2 Best Hip Flexor Exercises In sprinting, your hip flexors need to be strongest When the leg is behind you Therefore it’s important the exercise: A) Gets you into that range B) Loads it sufficiently in that range Hip flexor fall backs are great for this (Plus you get bonus ab training) But, if you want to truly isolate the hip flexors in the end range position You can’t beat cable knee drives I like 30% of BW x 10 reps/leg as a target.