The Effect of Prior Muscle Activation on the Compound Muscle Action Potential (CMAP)
Condition: Focus: Effect of Muscle Activation on CMAP in Normal Humans
Study type: Interventional

Summary: 
      The purpose of this investigator-initiated study is to determine the effect of prior muscle
      activation on the response obtained by nerve conduction studies (the compound muscle action
      potential [CMAP]) looking at the amplitude, area, and duration of the CMAP and evaluating the
      length of time the CMAP is larger than at baseline. On the opposite side, the corresponding
      CMAP will be tested periodically, but there will be no muscle activation on that side.

      Null Hypothesis: While controlling all possible technical and other known physiological
      variables, prior activation of a muscle has no effect on the amplitude and area of the
      compound muscle action potential (CMAP); and the CMAP does not change over time in the
      relaxed muscle (on the opposite side).

      The investigators suspect that there is an effect of prior activation of the muscle on the
      subsequent CMAP recorded from that muscle.
    

Detailed description: 
      Nerve conduction studies (NCS) will be performed with supramaximal nerve stimulation, surface
      stimulation, surface recording, and with best possible technique controlling as many
      variables as possible including the location of the recording electrodes and with a warm
      muscle and nerve (measuring temperature at the skin) in each of 3 "arms" of the study:

        -  ulnar nerve stimulation at the wrist recording from the hypothenar eminence,

        -  median nerve stimulation at the wrist recording from the thenar eminence, and

        -  peroneal nerve stimulation at the ankle recording from the extensor digitorum brevis
           muscle.

      NCS will be performed in a rested muscle (rested for 15 minutes or longer) and then multiple
      times for up to 40 minutes after maximum isometric contraction (activation) of the tested
      muscle for a defined length of time. The defined lengths of muscle activation include:

        -  "a brief twitch" (activation for a fraction of a second),

        -  2 seconds,

        -  5 seconds,

        -  10 seconds, and

        -  20 seconds (two epochs of 10 seconds of activation with 1-2 seconds of rest between the
           two epochs).

      The CMAP will be recorded multiple times from the muscle which was activated (pre-activation;
      as well as post-activation at multiple times after muscle activation: immediately, 5 sec, 10
      sec, 15 sec, 20 sec, 30 sec, 60 sec, 90 sec, 2 minutes, and every minute up to as long as 40
      minutes). Similar recordings will be made after each of the 5 durations of muscle activation
      ("a brief twitch," 2 seconds, 5 seconds, 10 seconds, and 20 seconds) of each of the three
      muscles (hypothenar, thenar, and EDB). CMAP amplitude (baseline to negative peak), area
      (under the negative curve), and duration (of the negative CMAP) will each be measured at each
      timepoint; and skin temperature in the region of the "active" recording electrode will be
      measured. Each data type will be compared over time in a series, identified as muscle from
      which recorded, duration of muscle activation performed prior to the recording, and time
      after the end of muscle activation.

      On a few occasions during the testing of the CMAP on the side on which the muscle is
      activated, there will be recording of the CMAP from the corresponding muscle on the opposite
      side, but that second side will be relaxed the entire time of testing (for 4-5 hours).

      If the CMAP changes more than a small amount on either side, F waves may be tested while the
      muscle is at rest.

      Each subject will participate in each of the 3 "arms." Testing for the five series of
      recordings from each muscle is anticipated to take 4-5 hours, i.e., after screening, 12-15
      hours total for testing the 3 muscles in each subject.
    

Intervention name(s): Hypothenar muscle activation--maximum, voluntary, isometric; Thenar muscle activation--maximum, voluntary, isometric; EDB muscle activation--maximum, voluntary, isometric; Relaxation of muscle
Intervention type(s): Other; Other; Other; Other
Intervention description(s): Each subject will perform maximum, voluntary, isometric muscle activation (of the target muscle) for each of various durations ("single brief muscle twitch," 2 seconds, 5 seconds, 10 seconds, and 20 seconds [two epochs of 10 seconds of muscle activation with 1-2 seconds of rest between the two epochs]).; Each subject will perform maximum, voluntary, isometric muscle activation (of the target muscle) for each of various durations ("single brief muscle twitch," 2 seconds, 5 seconds, 10 seconds, and 20 seconds [two epochs of 10 seconds of muscle activation with 1-2 seconds of rest between the two epochs]).; Each subject will perform maximum, voluntary, isometric muscle activation (of the target muscle) for each of various durations ("single brief muscle twitch," 2 seconds, 5 seconds, 10 seconds, and 20 seconds [two epochs of 10 seconds of muscle activation with 1-2 seconds of rest between the two epochs]).; The muscle on the opposite side will be maintained at rest.
Allocation: Non-Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Muscle; Activation; Effect; Compound muscle action potential