A study by the University of Victoria has found a potential link between birth weight and kidney health in ultramarathon athletes, suggesting that extreme endurance exercise may influence the body's response to such intense physical demands. The study, which also found that birth weight could play a role in kidney resilience under extreme physical conditions, was conducted through blood testing to measure kidney function and potential damage before and after their races. Those who weighed less or more at birth could have a greater risk of kidney stress or damage during extreme endurance races, as their organ development was likely impaired during growth in the uterus. The findings suggest that ultra-endurance events may be doing more harm than good for the body.