Introduction
Hamstring injuries are among the most common in sports that involve sprinting, such as football. Achieving maximum speed is crucial not only for game performance but also for reducing the risk of hamstring injuries. Introducing sprint training into the competitive microcycle of football players is essential to minimize the risk of hamstring injuries and ensure safer player preparation. This article provides an overview and practical guidelines for strength and conditioning coaches, offering a model for reducing hamstring injuries and optimally managing internal and external loads during sprint training.
Anatomy of the Hamstring Muscles
The posterior chain muscles of the back of the thigh include the semitendinosus, semimembranosus, and biceps femoris muscles – short and long heads (ST, SM, BF), which proximally attach to the ischial tuberosity (except for the BF short head). The ST, SM, and BFlh are biarticular muscles involved in hip extension, knee flexion, and rotation (medial and lateral). Distally, the ST and SM attach to the tibia, while both BF heads attach to the fibula. The posterior chain thigh muscles are innervated by the sciatic nerve, which exits at the level of the S1 vertebra. These muscles strongly contract during movements requiring hip extension or controlling the speed of hip flexion, while the gluteus maximus contracts during powerful hip extension.
The adductor magnus also performs hip extension, attaching to the ischial tuberosity, with its ischial portion sharing innervation with the tibial branch of the sciatic nerve. Reduced functional capacity of the adductor magnus and/or gluteus maximus can lead to increased hamstring load (Afonso et al., 2021).
Hamstring Overload in Football
The effects of fatigue on the posterior thigh muscles are evident during gameplay. Research suggests that with a high match frequency, hamstring muscle function can be impaired for up to 72 hours after a match. Studies show that on the third day post-match (MD+3), players recorded significantly reduced sprint performance. In 10- and 30-meter speed tests, they posted slower times than pre-match, their ability to generate maximum horizontal force decreased, and their top speed was also diminished. In other words, 72 hours post-match is insufficient for a full recovery of mechanical capabilities required to apply horizontal force and accelerate to maximum speed, which explains the poorer sprint results.
The consistent decrease in hamstring strength up to 72 hours post-match, combined with increased fatigue, highlights the significant role these muscles play in overall leg function during movement. This suggests that after a match, there is not only a prolonged decrease in sprint performance but also a lasting reduction in mechanical properties that could increase the risk of hamstring injury (Carmona et al., 2024).
The Importance of Achieving Maximum Speed
Depending on the specific context of each sport, the goal of athletes when sprinting is to cover a certain distance in the shortest possible time. During a football match, a player performs on average “17 to 81 sprints lasting 2 to 4 seconds, usually over distances shorter than 20 meters” (Gómez-Piqueras & Alcaraz, 2024). Approximately 70% of these sprints are performed while the player is already moving rather than from a stationary position. Therefore, when incorporating sprint training into football, it must be considered that these sprints are mostly “flying sprints” with a curved rather than linear trajectory.
All these rapid actions have increased in recent years in professional football. In most cases, goals and decisive actions precede such efforts. Footballers must be physically well-prepared to cope with these demands. Better adaptation to the sport’s requirements and the implementation of multifactorial prevention protocols might explain the general reduction in injury rates. However, hamstring injuries remain the most common in football.
UEFA data shows that hamstring injuries have increased by 4% annually in recent seasons, now accounting for 24% of all injuries in men’s professional football. These injuries pose a significant burden on performance and finances, resulting in an average of 90 days and 15 missed matches per club per season. Most of these injuries occur when players run at speeds exceeding 25 km/h and at more than 80% of their maximum speed (Gómez-Piqueras & Alcaraz, 2024).
Analyzing the most frequently injured muscles within the hamstring group, it appears that the long head of the biceps femoris (BFlh) is the most commonly affected. This is because sprinting generates large forces that cannot be replicated in the gym with traditional strength training. At a speed of 9 m/s, the forces on the hamstrings reach 6-8 times body weight (Dorn, Schache, & Pandy, 2012).
Among the various components of training in elite football, considering both performance and injury prevention, exposure to maximum sprint speed stands out as one of the key and crucial factors. Studies indicate that exposure to speeds close to maximum sprint speed (MSS), particularly above 95% MSS (rather than at lower intensities), during training close to match day (MD-2) is associated with lower hamstring injury rates.
These findings highlight the importance of maximum speed exposure in reducing hamstring injuries. Achieving optimal exposure to maximum speed on MD-2 requires careful adjustment of training content in the preceding days (MD-4 and MD-3). Additionally, in shorter microcycles, as observed, exposure to maximum speeds is usually reduced, potentially diminishing its importance for injury prevention (Buchheit et al., 2024).
Sprinting as a Preventive Factor
When a player sprints, the level and timing of activation in the hamstring muscles differ significantly from the activation during common strengthening and prevention exercises for this muscle group. Comparing the effects of sprinting with the most commonly used hamstring injury prevention exercises, such as the Nordic hamstring exercise, it becomes evident that sprinting activates the long head of the biceps femoris (BF) more.
Research shows that BF activation is greater during sprinting than during the Nordic hamstring exercise. When a player exceeds 80% of their maximum sprint speed (MSS), BF activation is significantly higher than that of other involved hamstring muscles, but training at speeds above 90% MSS significally reduces the risk of injury.
Although sprint training is considered an effective strategy to reduce injury risk, we cannot assume that injuries can be prevented solely by this type of work. As previously mentioned, hamstring injuries are complex and multifactorial, so prevention must include a multi-component program that creates the necessary adaptations. This includes other variables (load management, strength training, HSR, individual deficits, etc.) alongside sprint training (Gómez-Piqueras & Alcaraz, 2024).
In this first part of the blog, we explored the anatomy of the hamstring muscles, we highlighted the importance of achieving maximal sprinting speed as a crucial element of athletic performance. Additionally, we discussed how sprinting can serve as a preventive factor in training, helping to reduce the risk of hamstring injuries.
In the second part, we will delve into the practical aspects of incorporating maximal sprinting speed into a weekly microcycle. This will include an analysis of training structure, frequency, and intensity. We will provide practical examples and guidelines to help coaches effectively implement sprint-focused training programs that not only enhance performance but also minimize the risk of injury.
