This is what happens in the hamstring muscles during a proximal dominant hamstring exercise! :) Great visual representation based off a study by Bourne et al. (2016), showing that proximal hamstring exercises are best for biceps femoris hypertrophy. The study investigated the Nordic Hamstring Curl and the 45 Hip Extension exercises, not the Razor curl, which is shown in this video. Video made by Lachlan Wilmot - Athletic Performance Coach | Trust me, I'm a Physiotherapist