How many times a week do you work out? Never mind, just cut the number in half; it probably won’t make any difference. That’s the suggestion of research conducted at the University of Alabama, where scientists randomly assigned 72 older, sedentary women to one of three exercise groups. As Gretchen Reynolds reports in the Well column, one group began lifting weights once a week and performing an endurance-style workout, like jogging or bike riding, on another day, while another group lifted weights twice a week and jogged or rode an exercise bike twice a week, and the third group completed three weight-lifting and three endurance sessions, or six weekly workouts. Reynolds reports that over the course of four months, the intensity and duration gradually increased, until the women were jogging moderately and lifting weights for 40 minutes each. The bottom line? When the researchers measured the women’s aerobic capacities, muscle strength, body fat, and moods, they found almost no differences in fitness gains. Reynolds writes that the women working out twice a week had become as powerful and aerobically fit as those who had worked out six times a week. So there. Read an excerpt of the study here.