After being out of lifting for three years due to a shoulder injury that never healed and now with my 17yo in the army after getting buff himself, my 13yo son demanded we work out...So, I'm very pleased and we are now working out at Planet Fitness utilizing a Super Slow technique which focuses on muscle concentration and overall muscle endurance. This serves two purposes: 1. I don't completely tear open my shoulder. 2. My 13yo son does not hurt his body in any way by moving too much weight. 50#s for 10 or 20 seconds per rep is much healthier than 100#s for 1 or 2 seconds per rep.