Judging force and pressure before a practical

[Physics quest]

Ok, I am wondering if its possible for me to calculate how much force or pressure I can take from carrying or moving something based on what I can already move. Is it possible to predict how much pressure I can take on my hands, or how much I can potentially create?

For example (not necesserily real figuires of what I am capable of, I am just making an example);

lets say I can easily lift, let's say 50 pounds without a problem, is it possible to find out without lifting anything else, how much I could logically lift before I have to struggle? Its the same with moving say, heavy boxes or crates. I can quite easily flip over, push X amount of weight, let's say 100kg, but if I wanted to actually lift the box off the ground is it possible to find out how much effort it would take me? given the weight of the object and how I moved it before.

I assuming now there's probably no way to find out, but there must be some way of finding out how much pressure something can take before it breaks or how much strength a bridge has before its supports cannot take anymore. Physical engineering I am assume has a way of finding out how strong supports have to be, beforehand to hold up X amount of bridge and weight of vehicles.

 

[JHamm]

The problem is that biological systems have a lot more to them than mechanical ones. For instance your ability to lift a weight depends not only on your strength but also your technique, your fatigue and your ability to recruit type I muscle fibers or a higher number of motor units (something gained through practice). There are calculators that attempt to predict your maximum from a weight you can lift a maximum of 3, 5, 10 etc times but they are simply estimations; knowing you can lift something easily doesn't really tell you what your maximum is, I'm sure we could all lift 50 pounds with ease but our maximums will likely be widely spread.

 

[Physics quest]

Hm, can you point me/link me to any of those calculators? I don't need to be dead spot on but if there's any that can give me some form or estimation maybe it could help me.

Thanks.