Cumulative Load

Stress fractures account for up to 20% of injuries managed in sports medicine clinics (Abbott et al. 2019), and many of which are recurring (Rizonne et al., 2017). These injuries need weeks to heal often resulting in missing large portions of competitive seasons and possibly shortening athletic careers. The need to monitor an athlete’s training loads is paramount. Physiologic measures such as resting heart rate, heart rate variability, etc. are standard practice for many elite athletes. Similarly, performance outcomes such as rep times, distance covered, weight lifted, etc. are obvious indicators of loading response. A metric far less captured is the cumulative physical load endured with training.

 A bone’s normal response to increased loading is remodeling to sustain further stress. Should the rest be insufficient between re-exposure to loading and/or the bone’s energy stores be lacking, the bone will fatigue and injury may ensue. Bone injuries occur on a continuum with worsening from increased bone or marrow signaling, to microcracks to more severe stress fractures.

 While training loads are a critical factor in the risk of bone stress injuries, propensity of developing an issue is multifactorial, dependent on things such as nutritional status, hormone levels, psychosocial stress, sleep, etc. For this reason, we as sports scientists would be wise to consider training loads with an integrative, holistic, and cumulative approach. As suggested in a recent review by Hamstra-Wright, Huxel Bilven and Napier, athletes should carry a ‘cumulative risk profile’ that influences their training load capacity (2021). 

 Research such as this highlights the need to capture these critical metrics and subsequently tailor our athlete’s programs accordingly.

 A huge shout out to @plantiga for continuously pushing performance technologies forward. Their sensors brilliantly capture and display cumulative loading for each leg individually and combined.