Firing rates for individual motor units grouped based upon recruitment threshold.

<p>Mean firing rate for individual motor-units of the biceps brachii separated into groups or bins corresponding to 10% of MVC. Panel A are data from contractions performed at 50% of MVC, Panel B are data from 80% of MVC. Number in brackets above each bar indicate the number of motor-units in each bin. *indicates a significnat difference between bout 1 and bout 2 (p < 0.05). Values are means ± SD.</p

Relationship between recruitment threshold and firing rate for each participant.

<p>Linear regressions between recruitment threshold and mean firing rate of the biceps brachii for each participant during contractions at 50% (A; Bout 1 and B; Bout 2) and 80% (D; Bout 1 and E; Bout 2) of MVC. Panel C and F show the mean relationship across all participants for Bout 1 (solid lines) and Bout 2 (dashed lines) at 50% and 80% of MVC, respectively.</p

Example of raw EMG and individual firing incidences.

<p>Example of raw EMG signal collected from the 4 pin sensor during a contraction at 50% of MVC are shown in Panel A. Individual firings incidences of the 25 motor-units detected by the decomposition algorithm are shown in Panel B. Each bar represents the firing time of an action potential. The force tracing from the trapezoid contraction is shown by the overlaid solid line.</p

Surface EMG recording from the bicpeps and triceps brachii.

<p>Mean RMS amplitude in the biceps brachii (Panel A) and triceps brachii (Panel B) as well as median frequency in the biceps brachii (Panel C) and tricep brachii (Panel D) and during eccentric exercise. ** indicates a main effect for time. ^a indicates a significant difference “start” of the initial set; ^b significant difference from “end” of initial set; ^c significant difference from “start” of the middle set; ^d significant difference from “end” of the middle set; ^e significant difference from “start” of final set. †† indicates a significant main effect for bout. Values are mean ± SD.</p

Onion skin plot of firing rates and recruitment thresholds for individual motor units.

<p>Mean firing rate plot of the biceps brachii (Panel A) or “onion skin” plot for a single participant prior to Bout 1 of eccentric exercise during a contraction at 50% of MVC. The solid black line shows torque production and the remaining curves represent individual motor units and their average firing rates over time. Panel B shows the linear relationship between recruitment threshold and mean firing rate for each identified motor unit.</p

Overview of experimental design and procedures.

<p>Overview of experimental design and procedures.</p

Assessments of muscle damage.

<p>Change (as a percentage of “pre”) in isometric strength of the elbow flexors (Panel A), ratings of muscle soreness in cm (Panel B), and elbow range-of-motion (Panel C) over one week following Bout 1 and Bout 2 (separated by 3 weeks) of eccentric exercise. † indicates a significant difference from Pre. * indicates a significant difference between bouts. ** indicates a main effect for bout. †† indicates a significant difference from Pre (main comparison). Values are mean ± SD.</p