Here's the situation a lot of masters cyclists know in their legs. You've trained consistently for years. The base is in. The threshold work is in. The volume is reasonable for the time you've got. And the FTP test on Sunday says exactly the same thing it said three months ago.
You're not under-trained. You're not overtrained. You're stuck. The system has adapted to the stimulus you've been giving it and stopped responding. Doing more of the same isn't going to change that. Doing the same harder isn't going to change that. Something different has to enter the week.
For a lot of masters cyclists, the missing stimulus is sprint interval training. Not VO2max work. Not threshold extension. Properly all-out, 30-second, lung-burning, leg-trembling sprints with full recovery between them. The session is short. The cost is real. And for a stalled rider with eight to ten years of training in the legs, it's often the cleanest way to get the engine moving again.
What SIT Actually Is
The classic Sprint Interval Training protocol — the one most of the research is built on — is straightforward:
- Effort: 4–6 × 30 seconds, all-out maximum.
- Recovery: 4 minutes of easy spinning between efforts.
- Total session time: 25–30 minutes including warm-up and cool-down.
Two things make this different from VO2max intervals or threshold work. The first is the intensity. SIT is not "hard" — it's all-out. You're producing the highest sustainable power you can hold for 30 seconds, which for most trained cyclists is somewhere between 130% and 200% of FTP. By the end of the third sprint you're hating life.
The second is the recovery. Four minutes between 30-second efforts is far longer than VO2max prescriptions, and it's not optional. The recovery is what allows each subsequent sprint to be genuinely maximal. If you cut the rest in half, you're no longer doing SIT — you're doing a different, less effective session.
Most masters cyclists who try SIT for the first time underestimate how brutal it is. The first sprint feels manageable. The second feels hard. The third has you questioning life choices. Four through six are an exercise in willpower more than physiology. That's the session working.
Why SIT Works When Other Sessions Don't
The research on SIT goes back over two decades and the consistent finding is that brief, repeated maximal efforts drive surprisingly large adaptations in both aerobic and anaerobic systems. The mechanisms are now well understood:
Mitochondrial signalling. Maximal efforts trigger a strong AMPK and PGC-1α response — the same signalling pathways that drive mitochondrial biogenesis. The signal per minute of work is significantly higher than steady-state riding, even though the total work is much smaller.
VO2max stimulus. SIT efforts pull oxygen demand to or above VO2max within seconds and hold it through the recovery period (oxygen consumption stays elevated as the body clears metabolic byproducts). The cumulative time near VO2max across a SIT session can match or exceed a much longer VO2max interval session.
Type II fibre recruitment. Maximal effort is the only way to fully recruit your fast-twitch (type II) muscle fibres. Most training never asks them to work properly. SIT does, and the type II fibres respond by developing more mitochondria and better aerobic capacity — exactly what masters cyclists need as they age.
Lactate clearance and tolerance. Repeatedly producing high lactate and recovering from it improves both buffering capacity and lactate-as-fuel utilisation. Translates to better performance on hard climbs and surges.
When I had Stephen Seiler on the podcast about polarised training, he was clear about the place of high-intensity work in that model. Polarised training isn't anti-intensity — it's pro-quality intensity. The 20% of training that should sit at high intensity is supposed to be hard. Properly hard. SIT fits that 20% better than most session formats because it forces the intensity to be unambiguously maximal.
How SIT Differs From HIIT
This catches a lot of cyclists out. HIIT and SIT are not synonyms.
HIIT (High-Intensity Interval Training) typically uses 1–5 minute efforts at or just above VO2max power — somewhere around 105–115% of FTP. The classic Tabata is technically HIIT (20 seconds on, 10 off) but most cycling HIIT prescriptions are 3–5 minute efforts. The work is hard but not all-out. The adaptation profile favours VO2max and threshold extension.
SIT (Sprint Interval Training) uses 20–30 second all-out efforts — well above VO2max — with substantially longer recovery. The intensity is genuinely maximal. The adaptation profile favours peak power, neuromuscular coordination, and a different signalling pattern that drives mitochondrial biogenesis efficiently.
Both have their place. For masters cyclists who've already done a lot of HIIT-style work, SIT is often the missing stimulus. For cyclists who've been doing nothing but easy riding for years, HIIT is usually the more accessible starting point.
A Build-Up Programme for Masters Cyclists
Don't start at 6 × 30 seconds in week one. The musculoskeletal system needs time to adapt to maximal efforts, and masters cyclists especially have less margin for tendon and connective-tissue strain than they did at 25.
A sensible four-week ramp:
- Week 1: 3 × 20 seconds maximal, 4 minutes recovery. Just enough to wake up the system.
- Week 2: 4 × 20 seconds maximal, 4 minutes recovery.
- Week 3: 4 × 30 seconds maximal, 4 minutes recovery.
- Week 4: 5 × 30 seconds maximal, 4 minutes recovery.
- Week 5+: 6 × 30 seconds maximal, 4 minutes recovery. Hold this for the remaining 3–4 weeks of the block.
The whole block runs 7–8 weeks. One SIT session per week, ideally on a Tuesday or Wednesday, with the rest of the week built around it.
The Warm-Up That Protects You
A SIT warm-up is more important than the warm-up for any other session. Cold tissues plus all-out effort is how you tweak a hamstring or pull a calf.
The protocol:
- 10 minutes easy spinning, gradually building.
- 3 × 30-second efforts at sweet spot intensity (roughly 90% of FTP), 90 seconds recovery between. Wakes up the legs.
- 2 × 10-second pickups at near-maximal effort. Final priming.
- 2 minutes easy.
- Start the first sprint.
