PT on the Net Research

Flexibility Training - Part 1

We as fitness professionals have long learned that flexibility is one of the four components of fitness, along with muscular strength, muscular endurance and cardiovascular endurance.

There is much evidence both for and against the benefits of various flexibility training or stretching protocols. This article is not intended to delve into the pros and cons but to present specific kinds of stretching protocols in a practical manner. Stretching major muscle groups will be discussed. The goal is for the personal trainer to start developing a competency in stretching as a vital component of a comprehensive training program.

Components of Professional Flexibility Training

Trainer Responsibility

We must assume the responsibility of "touching" someone. Whether stretching or working with a client in any capacity, we must be certain that we are being safe and thorough in our documentation regarding health history (PAR-Q) postural assessment and movement/flexibility assessment. It is, therefore, assumed that the trainer:

Warm up

The question "how much time is necessary for a warm up" illicits many answers. Perhaps instead of a specific, designated time, we as trainers should adhere to the goal of a warm up (i.e., increase in core body temperature, lubrication of the joints, etc). Therefore, a person getting out of a cab at 6am in the morning would need a different (and more of) a warm up than a client who moves throughout the workday and comes to the gym at 6pm.

Range of Motion

Although defined many different ways, I use Range of Motion to refer to the maximum movement around a joint. There are many things that can contribute to the range of motion around a joint. Scar tissue, inflammation, muscle bulk, fatty tissue, bony landmarks and weak muscles can all decrease the range of motion around a joint. Another contributing factor to the range of motion around a joint is the inflexibility of an individual muscle. Herein lies the difference between range of motion and flexibility


The degree to which an individual muscle will lengthen. Again, this is but one of the contributing factors to the range of motion around a joint. It is important for the trainer to appreciate the relationship between range of motion around a joint, and the flexibility of individual muscles that surround that joint. Range of motion, again, refers to the movement around the entire joint, and includes many factors. Flexibility refers to an individual muscle, and the lengthening of the muscle fibers and surrounding fascia.

What about hypermobility? If the ligaments that surround a joint are too lax, the joint can be hypermobile, and many times presents itself as unstable. It is then our decision of whether the individual muscle around that joint should be stretched or not. This is a question of risk versus benefit, and is greatly determined by the client’s goals and overall condition.


The point at which the client begins to feel a stretch. This is the point at which the muscle fibers are at their longest, at which some other mechanism is necessary to increase this endpoint, e.g. gravity, a towel, or the personal trainer. The trainer’s ability to detect the endpoint requires a great deal of sensitivity. A muscle’s endpoint will not be the same for everyone-or even for the same person at different times of day. The ability of a trainer to stretch a muscle far enough for it to be beneficial, but not so far as to destabilize a joint, or injure the muscle, is largely dependent upon the trainer’s ability to feel a muscle’s endpoint.

Core Stabilization

To be efficient at stretching, the bones at which the muscles originate must remain still. For example, when holding a rubber band in your left hand, and lengthening it with the right hand, you get to the point where you feel the rubber band is stretched as far as it can be. If you then move the left hand further towards the right, the rubber band decreases in stretch. That is exactly what happens during stretching when one of the bones at which the muscle originates. For the lower body, the pelvis must remain still; and for the upper body the shoulder girdle must remain still. Keeping the core muscles of the body engaged will help keep the pelvic girdle and shoulder girdle still.


There should never be any discomfort while stretching. The client must be able to distinguish a stretching feeling from a tingly, or radiating feeling, or sharp pain. The trainer must then stop the stretch, reassess the alignment, and perhaps discontinue until medical clearance is obtained.

PNF: Proprioceptive Neuromuscular Facilitation

PNF is a broad term that describes the neurological principles of the body. For example, if you stand on one leg, you will feel lots of movement around your ankle, your foot, perhaps your knee, and further up the chain. It is not necessary for you to actively engage any individual muscles to maintain balance; your body is "reacting" to the situation, and making the necessary adjustments. The sensory organs located in and around that joint are responsible for this (1,2). This is an example of PNF in practice. These principles are the intricate coordination of movements and reactions to the environment around the joints. In very brief review, two automatic responses that are responsible for joint and muscle protection are the muscle spindle, and golgi tendon organ. The muscle spindle is located in the muscle belly, and senses when a muscle is stretching too far, or too fast. Its protective reaction is to cause the muscle to contract, i.e. the myotatic stretch reflex. The golgi tendon organ, by contrast, is located in the muscle tendon, and senses too much tension. Its protective reaction is to cause the muscle to relax.

