How should the arms be properly used? I remember going through threads and I read about how in sprinting you should only focus on the down stroke of the arm and the motion should originate from the shoulder. Correct me if I’m wrong.
For most, the cognitive emphasis is as you stated (down) with the primary rotation occurring at the humerus (shoulder motion). Palm moving from ~chin to past the hip.
The elbow should be held at ~90, however, it will close more during front side <90 and open more than 90 during back side action the higher the velocity.
There are instances, however, in which front side mechanics will specifically be cued.
The role of the arms contribute to the sprinter’s momentum. The rotation of the thoracic spine which, in turn rotates the shoulder girdle from an axial (birds eye) view, provides counter- rotation relative to the hip action.
If you’re curious as to the significance of arm action, go out to a field or track and attempt to sprint with your elbows fully extended (straight arms) and note the difficulty (long lever = more power yet lower frequency). Then attempt to sprint with your elbows fully flexed (short lever = less power and higher frequency).
Torque is optimized at 90 degree angles thus this is the objective for the elbow angle when sprinting, however, as stated, the angle will close more in front and open more in back the higher the velocity.
Arms are for balance, try moving quickly on a narrow beam, arms up, crossed, out.
the arm movement is controlling balance.
The action affects force reaction.