Tight hamstring muscles require regular stretching. There are numerous ways to stretch the hamstring muscles. We explain the more common hamstring stretching exercises and why they work.
Assessing hamstring flexibility
The athlete lies on their back and relaxes. The therapist gently lifts a relaxed, straight leg up until the athlete indicates it is uncomfortable to go further. The therapist should notice an increased resistance even before the athlete feels a stretch. The athlete will then feel the stretch beginning and eventually can go no further. Ideally the leg should go vertically upwards without pain for good flexibility. The image opposite shows a 90 degree range of motion which is considered good. Below 80 degrees is considered tight.
Why does it work?
When you initiate the stretch, signals from muscle spindles go to the spine which sends back signals to contract the muscle or resist the stretch. After 6 seconds or so the golgi tendon organs send signals overriding the signals from the muscle spindles enabling the muscle to relax into the stretch.
Static stretch seated
Sit with on the floor with the leg to be stretched out straight and the other bent out of the way. Rotate the straight leg inwards and lean forward at the hips to feel a stretch under the thigh. Hold stretch for 30 seconds. Repeat the stretch throughout the day at least 5 times. This stretch can also be repeated with the foot turned outwards.
Standing hamstring stretch
Stand with the leg to be stretched just in front of the other one. Bend the back knee and lean forwards from the hips. Place your hands on the bent leg's thigh, to balance yourself. If you can't feel a stretch, lean further forwards or tilt your pelvis forwards. Hold for 30 seconds. Repeat regularly throughout the day.
Hamstring stretch on the back
Stretching the hamstring muscles by lying on the back and straightening the leg upwards targets the muscle fibers nearer to the knee whereas the sitting hamstring stretch stretches the muscle fiber higher up the muscle nearer the buttocks.
This involves gentle swings of the leg forwards and backwards gradually getting higher and higher each time. Around 10 to 15 swings on each leg should be enough. The stretches can be done early in the morning (be careful not to force it) as this will set the length of muscle spindle for the rest of the day.
Why does it work?
This works by using the properties of muscle spindles. A muscle spindle is a sensor in a muscle that senses amount of stretch and speed of stretch. By gradually taking the leg higher and higher the muscle spindle allows it to go safely and lengthen the muscle. If the muscle is forced then a stretch reflex is initiated which causes a reflex contraction (shortening) of the muscle. This is called ballistic stretching and can damage muscles.
PNF (proprioceptive neuromuscular facilitation)
These are stretching techniques involving the stretch reflex. One type is called CRAC stretching (Contract, Relax, Agonist, Contract). The method is as follows:
Warm up gently either by a short run or lying on your back and pushing a straight leg down 20 times against light resistance. Lie on back and get a partner to lift one leg up gently as far as it will go. Contract - Push against resistance with a straight leg at 25% effort. The resistance must be great enough so that the leg cannot move. Hold for 10 seconds then relax. The athlete then uses the hip flexor muscles (agonists) to pull the leg up as high as they can, keeping it straight and holding this for up to 10 seconds. Repeat the process until no more gains are possible (contract).
Why does it work?
PNF stretching methods make use of the 'stretch reflex' as mentioned in Dynamic stretching. The muscle spindles sense stretch and speed of stretch, golgi tendon organs sense tension in the muscle. When an agonist muscle contracts (quadriceps) there are nerve impulses sent to the hamstrings (antagonist) to relax. (They would have to as if you straightened a bent leg it would not move unless the hamstrings relax). There is also a theory that the muscle becomes stronger in a stretched position so the nervous system can allow it to stretch further without fear of tearing.
Overall program for stretching hamstrings
Dynamic stretching first thing in the morning as this sets the length of the muscle spindles for the rest of the day. Dynamic stretching should also always be done prior to fast, explosive exercise as part of a warm-up
Static stretching - hold for 30 seconds, repeat 5 times, can be done 3-5 times a day. Once in the evening is often enough though to maintain.
PNF / CRAC - this can be done daily but do not over do this as you could tire the muscle out. If in doubt three times a week is ok.
If you continually have problems with tight hamstrings especially if it is only on one side then you might have restricted nerves in the back or piriformis syndrome.