From this Science News article Use Weights, Not Aerobics, To Ease Back Pain, Study Suggests:
Many years ago when I first started strength training I followed the conventional wisdom that stated that you had to give yourself a day off between strength training sessions to let your body recover and become stronger. I was a man in a hurry, so I strength trained Monday, Wednesday, Friday, Sunday, Tuesday, Thursday and Saturday - repeat - and I never missed for five straight months.
For many, gyms end up being collection agencies disguised as gyms. They depend on people not sticking with their resolutions.
· What good is an exercise program where you go three times a week and you go for two weeks or two months and never go again? This is the scenario that is replayed yearly by millions. Many are repeat offenders. The only thing that ends up lighter is their wallet. People waste thousands on programs they don’t stick to.
· Eleven percent of Americans are members of health clubs. There are more former members of health clubs that there are presently members.
· 30 percent of health club members do not renew their memberships.
· Of that 30 percent a small minority of them use the facility consistently over the course of a year
· You join and then they entice you with large packages of personal training sessions.