Today we return to discuss mid- to late-stage management of hamstring strain injuries (HSI). In previous posts we have reviewed the examination and early-stage care.
During the examination we work to determine the grade of injury, current functional status and activity tolerance, and a few other low hanging fruits to guide rehabilitation. During the early-stage we look to reduce symptoms, initiate a progressive loading program for the hamstrings, and begin progressing activity level according to pain threshold.
From a healing standpoint, this should take us from the acute inflammatory phase (first week or so following injury), through the proliferative phase, and into the tissue remodeling phase (>3 weeks). The length of these phases is somewhat proportional to the degree of injury, and we should expect they may take longer in higher grade injuries.
The primary goals of mid- to late stage rehab for HSI are:
- Progress the intensity of loading (including eccentric training)
- Reintroduce patterns of movement at progressive intensities according to pain threshold
- Mitigate the risk of reinjury
As established in the early-stage rehab post, a key component of a successful HSI rehabilitation will include progressive loading that includes eccentric training. While this process likely begins with graded isometrics and hip dominant movements, evidence supports (level II and a recommendation grade of ‘B’)[1] adding eccentric training to a conventional rehabilitation program to significantly reduce RTP times and reduce re-injury rates.
The Nordic Hamstring Exercise (NHE) gets significant shine on the subject of HSI and eccentric training. A study by Dyke et al.[2] found that the NHE reduced the incidence of HSI by 51%. Another study by Goode et al.[3] found that the efficacy of the NHE program and prevention of HSI was dependent on compliance and achieving appropriate dosage. An example NHE loading progression can be found below:
If the efficacy of reducing HSI is dependent on effective dosing, what is the correct dosing? The answer to this question depends on the intensity of loading. Higher intensity bouts of loading require greater recovery. Lower intensity bouts of loading require less recovery.
I’m not aware of any research quantifying the force of contraction for these NHE progressions. I think it’s safe to assume that the intensity is lowest with isometrics, and highest with full completion of the movement through the concentric phase. Do your best to quantify with RPE or perceived intensity/effort and make educated judgements on dosage.
Additionally, unless the athlete has access to a gym or strength/conditioning setting that enables them to perform NHE variations regularly it is unlikely they will be able to complete the desired exercise prescription. In these cases, it is critical that you as the clinician are taking time to provide an effective home program with adequate lateralizations and alternatives to these exercises. See below for an example hamstring loading program that could be prescribed to an athlete in the mid- to late-stages of rehabilitation.
| Frequency | Dosage | Purpose/Goal | Example Exercises | |
| Isometric | 1x/day | Accumulate 30-45+ seconds of work for 2-3 sets (e.g. 2 sets of 5 reps of 10s holds or 3 sets of 30s holds) | Reduce sensitivity to load (analgesic effect) | NHE isometric, single/double leg elevated bridge isometric |
| Eccentric | Every other day | 2-3 sets of 12-15 reps to begin, may reduce reps as intensity increases | Intro higher intensity loads through a ROM, increase time under tension (TUT), increase control with deceleration | Bridge eccentrics with sliders, NHE eccentric phase only, GHD variations |
| Concentric/Tempo | Every 3-4 days | 3-4 sets of 6-12 repetitions | Maximize strength/capacity and TUT | Hamstring curls on tempo, GHD and NHE variations w/ assistance as necessary |
| Elastic Loading | Every 1-3 days depending on activity | Variable and related to intensity/type of activity | Replicate and reintroduce the demands of sport specific tasks | Running and sprint progressions, kicking progression |
| Plyometric | Every 3-4 days | 3-5 sets of 3-5 reps accumulating total repetitions between 60-100+ depending on training age with various movements | Increase maximal power, enhance neuromuscular drive | Bounding, hopping, and jumping variations |
Each of these progressions may be introduced on a session by session basis as pain threshold allows. Athletes with a lower grade injury may tolerate a quicker progression than those with higher grade injuries however progressions will take place on an individual basis.
Continuing the Activity Progression:
As the athlete moves into the mid-stage of HSI rehabilitation, a primary goal is to reintroduce the required locomotive patterns (multi-directional movement patterns like jogging/running, shuffling, cross over stepping etc.) at progressive intensities according to their pain threshold. Current functional status is determined at initial evaluation (or within the first few sessions) by performing an activity progression as outlined by Hickey et al. [SOURCE].
During early-stage rehabilitation, locomotive activities may include ambulatory and marching patterns. As symptoms allow locomotive activities transition into linear jogging or running at 70% perceived effort. This is a natural point to begin introducing other directions or patterns of movement (mentioned above) as well as skipping. Skipping allows the clinician to begin turning the dial to enhance force production/absorption (traditional skipping performed for height, length, or both) and begin patterning sprint mechanics (A- and B-skipping variations).
