The point of physiological failure during exercise, whether it's cardiovascular or muscular, indicates an individual's specific weaknesses and guides training protocols for targeted adaptation.

“So if you got off and I started asking you a series of questions, and you're like, and I basically said why'd you quit? Why did you jump off the treadmill, why'd you stop? And you were like my chest, like I couldn't catch my breath. I thought my heart was going to explode. Okay great. If you ask me and I said my legs were on fire, like I was breathing hard but I couldn't take another step, this is a very rough indicator of different places of physiological disruption.”