Managing recurrent hamstring injuries in an elite sprinter

Sport physiotherapists are likely to encounter hamstring strain injuries (HSIs) many times throughout their careers, particularly if working with athletes in sprint-focused sports. Half of track & field athletes will sustain an HSI in their career, with one in five having an HSI each season ^[1]. The incidence and recurrence rates of these injuries can vary from 5-60%, depending on injury severity and location, placing a large burden on medical teams ^[2].

These injuries also have a direct impact on athletes’ availability for competition and sports performance outcomes. The chance of competitive success is up to seven times lower when athletes attend fewer than 80% of the training sessions in the six months prior to the competition ^[3]. Time loss due to HSI also has a significant economic burden, with impacts to both individual and team success ^[4].

A 22 year old elite male 100-200m sprinter has an extensive history of HSI, beginning when he was 18 years old. Since starting his career, this athlete has experienced five HSIs, occurring bilaterally, with all confirmed injuries occurring to the bicep femoris long head (BFlh). This has drastically impacted his ability to train and compete at important competitive events.

• 2020: HSI to left limb – no imaging available
• 2021: HSI to right limb – no imaging available
• 2022: HSI to right limb – BAMIC 2b – BFlf
• 2023: HSI to left limb – BAMIC 3c – BFlh
• 2024: HSI to left limb – BAMIC 3c – BFlh

The athlete is based in Tasmania, Australia. Tasmania is an island state with less access to high performance equipment and technology than is common in professional sport environments. When I met him, he was most concerned about the two most recent injuries, both to his left limb.

The 2023 HSI occurred while competing in a sprinting event. MRI confirmed it was a BAMIC 3c BFlh proximal tendon injury. It occurred late in the season, which enabled a slow and conservative rehabilitation protocol throughout the off season. The athlete returned to high speed running four months post-injury, before competing at a high level for five months. He was able to run a personal best (PB) time.

Three weeks after his PB, he experienced a sharp pain and a pop in the same location (left proximal posterior thigh) during a local competition. This injury — his third to the left limb — occurred in the final 30m of the race. His coach reported that the athlete appeared to be overstriding, with a significant forward trunk lean at the time of injury. Hamstring strain increases exponentially with increasing running velocity, with elite sprinters often reaching their peak velocity in the final 30-40 meters of 100m events ^[5].

Based on the athlete’s history of proximal tendon injury and the high speed running mechanism, I suspected a proximal tendon injury. We arranged an MRI to give a clear understanding of the severity of the injury, and how it related to the previous left side HSI that occurred nine months earlier. After reviewing the imaging and comparing it to previous scans, the new injury was a significant tear adjacent to the 2023 HSI. The injury extended from the proximal tendon and into the previously uninjured intramuscular aponeurosis. This was a significant exacerbation of the previous HSI, leading us to hypothesise that the previous rehabilitation had not adequately prepared the athlete for the demands of high speed running.

When managing an athlete with recurrent and challenging presentations, practitioners should consider both functional and physiological criteria, including tissue healing and maturation times. In low grade HSI to muscle fibres, return to play (RTP) will commonly occur 21 days post-injury. Biologically, at 28 days post-HSI, scar tissue is still immature and may not be capable of tolerating high levels of tissue strain, increasing the risk of reinjury ^[6]. In tendon injuries, the collagen maturation process can take up to 12 months, potentially decreasing its capacity to tolerate load ^[7].

Since this athlete had experienced a high grade proximal tendon injury nine months earlier, it is plausible that the previous injury’s maturation process was incomplete, leaving him vulnerable to tissue strain ^{[8, 9]} .

How previous injuries set up the next one

Since previous HSI is the biggest predictor of future HSI, exploring these injuries is critical. Attributes to explore are which muscle was injured; whether it was a myofibrillar, tendinous, or an intramuscular aponeurosis injury; and whether imaging was available. Practitioners should also review any available information about previous rehabilitations, paying attention to whether those included a structured and progressive running program. The extreme loads tolerated by the hamstrings during high speed running cannot be replicated through gym based loading, often leading to a spike in load the athlete is unprepared to tolerate upon RTP.

Practitioners should also explore musculoskeletal injuries above and below the site of concern, and on the unaffected limb. These may all contribute to aberrant movement patterns and increases in biomechanical load due to fatigue, weakness, or restricted range of motion.

This athlete had no general health concerns, but did have several musculoskeletal injuries over the past four years.

His original left sided HSI occurred in 2020, prior to receiving a high performance scholarship. This was diagnosed clinically as a grade II musculotendinous junction injury. No imaging was available to confirm this diagnosis, although the location of injury and the way it was described suggests it may have been a hamstring tendon injury. Rehabilitation took eight weeks, and included a progressive strengthening program and plyometrics, but no structured running program. The athlete was able to return to competition, but experienced ongoing hamstring tightness and pain. The hamstring tightness and pain had persisted since the initial injury.

