Spartacus;
The SLJ test only proves that max strength is going up. There is a balance and, in some instances, a tradeoff required between all elements for success in sprinting. This balance dictates that, if everything is in place for a great performance, the SLJ test might very well go down!
Charlie, I am just giving an opinion from my own observations made during the last 25 years. I also point to a 400m running friend who did a standing long jump test on a Thursday for a personal best and ran 49.29 on Saturday shattering his former best of 50.04. In other words, if one can maintain or improve their gross power while undertaking specific components of sprinting training, then one is even more likely to run a personal best.
Again, I agree with your comments about all ingredients being right for an optimal performance. However, i note fom my own experience, that when I ran a personal best for 300m (35.9), I also ran 50.4 and achieved a personal best standing long jump (2.90m). I actually did no weights and used the jumping test as a measure of my power from bounding twice a week.
I do acknowledge your previous points that being ready for an optimal 100, 200, 400m may well reduce your qualities over a short 30m distance. Yet, if one can maintain peak maximal power while developing specific components of the race, then one will also achieve a personal best. After all, any method that works is a successful method.
Maybe I (and others) was able to achieve dual objectives being a lesser standard of athlete and on the way up in terms of improvement. Yet, Ben johnson also did personal bests in squats (a maximal strength test) in the same period as his personal bests (9.83 & 9.79).
There are many ways to train, and as long as all related components go in the right direction as much as possible, then success will be achieved.
I second what Spartacus said. I have noticed the same relationship both in my own training and others I have coached. Also, I would like to propose that SLJ is not as height dependant as some of you think. Throwers jump well because of their superior strength/bodyweight ratios. Also, Ray Ewry was not the best jumper of his era. There were several of his contempories who were superior to Ewry, but were professionals. The best of the lot was but 5’5".
dummies question: where do u all measure distance from? from toe to toe? or like in LJ, from toe to heel.
that could account for 30cm difference.
suddenly the 260cm SLJ i did in the backyard turns into a 290cm jump!
The SLJ is no valid indicator for explosive power as other tests are. The Counter Movement Jump -CMJ- and the Squat Jump -SJ- have been evaluated and measured extensively by C. Bosco PhD and are both more valid and corelated to sprint performance. You can use the ERGO-JUMP device to make the Test.
I would be nice if athletes could do some safet tests to see if any pattern of explosiveness can be tracked. I have one athlete that can do a two handed dunk with no run up (5-9) but my fastest had a 33 inch vert.
Clemson the problem is all these jump tests have too much skill/technique issues involved.
I was thinking that a static jump from the bottom of a full squat position with arms around the back of head would be a more valid test. No arm swing, and no stretch reflex involvement. Just pure concentric explosion.
I myself have added 13inches on my SLJ since I started training 1.5 years ago, despite gaining 27 lbs 
Loving the avatar Col, how would you take the measurement on such a test?
well I guess you could use those contact mats, or something like the Micro Muscle lab or those tape measure things that you hook up to the waist