How do I know I'm doing high-enough intensity? The abstract says "Six 40-s intervals at 100% of V_O2 peak" of cycling. I guess that means pedal as hard as I can

How do I know I'm doing high-enough intensity? The abstract says "Six 40-s intervals at 100% of V_O2 peak" of cycling. I guess that means pedal as hard as I can for 40 seconds, rest for 20, repeat.