Strain and StretchFit

by | May 22, 2023 | General Stretching

Strain Relaxation


Strain relaxation is a gentle and non-invasive technique, used for addressing musculoskeletal and stress related tension in the body. It is suitable for individuals who may be sensitive to more forceful manipulations or who have acute or chronic pain conditions. By positioning the body in a position of mild stretch/strain, the therapist or teacher aims to release tension and promote relaxation in the affected muscles and other soft tissues. As we will see below, it has both short- and long-term benefits.

Image 1

Image 1.

During a lying backbend, the tissues on the front of the body are elongated gently. Over time, they will adapt to this stress, remodel and grow longer.

Geek out with the science….

Strain relaxation pertains to the behaviour of muscle and connective tissue such as muscles, tendons, and ligaments, when they are subjected to prolonged or constant stress. (“Stress” in this case is positive and means stretching.)

When a tissue is held in a stretched position for a period of time, (2 or 3 minutes) it will gradually relax, reduce its tension and lengthen. (Consequently, less strain is needed to hold it there with time.) Over a longer period of time (several months) the tissue will gradually elongate (grow) and rearrange, leading to a more permanent reduction in tension and an increase in tissue compliance.



Image 2

Image 2.

A material held at a constant strain will require less stress to hold it there with time. At StretchFit, strain relaxation is one of the proven techniques we use to safely and effectively improve flexibility.

Image 3.

Image 3

When the calf muscles are stretched like this, they will become microscopically longer, less tense and better able to accommodate greater lengthening without injury.

Changes in the brain

While the mechanical aspect of strain relaxation is prominent, there is also a neural component involved. The sustained stretch applied to the tissue triggers sensory receptors called mechanoreceptors, which send signals to the nervous system. These signals can result in the modulation of muscle tone and a decrease in the perception of pain. This can result in both a short- and long-term decrease in body pain.

What happens over time to your cells when stretched?

The rearrangement and lengthening of muscle and collagen fibers in response to mechanical stress is a process that occurs over a period of time, not instantaneously. (The timeline for collagen rearrangement and tissue remodeling can vary depending on factors such as the magnitude and duration of mechanical stress, tissue type, individual physiology, and the specific stage of tissue healing or adaptation) This process is known as mechanotransduction.

Mechanotransduction refers to the conversion of mechanical forces into biochemical signals within the cells. When mechanical stress is applied to muscles, tendons, and ligaments, it triggers a cascade of cellular responses that eventually lead to structural changes in the tissue. Importantly, the type of stress determines the type of remodelling.

Longitudinal stress is when a muscle experiences tensile forces and is stretched beyond its resting length, either actively or passively. Controlled and gradual exposure to longitudinal stress through stretching leads to increased tissue length as the predominant form of remodelling.

The changes in muscle length when muscle fibers experience longitudinal tension occur through “series adaptation,” Series elastic elements, such as tendons and connective tissues, are responsible for transmitting forces between muscle fibers and bones. Through stretching, the series elastic elements undergo remodelling and adaptations, creating changes in muscle length.

A good contrasting example is provided by the looking at resistance/strength training. During resistance training, muscles are exposed to a different type of stress.

With repeated high intensity muscle contraction, the actin and myosin filaments within the muscle fibres slide past each other, causing the muscle to shorten and generate force as the fibers are pulled in the direction of the force. Controlled and gradual exposure to this type of stress leads to muscle growth, known as hypertrophy, an enlargement of the muscle fiber diameter and increased strength. This increase in fiber diameter contributes to the visible enlargement of the muscle itself. Hypertrophy primarily occurs through the addition of muscle fibers in parallel rather in “in series,” which leads to an increase in the cross-sectional area of the muscle.


The stress of heavy lifting results in and enlargement of muscle fibres. The stress of elongation of muscle results in increased length of soft tissue fibres. Think of a chain- after heavy lifting the chain grows wider and thicker. After stretching, additional links are added to the chain. Strain relaxation is a gentle an effective way to add some links to your chain!

It’s important to note that these processes occur gradually and require adequate time for the tissues to respond and adapt to the mechanical stimulus. Temporary changes like the instant changes in muscle size after weight training or muscle length after a bout of stretching are just that-temporary. They are altered states. For altered traits, training needs to be practised consistently for a minimum of 4 weeks, and generally from 4 weeks to 6 months.