QUICK ANSWERS

Quick answers

Short answers to common questions about HIIT, Tabata, rounds, rest and heart rate, each with its sources

Each answer starts with the short version, then explains it, citing the studies and guidelines behind it. For the longer reads, see the guides.

YOUR NEXT SESSION STARTS HERE

Bring the effort.
We’ll keep the time.

Cero is free to download for iPhone, iPad and Apple Watch.

Download Cero
Cero’s simple timer on iPhone 18 Pro, with the green wave about half full during a high-intensity interval

Cero is a timer, not a medical device. If you’re new to hard exercise, are pregnant or have a health condition, check with your doctor first, and stop if you feel unwell.