Proprioceptive neuromuscular facilitation
Although research shows flexibility training reduces post workout soreness, decreases musculoskeletal injury and increases range of motion, people often neglect this aspect of fitness. Flexibility is especially important for the aging population. ACSM's Guidelines for Exercise Testing and Prescription states, "A well-rounded program of stretching can counteract the decline of flexibility in the elderly [as well as] improve balance and agility." For the professional and recreational athlete, improved flexibility decreases the chance of injury and enhances performance. As fitness professionals, it is our duty to see to the wellness of our clients. Not only must we strive to increase their strength and cardiovascular fitness, but we need to increase their flexibility as well.
Proprioceptive neuromuscular facilitation (PNF) was first developed in the 1940s and early 1950s by Herman Kabat M.D., Ph.D., physical therapists Margaret Knott and Dorothy Voss, as a treatment modality for paralysis patients. Originally designed to facilitate flexibility, strength and coordination, PNF has found a loyal following in mainstream fitness circles.
Research
Research indicates that PNF is not only a superior style of stretching, but has benefits beyond improving flexibility and range of motion. A study published in Coaching Science Abstracts also found increases in strength, concluding, "PNF stretching could be an alternative to or supplemental method for standard weight training programs."
The Physiology of Flexibility
Muscle spindles, located within muscle cells, protect the muscle from injury. They sense how far and fast a muscle is being stretched and, when activated, produce the myotatic stretch reflex. This reflexive action causes the muscle to contract to prevent overstretching the joint. For example, if you are lying on your back performing a hamstring stretch, at the maximum of your flexibility your leg jumps and twitches. At this point, the muscle spindles have been activated and are telling the muscle to contract to prevent any further stretching.
Also located within the muscle tendon is another sensor called the golgi tendon organ (GTO), which functions in sensing how much tension is being placed on the tendon. However, the GTO differs from the muscle spindle in that, when activated, it relaxes the muscle.
A maximal muscular contraction eliciting a greater relaxation response is called the inverse stretch reflex. The inverse stretch reflex is the basis of PNF stretching, allowing a greater stretch of the muscle by utilizing the neuromuscular responses of the body. An example of this relaxation technique is tensing a muscle before relaxing it.
PNF is a specific flexibility protocol using a combination of isometric contractions stretching techniques. There are a couple PNF styles practiced today. For the fitness professional, the most practical style of PNF is the CRAC (contract-relax, antagonist-contract) technique.
When to Stretch
New research suggests stretching before a workout produces minimal benefit. While there is no evidence stating a pre-workout stretch is harmful, stretching at the end of a workout is more efficient.
PNF Stretches
PNF stretching is performed best with a partner, but most stretches can be performed alone. When using a partner (e.g., if pairing up in a group fitness class), it is imperative for the partner to be attentive and focused on the stretcher.
Hamstring Stretch
The stretcher assumes a supine position on the ground with one leg bent at a 45-degree angle and the other leg extended. The stretch begins with the stretcher lifting the straight leg until a comfortable stretch is felt through the hamstring. The partner may hold the stretchers leg in a straightened position, but should not push forward. Hold this static stretch for 15 seconds.
At this point, the stretcher should isometrically contract the hamstring for six seconds. Then, the stretcher contracts the hip flexors to pull the leg back, thereby deepening the stretch. Again, the partner can assist by holding the leg in a straightened position for another 15 second stretch. Switch legs and repeat. If no partner is available, wrapping a towel around the foot or ankle and holding the ends of the towel can achieve a similar stretch.
Pectoral Stretch
This stretch can be easily performed without a partner by using a doorway or other stationary object for resistance. The stretcher begins by raising one arm to a 90 degree angle at the elbow, with the upper arm parallel to the ground and forearm perpendicular to the ground. Placing the forearm and open palm against the doorway, the stretcher will turn the body away from the arm until a comfortable stretch is felt through the chest and into the shoulder. Hold this stretch for 15 seconds. Then, isometrically contract the pectoral muscle, attempting to adduct the arm. Hold this contraction for six seconds. Relax the pectoral muscle and deepen the chest stretch by turning the body away from the arm for another count of 15 seconds.
Once the basics of PNF stretching is understood, one can apply this method to almost any muscle group or stretch. PNF stretching is a valuable tool for personal trainers and group fitness instructors, but care should be taken when using this advanced form of stretching.
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