Muscle activity in rat locomotion: movement analysis and electromyography of the flexors and extensors of the elbow.

Footfall patterns and time sequence of activity are described for white rats conditioned to run freely in an activity wheel (which they drive). Motion is described in terms of soft contact, hard contact, soft contact, and flip phases. Duration of stride decreases and length of stride increases from walk to trot to canter to gallop. Myographic analysis shows that the brachialis has a major tonic function after it fires strongly during the flip phase and during much of the hard contact phase. Animals running at canter or gallop show major asymmetries between forelimb muscles on the first paw and on the lead paw sides.