The perfect exercise doesn’t exist. The good-enough exercise is anything you do regularly without injuring yourself. But maybe you want more than good enough. One place you could look for insight is studies on how 20 college sophomores responded to a particular 4 week exercise program, but you will be looking for a long time. What you really need are metrics that help you fine tune your own exercise program.

VO2max (a measure of how hard you are capable of performing cardio) is a promising metric for fine tuning your workout plan. It is meaningful (1 additional point in VO2max, which is 20 to 35% of a standard deviation in the unathletic, is correlated with 10% lower annual all-cause mortality), responsive (studies find exercise newbies can see gains in 6 weeks), and easy to approximate (using two numbers from your fitbit).