Affiliations: [a] Department of Nutrition and Health Sciences,
University of Nebraska-Lincoln, Lincoln, NE, USA | [b] Oklahoma State University, Department of Health and
Human Performance, Stillwater, OK, USA
Note: [] Corresponding author: Joel T. Cramer, Department of Nutrition
and Health Sciences, FNSCA, CSCS,*D, University of Nebraska-Lincoln, 110 Ruth
Leverton Hall, Lincoln, NE 68583-0806, USA. Tel.: +1 402 472 7533; E-mail:
[email protected]
Abstract: BACKGROUND: The rate of torque development (RTD) and the rate of
velocity development (RVD) have previously been described as related; however,
a direct comparison has not been performed. OBJECTIVE: The purposes of this study were to compare voluntary and
evoked RVD and RTD during the same maximal isokinetic leg extensions muscle
actions and to indirectly explore the influence of motor unit discharge
frequency on these variables. METHODS: Sixteen men completed three maximal voluntary and three
maximal evoked isokinetic leg extension muscle actions at
60°·s^{-1}. Peak RVD, general RVD, peak RTD, and
electromechanical delay (EMD) were calculated from the voluntary and evoked
muscle actions. Voluntary and evoked RTD and RVD were also calculated for each
10 ms epoch up to 200 ms of the muscle actions. RESULTS: There was no interaction between voluntary and evoked RVD
across time (p=0.12), but there was an interaction for RTD (p<0.01).
However, peak RTD occurred prior to the isokinetic load range. Peak RTD
(p<0.001), peak RVD (p< 0.01), general RVD (p< 0.01), isokinetic load
range (p<0.001), EMD (p<0.001), and PT (p<0.001) were greater for
voluntary than evoked muscle actions, which was expected due to the influence
of voluntary motor unit firing rates. CONCLUSIONS: Overall, these results suggested that the calculation
of RTD during the acceleration phase of an isokinetic muscle action may not be
valid due to the unknown load and increasing velocity. Furthermore, the RVD may
be influenced by motor unit firing rate, but to a lesser extent than RTD.
Keywords: Involuntary, explosive neuromuscular characteristics, electrical stimulation, rapid force production, acceleration range of motion
