Sunday, August 9, 2009

Posture and performance
In previous articles we discussed how postural distortions can increase the chances of cumulative injury.Here we will discuss posture and it relationship with performance.Optimum posture and alignment provides optimum structural and functional efficiency to the kinetic chain. If one component of the kinetic chain is out of alignment it creates patterns of tissue overload and dysfunction which leads to decreased neuromuscular control, and decreased performance.Optimum posture and alignment provide optimal shock absorption, weight acceptance and transfer of force during functional movements.In optimum posture least amount of energy is spent statically and during functional tasks.
Ideal functional posture maintains the structural integrity of the kinetic chain and optimum alignment of each component. This promotes optimum length-tension relationships, force-couple relationships, and joints kinematics. There is an optimal length at which a muscle can develop maximal tension.If the muscles are shortened or lengthened beyond the optimum length, the amount of force that can be generated decreases.The central nervous system is designed to optimize the selection of muscle synergies to produce movement.Muscles work as force couples to produce force, dynamically stabilize, and reduce force.Joint arthrokinematics refers to the optimal movement at the joint, roll, slide, glide and translation. Optimum length-tension relationships and force-couple relationship ensure normal efficient joint kinematics.
For example, if one muscle is tight (altered length-tension relationships), the force couple around that joint are altered, normal movement at this joint is altered. This will alter proprioceptive input to the central nervous system.Proprioception is the cumulative neural input to the central nervous system from all mechanoreceptors of the entire kinetic chain.Mechanoreceptors are highly specialized neural structures that convert mechanical information into electrical information, which is than relayed to the central nervous system.
When the muscular, articular and neural systems are activated during function, the cumulative information from all the structures is sorted out by central nervous system.
This process allows the appropriate motor program to be chosen to perform an activity.This ensures that the right muscle contracts at the right joint, the right amount of force, and at the right time.
If any component of the kinetic chain is dysfunctional, (tight muscle, weak muscle. Joint dysfunction) than neuromuscular control is altered, which decreases force production, force reduction and stabilization.Reciprocal inhibition is a process where a tight muscle causes decreased neural drive to its antagonist. For example, a tight psoas (hip flexor) will decrease the neural drive to the gluteus maximus (buttocks), this alters normal force-couple relationships. The activation and force production in hip extension of the prime mover (gluteus maximus) is decreased, leading to compensation by the synergists (hamstrings) and stabilizers (erector spinae).This process is called synergistic dominance, where a synergist compensates for a prime mover to maintain force production.This alters joint alignment, which further alters the normal length-tension relationships around the joint that the muscles attach to.
Optimum posture enables the development of high levels of functional strength and neuromuscular efficiency.

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