When you use the two-way stretch you are reaching in opposite directions to fully activate your body and extend outward from your torso. The more completely your body extends from its center, the deeper your core can work. In Pilates, the core includes the muscles of the torso on all sides of the body, including the hips, buttocks, stomach, back and inner thighs.
Muscles are elastic tissue that stretch and contract to generate force. Muscles often work in opposite pairs, for example: the bicep works to pull the forearm, while the tricep works to extend it.
So when the bicep is contracting, flexing and becoming short the tricep is extending, stretching and becoming long. If said tricep was really tight and couldn’t stretch all the way, then we couldn’t flex our bicep all the way. This doesn’t just affect movement, but passive posture. For example, if your bicep was really tight while your tricep was really weak you would end up with a slightly flexed elbow, at rest.
The human body is amazing. Every muscle in the the body is designed to work together with each other in unison. When the joints/form of an exercise or movement is out of line, muscles are over or under activated. This causes the muscles to become stressed, and they scramble to the other muscles to help out. When poor movement takes over, this is why muscles strain or tear. For major Shoulder and Hip joints, athletes MUST understand external rotation positioning and how it relates to muscle balance.
Bicep Curl & Tricep PushDown
When your shoulders are externally rotated in a Bicep Curl, you get the perfect mix of Bicep flex and Tricep Stretch. When shoulders are shrugged (Internal/Anterior position) you are going to OVER FLEX you bicep and UNDER STRETCH your Tricep. Although the bulk of this may look bigger, it negatively affects the mobility of how you are designed to move.
Kicking, Punting and Running Hips work exactly the same. When your hip position is neutral, you use your quads, butt, and hamstrings in unisom for maximum power and range of motion. When you have an ANTERIOR PELVIC TILT, muscles go out of balance and become targets for strains or tear.