The First 20 Minutes

The book references many studies, but I wonder how Gretchen Reynolds chose which ones to highlight and how she balances their credibility.

Some of the advice challenged my assumptions about working out, like the importance of just 20 minutes. I'm curious if others tried these methods and saw results.

That specific time window seems so precise—was it based on particular research or a personal fascination with that moment? Would love to hear the backstory.