significant insight into hamstring injury risk. However in the measures during the season, reductions in the horizontal force production during sprints within that individual showed a significant risk ratio increase for consequent hamstring strain injury. What they were finding was that as players were losing the ability to push themselves horizontally during sprints across the season, they were becoming more likely to have a hamstring injury in the weeks following the measurement that showed it had reduced. 

Why this is valuable is that it provides a potential insight into a performance measure, i.e horizontal force production during acceleration and sprinting, as a risk factor for developing muscle strain injuries. It highlights that the complex interaction of the hamstring in the chain of tissues that propel athletes during sprints can be put at risk if the properties of the overall output (horizontal force production) reduces. It create a further area for monitoring in performance settings to identify potential areas for injury risk that may present under the fatigue and potential detraining of areas during a competitive season. 

Using this information we started to investigate and assess hamstring strain injuries in athletes that we manage in our clinical setting. Unsurprisingly in the assessments of athletes returning from hamstring strain injuries, tasks that required hip extension movements with an extended or near extended knee were consistently slower to improve (both force and rate of force development) than those with the knee bent. Our clinical findings were matching those of the work of Lord and Blazevich but in a clinical setting rather than with running in a previously injured group. Not only has this been informative but it is guiding how we approach rehabilitation with these athletes.  In our next article we will look at what tasks can be implemented to assist with horizontal force production in running and in hip extension tasks across the force velocity spectrum in a rehabilitation setting. 

Read the article here: https://www.mdpi.com/1660-4601/18/15/7827