Continuous fartlek style running will get you to 155+ bpm. Back off the pace to actively recover to 120 bpm, then go after it again.
Problem is, you need to be fit to do this right, reducing the risk of injury. Always preferred fartlek to repeat intervals on the track. Both have their place however.
If anyone is new to fartleks, it’s a Swedish word that means ‘speed play’. They’re an excellent tool for training.
Maybe be careful the first few times you type that on a phone - my poor running coach got a lot of text messages about ‘fart leaks’ when I was trying to report on my training. They are not the same.
Edit - If you’d like to try one, Mona fartleks are pretty well known.
