In the past eight months, three well-known triathletes have had sacral fractures. Jan Frodeno (GER) and Ben Hoffman (USA) withdrew from the 2018 Ironman World Championship due to sacral stress fractures. Then on April 17th, Lionel Sanders (CAN) announced on Instagram that he had sustained a sacral fracture. The definitive cause of the fracture is unknown, but Sanders did recount an incident on Instagram and YouTube:

On March 18th, I rode up to a water fountain and tried to be cool and balance at the fountain while taking a drink. I lost my balance and fell over directly onto my hip/butt, without having time to unclip. The embarrassment was far greater than any pain, so I immediately got back onto my bike and rode away. The next day I became symptomatic.

Lionel Sanders withdrew from Ironman 70.3 Oceanside with a sacral fracture.

“The sacrum is incredibly resistant to stresses, making fractures in this region very uncommon,” says Dr. Paddy McCluskey, the Chief Medical Officer and Medical Lead at the Canadian Sport Institute in Victoria, British Columbia, for Triathlon and Athletics Canada.

So, what are the common ways a sacral fracture occurs?

“The two common ways a fracture occurs at the sacrum are through trauma (high energy fractures) and stress (low energy fractures),” says Dr. McCluskey.

High and low energy fractures

Examples of high energy fractures are those sustained upon acute impact. For instance, a cycling crash at high speeds. A low energy fracture occurs after chronic impact and stress. For example, stress fractures are a common injury for elite runners.

Jan Frodeno had a great 2018 campaign, but withdrew from the Ironman World Championship with a sacral stress fracture.

Increased risk of sustaining a sacral fracture

“The sacrum has to be a very strong bone in order to withstand impact,” says Dr. McCluskey. “Those with low bone density are at a greater risk to sustain a low energy fracture (not just at the sacrum).” This commonly occurs in the elderly population, although some individuals may be genetically predisposed to have lower bone density.

“Another way a sacral fracture can occur, is if the individual is in a sustained state of energy deficiency,” says Dr. McCluskey.

Related: Pushing the limits of performance: Sacral stress fractures

It’s not uncommon for elite endurance athletes to go through periods of reduced energy availability in order to lose weight and optimize performance. However, if guidelines are not put in place, athletes run the risk of injury. “When energy deficiency occurs over a longer period of time, on top of the training hours of endurance athletes like Ironman triathletes, the risks of stress fractures and sacral stress fractures rise,” says Dr. McCluskey.

Once an athlete enters a state of energy deficiency or starvation, the body prioritizes basic metabolic functions to sustain life. “First on that list is the brain and heart,” says Dr. McCluskey. “Farther down is bone metabolism (cell turnover) with skin and hair health.” So, when energy resources are limited bone, skin and hair health can begin to deteriorate. Though there may be other factors, low energy availability significantly increases the risk of endurance athletes sustaining a stress fracture. “When stress fractures occur at the sacrum – nutrition is a key factor,” says McCluskey.

Report error or omission