Climbers are one of the best upper/lower body exercises you can do. Despite its effectiveness it does not hyper-stress any joints. 

What's involved: Shoulders, triceps, lower abs, front hip flexors, core. 

Powered by: Lower abs, front hip flexors.

Tip:Flatten your stomach as you perform this exercise pulling in the lower abs and aligning them better. It helps create tautness in them and gives you better results, faster. .