Neuromuscular adaptations to electrostimulation resistance training

Area of Science:

• Exercise Physiology
• Neuromuscular Adaptations
• Muscle Physiology

Background:

• Electrostimulation resistance training (ERT) is a method to induce muscle adaptations.
• Understanding the neural and muscular responses to short-term ERT is crucial for optimizing training protocols.

Purpose of the Study:

• To investigate the muscular and neural adaptations of the quadriceps femoris muscle to short-term ERT.
• To examine changes in maximal voluntary strength, muscle activation, and single-muscle fiber properties.

Main Methods:

• Combined in vivo and in vitro analyses were performed on the nondominant quadriceps femoris muscle of a healthy individual.
• Evaluated maximal voluntary strength, neural adaptations (cross-education, muscle activation), and muscle fiber characteristics (MHC isoforms, cross-sectional area, specific tension).

Main Results:

• Maximal voluntary strength increased by 12%, accompanied by neural adaptations like increased muscle activation.
• Significant changes observed in myosin heavy chain (MHC) isoforms, with increased MHC-2A and decreased MHC-2X.
• Single-fiber analysis revealed increased cross-sectional area for type 1 and type 2A fibers, and enhanced specific tension in type 1 fibers.

Conclusions:

• Short-term ERT induces both neural and muscular adaptations, including strength gains and alterations in muscle fiber properties.
• Neural adaptations suggest involvement of spinal and supraspinal structures in electrically evoked contractions.
• Electrostimulation resistance training significantly impacts single muscle fibers, with a preferential effect on slow type 1 fibers.