Reciprocal Inhibition is a process that the body uses to create movements. All movement is controlled by opposing sets of muscles, called Agonists or prime movers, and Antagonists that create the opposing force which returns the part being moved back to its original position. Movement is also aided by other surrounding muscles, called Synergists, and they mostly function as stabilisers, so that movement can occur in a controlled way.
For example, if you wish to extend your knee, the Quadriceps must contract but this can only happen if the Hamstrings relax, because they are the antagonists for this movement. The nervous system controls this as a reflex action, it is not a conscious process.
Muscles must have a balanced relationship to each other to function correctly. If you only exercise one part of an opposing muscle group, it becomes overactive and tightens, and then the antagonist muscle will weaken because it is hardwired neurologically to relax, if its antagonist is contracted. Weak muscles also become tight and it has been noticed that the larger movement muscles inhibit and weaken the stabiliser muscles.
If unbalanced exercise routines are followed, weakness can occur in the hips and lower abdomen, due to reciprocal inhibition. A predictable pattern of strength and weakness, called Pelvic Crossed Syndrome occurs in many athletes, especially runners and dancers- those who use their legs a lot. It has been found that:
- Tight Hip Flexors inhibit the Gluteus Maximus,
- Tight Adductors inhibit Abductors (Gluteus Medius and Minimus),
- Tight Hamstrings create tight lower backs
- weak Gluteal muscles cause the lower abdominal muscles to weaken.
This process is largely neurological and the solution is not to simply exercise these muscles, because it is very easy to overtrain the stabiliser muscles of the hips, causing pain and stiffness. Because these weaknesses are caused by the nervous system, the body leads to relearn correct movement patterns, and this is best done by trained professionals.
Yoga sequences that mostly consist of postures designed to strengthen the legs can also create these imbalances and weak hips lead to sacroiliac instability. An unstable sacroiliac joint is very vulnerable in lunge positions and leads to lower back pain, especially in those who also play sports and have strong legs. Athletes should rather do sequences and asanas that concentrate on core body strength, more leg strength is the last thing they need.
Physiotherapists have also noted that exercising when fatigued can weaken muscles: if you continue to perform movements when muscles are tired, the correct muscles cease to work and other muscles are substituted to continue performing the movement, leading to incorrect muscular habits, which are learned by the nervous system and will continue to be used unless correct movements are retrained. Holding asanas for too long can therefore be destructive, it’s important to know when to stop.
De Franca, 1996, Pelvic Locomotor Dysfunction
Kendall, McCreary, Provance, 1993, Muscles, Testing and Function
Cook, 2003, Athletic Body in Balance