Muscle conduction velocity, strength, neural activity, and morphological changes after eccentric and concentric...

Area of Science:

• Exercise Physiology
• Neuromuscular Adaptations
• Sports Science

Background:

• Concentric and eccentric muscle actions are fundamental components of resistance training.
• Understanding their distinct and overlapping effects on neuromuscular adaptations is crucial for optimizing training programs.
• Previous research has yielded varied results regarding the specific adaptations induced by each training type.

Purpose of the Study:

• To compare the effects of 6-week concentric (CON) versus eccentric (ECC) training on neuromuscular adaptations in young adults.
• To investigate changes in strength variables, muscle conduction velocity, neuromuscular activity, muscle thickness, and echo intensity.

Main Methods:

• Twenty-two participants underwent 6 weeks of twice-weekly isokinetic training, divided into CON and ECC groups.
• Assessments included concentric, eccentric, and isometric peak torque (PT), rate of force development (RFD), muscle conduction velocity (CV), and vastus lateralis (VL) muscle thickness and echo intensity via ultrasonography.
• Training volume progressed from 2x8 to 5x10 repetitions.

Main Results:

• Both CON and ECC training similarly increased concentric and eccentric peak torque (PT) and vastus lateralis (VL) muscle thickness, conduction velocity (CV), and rate of force development (RFD).
• Eccentric training uniquely led to significant increases in isometric PT.
• Both groups showed reduced VL echo intensity, indicating improved muscle quality, with significant correlations between training variables and neuromuscular outcomes.

Conclusions:

• Both concentric and eccentric training protocols effectively improve dynamic strength, muscle thickness, and quality in the early stages of training.
• Eccentric training offers an additional benefit by enhancing isometric strength.
• These findings suggest that incorporating both training modalities can lead to comprehensive neuromuscular development.