Coordination between breathing and forearm movements during sinusoidal tracking.

Time relationships (coordination) between breathing and rhythmical limb movements were analyzed during sinusoidal tracking movements of the forearm in 11 healthy subjects. The tracking rate was varied systematically between 0.1 and 1.0 Hz in 0.1-Hz steps. The aim of the study was to elucidate whether rhythmical tracking movements can entrain breathing, and whether this entrainment depends upon the movement rate. Subjects exhibited coordination between tracking movements and breathing at various rate ratios (1:1, 1:2, 1:3). At tracking rates of between 0.2 and 0.6 Hz, 1:1 coordination occurred with a maximum at 0.3 Hz; this rate range was called the 1:1 entrainment band. Coordination of 1:2 occurred at between 0.5 and 1. 0 Hz (the 1:2 coordination band) with a maximum at 0.7 Hz. Coordination of 1:3 could be detected at between 0.5 and 1.0 Hz. Different subjects showed 1:n entrainment bands at similar locations but different widths of the rate range studied. The breathing rate during tracking was significantly higher than at rest, and it was correlated positively with tracking rate. This correlation, however, depended upon the width of the entrainment bands. Breathing rates varied between 0.2 and 0.6 Hz for all coordination patterns. We conclude that the occurrence of fixed time relationships is an expression of the strength of central nervous system coupling between the two processes. The frequency of coordination between breathing and rhythmical tracking movements depends critically upon the movement rate.