The idea that a leaner body makes for a faster stride is common among distance runners. But it’s inaccurate and sets a dangerous ideal. Runners who are excessively lean are prone to injuries, infectious diseases, mental health problems and loss in bone density, said Michael Fredericson, MD, a professor of orthopaedic surgery who has served for decades as the Stanford University track team head physician. Female runners are more likely to suffer these effects, he noted.

During his career as the head team physician, Fredericson has seen so many athletes with problems related to low body weight — including bone stress injuries, menstrual irregularity and osteoporosis, or loss of bone density — he decided to study ways to prevent it.

Physical activity is a powerful medicine that can promote health and change the trajectory of aging. However, in the modern world, we have drifted away from incorporating physical activity into our lives. As the barriers to daily movement have gotten stronger, the burden to exercise has gotten greater. As scientists learn more about the pathways of disease, the causes of aging and the mechanisms by which exercise exerts its benefits, we can develop targeted exercise strategies that can slow (i.e. “hack”) the aging process. In this session, we will discuss how physical activity can slow aging and how different types and amounts of activity can optimize desired health and fitness outcomes.

Dr. Michael Fredericson, director of the PM&R Sports Medicine and co-director of the Stanford Center on Longevity at the Stanford University School of Medicine, said the way the study was conducted it was unclear if the people who exercised in the morning were “systematically different from those who exercise at other times in ways not measured in this study.”

“For example, people who exercise regularly in the morning could have more predictable schedules, such as being less likely to be shift workers or less likely to have caregiving responsibilities that impede morning exercise,” Fredericson said.

Stacy Sims, MSC, PHD, is a forward-thinking international exercise physiologist and nutrition scientist who aims to revolutionize exercise nutrition and performance for women. She spoke with Katie Couric about why exercise is so important for women as we get older, and the best exercises for women in different stages of menopause.