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)
Accelerated
rehab programs for Hamstrings (progress to next level when pain free at
previous stage
Start gentle stretching after
initial rest of 24-48hf
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%
Stage10 - 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
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| Eccenteric loading of Hamstring |
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| Hamstring Curl |