Endurance training does not affect maximum exertion/distance capacity in Anolis carolinensis lizards

Locomotor performance abilities are key predictors of survival and reproductive success in animals and understanding how selection targets them can provide insights into how morphology and physiology relate to fitness. But despite the large body of work on performance traits, along with well-established protocols to measure them, performance can be challenging to measure. Endurance, for instance, is commonly measured by recording how long an animal can run at a set pace until exhaustion, which is time consuming and requires dedicated equipment. Consequently, exertion or distance capacity, measured as distance run until exhaustion when chased, is often used as a proxy for endurance, but the relationship between these two metrics has never been assessed even though they likely rely on different underlying physiological mechanisms. We tested experimentally for a relationship between endurance and exertion by training green anole lizards for sprinting and endurance and measuring whether exertion capacity responds to either type of training. Prior to training and across treatments, males displayed a mean (±s.d.) exertion capacity of 14.08±0.29 m and females 12.03±3.52 m; after training, this was 14.78±3.57 m and 12.19±2.21 m, respectively. We found that exertion capacity was unaffected by either type of training in green anoles. We also show that a positive relationship between endurance and exertion capacity pre-training exists only in females and that this relationship is inconsistent among studies. Exertion should be studied as a locomotor trait in its own right and not as a proxy for endurance.