In my humble opinion, I'm not impressed with the level of expertise with the trainers.I blew my back out, herniated a disc, which caused numbness in my left leg after a few workouts. Needless to say I had to have a microdiscectomy and a laminectomy. The weakness may have been there but I believe the routine exacerbated the problem. The workouts are great I enjoyed it but I don't think they properly monitor you enough, especially if you're struggling with a particular exercise. I'm 64 relatively in decent shape,so be extra careful.