How long should your intervals be?

Riders ask which intervals are best. It is the wrong question, in a specific and fixable way: interval length and intensity are not two choices but one, and the thing that decides both is what you are trying to improve.

The trade you are making

Short efforts can be very intense but you cannot accumulate much time at them. Long efforts accumulate a lot of time but cannot be intense. Every interval session sits somewhere on that curve, and moving along it changes which system you are stressing.

This is why "harder is better" fails as a principle. A 20-minute effort ridden at VO2max intensity is not a superior session — it is an abandoned one.

Choosing by what your event demands

• Criterium or fast club run: short efforts and repeatability. The demand is dozens of accelerations, not one long push — see your first criterium.
• Hilly road race: 3–5 minute efforts and over-unders, because the decisive moments are climbs with imperfect recovery between them.
• Gran fondo: long threshold and sweet spot, plus genuinely long rides. The limiter is durability, not ceiling — pacing a gran fondo with power.
• Time trial: 8–20 minute efforts at or just under race pace, with the position rehearsed at the same time.
• Hill climb: intervals of exactly the event's duration, at the event's gradient — see hill climb events.
• No event, just want to be fitter: mostly long easy riding with one threshold session and one shorter, harder session each week.

Three rules that save a lot of wasted sessions

1. Pick the intensity you can hold for the last rep, not the first. A session where reps one and two are excellent and four to six collapse has delivered two useful efforts. One where all six are slightly conservative has delivered six.
2. Match the recovery to the purpose. Long recoveries for maximal work, short and incomplete recoveries when the incompleteness is the point — as in 30/30s.
3. Count total time at intensity, not the number of reps. Four times five minutes and six times three minutes are broadly comparable sessions. Ten times one minute is not, whatever it feels like.

Progress the session, not just the power

When a session gets easier, the instinct is to raise the watts. Often the better move is to add a rep, or lengthen each effort, or shorten the recovery. Those progressions build the quality you actually wanted — being able to do more of the same — rather than chasing a number that may not be sustainable.

A trainer makes all of this considerably easier, because the targets are held for you and the comparison between this week and last is exact. Moveee Indoor runs the workout in a browser tab with the resistance stepping through each effort automatically, and saves the full power stream so you can see whether rep six really held its target or quietly sagged — which is the single most useful thing to know when deciding how to progress next week.