Is it possible that speed endurance and the elastic requirements for jumps (i.e. long jump) are somehow related? After some anecdotal evidence I might be inclined to think so.
Besides that, from Supertraining:
-Strangely enough, even after all the methods listed above, it’s anaerobic endurance training that appears to have the greatest effect on tendon and ligament strength (Siff, 2003). This may be due to the link between lactic acid production and the increase of a certain collagen synthesizing enzyme (Booth & Gould, 1975). Regardless of what it’s due to though, any anaerobic endurance training is great for increasing tendon stiffness.
-Regarding specifics, anaerobic endurance training generally consists of any kind of intense work between 40-60 seconds in duration. This can be sprinting, continuous weight lifting, or even cyclical jumps. No matter what’s used, as long as the intensity is high enough and the set duration is correct, the right training effect will be found.