Pandiculation: nature's way of maintaining the functional integrity of the myofascial system?

Pandiculation is the involuntary stretching of the soft tissues, which occurs in most animal species and is associated with transitions between cyclic biological behaviors, especially the sleep-wake rhythm (Walusinski, 2006). Yawning is considered a special case of pandiculation that affects the musculature of the mouth, respiratory system and upper spine (Baenninger, 1997). When, as often happens, yawning occurs simultaneously with pandiculation in other body regions (Bertolini and Gessa, 1981; Lehmann, 1979; Urba-Holmgren et al., 1977) the combined behavior is referred to as the stretch-yawning syndrome (SYS). SYS has been associated with the arousal function, as it seems to reset the central nervous system to the waking state after a period of sleep and prepare the animal to respond to environmental stimuli (Walusinski, 2006). This paper explores the hypothesis that the SYS might also have an auto-regulatory role regarding the locomotor system: to maintain the animal's ability to express coordinated and integrated movement by regularly restoring and resetting the structural and functional equilibrium of the myofascial system. It is now recognized that the myofascial system is integrative, linking body parts, as the force of a muscle is transmitted via the fascial structures well beyond the tendonous attachments of the muscle itself (Huijing and Jaspers, 2005). It is argued here that pandiculation might preserve the integrative role of the myofascial system by (a) developing and maintaining appropriate physiological fascial interconnections and (b) modulating the pre-stress state of the myofascial system by regularly activating the tonic musculature. The ideas presented here initially arose from clinical observations during the practice of a manual therapy called Muscular Repositioning (MR) (Bertolucci, 2008; Bertolucci and Kozasa, 2010a; Bertolucci, 2010b). These observations were supplemented by a review of the literature on the subject. A possible link between MR and SYS is presented: The neural reflexes characteristically evoked through MR are reminiscent of SYS, which both suggests that MR might stimulate parts of the SYS reaction, and also points to one of MR's possible mechanisms of action.