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How Do Hamstring Injuries Happen? Mechanisms of Hamstring Injury

Hamstring injuries can be devastating both for athletes and for the teams they play for – and the problem isn’t restricted to any one particular sport. Data compiled by IQVIA, a company retained by the NFL to analyze injuries throughout the season, revealed that hamstring strains are the most common injuries suffered by NFL players (8). This is clarified further by injury analytics company Athlete Game Lost, who showed that throughout the course of the 2023/24 NFL season, 170 unique hamstring related injuries occurred which resulted in lost training or game time. In the NBA injuries to the knee, foot and ankle might be more prevalent, but the hamstrings are the most strained muscle group (3), with 210 hamstring injuries occurring in the NBA between 2016 and 2021. Hamstring injuries are the most frequently sustained injury in Major League Baseball (6), and are the most common reason for time out of play in both Major League and Minor League Baseball (7). In soccer, hamstring injuries in the men’s professional game have doubled in 21 years, and now represent 24% of all soccer injuries (4).

Clearly, professional organisations across all sports have a strong incentive to reduce hamstring injuries – but how do they happen in the first place? Here we look at the mechanisms of the hamstring injury.

Hamstring Strains – Injury Mechanisms

Based on injury mechanisms, hamstring injuries can be divided into three distinct categories: sprint injuries, stretch injuries, and overuse injuries:

1) Sprint Injuries: the most common mechanism of hamstring injury Sprinting is by far the most common mechanism of hamstring injury. They occur during the late swing phase or the early stance phase of the sprint cycle, when the hamstrings are simultaneously lengthening and absorbing energy (2). At this point, the hamstring muscles are producing peak force and reaching peak strain, and these forces may exceed the level of tolerance that the musculo-tendonal unit has to withstand them. It is here that the hamstring will fail, and injury will occur.
2) Stretch Injuries: high time loss injury Stretch injuries occur when the hip is flexed and the knee extended, and usually happen as a result of the athlete attempting to perform a sport-specific movement action, such as punting a ball or picking a ball up from the ground while running at full speed (2). Although stretch injuries occur much less frequently than sprint injuries, they do result in a much longer athlete absence, and therefore measures must be taken to reduce them.
3) Overuse/Gradual Onset Injuries Excessive athlete load and overuse injuries generally happen because the repetitive or high intensity movement actions associated with sport cause structural damage to occur in the hamstring muscle. This leads to an increase in stiffness and soreness, and a reduction in the force generating capacity of the hamstring. If the athlete is not allowed sufficient recovery to allow regeneration to take place, or if excessive loading is reintroduced too early in the athletes restorative cycle, the hamstring may be at increased risk of injury.

Understanding the Mechanisms Means We Can Find A Solution

Knowledge surrounding the mechanisms of hamstring injury, and the circumstances under which they occur, equips practitioners with a clearer insight into which preventative measures they can implement to reduce them.

Mitigating Sprint Injuries

Sprinting is the most common hamstring injury mechanism, therefore training to improve athlete tolerance to high-speed running is vital. To achieve this, injury prevention exercises must recreate the loading demands that the hamstring is exposed to during the sprint:

Eccentric hamstring strength training is the most widely researched and recommended evidence-based strategy for hamstring injury prevention, and has been shown to significantly reduce the risk of primary and secondary hamstring injuries by between 65%–85% (1).
Evidence also suggests that regularly achieving peak or near-peak running speeds in training is associated with a lower risk of hamstring injury, with a recommendation that athletes should be exposed to running speeds within 95% of their individual maximum speed to reduce injury risk (1).

Mitigating Overuse Injuries

Sudden, large and rapid increases in load above levels that athletes are habitually accustomed to increases the odds of them sustaining a hamstring injury (1). One of the ways that has been proposed to address this is to monitor the relationship between acute workload and chronic workload (ACWR).

Chronic load is described as the athlete’s average physical output from the previous three-six weeks, and acute load is the output generated from a single weeks training and competition. The ACWR model states that an acute:chronic workload target should be in a ratio of 0.8-1.3 in order to develop physical capacity without excessive risk of injury (5).
Maintaining a high chronic workload means athletes will develop the physical qualities and improved fitness needed to tolerate high physical demands, providing protection against injury. Restricting training loads in an attempt to reduce injury can be counterintuitive, as athletes are put at greater risk of injury during competition.

Data Tracking and Athlete Management Is Vital to Reduce Hamstring Injuries

When we consider the mechanisms of hamstring injury, and the interventions that have been developed to mitigate them, it becomes clear that the injury reduction process has to be supported by data. How else do we monitor athlete load, sprint speed exposure, eccentric strength, and the many other factors which contribute to performance development? This data is nearly always collected by multiple different sources – medical staff, fitness staff and coaching staff. Different departments use different technologies, with the result that data often remains isolated on different databases – but to have any impact, this data has to be brought together and made meaningful. This requires a high-performance data management platform. An effective data management system is capable of communicating with multiple different athlete tracking technologies, and enables all relevant data to be analyzed not in isolation, but according to how they relate to each other, making the whole greater than the sum of the parts. Data management ensures that all metrics are collected collaboratively, and that the right information is going to the right people at the right time, using a dashboard that creates simple reports that everyone can understand. This ensures that an integrated approach is adopted, and that the risks associated with hamstring injury mechanisms are minimized as much as possible.

Where Apollo Makes a Real Difference

ApolloV2’s athlete performance software unlocks data silos allowing coaches, trainers, doctors and players to become masters of data-driven performance with real-time data visualization and collaboration tools. Our software is integrated with over 70 performance focused technologies used by college and professional athletes. With ApolloV2, teams have the information they need to minimize hamstring injuries and optimize player availability. To learn more about using ApolloV2 for injury prevention email info@apollov2.com

Written by Adrian Lamb, ApolloV2 Sports Scientist

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