Concentric versus eccentric training: Effect on muscle strength, regional morphology, and architecture

The different architectural adaptations and the regional changes that occur with eccentric (ECC) vs concentric (CON) muscle actions are not fully understood. The purpose was to investigate regional changes in vastus lateralis muscle (VL) after ECC and CON training. Sixteen males (23 +/- 3 years) performed ECC or CON training twice weekly over 5 weeks, using a single-leg design. Both training modalities caused similar increases in knee extensor strength (measured with dynamometry) (10%-13%) and muscle volume (8%) (measured with 3D ultrasound) after 5 weeks of training. Anatomical cross-sectional area at the mid-point of the muscle was greater after CON training (9%), but greater at the distal end after ECC training (8%). CON training increased fascicle angle at the mid-point (8%), with little change at the distal end (2%). There was a small increase in fascicle length at the mid-point after CON training (3%). Conversely, ECC training caused a greater variation in regional and architectural adaptations. Fascicle length increased at both the mid-point (6%) and distal ends (8%) after ECC training, and similar changes in fascicle angle were also observed in both regions (3%-4%). Different region-specific changes are evident after CON and ECC training, with implications for performance and injury risk.