A great excerpt on a variety of stretches and stretching techniques, with some added comments by me for some research background.
Methods of Stretching Hamstrings
Much research has been dedicated to studying the best technique of stretching, optimum frequency, and duration to achieve the best gains in flexibility. The different stretching methods, ballistic stretching, static stretching, pnf stretches, have all been demonstrated as effective in increasing hamstring flexibility.
Many studies on flexibility tend to focus on hamstrings because they are often tight, it is relatively easy to stretch them, and easy to measure range of motion. Studies generally show that even a single stretch is beneficial for improving flexibility although results only last a few minutes. Exercises must be done over the long term to achieve long term results. You can liken stretching the hamstrings to stretching a rubber band. The rubber band will eventually bounce back to its original length unless stretched again. In that way there is a carry over from one hamstring stretch to the next.
Hamstring tightness can be a limiting factor for the optimal performance of particular sports and an intrinsic risk factor for sports injuries. Static stretching has been consistently reported in the literature as an effective tool in preventing injuries related to lack of flexibility. The relative safety of this type of stretching makes it a good one for a healthy general population.
Standing Hamstring Stretch
Floor Hamstring Stretch
Stretching Hamstrings Using PNF Techniques
The PNF techniques use the development of tension in a muscle by contraction to facilitate the relaxation and therefore stretch a muscle. By facilitating the relaxation of muscles we can improve circulation and improve extensibility of myofascial tissues.
PNF (proprioceptive neuromuscular facilitation) uses inhibition techniques to assist relaxation of the muscle being stretched. Contract-relax, hold relax, and contract-relax antagonist-contract are commonly used. Optimal length of contraction used in these techniques has been found to be 3 to 6 seconds.
1. To perform a self PNF stretch (hold-relax) for the hamstring in standing, stand behind a chair and place one heel on the chair. Straighten your elevated leg and relax into the “standing hamstring stretch” Push your heel actively down into the chair to contract the hamstrings and hold this for 3 to 6 seconds. Then relax and gently force yourself further forward. Repeat this 3 or 4 times.
2. To perform a self PNF hamstring stretch (contract-relax antagonist-contract) using a strap to stretch the hamstrings in lying is another very effective method of stretching hamstrings. Lie on your back and loop the strap around the ball of your foot holding the ends of the strap with both hands. Be sure to keep your chin down and shoulders back. Exhale while pushing your heel up toward the ceiling. Hold this stretch for 20 to 30 seconds. Now push down with your heel into the strap toward the floor for 3 to 6 seconds. Then try and straighten your knee and actively push your foot up toward the ceiling contracting your quadriceps. Hold this for 3 to 6 seconds. Relax and hold your stretch for 20 to 30 seconds. You can add dimension to this hamstring stretch by bringing your heel to one side and then the other to target different parts of the hamstrings and posterior leg fascia.
Stretching Hamstrings Using Dynamic Stretching Techniques
Dynamic stretching should be done after the muscle is warmed up and can be done before a workout to improve hamstring flexibility without hindering performance in those sports that require strength and power.
1. The straight leg toe touch is performed in standing. Start with good posture, chest up and shoulders back. Flex your shoulders such that your arms are straight in front of you at 90 degrees. Try to maintain a tall posture throughout this stretch, tighten your abdominals and keep your back straight. Swing your leg forward while straight to try and touch your toes to your fingers. Lower your leg and alternate with the other side.
2. The one-leg bird stretch also requires balance and stability. Start with an upright posture, chest up, shoulders down and relaxed. Lift your straight left leg behind you as you slowly bend forward at the hips and try to touch your toes. You will look like the letter “T” with the leg being stretched being the one planted on the ground. Hold this position for 2 or 3 seconds. Remember to always maintain a neutral spine.
Using the foam roller to stretch hamstrings
To use the foam roller to assist in releasing hamstrings sit on the roller with the roller on the floor as illustrated with the foam roll under the bottom part of your hamstrings. Slowly roll back and forth and side to side working your way up toward the glutes. By bearing weight through one leg at a time you will increase pressure on the one side. Bearing weight through both thighs lightens the pressure.
Although depending on fitness lever, goals, and types of training, all these stretches can be beneficial to improve flexibility, studies have suggested greater efficacy of some methods for achieving muscle elongation after stretching regimens (see here http://www.ncbi.nlm.nih.gov/pubmed/15705041 but also here http://www.ncbi.nlm.nih.gov/pmc/articles/PMC522148/).