A progression run is a run that begins at a runner’s natural pace and ends with a faster segment at anywhere from marathon down to 10K pace. These runs are generally intended to be moderately challenging.
Running gait can be divided into two phases in regard to the lower extremity: stance and swing. These can be further divided into absorption, propulsion, initial swing and terminal swing. Due to the continuous nature of running gait, no certain point is assumed to be the beginning. However, for simplicity it will be assumed that absorption and footstrike mark the beginning of the running cycle in a body already in motion.
Footstrike occurs when a plantar portion of the foot makes initial contact with the ground. Common footstrike types include forefoot, midfoot and heel strike types. These are characterized by initial contact of the ball of the foot, ball and heel of the foot simultaneously and heel of the foot respectively. During this time the hip joint is undergoing extension from being in maximal flexion from the previous swing phase. For proper force absorption, the knee joint should be flexed upon footstrike and the ankle should be slightly in front of the body. Footstrike begins the absorption phase as forces from initial contact are attenuated throughout the lower extremity. Absorption of forces continues as the body moves from footstrike to midstance due to vertical propulsion from the toe-off during a previous gait cycle.
Midstance is defined as the time at which the lower extremity limb of focus is in knee flexion directly underneath the trunk, pelvis and hips. It is at this point that propulsion begins to occur as the hips undergo hip extension, the knee joint undergoes extension and the ankle undergoes plantar flexion. Propulsion continues until the leg is extended behind the body and toe off occurs. This involves maximal hip extension, knee extension and plantar flexion for the subject, resulting in the body being pushed forward from this motion and the ankle/foot leaves the ground as initial swing begins.