If you have energy for one more interval (high intensity, shorter duration effort) during endurance training, should you do the interval, or is it more beneficial to finish the workout before reaching empty? Sports physiologists suggest that the body is like an iPhone battery. It performs best between 80-20% of charge. Draining the battery (body) too much causes the battery to lose functionality, and maintaining a constant 100% charge decreases total battery life. We can take steps to expand our functionality in that sweet spot, but ultimately, there is a threshold for return on investment.

How might we understand that the attributes of ‘grit,’ ‘fortitude,’ and ‘never say quit’ are noble but potentially misguided if not utilized in the right circumstances? Leaving one more interval (effort) in our capacity may be more impactful than finishing the workout (project) in total exhaustion. What is your ideal performance bandwidth if you selected a percentage of effective output (like a mobile phone battery)?