I’ve been doing stuff like step ups lately and some isometrics. The step ups are working my concentric strength quite well. In concentric strength we’re recruting high number of units per contraction which is one way of looking at power. Though eccentric contractions seem to biuld the fast twitch fibres well and develope the ability to store energy, the reactive strength using the stored energy and releasing it efficiantly, which again, is of vital importance to sprinting. 
3 questions;
- Am I compromising reactive strength by not using normal methods but instead using long hold isometrics, and concentric /eccentric step ups that don’t utilize the stored energy (becuase once you’ve put yer foot on the groung and re-set yourself you’ve lost allmost all the previously stored energy).
- Is reactive strength more important to sprinting speed (5-100 meters) than starting strength/concentric power?
(Of course starting strength most important pushing out of the blocks.) - Do normal lifting methods/ e.g 2 secs down - 0-1 sec at bottom - x secs upwards develope MORE concentric strength or LESS concentric strength than “break the chain” type lifting?(e.g 2 secs down - rest on box for 5 secs OR re-set position such as with step ups/ dead lifts etc.)
Answers to any of above appreciated.