Hamstring injury

Anatomy – Hamstrings are a group of three muscles

Medially Semimembranosus and semitendinosus and

Laterally Biceps femoris, which as a short and long head  

They are known as bi-articular muscles because they cross two joints – the hip and knee, and this gives you a phenomenon known as Lombard’s paradox.

Lombard’s paradox: High knee position during sprinting, Hip extends under pull of hamstrings and Knee extends by pull of Quadriceps.  This is paradoxical since hamstrings shorten in proximal and lengthen distally. This produces tremendous straining forces within hamstrings that have to be resisted or the muscles will tear.

Hamstrings lengthen considerably during sprinting (110% of their resting length in Biceps femoris) and have to cope with considerable forces (again Force the greatest in Biceps Femoris) towards the end of swing phase. Most of the force is generated by Muscle itself but 1/3 from elastic recoil of tendon. Biceps femoris is more prone to injury and worse prognosis.

Risk factors for injury

-       Muscle Fatigue (eg: injuries tend to happen at second half of football season)

-       Lack of Race-fitness (Early season, when athletes are not fit enough yet)

-       Previous Hamstrings injury (usually re-injury at same spot, if no rehab is done properly)

-       Poor flexibility of Hamstrings or quadriceps

Muscles work in 3 ways of contraction; Concentric (shorten during loading), Isometric (same length) and Eccentric (lengthen during loading) loading.  During movement, muscle cycles between concentric and eccentric phases (so-called Stretch-Shortening cycle) If they are weak when lengthening or poor eccentric strength, they are prone to have tear during stretching phase.  For example;

-       Weak at end-range (lack of strength when the muscle is in a lengthened position) – prone to injury

-       Strength imbalance between left and right (prone to injury on weaker side)

-       Dominance of quadriceps strength over hamstrings

-       Subtle back injures – slipped disc, weak core


Prognostic factor in acute injury

-       Time to return to walking without pain (If <24hr, usually good px)

-       Medical hamstrings injury (good prognosis)

-       Distal injury (the more proximal, the worse prognosis)

-       Flexibility and strength immediate after injury SLR/Knee bending (Usually not accurate)

-       Size of injury on an MRI or USS scan (very accurate)

90% of injury improves in first 6 weeks, but it takes about 6 months to heal 100%. Significant risk of re-injury if poorly rehab or return to sport early.

Rehabilitation for Hamstring injury

-       RICE in acute phase for 24 – 48hrs

-       Early stretching and mobilization

-       Early return to brisk walking and jogging

-       Accelerated rehab progressions

-       Eccentric loading – Nordic exercise or hamstring curls

-       Rapid concentric loading (late stage when running 80% or faster)

Eg of Accelerated rehab programs for Hamstrings (progress to next level when pain free at previous stage)

-       Start gentle stretching after initial rest of 24-48hrs

-       Stage1 – Slow walking

-       Stage2 – Brisk walking

-       Stage3 – Jogging (40%)

-       Stage4 – Striding over 100m up to 50% of maximum running speed (10 reps)

-       Stage5 – Striding over 80m up to 60% (8reps)

-       Stage6 – Striding over 70m up to 70% (6reps)

-       Stage7 – Accelerate over 60m up to 80% (6reps)

-       Stage8 – Accelerate over 50m up to 90% (6reps)

-       Stage9 – Full training up to 100%

-       Race fitness

Benefits of eccentric loading

-       Prevents further injury

-       Treats injuries

-       Optimum length of muscle is increased – meaning athlete has more strength at end-range (when muscle is at its most vulnerable)

-       Studies showed that sprinting times are improved with eccentric loading

Eccenteric Hamstring loading

Hamstring Curl

Reference: The good, the bad and the painful by Dr. Leon Creaney