Biceps femoris long head sarcomere and fascicle length adaptations after 3 weeks of eccentric exercise training

•Biceps femoris long head fascicle and sarcomere lengths increase after 3 weeks of Nordic hamstring exercise training.•Architectural adaptations occurred only in the distal portion of the muscle.•Increases in fascicle length in response to 3 weeks of exercise training were not the result of serial sarcomere addition.