ROFLMAO you can't compare quantum physics to Newtonian mechanics.
The two are sooooooooo different. For example; it's possible for an electron to be in two places at once. It's even possible for an electron from your body to be inside a wall. Are you going to find the same set of Ivanko plates in two places at once, much less inside a wall? Probably not.
The few equations you'd be looking at if we're talking about weight lifting are;
PE = mgh
KE = .5mv^2
F = ma
You could get into more complicated formulas but these are the three that you'll derive everything else from.
You could get momentum in there as well (p = mv) but that's not needed in the general scheme of things unless you're talking about movement from dead-stop (paused).
There is absolutely NO need to get into relativity with speeds this slow and masses this large. You won't take relativistic principles into account until said object reaches ~3.0*10^7 m/s. Needless to say, neither of us are going to be breaking the sound barrier while benching anytime soon. Or ever, for that matter.
I get where you're coming from, but you're complicating this way too much. Skip the relativity and stick to Newtonian mechanics. Relativity just isn't applicable here.
If you want to calculate the amount of force being exerted on a bar then you'll need to videotape yourself. Determine average bar acceleration on both lifts (the max effort and the speed lift) by plotting a series of data points over time based on the position of the bar vs. time. Calcuate said accelerations. Compare these to the weights being moved in terms of force output in relation to mass and you should be able to find some sort of relationship or at least come to a conclusion. This should be done using quite a few samples if you're serious about this science fair project.
Perform an actual experiment and then compare the results. Determine this for yourself. Empirical evidence and data is crucial, imo. Make sure you're accelerating the bar as quickly as possible (assuming you try to do this) in both lifts to get a relatively accurate comparison.
-To above, acceleration does decrease/increase. It's called "jerk" (change in acceleration).