The strechcordz is a good tool for strengthening, except that the resistance on the yellow cord turned out to be too light for me.

This is my third set of StrechCordz. The first one was a bit too soft. It worked for many exercises, but in some rooms I had to stretch them very far to get enough resistance. The second and third are identical - one for home and one for my suitcase. These will exercise all upper body muscles. The only thing you have to do is find a sturdy connection point. In hotels, that is almost always the door handle leading to the hallway. I got rid of my cable-weight machine because these take up less space and work just as well. I mostly use them for rows, overhead presses (lean forward and press away from the anchor position). I prefer the Charles Atlas dynamic tension exercises (no equipment) for bicep/tricep (although StrechCordz can work these muscles too), and one-leg squats for quads/gluts. I also used these for swim pulls and close grip pulldowns when I was doing triathlons (4 consecutive Kona qualifications).