Flexibility is one of the principal components of fitness, and an essential element of athletic improvement and healthy living.
Flexibility is one of the principal components of fitness, and an essential element of athletic improvement and healthy living. It is often neglected as a part of training, and frequently is only incorporated after an injury or movement issue has arisen. Flexibility training will most likely become a priority for most athletes at some point in their athletic career. Appropriate flexibility can play a large part in reducing the likelihood of injury, and improving the performance of those who have insufficient flexibility. The improvement relates to increasing the range of motion (ROM) that is allowed around a given joint. The amount of movement allowed is governed primarily by the muscles and ligaments that surround and supply movement to the joint. Flexibility requirements differ among different populations; e.g. the flexibility required by a gymnast is very different to that of a sprinter or weekend warrior, but nonetheless is important to all three groups, and should form one component of a comprehensive training program.
Flexibility can be improved through a number of methods:
- Static stretching
- Dynamic stretching
- Proprioceptive Neuromuscular Facilitation (PNF)
Static stretching is achieved through the controlled lengthening of a muscle to the end of its range of motion, and holding at this point of tension for prescribed durations. This can be done through active methods where the opposing muscle places the tension onto the stretched muscle i.e. contraction of the quadriceps and hip flexor muscles placing a stretch on the hamstring in an active straight leg raise. The same stretch can be completed passively by having a partner place your leg into the appropriate position, or by moving your body so that it acts to place a stretch on the hamstring i.e. partner-assisted straight leg raise, or sit-and-reach stretch, respectively. Static stretching is primarily a developmental method of stretching, and it can be used for post-exercise recovery and cool down. However, it is not the most appropriate stretching method for pre-performance as prolonged static stretching immediately pre-competition may reduce power output and force production for a (short) period of time after stretching.
Static stretches should be held at a point of tension for between 15-30 seconds. This should be repeated 3-4 times for each muscle that requires flexibility improvement. A 1:1 stretch-to-rest ratio should be used as this allows for a left/right alternation on isolateral stretches i.e. quadriceps. Timing rest periods may be more suited for bilateral or trunk stretching i.e. back extension.
Dynamic range of motion is a key factor in sports performance. In fact, the risk of injury is increased in sudden dynamic movements at the end range of flexibility. Therefore, the ability to move dynamically through a sufficient range of motion required for performance is an essential ability of sports people. Dynamic flexibility is developed through the use of rhythmical swinging actions and movements that, where possible, are similar to the actions used in the sport i.e. leg swings for the hamstring/kick and follow through to leg swing for kicking sports.
A dynamic stretch should be used before training sessions to assist the pre-performance preparation of the muscles to be used. General recommendations are 8-12 repetitions repeated 2-4 times for dynamic flexibility development, or repeated 1-2 times for pre-performance preparation.
Proprioceptive Neuromuscular Facilitation (PNF)
PNF stretching works on the basis of inhibition of the monitoring systems used by the body within the muscle:
- The muscle spindle
- The golgitendon organ (GTO)
The muscle spindle is located in the belly of the muscle and monitors the length of the muscle in relation to the maximum allowed length. In muscles that are over-stretched, the muscle spindle will reflexively induce a contraction to shorten the stretched muscle. This can be seen when a stretch is brought to an extreme end of range, and involuntary muscle tremor occurs. This tremor is caused by the muscle spindle firing in order to reduce the stretch placed on the muscle.
The GTO is located near the musculo-tendon junction and is responsible for monitoring the tension placed on the muscle. In situations of excessive force being placed on the muscle, the GTO acts to stop the contraction of the muscle by reflexively inducing momentary fatigue. This occurs to protect the muscle from potential damage due to an excessive level of force acting upon it.
The PNF stretch sequence
To inhibit the actions of the muscle spindle and the GTO, it is necessary to initiate a stretch and couple it with a contract-relax pattern. This is best achieved with a partner who can move you into the stretch position and maintain the stretch. PNF stretching has three main variants:
A 10 second passive stretch is held at the point of tension, after which a muscular force is applied against mild resistance that maintains isometric tension for 6 seconds. The contracted muscle now releases the tension applied and should allow for an increased stretch, held for 30 seconds.
A 10 second passive stretch is held at the point of tension, after which the stretched muscle applies mild force against resistance that allows the limb to move through a full concentric range of motion. Having completed the resisted range of motion, the muscle is relaxed and re-stretched passively for 30 seconds.
Hold-Relax with agonist contraction
A 10 second passive stretch is held at the point of tension, after which the stretched muscle applies mild force against resistance at the point of tension for 6 seconds. A relaxation is initiated in the stretched muscle, and agonist muscle contraction is initiated to assist an increased stretch that is held for 30 seconds.