A critical review of evidence concerning long-loop reflexes excited by muscle afferents in man

It is the thesis of this review that the origin of the intercurrent facilitation at 50 to 400 msec in the standard recovery curve of the H reflex, evoked with paired stimuli, is a complex. It is composed importantly of central feedback effects from the conditioning reflex contraction, influences mediated by cutaneous group III afferent nerve fibres excited by the percutaneous stimulus, and with a possible additional modest contribution by long-loop, spino-bulbo-spinal influences.