The bilateral hamstring tightness and pain had been present for most track based training sessions. The athlete also reported experiencing delayed onset muscle soreness in the hamstring region after most gym sessions. Although this soreness had been present before the original HSI in 2020, it had increased with each subsequent injury. The tightness and pain had not limited performance, and the athlete completed his prescribed track sessions as planned.

Another relevant injury was tibialis posterior tendinopathy in the right foot. This was causing mild pain, primarily during acceleration at track sessions, and was exacerbated by wearing spikes. The athlete wore a custom orthotic in his daily footwear, which alleviated most pain, but he was unable to wear this orthotic in his spikes, resulting in an inability to push off the ground aggressively on his right foot due to pain.

Clinical assessment of the athlete post-injury #5

Initial assessment for this athlete involved a standard hamstring muscle assessment. The pain he experienced on stretch, contraction, and palpation, alongside the acute injury mechanism indicated an HSI, which an MRI confirmed.

Further objective assessment revealed findings that may have been contributing to the recurrence of HSIs.

Assessment of the right foot, where the tibialis posterior tendon injury occurred, showed increased pronation in weight bearing positions and a significant decrease in dorsiflexion range of motion. The importance of this became more apparent when the athlete returned to block starts on the track (Figure 1). In a sporting context, injuries will often occur in the area of the body doing the most work. This athlete was drastically off-loading his right side during acceleration, which can result in increased load on the left limb, the side with more serious and frequent injuries for the athlete.

Further assessment found 30% less adduction force capacity on the left side than the right. EMG data has found that glutes, hamstring, and adductors work synergistically during late stance phase to generate forward propulsion. Hamstring and adductor muscles are also highly active during the late swing phase, which is when hamstring injury often occurs ^[10]. The athlete’s decreased adduction force capacity may be a contributing factor to his HSI due to the relative increase in work by the hamstrings when decelerating the shank.

We also assessed trunk endurance. The athlete’s regular abdominal plank, side plank, and Biering-Sorenson test duration were all lower than expected for an elite level sprinter. Based on normative data, he did not reach the threshold of 120 seconds for male athletes in any of the tests ^[11].

The final key objective finding was self-reported difficulty with knee flexion and hip extension, when the exercise biased the lateral hamstrings. We tested this with hip and tibial external rotation, with the athlete describing an increase in difficulty when completing these tasks. Previous rehabilitation included specific hamstring loading exercises with a focus on specific muscle activation. The increased difficulty he reported may indicate he had off-loaded this region. EMG activity of the BFlh decreases after HSI compared to contralateral uninjured controls ^[12], demonstrating the role for more precise exercise prescription.

For any athlete that presents with an acute injury, it is critical to thoroughly test all possible differential diagnoses.

In this athlete’s case, this entailed testing for stretch, contraction, and palpation pain (all of which are expected in HSI); clearing the lumbar spine and the sacroiliac joint; and assessing for non-acute pathology such as bone stress injuries and tendinopathy. Although, subjectively, this was very likely to be an HSI injury, assumptions can lead to bad habits, particularly in the sports medicine setting where we often talk to our athletes daily and may assume we already know their complete case history.  

The differential diagnosis testing led to a complex picture of potential contributing factors that would be important for his long term management. It is biologically plausible that failing to identify these factors in the past has contributed to his ongoing difficulty with hamstring injuries, challenging his ability to thrive in his sport.

Rehab goals must include preventing recurrence

Prior to ceasing acute physiotherapy management, the athlete had to satisfy a few additional markers beyond the standardised management of the acute muscle injury. First, he had to address the ongoing right tibialis posterior tendon pain; and, in collaboration with his coach, address the biomechanical issues identified during block starts.

The adductor muscle group acts synergistically with the hamstring muscle group during high speed running, particularly during the late swing phase when hamstrings are most vulnerable. Therefore, he had to improve adduction strength to male normative values ^[13] and side-to-side symmetry. Trunk rotation or side bending, which can be associated with poor trunk endurance, have been linked to HSI ^{[14, 15]}, so he had to improve trunk endurance measures to normative values ^[11]. Last, because muscle activity of the hamstring muscles becomes medially biased after injury ^[16], he had to improve his capacity to load the lateral hamstrings.

This athlete’s management differed from standard HSI rehabilitation. We considered the complex interaction between contributing factors as well as the acute pathology, which ultimately led to increased time away from high speed running and competing.

