title: Long-latency contributions to reciprocal inhibition during various levels of muscle contraction.
abstract: Reciprocal inhibition is a functional term and refers to the proportional decrease in antagonist motoneuron activity that accompanies an agonist contraction. A condition-test (C-T) H-reflex paradigm (conditioned stimulus applied to the common peroneal nerve; test reflex elicited by posterior tibial nerve stimulation) was used during: (1) rest, (2) a tonic isometric tibialis anterior (TA) contraction at 10% of its maximal voluntary contraction (MVC) and, (3) a TA contraction at 25% MVC. The purpose of the study was to assess whether or not long-latency contributions to reciprocal inhibition of soleus H-reflexes changed with increasing levels of TA contraction. C-T intervals ranged from 5 to 150 ms. Subjects (n=14) had long-latency inhibition at rest (x = -35.0 +/- 18.7%). This inhibition was enhanced during 10% (x = -46.1 +/- 17.9%; p = 0.17) and 25% MVCs (x = -56.3 +/- 14.0%; p < 0.01). Findings indicate that long-latency contributions to reciprocal inhibition of the soleus motoneuron pool are enhanced with increasing force of TA muscle contraction up to 25% MVC. These results indicate that long-latency contributions to reciprocal inhibition of soleus H-reflexes are not static but rather are task-specific and change in relation to levels of TA muscle activity.
authors.affiliation: Motor Control Research Laboratory, Physical Therapy Department, The University of Montana, Missoula, MT 59812, USA.leonard@selway.umt.edu
authors.forename: C T
authors.initials: CT
authors.lastname: Leonard
authors.forename: D Y
authors.initials: DY
authors.lastname: Sandholdt
authors.forename: J A
authors.initials: JA
authors.lastname: McMillan
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004576:Electromyography; D006181:H-Reflex / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D009433:Neural Inhibition; D011930:Reaction Time / Q000502:physiology*