NSCA Sprinting And Running Practice Test

During sprinting, the leg that is in contact with the ground goes through both braking and propulsion within the same stance phase. When the foot lands, the muscles work eccentrically to absorb force and slow the body's forward momentum (eccentric braking). Almost immediately, they switch to concentric action to push off and propel the body forward for the next step (concentric propulsion). This sequence happens during the single-leg support portion of stance, when one leg is bearing the body's weight. The other phases don’t involve this combination. The flight phase has no ground contact, so there’s no braking or propulsion, and the recovery or swing phase is the leg moving forward in the air. Start in sprinting refers to beginning acceleration from blocks, which isn’t the continuous stance where braking followed by propulsion occurs.