Based on the current literature for RTP in elite track & field athletes, the recovery time of a similar injury is approximately 84 days ^[17]. This recovery time does not take into consideration more complex presentations, like the case we are exploring. 

One crucial step in managing a case like this is setting clear expectations and standards. We met with the athlete and his support team to explain the injury in detail, its implications for the upcoming competitive season, and typical physiological healing times, noting the increased time that tendon tissue takes to heal compared to muscle fibres. We discussed how the body starts to replace early, poor quality collagen with high quality and well-aligned tissue at around six weeks post-injury. This tissue then matures and improves over the next nine months ^[7], theoretically leading to a decrease in injury risk at completion of healing.

We split this athlete’s rehabilitation into four standardised phases.

Early phase: Tissue protection

The early phase prioritises tissue protection, completely avoiding tensile load that would result in hamstring lengthening/shortening. We also avoided eccentric exercise, which lengthens passive tendinous structures ^[18]. This stage is also an opportunity to begin targeting identified contributing factors (foot, adduction, and trunk).

Initial management focused on good quality early tissue recovery, while minimising the possibility of any further tissue retraction due to de-tensioning of the intramuscular aponeurosis, which we had identified during the initial MRI. In collaboration with the S&C coach, we prescribed strength based exercises to address hip adduction and trunk endurance. We also had the athlete load the foot and ankle complex, focusing on plantar flexion and foot intrinsic capacity.

Mid-phase: Begin to load

Pain-free high load isometrics re-introduce loading to the hamstring muscle group, progressing to isotonic and eccentric focused loading. We biased lateral hamstring musculature, using surface EMG as a bio-feedback tool and therapist assisted manual palpation as another source of feedback.

Once the medical team were confident that further tissue damage was unlikely to occur, the athlete completed a progressive loading program that prioritised high load while remaining pain free. This initially included high load isometric loading in various positions of hip and knee flexion and extension. I supervised this in the early stages to ensure the athlete was loading through the lateral hamstring musculature by externally rotating both the foot and hip during exercise, and also through palpation of BFlh to ensure strong, palpable muscle contraction.

Late phase: Return to load, velocity, and running

The athlete returned to high load and unrestricted hamstring loading, with both single and double leg variations. His movements had high rate of force development and high velocity. The return to running program included retraining his sprint biomechanics.

This transitioned him from rehab-based hamstring loading to S&C programming. Collaboration continued between the medical department and the performance department. This gave the athlete confidence in the team, but also allowed everyone to take advantage of the expertise of the entire support network. I asked the S&C to prescribe hamstring loading to continue biasing the lateral hamstrings, with an eye towards high RFD and high velocity movements. To ensure an increased emphasis on the quality of each individual sprint effort, we decreased the running volume of his high velocity training sessions.

The track coach and I worked together on the return to running program. The initial focus was on running technique drills, with the athlete focusing on trunk control and attacking the ground with foot and ankle stiffness. These sessions were often recorded and reviewed for side-to-side discrepancies, as identified in Figure 1. The athlete scored 1/12 on the Sprint Mechanics Assessment Score (S-MAS), indicating high quality sprint mechanics ^[19] (Figure 2).

Return to play

As the athlete progressed towards competition, we reassessed the factors that contributed to his injuries, checking that he achieved those key objective markers that we identified during his assessment. Going along with those factors, we integrated a prevention program into his ongoing S&C training.

Before clearing the athlete to return to competitive running, the medical team evaluated knee flexion and adduction force capacity, as well as trunk and calf endurance. Meanwhile, the performance team carried out additional tests, including Nordbord assessments, squat jumps, drop jumps, and reactive strength index (RSI) measurements. He showed no objective deficits in side-to-side comparisons nor against athletic normative values.

The athlete successfully returned to competitive sprinting and has remained injury-free throughout the latest season. He continues to complete his track based sessions, now training five times per fortnight instead of three times per week. His gym based program remains a key component of his routine, incorporating regular calf, hamstring, adductor, and trunk exercises for ongoing maintenance.

Recurrent injuries are one of the most challenging aspects of high performance sport. It’s easy to second guess your knowledge and management strategies, reverting to familiar approaches rather than adapting to new insights. However, being a skilled practitioner requires the confidence to pause, reflect, and reassess an athlete’s condition with fresh eyes, while also collaborating with the wider medical and performance team.

No athlete enjoys being sidelined, especially when dealing with recurring injuries.

While an extended rehabilitation period may seem frustrating in the short term, it often leads to better long term outcomes and a reduced risk of future injuries. By thoroughly reviewing an athlete’s medical history, critically evaluating past rehabilitation strategies (including your own), and developing a deep understanding of the physical demands of their sport, you can significantly improve the chances of a successful and lasting recovery.