TENSION is the force we input to our tissues (joint capsule, tendons, ligaments, muscles, fascia etc) that creates change. The type of force determines the type of change, and the TIME under that force determines the rate and quantity of change.
This concept can be used to increase muscle size and tissue resilience, as well as create joint space and lengthen tissues to allow for freedom of movement.
For example, when you lift weights as your muscle is working to move the weight- this is your time under tension, so throughout a set of 10 reps you accumulate 15-25 seconds of time under that tension. There are still debates and studies being done regarding exactly what times produce what results on a muscle, but we know that it creates change and the greater the load while under tension, the greater the change.
In a stretch, the accumulation of time and the intensity in which you force the stretch will be the determining factor of the change created. We know that the longer you spend under that tension, the greater the change in those tissues will be.
This is the scientific concept behind the PAIL’s & RAIL’s exercises we employ for increased mobility- so while you can make changes in shorter amounts of time under tension, you will create more and faster change with greater intensity and longer times under tension.