Hamstring strength and architectural adaptations following inertial flywheel resistance training.

Abstract Objectives To investigate the architectural and strength adaptations of the hamstrings following 6-weeks of inertial flywheel resistance training. Design Randomised, stratified training intervention Methods Twenty healthy males undertook 6-weeks of a conventional (n = 10) or eccentrically-biased (n = 10) flywheel leg-curl training intervention as well as a subsequent 4-week detraining period. Biceps femoris long head (BFlh) architecture was assessed weekly, whilst assessments of eccentric and isometric knee flexor strength and rate of force development (RFD) was conducted prior to and following the intervention and detraining periods. Results The participants who undertook the eccentrically-biased flywheel intervention showed a significant 14 ± 5% (p  Conclusions Flywheel leg-curl training performed with an eccentric bias led to significant lengthening of BFlh fascicles without a change in RFD, eccentric or isometric strength. These increases in fascicle length were lost following a 4-week detraining period. Conventional flywheel leg-curl training resulted in no changes in fascicle length and strength. These findings suggest that additional eccentric bias is required during inertial flywheel resistance training to promote fascicle lengthening in the BFlh, however this may still be insufficient to cause alterations to strength and RFD.