The phrase "intense bursts" refers to moments or actions that are extremely powerful, energetic, or forceful, but occur for a short period of time. Full definition
For puppies, several short intense bursts of exercise are better than one long walk. (c2cnd.org)
It mimics real life situations where you actually perform short intense bursts of activity. (fitmole.org)
We are told that trainees need to be able to work in intense bursts when required, with hours that are sometimes «brutal», especially in the transactional departments. (legalcheek.com)