Change of direction and agility tasks may be introduced according to a similar progression as athletes demonstrate appropriate tolerance for various multi-directional patterns of movement. Given that COD activities require athletes to move through both acceleration and deceleration I’d recommend ensuring these activities are largely pain-free when initiating. This is similar to the recommendation by Hickey et al.[4] in establishing the athlete’s current functional status.
From a sport specific conditioning perspective, clinicians should bear in mind a work:rest ratio to maintain/gain conditioning specific to the athlete’s sport. For example, I may choose a work:rest ratio of 1:3-5 for a soccer athlete as this biases toward glycolytic energy systems and the repeat higher intensity bouts of work experienced by field athletes. This becomes critical as the athlete transitions into end-stage rehabilitation where the primary goal is preparing them for full RTS demands.
Progressing intensity to build toward full effort occurs by using perceived intensity or work (RPE). If time allows, clinicians may proceed over predetermined time periods (i.e. this session 70%, next session 90%, and the following 100%) as symptom threshold allows. This may also occur within sessions according to symptom threshold in those cases with rapidly improving status. In determining when to progress activity and intensity, the main thing is the clinician has consideration for overall volume spent at each progression. This is important in the context of establishing a sufficient chronic workload to buffer against injury/re-injury and support the RTS process.
Mitigate the Risk of Re-Injury:
Clinicians can use a simple checklist to ensure athletes are adequately prepared to return to sport. Just as benchmarks like the AKE test and mapping the area of tenderness may be used as exit criteria to enter the mid-stage of rehabilitation, normalizing isometric hamstring strength, single leg bridge testing, and appropriately completing an activity progression are exit criteria to enter the late stage of rehab and help guard against returning to sport too soon. These were reviewed in greater detail in the first installment of this series.
In addition to these tests, I like to implement the Askling H-Test as part of RTS decision making criteria. Two studies included in Hickey et al.’s review implemented this test and found mean RTP times of 36 and 63 days with respective reinjury rates of 1.3% and 3.6% (the lowest reported in their study).[4] The test is quick to administer and provides some insight into apprehension related to ballistic hamstring movements. Check out the figure below detailing the protocol for the Askling H Test.
| Askling H Test The subject lies in a supine position with both legs outstretched.The clinician stabilizes the uninvolved leg with both hands.The subject is instructed to perform a ballistic Active Straight Leg Raise x10 reps for speed and height on the involved leg. Repeat on the uninvolved side.The clinician assesses: whether pain is present, gross symmetry of height, and overall willingness to complete the test. |
Check out the sample RTS checklist below. This battery of tests is not comprehensive in nature but does provide a simple guide to assist in clinical decision making.
| Hamstring Strain Injury Return to Sport Test Battery Isometric Hamstring Testing (mid- and outer-range testing positions): <10% asymmetry between sidesHamstring Bridge Endurance Test: <10% asymmetry between sidesNegative Askling H-Test Ability to complete repeat sprinting without pain (sport dependent) Completion of a sport specific return to play progression (see below)The athlete is performing at a level similar to before injury based on fitness or conditioning benchmarks. |
In addition to a testing battery, clinicians must have consideration for other risk factors in determining RTP timelines. Risk factors for HSI include a prior hamstring strain injury, increased age (>23 yo), athletes required to perform high speed running bouts (can be position specific), and prior injury to the same leg or opposite leg. Risk factors such as these may affect RTP time. Clinicians should also have consideration for the grade of injury in determining timeline.
Passing a RTS testing battery does not guarantee an athlete will not reinjure. Failing a RTS testing battery does not guarantee reinjury. However, if we view a RTS checklist as a report card, we’ll find that we are consistently working toward lower levels of risk of reinjury/subsequent injury.
Given the ambiguity of the previous statements. Clinicians must also consider how conditioning levels and graded exposure may help guard against future injury. This brings me to the next consideration of successful RTS. The acute to chronic workload ratio.
Using Chronic Workload as a Buffer Against Reinjury:
The acute to chronic workload ratio is a measure of risk that weighs the volume of acute workload during a given time period against the buffer of the trailing chronic workload. The basic premise is that higher acute to chronic workloads indicate greater risk of injury. Lower ratios may be indicative of ineffective programming or strategic deloading. Research has shown that higher chronic workloads are protective against future injury (with the caveat that they do make the athlete more sensitive to extreme spikes in acute workload). Much of the research conducted on this subject involves tracking a measure of load (often distance covered in practice in games via gps) over time. The principles can be applied to other measures of load like total weight lifted as well.
It isn’t practical for a clinician in the clinical setting to track every measure of load for a field athlete. However, understanding how the ratio works and the implications of time-loss injuries on injury risk is critical. Appreciate that the longer an injured athlete is out, the more time they may need to spend in the rehab or strength and conditioning settings to accumulate a chronic workload to buffer against reinjury upon RTS.
