Abstract
The overload imposed on the neuromuscular system under Electrostimulation (ES) can
be expressed by applied current intensity or by Electrically Evoked Torque (EET).
The aim of this study was to discern which of these two parameters is the one which
is determinant for the efficacy of training by ES. Test and training involved isometric
contraction of the flexion maintained at a joint angle of 25° (0° = extension). The
16 trained subjects received 15 sessions of 25 electrically evoked contractions, using
a monophasic rectangular waveform current at a frequency of 2500 Hz modulated at 90
Hz. Each stimulation lasted for 5 sec at the maximal tolerable current. Contrary to
the control group (n = 16), the trained group significantly increased their MVIC (15.6%).
The individual strength gains ranged from -5% to 49%. No correlation was found between
current level and strength modifications. A direct relation was established between
the EET and the strength gains (a minimum threshold of EET must be reached during
at least 8 sessions to induce strength increases). The “overload principle”, previously
described for voluntary contraction strengthening, seems to be suitable for electrical
stimulation and concerns the EET shown on the ergometer as the effect of the contraction
of agonist and antagonist muscles.
Key words
Electrostimulation - isometric contraction - “overload principle” - strength - training
