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Safe and Effective Stretching

Three principles for applying force with clients.

For years, stretching has been viewed as
a necessary part of personal training, yet stretching itself has received little attention. Recent research on how forces act on the body gives us a new way to think about stretching and provides effective and safe stretching techniques for clients.

When stretching a client, a personal trainer produces a force on the client’s body. Force is defined as mass (weight) × acceleration (the time rate of change in velocity). The most dangerous forces that act on the body during stretching are those that act directly on joints. Over time, joints deteriorate naturally from “wear and tear” and age. Stretching should not contribute to this process. The goal is to maximize the benefits of stretching while minimizing the forces that act on joints. To achieve this result, remember three principles when applying force: (1) where? (2) what direction? and (3) how much?

Place Hands Safely

Safe Stretching Principal #1: Where? refers to hand placement on the client’s body. Do not place your hands directly on the joint; that is unnecessary and dangerous. The safe way to apply force is to position your hands 1 to 11/2 inches below or above the joint. In this way the soft tissue that supports the joint absorbs the stress of the force. Hand placement also influences the client’s form. When direct force is applied to a joint, the client’s natural tendency is to bend it.

Photo 1a on the following page shows incorrect hand placement for a supine hamstring stretch. The trainer’s hands are on the back of the client’s knee. As a result, the client bends his knee. Photo 1b shows the correct hand position for the start of the hamstring stretch. The trainer’s hand is on the client’s leg, about half an inch above the ankle. Photo 1c shows the correct hand position for the finishing point of the hamstring stretch. As a result of the trainer’s hand placement, the client’s knee is “soft,” but not bent.

Don’t Push Down

Safe Stretching Principal #2: What direction? refers to the angle at which the force is applied. Do not push downward on the client. Instead, when the client is lying on his back, apply the force parallel to his body. This minimizes the force acting straight down on the joints.

Photo 1a shows the incorrect application of force. The trainer uses a force perpendicular to the client’s body, coming straight down on top of the hip joint, causing the client to lift his hip off the mat. Photo 1b shows the correct starting position for the hamstring stretch. The client is lying down with his leg extended. The trainer prepares to stand up and step forward into the stretch in a parallel
direction. Photo 1c shows the correct direction of force application: parallel to and away from the client’s body. The trainer does not push down on the client, and as a result the client is able to keep his hip on the mat.

The parallel application of force is
warranted for most lower-body stretches performed lying down or sitting. These stretches include, but are not limited to, the supine hamstring stretch (shown), the supine knee-to-chest stretch and the prone quadriceps stretch. Never apply force downward on the client; this goes for lower-body, torso, neck and upper-body stretches performed lying down, sitting or standing.

Use Light Force

Safe Stretching Principal #3: How much? refers to the amount of force to apply. The client’s flexibility determines this. You can apply more force and produce a better stretch than a client can alone. However, be careful not to use too much force. Hold the stretch for at least 60 seconds, which is consistent with current literature on long-term adaptation to stretching.

Photo 1a shows the hamstring stretch when the trainer applies too much force. The client counteracts the excessive force by bending his knee and lifting his hip off the mat. Photo 1c shows the same stretch when the trainer applies an appropriate amount of force. The client does not bend his knee or lift his hip off the mat.

The appropriate amount of force will vary from client to client. To ensure safe stretching, obtain background information, including age, fitness level, flexibility test results, prior experience with programs like yoga, general stretching experience, and existing and past medical conditions that influence flexibility.

Communicate for Comfort

In addition to understanding the variables that influence flexibility, you must establish communication with the client. Teach a few relative terms and how to use them. Define “tension” due to stretch versus “pain.” A client may assume that stretching is painful. Assure her that pain is not necessary, but tension in the muscle is. Explain the difference between muscle tension and joint tension. Joint discomfort during stretching is not normal. If the client reports joint discomfort, release the stretch to a comfortable point.

Communication is important before stretching and essential during it. Be attentive to the client’s wants and needs. Let her know in advance what questions you will ask and how her responses will be used. Use your own judgment and knowledge of the client to develop a dialogue. Here are a few suggestions:

“Tell me when you feel the stretch.”

“Let me know when the muscle feels tight.”

“I am about to begin the stretch, and I need you to tell me when to stop.” (Hold the stretch at the client’s request.)

The key to knowing how much force to apply is paying close attention to the client. Learn to read body language. The client may not tell you that the force is too much. Look for evidence that form has collapsed: excessive bending at the joints, the body coming off the mat during a lying stretch, a shift in body position, a change in facial expression or body language, or shallow breathing. If any of these occur, you have applied too much force. If the client is pushing back, ask if the stretch is too much and if she is resisting. If so, release the stretch to a comfortable point.

Stretching is an important part of any personal fitness program. Effective and safe stretching depends on the correct use of force. When applying force, a conscientious trainer uses the three principles of where?, what direction? and how much? Used correctly, these safe stretching principles will enhance your training repertoire and increase effectiveness of stretching.


Photo 1a: Incorrect supine hamstring stretch.

Trainer Notes:
1. Incorrect hand placement: Trainer’s hands are on back of client’s knee.
2. Trainer is pushing down on client. Force is applied to client’s knee and hip.
3. Trainer is applying too much force. As a result, client’s form is unsafe and ineffective. Client bends his knee and lifts his hip off mat.


Photo 1b: Correct starting position for supine hamstring stretch.

Trainer Notes:
1. Correct hand placement: Trainer’s hand is 1 to 11/2 inches above client’s ankle.
2. Trainer prepares to stand up and step in toward client.Photo 1c: Supine hamstring stretch: Correct stretch position.

Trainer Notes:
1. Correct hand placement: Trainer’s hands are 1 to 11/2 inches above client’s ankle.
2. Trainer is applying a force parallel to client’s body lying on mat, being careful not to push down on client.
3. Trainer is applying appropriate amount of force. As a result, client’s form is good. His knee is “soft” but not bent, and his hip is on mat.

Red indicates trainer’s application of force.
Blue indicates client’s form as a result of force application.


Ashmore, A. 1998. Manual Force Modulation and Position Control in Persons With Parkinson’s Disease. Doctoral Dissertation, University of Texas at Austin.
Enoka, R.M. 1994. Force. In Richard Frey (Ed.), Neuromechanical Basis of Kinesiology (pp. 35-80). Champaign, IL: Human Kinetics.

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