What does the PSSS and ASSS systems utilize during running?

The PSSS (Proprioceptive Stretch Shortening System) and ASSS (Active Stretch Shortening System) systems specifically leverage the stretch-shortening cycle during running. This physiological phenomenon describes how muscles can efficiently produce force through a rapid stretch followed by a shortening action.

When a runner’s foot strikes the ground, the muscles and tendons undergo a brief eccentric contraction or stretch. This stored elastic energy in the muscle and tendon is then utilized during the concentric contraction phase (when the muscles shorten) to propel the runner forward. This mechanism not only contributes to enhanced power and efficiency in running but also helps in injury prevention by optimizing muscle and tendon loading.

This understanding underscores the importance of the stretch-shortening cycle in both training and coaching, as it can influence how runners improve their speed and endurance while minimizing fatigue and risk of injury.