effects based on resting time energy sources reps sets?

I have been doing the PR for a while now and have seen lots of improvement in them, but it has not carried over to anything more difficult.

Just to step it up a notch I wanted to mix things up for a month or so. What would the effects of something like below be?

Doing basics exercises like pull ups, dips and push ups, it seems like I can do 3 sets of 50% of my max with about 45 second rest between.

I am considering doing this every other day or so until I can do 5 sets of 50% and then retesting the max.

I'm curious though if there is any benifit to doing anything at 50% of max for three to five sets. Also how does the 45 second rest play in? Any less and I cant get the third set in with good form, and much more and I could probably pull off more that three sets.

Are you looking to be able to perform more reps or to get stronger? Conditioning or maximal strength gains.

I would not mind being stronger, but mostly I need to be able to perform for two to two and a half hours. Mostly realatively low to medium strength, with the occasional "oh hell" moment where I need all the strength I can muster.

I am training for cross country motorcycle races.