If you work long enough in this field you will eventually run into a hamstring injury (HSI). Practitioners involved in the reconditioning process have to understand the intricacies of the hamstrings. A quick review of anatomy: the bicep femoris (BF) long and short head are the lateral hamstrings, and are the major drivers in hip extension and externally rotating the leg. The medial hamstrings are the semitendinosus (ST) and semimembranosus (SM), which drive knee flexion and internal rotation.
61% of HSIs occur during sprinting, particularly during late swing and early stance phase. 30% are during open chain activities such as kicking, and 13% during closed chain activities such as landing or cutting [1].
As the overlap in numbers suggests, more often than not these injuries occur during a combination of these activities. The sport and constraints provide context about the mechanism, which gives us insight into how to address the reconditioning process.
The most commonly injured muscle is the BF long head (79.6%), followed by the semimembranosus (13.4%), semitendinosus (8.6%) and BF short head (1.1%) [2]. The prevalence by location of the injury along the muscle length is nearly evenly split between proximal, medial and distal; and the location of the injury does not significantly impact the time until return to play.
HSIs are categorized grade 1 through 3. Grade 1 is characterized by a micro tear, slight pain with stretching, and minimal strength loss. This accounts for 70% of HSIs, with a layoff of 17 + 10 days. Grade 2 injuries are characterized by moderate tearing of the muscle fibers, intense pain with stretching, minimal edema, and significant weakness. These are 23% of all HSIs and have a layoff of 22 + 11 days.
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Grade 3 are the most severe: a complete tear of muscle or tendon, possible mass or depression of tear site, no ability to load leg, and significant edema. Only 3% of HSIs are grade 3, and the layoff is 73 + 60 days [1].
Understanding the details of the injury help us create a road map for an effective return, guiding exercise selection to movements that bias each specific muscle. Just like we do with sport, we can reverse engineer the HSI to design reconditioning protocols. For example, a Nordic will bias the ST much more than an RDL, for example [5]. If the injury is more proximal, we would focus on more hip dominant strategies, or conversely, more knee dominant work for a more distal injury [4].
Athletes are significantly more likely to suffer an HSI late in the game [3]. This could mean that the athlete has a capacity issue, leading us to focus on more endurance qualities. Or it could be related to high speed exposure. In that case, we would assess the athlete’s movement strategy.
Cause and effect: Sprinting in hamstring injuries and rehab
I divide hamstring reconditioning into two progressions: sprinting and isolated rehab. The sprint progression is the focal point of the reconditioning process. The isolated rehab is vital but ancillary.
Sprinting increases bicep femoris fascicle length more than eccentric training alone [7]. Returning to running has always been a key landmark in reconditioning, but it often entails jogging on an AlterG, in the pool, or on dry land. This is counterintuitive to the athlete’s health and performance.
Hamstring activity during jogging does not mimic the activity during sprinting [6]. Jogging promotes poor posture and is not intense enough to drive adaptation, but it’s just enough work to delay recovery. Therefore, sprinting should be the primary mode of activity when working back from HSI.
Sprinting is the most taxing central and peripheral activity an athlete can do. It is often a part of why HSIs occur in the first place, which is why it can be a vaccine when done correctly.
A sprint based model will have much higher transfer to specific tissue prep, magnitude, and rate of force development than a general rehabilitation program. If our job is to recondition the athlete to return to their sport, it only makes sense to use the most intense mode of activity as the primary gauge for return.
This model progresses short to long, slow to fast, and linear to multi-directional. The intra-session progression moves from the warm up, to technical, to stimulus, and then physical work.
The warm up consists of general movement, mobility, pillar prep, and then locomotive drills that bleed into our technical portion. The warm up is the catalyst for the rest of the session, but can be difficult based on severity of injury. Be careful to not over stretch the injury site, as this will cause undue harm especially early on in the healing process.
This is also where we will begin re-teaching some of the fundamentals of sprinting. Lumbo-pelvic control (LPC) is a risk factor in sprinting, and interventions can help mitigate some of these risks [6]. Injury is an opportunity to refine details that may otherwise be hard to address in the team setting, so take the time during the warm up to address LPC.
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The technical portion is a series of low level drills to assess the athlete, identify what they are capable of that day, and begin building sprint specific physical qualities. The stimulus is the sprint progression itself, as it is the most taxing portion of the session. During the physical section, we progress to any isolated rehab or general strengthening exercises.
All reconditioning stays below a 4 on a pain scale of 0-10. Crossing this threshold when starting training or a new progression tells you that the intensity is too high and you need to regress. If the athlete is in the normal range to begin and then crosses this threshold as training goes on, they have reached their capacity for that session, and we need to move on or end the session.
As a general rule of thumb, we should never see a three point jump over the course of a reconditioning session.
The sprint drills are broken up into gear 1 (ankle), gear 2 (shin), and gear 3 (knee). By progressing from the ankle to the knee we can control the amount of hip flexion, and therefore the amount of stretch, we place on the injury site. Start with slow, methodical drills, such as walking and power marches, before progressing to faster high knee or dribbling variations. Perform 1-4 sets of 1-4 reps, with 10-15 yards per rep.
