An involvement of the ANS, “sympatho-adrenal" hyper-tonus is a commonly accepted as an important element in pathogenesis of myalgia, tex fibromyalgia, (Martinez-Lavin 2007). Aberration in the autonomic functioning in persons suffering from localised muscle pain have been documented in our previous studies. For example attenuation of heart rate variability was reported. However there exist inconsistency of results and difficulties in interpretation of some effects (e.g. relative increased of sympathetic activity, and/or decreased parasympathetic effects), since changes in heart rate variability may depend on many factors.
Physical activity plays important role for balanced responses to mental and physical challenges. Reduced physical activity lead to increased of symptoms acuity, however changes in everyday physical activity in patients with MSD have a more complicated character, then only reduction in the averaged levels. For example Weering et al. (2007) reported increased activity during day time, and relative decreased activity during evening.
These observations are in line with our own recent data, which indicated relative increased physical activity during mornings and decreased activity during evenings rest in persons with pain in neck-shoulder area. The pain subjects showed also a stable increase of heart rate during day and night hours of HRV monitoring. It seems to be important to know more about relationships between individual patterning of physical activity, ANS-related changes in cardiovascular adaptation capacity and perceived muscle pain.