Endurance runs are long-distance running events that test a person's stamina and endurance. There are several alternative words that can be used as synonyms for these types of runs. The first is "marathon," which typically refers to a race of 26.2 miles or more. Another synonym is "ultra-running," which describes runs that are longer than a marathon, often 50 miles or more. "Long-distance running" is another term that can be used to describe endurance runs, focusing on the distance rather than the intensity. Finally, "endless running" is a descriptive phrase that can be used to convey the difficulty of long-distance running events and the mental and physical toughness required to complete them.