This article is about rehabilitation a muscle strain to the hamstring, although the principles could be applied to many other muscle injuries. An injury to the hamstring is now one of the most common injuries in sports, especially where acceleration and deceleration is required, such as football and sprinting. They can often cause a long absence from sporting activity, and the first month after injury there is the highest risk of re-injury, so ensuring the injury is properly rehabilitated before return to sport is crucial.
The hamstring muscle group are three muscles which run down the posterior upper part of the leg. They are the Biceps Femoris, Semimembranosus and semitendinosus (see Image below).
Severity of Muscle Strains
Muscle strains can be graded between 1 and 3, from a mild strain (Grade 1) where around 5% of the fibres are torn, a Grade 2 where between 5-50% of the fibres are torn, to a Grade 3 which can be a complete rupture of the musculotendinous junction (where the tendons attach near the bone) or an avulsion fracture (where bone fragment is pulled away from its main body by soft tissue). There would typically result in severe pain and complete loss of function in terms of being unable to bend your knee.
A return to sport is possible within 16 weeks of a Grade 2 or Grade 3 strain, although is dependent on many factors, such as site of injury and amount of tissue damage. A serious strain, avulsion fracture or tear to the musculotendinous junction could be much longer i.e. between 3-12 months.
Things to Think About
In terms of rehabilitation generally, you need to think about the following factors:
- Specificity of the muscle, what it does and how we can target it in our exercise selection. For the hamstrings, it is a stabilising muscle for the hip when the trunk is flexed or walking, but also assists with hip extension (moving the leg back when walking) and is the primary mover for knee flexion (bending the knee). However, you also need to consider what your sport or job is. If you are a sprinter, you may have different requirements from the hamstring than a long distance runner, for example.
- The architecture of the muscle – the Biceps Femoris has pennate muscle fibres (slanted), which offers more limb stiffness and resistance to motion, and the belly of the muscle is fusiform, where the fibres run parallel to the direction of motion of the limb, so it can assist with limb motion. Whilst the Biceps Femoris contains fusiform fibres to produce limb motion in the main belly, some of the fibres have been shown to be bipennate where they attach at a slant on both sides of the tendon which inserts to the bone at the top of leg (called the ischial tuberosity).
- Whether the muscle fibres are ‘slow twitch’, which means they are used as postural muscles for the skeleton, so they are slow to fatigue and prone to shortening, or ‘fast twitch’, which means they are used for movement of the skeleton and are prone to lengthening. Whilst the Biceps Femoris muscle and the hamstrings as a group do both, they are primarily postural, slow twitch fibres and therefore prone to shortening.
- The length of the free tendon (the tendon that is not attached to the muscle at the musculotendinous junction i.e. near the top of the leg). The longer the free tendon, the greater energy storage and release is inferred. The hamstring is said to have a relatively long free tendon.
- The recovery from an injury is not uniform and will be influenced by a multitude of intrinsic and extrinsic factors such as age, previous history, strength, flexibility and rehabilitation and training program.
- Muscles have a high level of plasticity so can strengthen or weaken very quickly. It is important you continue to exercise other muscles of the body whilst the injured muscle/limb is immobilised.
- However, time for adaptation must be allowed and you must not move too quickly by over stressing the tolerance of the muscle and allow it to regress.
- Apply the FITT principle (Frequency, Intensity, Time and Type) when rehabilitating the muscle.
- If an exercise causes pain after, you can regress the exercises so as to not cause re-injury. Conversely, if the exercises are too easy, you must not underload the muscle, and look to progress quicker using progressive overload.
The Rehabilitation Process
The rehabilitation stage can be broken down into three stages, which are the Acute Phase (0-72 hours after injury), Sub-Acute Phase (72 hours to 21 days), and the Post Acute Phase (21 Days +), although ideally you would need to progress these stages based on the individual – these are just guidelines.
Acute Phase
Around 2 days post injury, or when you can tolerate it (e.g. without causing too much pain so as to prolong or affect the inflammatory response and repair process), you can begin very low loads to minimise muscle wasting and neuromuscular regression. For the hamstring, this can be applying an isometric load (contracting the muscle at a constant tension without any movement) in a mid range joint position and open chain positions (so in positions that are not fully weight bearing and with gravity eliminated).
Gentle stretching and mobility movement can also be used whilst sitting down to assist proprioceptive control and increase range of movement of affected joints.
We can use “exit criteria” to be able to progress the next stage of rehabilitation. So, once isometric loading and gentle mobility exercises can be performed pain free, without morning stiffness and irritability and you can stretch the hip and flex the knee to 75% compared to your good side, then you can progress to the next stage of rehabilitation.
