Irregular periods are extremely common among female runners. However, just because something is common, it doesn't mean that it's normal. Menstrual cycle disturbance can be an early warning sign of something called low energy availability. This is when the athlete is burning more calories than they're taking in.

This situation drives the body into a kind of crisis mode during which it will only focus on short-term physiological processes such as movement and respiration. Processes related to longer-term physiological health are temporarily put on hold. One of these processes would be the maintenance of bone health. This can lead to lower bone density and running injuries such as shin splints or stress fractures. These injuries are very frustrating on their own, however, if left untreated, low energy availability can lead to serious long-term health problems such as osteoporosis or fertility issues.

An early sign that a runner is in a state of low energy availability is the disruption of the menstrual cycle. This situation can affect runners of any age and any ability and it is far more common than we used to believe. Mark Hutson is an expert on this topic and currently finishing up a Ph.D. in this important area of research. He joins me on the show today to discuss how runners can monitor for the signs of low energy availability and how they might seek to address the issue.