Start talking about sprinting and it won’t be long until you the discussion turns to hamstring injuries. Hamstring injuries are a major concern of any athlete that has to sprint. Soccer has a notorious hamstring problem, but they are not alone. Hamstring injuries are also the most prevalent form of non-contact injury within sports like athletics, American Football, rugby union, Australian Rules Football, cricket, and basketball.
The hamstring problem
To give you a look at the scope of the hamstring problem, let’s take a look at some data. During the 2016/17 football season, the twenty clubs that comprise the English Premier League suffered 614 significant injuries to their players, resulting in the loss of over 20,000 training days. Such injuries are obviously costly to the teams; focusing solely on the injured players wages, the clubs lost over £131 million due to these various injuries. Within this season, the most frequent injury type occurred within the hamstring muscle group, representing 27% of all injuries.
Along with the substantial financial implications, hamstring injuries are also costly in terms of time, with average recovery times ranging from 8 to 73 days depending on the severity of the injury. In addition, when players are injured, they’re unable to play in matches, and such unavailability of squad members has been shown to diminish team performance. For example, in an eleven-season study of 24 European soccer clubs, lower rates of injury were associated with a better overall team performance, as measured by both number of points gained per match and final league position.
Perhaps even more worrying, a prior hamstring injury itself increases the risk of suffering a second hamstring injury in the future, as well as other injury types, and has been shown to impact physical performance months, and even years afterwards, demonstrating the long term consequences of hamstring injuries. As a result, avoiding, or at least reducing, hamstring injuries has become a hot topic in the sports science and medicine world, with many studies exploring how to reduce their incidence, and, especially, how to ensure that players can best return to full fitness following a hamstring injury, without increasing their risks of suffering a secondary injury in the future.
Sprint more to stay healthy
One new approach to thinking about the problem over the past few years has been Tim Gabbett’s work in analyzing acute:chronic workload ratio, best summarized in a British Journal of Sports Medicine editorial entitled “The training-injury prevention paradox: should athletes be training smarter and harder?” Here, Gabbett explored findings suggesting that higher overall workloads may be somewhat protective of injury, as they increase the overall fitness and robustness of the athlete ; as such, training too little is perhaps worse, from an injury perspective, than training slightly too much.
A recent paper published in the Journal of Science and Medicine in Sport explores this topic a bit further in the context of returning to play after an injury. Here, the authors collected data on lower limb injuries over five seasons at an Australian Rules Football club. During that period there were 85 injuries, of which 66 were carried forward to further analysis. In 43% of cases, injured players suffered a subsequent re-injury. What is interesting is that when you look closer at the second injury, three-quarters were injuries to a different tissue than the initial injured – suggesting that, in general, a lack of total load is problematic when it comes to rehabilitation from injuries, and not just at the site of previous injury. Within this context, greater total training loads – and, in particular, greater total sprint loads – were protective against future injury.
Finding the right balance
Their analysis of the rehabilitation process also backed up this conclusion. Within the running loads, it was found that higher volumes of sprint distance during rehabilitation was associated with the greatest protection from a second injury. But while more load might help the athlete avoid secondary injury, the sensible application of this load is also crucial. This study found that returning to running within four days of injury increased the risk of a second injury once return to play was complete. In other words, adding running load too soon increased the risk. Therefore the authors of this study recommend waiting at least five days before running (but not all loading) is resumed.
Adding more load to rehabilitation might help prevent a secondary injury, but there is a trade off: accumulating a greater amount of high speed running loads increased the time taken to return back to action, which is to be expected, given that it takes time to work up to, and accumulate, these high workloads. It seems a fair trade off to me: longer time in the rehabilitation phase equates to a smaller chance of re-injury.
So, pulling this all together, the key take-homes are:
- Leg muscle injuries, particularly hamstring injuries, are common in all sports that require running.
- Higher workloads appear to offer more injury protection than lower workloads, providing the application of this load is sensible.
- When returning from injury, the chronic workload is low due to the recovery period; this in turn increases the chance of a subsequent injury.
- Waiting longer than 4 days to return to running (such as low velocity running) is associated with better outcomes.
- A greater accumulation of maximum speed running during the rehabilitation phase is associated with a smaller chance of subsequent injury.
Next time you or your athletes suffer an injury to a leg muscle, try to ensure they are exposed to high speed running a repeated number of times prior to them returning to either competition (if in-season), or high intensity team-based training – the evidence suggests this will reduce their risk of future injury.