content: none of our ancestors did this on a weekly basis.  Going how far back? Hippocrates prescribed gym exercise for physical and mental health. Milo of Croton invented weight training about a century prior. Ayurvidic prehistoric oral tradition prescribes exercise for much the same reasons as Hippocrates. I might also suggest looking into the concept of cross-training to prevent injury and considering how that may apply to being a more effective laborer, hunter, and provider, especially for those of us trapped in unnatural routines by modern society's demand for hyper-specialization.   have you ever seen another animal waste its time and energy on working out with tree branches?  Animals climb tree branches and "waste" calories with play. Body movement is necessary for mental and physical wellbeing and surrogate activities are sometimes needed, lest peace rob you of your strength.