Sprinting is a hindbrain activity – there shouldn’t be a lot of thought going into it. The slower we move, the more forebrain dominant it becomes, meaning we have more time to think.
These drills are much slower than sprinting and provide an excellent opportunity to coach and re-pattern some of the movements. Take advantage of this time to set the athlete up for success down the road. Prioritize posture, keeping a stacked column, forefoot striking, and a vertical, elastic impulse. In severe cases with long layoffs, a pool can be a great place to start this progression as it reduces load, and the water’s hydrostatic pressure will provide an analgesic effect.
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Every athlete and injury are different, but there are key locomotion landmarks that we can work towards regardless of those factors. All models are incorrect, including mine below, so find your own that you are comfortable coaching and expand from there.
Athletes sequentially increase velocity with every step they take during acceleration. Even the best accelerators in the world can only reach submaximal velocities over 10 yd. Every increase in distance equals an increase in intensity, and hamstring activity significantly changes from submaximal to maximal [6], so begin the progression with 10 yd accelerations and gradually extend the distance once the athlete can tolerate this intensity.
Once the athlete has cleared all benchmarks for return to running and can complete low level drills within our pain limitations, we can progress to our sprint progression. The goal of this progression is to build out sprint capacity within our threshold.
Place cones at a start line, at 10 yd, and at 20 yd. This gives an equal length for acceleration to deceleration. It is important to teach athletes to gradually decelerate over the entire deceleration zone. Abruptly slamming on the breaks can cause microtraumas that can accumulate over time, leading to increased pain and even reinjury.
Record the athlete’s perceived intensity of each rep (0-100%) as well as pain level (0-10). Start the athlete in a two point falling start to give them some momentum into the acceleration. This helps avoid sudden spikes in muscle tension through the hamstring. If they still struggle with the start, move them back five yards from the start line and have them skip or jog into the acceleration, eventually progressing to a static two point start and then various start positions based on their individual needs.
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Resisted sprinting is a great tool to introduce early in the process, as slowing things down may reduce pain and help build some more sprint specific physical qualities.
Change of direction, agility, and curved running are vital to the reconditioning process as we have to expose the hamstrings to different angles and constraints before returning the athlete to play. However, we want to make sure that we do not introduce too many variables into training, especially early in the process. The more variables, the more we have to account for, and the harder it is to determine between what may have caused pain.
Rest times are an important variable that we can manipulate for our desired effect. The most general rule of thumb for sprinting is to rest one minute for every 10 yd of sprinting. If the goal is high output, this is a great starting point. However, if the goal is to increase work capacity we can shorten this time.
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A good starting point is one set of eight reps of 10 yds at 65% intensity. If they cannot do this at < 4 / 10 pain, they are probably not quite ready to return to running and will remain with drilling.
Guide the athlete to run at a pace they are comfortable with and slowly progress as tolerated. Intensity may be stagnant as the body heals. We can still continue to increase volume and complexity as long as they don’t exacerbate symptoms. By building through volume, we can increase tissue capacity and load tolerance. This is great for athletes returning to in season demands, as they use rehab to build up a substantial tolerance to high speed distance and repeat efforts.
Determining the right amount of volume goes back to reverse engineering the injury and the sport. For example, the forwards on the soccer team I train average roughly 400 yd of high speed distance during MD-3 training sessions. This becomes a benchmark for volume we can build towards. Once the athlete has a reasonable pain free competency with short accelerations, we can adjust the volume.
Some situations may call for intensity to be the primary gauge for reconditioning. For example, a college sprinter sprints 200m per session throughout the week in training. We can approach this volume by building to it through short accelerations. Once the athlete shows they can tolerate the distance, we can then gradually increase intensity. We can then decrease our volume while increasing the intensity until we expose them to their peak velocity.
Strength work is a necessary piece of hamstring rehab
We have to make sure we are blending the sprint progression with the isolated rehab. Too often in the performance environment, the two progressions get divvied up between the performance team and the sports medicine team, with little or no communication. This causes poorly organized training that could put the athlete at increased risk of reinjury. Instead, we need to marry the two stimuli to create enough stress for adaptation while simultaneously leaving time and energy for recovery.
As with the speed progression, we will track pain and keep it < 4 / 10, but over the course of each set as opposed to reps.
The primary functions of the hamstrings are to extend the hip and flex the knee, so we will use these movements for our progression. Every athlete will progress through these movements differently. A more proximal HSI will tolerate knee flexion exercises better than hip dominant ones, and vice versa for an athlete with a more distal HSI. Training both joint movements ensures we stress the injured hamstring muscles to varying extents.
Athletes will progress through each stage separately. It is normal for an athlete to be multiple steps ahead in one progression while stagnant on the other. For example, a grade 2 proximal hamstring may only be able to tolerate long lever isometrics, but can still perform eccentric Nordics.