Sub-Acute Phase
Assuming you can walk and weight bear on the injured limb without pain, you could progress to some closed chain (closed chain is where your feet remain fixed to the ground or an object, rather than moving freely) and eccentric loading exercises (eccentric means to lengthen the muscle). For example, such eccentric movements could involve straightening the knee in a seated position, supported Nordic hamstring curls or bridges with a towel or swiss ball). This may be after 4 days, but could be later (i.e. one week), dependant on how you respond to the initial exercises.
Eccentric and closed chain exercises assist with proprioceptive activity in joints and tendons (to mimic every day and sporting activity) and to assist with posture and stabilisation.
Eccentric loading (remember – where the muscles lengthens) is key to rehabilitating a hamstring injury given strains occur most often as the hamstring is working eccentrically to decelerate the femur and knee in the swing phase of walking, and has been consistently highlighted as a key component of successful muscle rehabilitation (Eccentric Muscle Contractions; Journal of Orthopaedics and Sports Physical Therapy; LaStayo et al).
Walking/running should be commenced as soon as possible after the acute phase, starting with a steady walk (perhaps on a treadmill) of up to 5-10 minutes, and progressing speed and distance once there has been shown to be minimal after pain or delayed onset muscle soreness (DOMS).
Incorporating core exercises to ensure lumbo-pelvic control has been shown to reduce recurrence of hamstring injuries (Sherry and Best; 2004).
It is also important to incorporate open chain (e.g. where the foot moves freely without being fixed to the floor or an object) eccentric loading exercise (to assist with ballistic movement of the leg and recruitment of specific hamstring muscles). For example, a knee extension machine could be used in the gym (which will also work the quad) or a rowing machine or, if you do not go to the gym, you could use a resistance band or kettlebell on your foot whilst seated. A rowing machine could also help to maintain some cardiovascular fitness.
Perhaps to confuse matters further, you must also not forget to integrate concentric (concentric means muscle shortening, such as when you bend your knee, the hamstring shortens in length) exercises in open chain positions. For example, a seated leg curl machine for knee flexion could be used in the gym or, if you do not go to the gym, you could lie on your front, and with one end of a resistance band around your ankle and the other affixed around a table or post, bend your knee and bring your foot towards your bum.
For frequency and volume of exercises and working to develop strength, repetitions of 6 or less are recommended for sets of 2-6. In terms of frequency, the aim is to allow sufficient recovery for adaptation to occur. For non-regular athletes, this may include a rest day in between exercises (so 3-4 days per week), whereas if you are an athlete recovering from a hamstring strain, you may do specific hamstring exercises for 2 days, with a rest day and then a further two days of exercises (so 5-6 days per week).
Exercises should be undertaken with pain thresholds at no more than 3 to 4 out of 10, and should be carried out slow and controlled. However, everyone is individual and you should monitor your progress with subjective scoring as to tolerance by using soreness and fatigue as markers – if you are very sore the next day, then perhaps dial down the load or repetitions, but if you have very little fatigue or soreness, then perhaps you need to dial it up.
Post Acute Phase
Assuming you have responded well to rehabilitation so far, you can begin to think about building endurance, power, motor learning and functional activities to mimic your sporting activity or job. The hamstring has both a postural (meaning it is used to hold your skeleton upright and in place) and phasic (meaning it is also used to move your skeleton) construction and this needs to be considered – remember the ‘slow’ and ‘fast’ twitch fibres discussed earlier.
The previous strength exercises should be continued into this phase of the program, building your endurance. For frequency and volume of exercises and working to develop endurance, repetitions of over 12 reps but fewer sets (2-3). I would also recommend to increase the speed at which you perform the movements.
However, you will now need to include multi directional movements, plyometrics (not suitable if lower back pain or arthritis), acceleration and deceleration drills and any sport/activity specific exercises. The exercises should be progressive, say once the exercises can be performed without fatigue and soreness, the number of sets can be progressed.
Return to Activity
The exit criteria to be used to start thinking about return to training in your specific sport or activity should be that:
- There is no reaction to rehabilitation;
- You have full pain free range of movement of the hip and knee;
- You have pain free strength to over 85% in comparison to contralateral leg (a dynamometer could be used to assess peak force of the hamstring and quad);
- You have been able to engage in sport specific tasks at a lower velocity (e.g. a footballer can run, control and kick the ball).
To allow return to competitive sport, you should be able to complete a training session with match/event intensity, have over 90% limb symmetry in strength, power and capacity and you should feel confident in taking part.
If you need any assistance with a rehabilitation program, exercises or treatment then please contact David at david@myhealthandharmony.uk or on 01535 410510.