Increasing speed is all about decreasing ground contact time. if the forefoot cannot be controlled and utilized with ideal ankle dorsiflexion and ankle stiffness; it will be almost impossible to redirect sprinting force and explode. Anerobic fitness and athletic performance is at the top of most fitness pyramids for a valid reason. Plantar flexion endurance is something undervalued in personal training and athletics. For most, it needs to be developed slowly due to the calf having an abundance of slow twitch fibers. The soleus is slow, and the gastrocnemius is fast twitch. Some adults and athlete’s are born with a a higher percentage of fast twitch, most are NOT. Search my mobility section and make sure you are doing your ankles PAILS and RAILS which practices isometric loading. Try my slant board single leg balance exercises. Perform skater squats, pistol squats, and finish your single leg movements in dorsiflexion. I usually perform 3 sets of 4 on each leg. Power up.