When we teach someone how to do static stretch, we tell him or her not to "bounce" or move too quickly or forcefully into the stretch. This is to prevent the myotatic stretch reflex from being triggered, by the muscle spindle. Then, after holding the static stretch for 15 seconds or so, there is a relaxation of the muscle fibers, i.e. the "inverse stretch reflex"; initiated by the golgi tendon organ.

The same thing happens when there is a contraction of the elongated muscle fibers, e.g. the golgi tendon organ causes a release; this is also called post isometric relaxation.

Since most fitness professionals learn static stretching, what will be presented here is "post isometric" stretching or "contract relax." There are many ways to manipulate the PNF principles of the body, and the trainer is encouraged to continue with further research and education. The knowledge of anatomy is crucial when stretching. Since there are many muscles that perform similar actions at a specific joint, only the major ones are named.

Hip Flexors and Quadriceps

These muscle groups are presented in sequence since the rectus femoris crosses both the hip and the knee, and can only be effectively stretched if done so at both joints.

The client sits at the end of the stretch table, with the right thigh almost off the table. Instruct the client to hold the left leg, while lying down on the table. Make certain that the client does not lie down without the left leg, as this is very stressful on the low back.

Always be sure that you are practicing good biomechanics (i.e., back flat, abs engaged, good posture).

Spot the client by facing the table. Take the client’s left foot and place it on the front of your body so the client does not have to hold the leg.

It is important to keep the left leg relaxed and alleviate any discomfort, as this takes the focus and effort away from the stretching on the right leg.

If the client feels pinching in the hip flexors of the left leg, you can try to ease up on the degree of hip flexion on the left side or change the angle slightly at which the left hip is flexed.

Assess if the client feels a stretch in the right hip flexors. Be certain they tell you what they feel, and point to where they feel it - as they may be feeling discomfort in the low back, which is not what we want!

In this position, you have gravity assisting in the stretch. Be very conservative in increasing this stretch. If the client’s thigh is below the level of the table and he or she feels no stretching with minimal assistance, it is highly probable that this muscle group does not need to be stretched.

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Post Isometric Relaxation (Contract/Relax)

Hold the client’s right leg at the endpoint of stretch. Cue the client to push the right thigh up into your hand with 50% effort for approximately 6 seconds. At the end of the 6 seconds, you should feel a "release" of the hip flexors, allowing the right thigh to fall further towards the floor. Then repeat this sequence 3-5 times, always starting at the new endpoint.It is very important to not force an increase in the stretch. If the muscle fibers do not release, simply try it again.

If someone’s rectus femoris is extremely tight, they will experience an intense stretch; you will also feel that the right thigh tries to lift up, thereby easing the stretch at the hip. You may have to reduce the stretch at the hip in order to stretch the quadriceps successfully without being too severe of a stretch.

The client may also report knee discomfort if this muscle is too tight to allow being stretched over both joints. If this is the case, reduce the stretch at the hip, and work only at the quads; over time as the rectus femoris increases in resting length, you will be able to increase the stretch over both the hip and knee.

Take your left leg and hold the client’s right leg in the stretched position by placing your shin right up to the client’s shin. This is a biomechanically advantageous position for the trainer, and very easy to maintain.

Cue the client to push the right shin into your left one with 50 percent effort for about six seconds. Tell them to either release, or relax; you should feel the muscle fibers relax, and the thigh may drop closer to the floor or the knee may flex more. Repeat the sequence at this new endpoint three to five times.

Stretching at Both the Hip and Knee Joints

Cue the client to simultaneously push the right thigh up into your hand, and push the right shin into your leg, with 50 percent effort for about six seconds. Repeat the sequence at the new endpoint three to five times. This is very difficult for the client as it is a deeper stretch and requires coordination and focus.


  1. Adler, S., Beckers, D., & Buck, M. (1993). PNF in Practice. Berlin: Springer-Verlag.
  2. Alter, M. (1988). Science of Stretching. Champagne, IL: Human Kinetic Books.
  3. Brotzman, S.B., (1996). Handbook of Orthopedic Rehabilitation. St. Louis, MI: Mosby-YearBook.
  4. Handel, M., Horstmann, H., Dickhuth, H.H., & Guelch, R.W. (1977). Effects of contract-relax stretching training on muscle performance in athletes. European Journal of Applied Physiology and Occupational Physiology, 76(5), 400-408.
  5. Lund, H., Vestergaard-Poulsed P., Kanstrup, IL, & Sejrsen, P. (1998). The effect of passive stretching on delayed onset muscle soreness, and other detrimental effects following eccentric exercise. Scandinavian Journal of Medicine and Science in Sports, 8, 216.
  6. Pollard, H., & Ward, G. (1997). A study of two stretching techniques for improving hip flexion range of motion. Journal of Manipulative Physiological Therapy, 20, 443.