Maintaining some form of training and practice involvement through the mid- and later-stage rehabilitation may lessen the time to achieve an adequate chronic workload. For example, a basketball athlete has demonstrated an ability to perform anticipatory COD drills and light plyometrics pain-free in the clinic. A clinician could release the athlete to perform warm ups, non-contact shooting and dribbling drills, and offensive walkthroughs with guidelines for time/reps, intensity, and acceptable symptom level at practice. This increases athlete buy-in, keeps them involved in the team setting, and allows them to maintain their athletic identity.
Setting a specific timeline for RTS once appropriate is another way to make load measurable. This may follow the below pattern for field/court athletes:
| Non-contact Offensive Drills |
| Non-contact Defensive Drills |
| Controlled Contact Drills |
| Time-limited Scrimmaging |
| Unrestricted Scrimmaging |
| Time-limited Gameplay |
| Unrestricted Gameplay |
The speed with which an athlete progresses through these stages is dependent on how much time is lost to training, the degree of urgency to return to competitive gameplay, and other clinical findings (degree of injury, other risk factors, clinical exam).
Drilling Competencies and Enhancing Movement Efficiency:
The final piece of the mid- to late stage rehabilitation involves addressing other “modifiable risk factors”. I’ve placed this in quotations due to there being limited high quality evidence for these considerations and that they are a part of a larger and more detailed conversation on the subject of motor learning and coaching which is beyond the scope of this series.
A few things I like to ensure I am screening for are balance/trunk control, the athlete’s ability to achieve active and passive hip extension (on both the involved and uninvolved limb), running mechanics and over-striding, and the ability to adequately access positions of force absorption/production.
I’ve included this last, as I view these drills and interventions as either the appetizer, side dish, or desert to the main course of progressive overload addressing benchmarks and preparing the athlete for the demands of their sport. These activities and drills may be included as part of a warm up, HEP, or cool-down with cueing as needed to achieve the desired performance. It is important to understand that movement occurs on a continuum and that athletes will select an individual movement solution based on prior experience, environmental and coaching constraints, and more.
Example Session for Mid- to Late-stage Rehabilitation:
| Phase of Session | Examples | Goals |
| General Warm Up (as time allows) (5-10 min) | Foam rolling, general dynamic mobility, low-intensity aerobic activity | Increase heart rate, body and muscle temperature, prepare body for needed ROMs |
| Specific Warm Up (5-10 min) | Progressive intensity locomotives, skipping, pose running/exchanges at wall, drills emphasizing foot strike | Activate and prepare the body for the main course of training, address common movement inefficiencies |
| Sport Specific Activities (10-20 min) | Change of direction drills and plyometrics with consideration for work:rest intervals relevant to the athlete’s sport | Expose the athlete to demands of support, enhance neuromuscular drive |
| Conditioning (10-15 min) | Sprint or running progression | Prepare the athlete for demands of sport |
| Loading Progression (10-20 min) | Eccentrics and progressive loading | Build strength/capacity of the hamstring as part of a comprehensive rehabilitation program. |
| Cool Down/Recovery (10-15 minutes) | Mobility, low intensity aerobic activity, structured cool down, modalities (e-stim or vasopneumatic devices) | Reduce sympathetic response by activating parasympathetic system, modulate pain/soreness as needed |
Conclusion:
The goal for this series was to highlight the recent hamstring strain injury CPG by the APTA; and to make it more digestible by putting it into practical terms for clinicians. I did my best to not only effectively represent the evidence, but to also add some of my expertise that I have found helpful in managing these injuries. My hope upon finishing reading this three-part series is that you feel more confident in evaluating, initiating a plan of care, establishing benchmarks, and assisting an athlete with a HSI through a successful RTS.
Citations:
[1] Martin, R. L., Cibulka, M. T., Bolgla, L. A., Koc, T. A., Loudon, J. K., Manske, R. C., Weiss, L., Christoforetti, J. J., & Heiderscheit, B. C. (2022). Hamstring strain injury in athletes. Journal of Orthopaedic & Sports Physical Therapy, 52(3). https://doi.org/10.2519/jospt.2022.0301
[2] van Dyk N, Behan FP, Whiteley R. Including the Nordic hamstring exercise in injury prevention programmes halves the rate of hamstring injuries: a systematic review and meta-analysis of 8459 athletes. Br J Sports Med. 2019;53:1362-1370. https://doi.org/10.1136/bjsports-2018-100045
[3] Goode AP, Reiman MP,HarrisL,et al. Eccentric Training For Prevention Of hamstring injuries may depend on intervention compliance: a systematic review and meta-analysis. Br J Sports Med. 2015;49:349-356. https://doi. org/10.1136/bjsports-2014-093466 [4] Hickey, J. T., Timmins, R. G., Maniar, N., Rio, E., Hickey, P. F., Pitcher, C. A., Williams, M. D., & Opar, D. A. (2019). Pain-free versus pain-threshold rehabilitation following acute hamstring strain injury: A randomized controlled trial. Journal of Orthopaedic & Sports Physical Therapy, 1–35. https://doi.org/10.2519/jospt.2019.8895
