What it is
Short maximal efforts with rest long enough that every rep is as fast as the first. The moment your times drop, the session is over — you are no longer training speed, you are training fatigue.
Conditioning Protocols
Sprint and bike interval protocols with the actual work-to-rest numbers — how long, how hard, how often, and when to stop the set.
Sprint Intervals
Maximum output, full recovery
The session
6–10 × 10–20 seconds all-out. Rest 2–3 minutes between reps, walking. Total working time is under three minutes; the session is twenty.
Where to run it
A flat field, a track, or a 6–10% hill. Hills are gentler on the hamstrings because you cannot reach the stride length that tears them.
Before you sprint
Ten minutes of easy running plus build-ups at 60, 70, 80 and 90 percent. Cold sprinting is the single most reliable way to pull a hamstring.
Frequency
Once or twice a week, never the day before or after heavy lower-body work.
Assault Bike Intervals
All the conditioning, none of the impact
What it is
The bike lets you go genuinely maximal without the eccentric load of running, which is why it is the right choice when the knees, ankles or hamstrings need protecting.
Short intervals
10–15 × 20 seconds hard, 40 seconds easy. Hold a target output and stop the set when you cannot hold it, not when the clock says so.
Long intervals
5–8 × 60 seconds hard, 60–90 seconds easy. This one is far more uncomfortable than it reads. Start at five.
Steady state
20–40 minutes at a pace where you could hold a broken conversation. This is the base most people skip in favour of intervals they are not fit enough for.
Frequency
Two to four times a week. It recovers faster than running, so it tolerates more frequency.
Three rules that apply to both
Progress the work, not the rest
Add a rep or add seconds of work before you cut the rest. Cutting rest first turns interval training into a slow grind and removes the quality that made it worth doing.
Stop the set on the number
Whether it is a sprint time or a watt target, the set ends when the number falls off — not when the planned reps run out.
Conditioning is not a punishment
It sits alongside lifting, it does not pay for a bad week of eating. Programme it, do not improvise it.
Maximal conditioning is genuinely demanding on the heart and lungs. If you have a cardiac history, are returning from illness, or have not trained hard in a long time, get cleared before doing any of this at full effort. Fitness guidance, not medical advice.