Getting A Sacral Stress Fracture From Running

This blog is as much for me, as it is for others, as I try to figure out how I went from running the fastest times in my life to having a stress fracture in my sacrum.

“Warden et al (2021) reported that bone stress injuries symptoms typically begin appearing approximately 3-4 weeks following a major workload ‘error’. Such errors may include insufficient recovery time between bone loading bouts (i.e., training sessions), sudden increases in weekly workload in terms of number of loading cycles (i.e., miles or kilometres run), and/or an increase in training intensity.” An excerpt taken from Brad Beer's article “Sacral bone stress injuries in runners”

Brad outlines multiple biological and biomechanical risk factors that can be attributed to the development of bone stress injuries. I believe mine to be training load based, a common cause identified by Warden et al (2021).

The Big Change To My Training Load

Compared with my previous training, the design of my training plan over the 2021-2022 summer period had one major difference—an additional 4th week in one training block. Usually, I train in 2-3 week blocks, knowing from previous experience that anything more generally leaves me feeling run down and lethargic. However, over the Christmas period I figured that being on holiday, the stress of an extra week would be countered by that extra recovery gained from chilling at the beach. This would also allow my programme to work a lot better logistically in terms of family commitments and subsequent training weeks in the lead up to the Tarawera Ultra. I also wanted to push my limits to see if I was capable of handling more (spoiler alert, I’m not!)

My weekly training load measured in TSS from TrainingPeaks
My weekly training load measured in TSS from TrainingPeaks

Being a professional coach and lover of data, I know my numbers. I know a training stress score of 700 or more in a week is my upper limit. Within my 4-week training block, I hit TSS numbers of 675, 546, 638, 639, and a recovery week of 438. Based on those numbers, I knew I wasn’t doing anything crazy on a weekly basis. However, our biology doesn’t operate on a Monday - Sunday schedule!

Where I believe I made the significant mistake that subsequently led to my sacral stress fracture was not only adding an additional fourth week but also running a long run (65km) with minimal recovery (5 days) from my previous long run (65 km), the combination of which drastically reduced my ability to recover from training.