Do you want to increase muscular strength …. or improve muscular function? The resting length of your muscles is important to consider.
A muscle can generate the greatest amount of force at full length. When a muscle is lengthened past the natural end-range there are less cross-bridges to create force.
POWER. The powerful hip muscles use end-range rotation to reach full resting length. When rotation is missing from the resting length of the muscle, power is compromised.
RESTING LENGTH. It’s easy to check the resting length of the hip muscles. From a comfortable stance, rotate one leg in all four anatomical positions….. flexion, extension, abduction and adduction. You should be able to freely rotate the leg internally and externally. Each position requires an equal amount of rotation in internal versus external rotation to provide the most stability in movement. Unequal or limited rotation in one direction means the resting length is compromised.
PROPRIOCEPTION. Muscle spindles are the proprioceptors of the muscle. Spindles signal the CNS to lengthen the muscle fiber. If end-range rotation is not present, sensory signals remain silent.
Stretching the muscle is not a permanent solution since stretching takes the muscle past the resting length and into connective tissue. And ordinary muscle contractions bypass the tight muscle fiber never reaching the muscle spindle. The muscle spindle (lengthening agent) along with the co-ordinated muscle fiber must work together.
A specific approach is needed to isolate the spindle and the co-ordinating muscle fiber.
According to Lephart ….3 stages are required to improve proprioception and restore resting length:
- Acquisition of the mechanical stimulus.
- Conversion of the mechanical stimulus to into the neural signal.
- Transmission of the neural signal to the CNS
Isometrics supply the mechanical stimulus for a targeted muscle contraction. But in order to increase neural signals… the muscle spindle connected with the fiber must also lengthen. Diagonal rotational patterns pull the spindles taunt and enable transmission of the neural signals to the CNS.
These diagonal PNF patterns have been long used for neuromuscular re-education. The isometric contraction plus lengthening via diagonal rotation stimulates the muscle spindle and the muscle fiber simultaneously.
Diagonal resistance on a product like StandingFirm® is a great way to bias end-range muscle fiber and increase spindle output for power and proprioception.