Muscle Cramping by Tanya Fry.

Muscle Cramping is a painful and debilitating experience. There are
many factors that may contribute to cramping such as dehydration, heat
illness, fatigue, nutritional issues… the list goes on.

Fortunately, the stretching technique "CONTRACT/RELAX/STRETCH with
RECIPROCAL INIHIBITION" is effective in providing relief in many of
these cases. "C/R/S/withRI" is based on the concept of how our nervous
system controls our muscles to allow for smooth and coordinated
movements.

Here’s how it works: Our muscles produce movement through
"opposition." Muscles can only "pull" they can’t "push."  Let’s look
at the leg for an example.

At the knee joint, the muscles on the front of the thigh – the
quadriceps – extend or straighten the leg. When this happens, the
muscles on the back of the thigh – the hamstrings – relax and lengthen (to allow
the quadriceps to produce the action of straightening the knee).

When you bend or "flex" your knee, the opposite happens. Your Central
Nervous System gives your hamstrings the signal to contract in order
to bend your knee; the CNS is also sending a signal to your quadriceps
to relax and lengthen so the movement can occur.

Without this mechanism, our actions would be difficult and choppy, not
smooth and coordinated.

This concept is incorporated into the C/R/S model through RECIPROCAL
INIHIBITION – producing an isometric contraction in the muscle that is
"opposite" the muscle you are trying to stretch.

You may have heard the phrase, "toes to your nose" when your calf
muscle cramps up.  The intention is to stretch the cramping muscle;
but in reality you are also facilitating a "Reciprocal Inhibition"
(relaxation) in the calf muscles by actively contracting the muscles
on the front of your leg.

To perform stretches with C/R/S with RI

1. Isolate target muscle to be stretched.

2. Produce an isometric contraction at the mid-range of ROM in the
"opposite" muscle for 7-10 seconds.

3.  Relax and take a deep breath

4. Exhale as you move the target muscle to new barrier.  Hold 20 secs. Repeat 3x

PROS  Great for cramping, painful sore muscles, working with muscle
imbalances and postural distortions

CONS  You have to work at it! Works great with a partner. Requires an
understanding of muscle actions.
Contraindicated with some cardiovascular issues.