The most important things are to identify what we can load, and then load it. The isolated rehab will progress from extensive isometrics to moderate intensity, to high intensity, and then, if needed, rate dependent work.
The extensive isometrics consist of short and long lever isometrics. I typically start with yielding isometrics, but in some extreme cases we may need to start with overcoming isometrics where the athlete drives into the ground at 25-50% MVIC for 1-3 sets of 20-30 seconds.
Starting with short lever positions avoids over stretching the injury site. The progression starts with double leg variations so the athlete can shift as much weight onto their good leg as needed. They progress to single leg variations and then finally loaded single leg variations. Through all stages, by going from double leg to single leg, we necessarily double the amount of load going through each leg. We also can begin to isolate the injured leg and use it as a gauge for progression.
Athletes can perform extensive isometrics every day, as they cause very little fatigue and structural damage.
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Once the athlete tolerates the extensive isometrics, start the moderate intensity exercises as soon as possible. This includes eccentric only slider leg curls and back extensions, each with 5 second eccentric contractions.
Eccentric contractions increase angle of peak torque, fascicle length, hypertrophy, and knee flexor strength [5]. Structural adaptations show up as quickly as two weeks, making it imperative to progress to these as soon as the athlete is ready [8]. A standard scheme is 1-3 sets of 6-12 reps, mirroring the progression of the previous stage from double leg to single leg to single leg loaded.
These moderate intensity exercises are sufficiently intense to cause muscular damage leading to DOMS and stiffness that could impede with our speed progression. To ensure recovery between exposures, perform them 2-3 times per week with at least one day rest between.
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Progress to more intensive loading variations, including eccentric overloaded Nordics and RDLs. The Nordic progression will start with band assisted, move to unloaded, and then loaded. The RDL progression will start with a single leg contralateral RDL, followed by kickstand variations, and finally bilateral. Athletes perform 1-3 sets of 3-6 reps with a 5 second eccentric contraction. These intensive variations are very taxing on the body and require significant amounts of recovery, e.g., twice per week with at least 72 hours between exposures.
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The last phase of the isolated rehab is rate dependent progressions. These progressions apply the athlete’s newfound force capabilities to higher rates similar to what they face during sport.
This can consist of banded oscillatory work, drops, switches, catches, and various sprinting drills. Normally, by the time an athlete is ready for this, they will be sprinting at moderate to high intensities, which could eliminate the need for this phase. However, stakeholders may disagree and you may not be the one who oversees the athlete’s clearance to return to run. When the athlete is prepared for high rate loading but has not been cleared for high speed sprinting, these rate dependent variations are useful tool to bridge that gap.
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Balancing the intensity and volume of the progressions is key. The lower the intensity, the more frequently they can do them. The higher the intensity, the more time for recovery they need.
This may seem counterintuitive, as generally when athletes progress the propensity is to increase the amount of work they are doing. But that approach can lead to excessive amounts of junk volume that impedes recovery and prevents athletes from pushing hard enough to actually improve. Excess volume robs the athlete’s energy resources that should be allocated towards healing.
Milestones for return to play from hamstring injury
Phase 1 starts as soon as the injury occurs. Phase 1 can also be known as the inflammatory phase, and lasts up to eight days, depending on the severity of the injury.
It starts with evaluation and the diagnosis: What is the injury exactly? What was the mechanism? Does this athlete have a history of HSIs? Take in as much of this information as possible and use it to formulate a plan.
This should ideally involve all parts of the performance team: nutrition, psychology, sports medicine, sport coaches, sport science and performance. Most coaches do not have access to these resources, so it is important to find ways to fill these buckets for a holistic recovery. Continue to train to the extent possible and provide passive treatments for the affected hamstring.
The exit criteria for Phase 1 are a normalized walking gate, > 4/10 pain during extensive isometrics, and manageable swelling.
Phase 2 is where the athlete will spend the bulk of the reconditioning process, and where we formally begin our speed and isolated rehab progression.
The athlete will continue to train the available qualities, but nothing on the affected limb.
The exit criteria for Phase 2 are < 10% hamstring ROM asymmetry, including both passive and active 90/90 hamstring stretch and a straight leg raise; and hamstring strength asymmetry of < 10% (measured with force plates) on a knee flexion isometric and a hip extension isometric. They must tolerate intensive loading and a proficiency in linear sprinting.
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Phase 3 is the systematic return to training. This must be in accordance with a documented plan that all relevant parties agreed to ahead of time.
Phase 3 works from small spaces to large, closed drills to open, and a progressive workload of 50% to 75% to 100% of the team’s regular training. As the athlete progresses back into the standard training, it is important that we continue to fill any empty buckets.
The exit criteria for Phase 3 are maintaining all previous benchmarks, no pain with any activity, tolerating the loading demands of sport, and a clearance from the medical staff.
Original post can be found here https://www.sportsmith.co/articles/dual-track-hamstring-injury-rehab-sprinting-and-strength-training-progressions/
