I would argue against this 100%. Science indicates that the older we get, the more we actually need to do smaller reps and heavier weights. As we age our hormonal levels change as well as our bone density, and this is directly correlated at lifting heavier. Also, think about Grandma and Grandpa, who are on the treadmill every day. They walk their asses off, but that doesn't create glute or core strength. When you need to turn the 1000lb elk over, how are you going to pull that elk over? Low rep, heavy (for you) strength training is critical. ESPECIALLY as we get older. More reps = more joint damage. Stress from weight on a joint is a factor, but if you work your way up, your joints will be able to adapt and manage.