A strong stride requires strong hip flexors because they pull the hip into hip flexion (think knee drive) when you swing your leg forward The hip flexors- iliacus, Psoas major and TFL are powerhouse muscles that need to be strong, and the faster your run, the more you use them For a full body strength routine designed for runners with a customized training plan, go through the @completerunnersclub so you have access to Physical therapists and run coaches as you run stronger, improve your running performance and prevent your risk for injuries