Flat-out intervals that torch your engine and your legs.
Build to full speed before you commit your full stride. Don't jump straight onto a fast belt cold.
Sprint intervals on the treadmill push your heart rate to its ceiling in short, repeatable blasts, with the belt enforcing an even pace so every interval is measurable and honest. The rest blocks between efforts are what let you hit genuine top-end intensity again and again, which is where the conditioning gains come from. It earns its place as the time-efficient engine builder, ten to twenty hard minutes doing what a long jog cannot.
Fast enough that you could not hold it beyond your interval, usually a pace that feels like 8 or 9 out of 10 effort. Start conservative, the belt does not slow down when you do, and build speed across sessions once your stride at pace feels safe.
A classic starting point is 20 to 30 seconds hard with 60 to 90 seconds easy or stepped off, repeated 6 to 10 times. As fitness climbs, shorten the rest or lengthen the work, never both in the same week.
Straddle the belt on the side rails, hold the handles, and only step on once your feet can match the speed, building your stride over a couple of seconds. Getting off is the reverse, hands to rails first, then feet wide. Never leap onto a fast belt cold.
