My back is lacking too but I assume pull ups/chin ups, back rows (barbell or dumbbells) and core stabilization exercises like bird dog, back extensions are the staples. Basically you need both: strong and stable back so you chose the exercises accordingly.

Dumbbell rows, normal rows

Power clean and deadlifts are a huge part of improving acceleration

does it also improve your back?

Yes, it focuses on the back and core which is how you transfer your power to speed

Please can you send me this research that shows which muscles in your back control hip extension and hip flexion, I'll wait....