Correlation between K complex, periodic leg movements (PLM), and myoclonus during sleep in paraplegic adults before and after an acute physical activity

K complex is the characteristic wave of stage II of sleep. The relationship between periodic limb movements (PLM) and the restless legs syndrome (RLS), and the incidence of K complexes and alpha activity has been previously described. The aim of the present study was to evaluate the effect of an acute physical activity upon K complex, PLM, and myoclonus during sleep in individuals who were paraplegic. We evaluated 84 polysomnograms from 28 volunteers with a spinal cord injury at the level of T7-T12, obtained during three consecutive nights. On day 3, the volunteers were submitted to a test of maximum effort (manual cycloergometer, with the equipment Cybex Met 300, with a progressive load increase of 12.5 w, every 2 min). The analysis of the polysomnographic recordings showed a positive correlation between the incidence of K complex and limb movements on nights 1, 2 and 3. Similarly, a correlation between the incidence of K complex and myoclonus was observed on nights 1, 2 and 3. An increased incidence of the total K complex was seen on night 3, 36 h after the test of maximum effort. Both total K complex and K complex/h were reduced on night 2, compared to basal recording (night 1). There was a reduction of sleep latency on night 2, whereas total sleeping time increased progressively on night 3, as well as REM phase on nights 2 and 3. These findings indicate that physical activity can affect or modulate the incidence of K complex and suggest that a positive correlation between PLM and K complex may occur in those who are paraplegic from a spinal cord injury. In conclusion, sleep can be consolidated after physical activity.