Skip any of that and you're rolling the dice on a strain. Masters cyclists in particular need 15–20 minutes of priming before asking the legs to produce maximum power.
How to Execute the Session
The mechanics matter. A few practical points:
Stay seated. Standing sprints recruit more upper body and tend to produce a less consistent power output. Seated, hands on the hoods, focus on cadence.
Build into each effort. Don't try to hit peak power instantly. Spend the first 3–5 seconds accelerating, the next 25 seconds holding the highest power you can without fading. The peak comes naturally.
Cadence matters. Most cyclists produce maximal power at 100–120 rpm during a 30-second effort. Pick a gear that lets you reach that range without spinning out. On a smart trainer, that's usually the same gear you'd use for steady tempo. Outdoors, gear selection is part of the skill.
Mental commitment. SIT only works if the effort is genuinely maximal. If you back off in the last 10 seconds because it hurts, the stimulus halves. The point of the session is the part that hurts.
Take the full recovery. Even if you feel okay at three minutes, take the full four. The next sprint depends on it.
How to Fit SIT Into a Weekly Plan
The one rule. Replace, don't add.
If you currently train five days a week with two quality sessions and three easy rides, your week probably looks something like:
- Mon: rest or easy
- Tue: VO2max or threshold session
- Wed: easy
- Thu: tempo or threshold session
- Fri: rest
- Sat: long endurance
- Sun: group ride or endurance
Adding a SIT session on top of two existing quality sessions is too much for most masters cyclists. The recovery cost stacks up and the second hard session of the week starts arriving with cooked legs.
The cleaner approach is to swap one of your existing quality sessions for SIT during the SIT block. The simplest swap:
- Mon: rest or easy
- Tue: SIT (replaces VO2max)
- Wed: easy
- Thu: threshold or tempo session
- Fri: rest
- Sat: long endurance
- Sun: group ride or endurance
You still have one steady-state hard session a week (Thursday) and one neuromuscular hard session (Tuesday, the SIT). The total weekly TSS doesn't go up dramatically; the stimulus mix changes.
What to Expect Across the Block
Week 1: feels brutal, body wonders what's hit it. Legs sore for two days afterwards.
Week 3: the soreness fades, the sprints feel familiar. Power on the first effort is climbing.
Week 5: noticeable change in feel. Hard climbs on the weekend ride have a different gear. The sustained power feels easier even though you've been training the opposite end of the spectrum.
Week 7: peak SIT block. Power numbers on the sprints are 10–15% higher than week one. The body is adapted to the stimulus.
Week 8 or 9: take a recovery week, then retest FTP. Most masters cyclists who haven't moved their FTP in 6+ months see a 5–15 watt jump after a proper SIT block. Some see more. The reason is mostly that the engine has been pulled up at the top end and the threshold has followed.
Why Masters Cyclists Specifically Benefit
Three reasons SIT is particularly well-suited to the 35–55 demographic.
Time efficiency. A 25-minute hard session is a viable proposition on a Tuesday evening when there's a family dinner at 7. A 90-minute VO2max session isn't. SIT slots into a real week.
Type II fibre preservation. Fast-twitch fibres are preferentially lost with age if they're not specifically trained. Andy Galpin made this point on the podcast — masters athletes who don't do high-intensity work lose type II fibres at roughly twice the rate of those who do. SIT recruits and preserves them.
Adaptation reset. Masters cyclists who've done years of similar training often need a different stimulus to break out of plateau. SIT is genuinely different from threshold work. The body responds to it.
The one caveat. If you have any cardiovascular concerns, family history, or you've not been seen by a doctor recently, get a check before you start a SIT block. The cardiovascular load on the heart during a maximal sprint is high. It's safe for almost all cyclists with a base of training, but the rare cardiac issue tends to show itself under maximal effort, not steady riding.
When SIT Doesn't Work
A short list of situations where SIT isn't the answer:
Plateau driven by under-recovery. If you're stalled because you're sleep-deprived and stressed, adding a maximal interval session makes it worse. Fix the recovery first.
Plateau driven by iron deficiency or other physiological limiters. Maximal training on low ferritin produces nothing useful and may dig the deficit deeper. Get the bloods first.
Plateau driven by under-fuelling. All-out efforts on glycogen-depleted legs are a recipe for a bonk and a wasted session. Ensure pre-ride fuelling is in place before adding SIT.
No base. SIT on top of a thin aerobic base produces a brief spike and then nothing. Build the base first; add SIT once it's solid.
This is one of the things the Plateau Diagnostic is designed to surface — whether the issue is genuinely a need for new stimulus, or whether something underneath needs sorting first. Adding SIT to the wrong problem won't fix it.
If you've been training hard and the numbers haven't moved in three months, the Plateau Diagnostic walks through a four-question audit to figure out what's actually limiting you. Four minutes, free.
A Final Note on Honesty
The thing that separates a successful SIT block from a failed one is intent. The session only works if the efforts are genuinely all-out. If you protect yourself in the last 10 seconds of each sprint because it hurts, you'll get half the benefit at the same cost.
This is one of the hardest things for masters cyclists to do. The adult brain is excellent at protecting the body from extreme effort. Pushing through that protection on a Tuesday evening when nobody is watching takes a particular kind of discipline. The riders who do it well are the riders who get the result.
For the broader masters S&C and metric framework, the masters cyclist guide to getting faster after 40 sits next to this one. The VO2max workouts for cyclists over 40 covers the longer high-intensity options. And the efficiency factor for masters cyclists is the metric to track alongside SIT to see whether the engine is responding.
Six sprints. 30 seconds each. 25 minutes total. Once a week, for eight weeks. If your FTP has been stuck and the rest of the week is solid, this is the stimulus you're missing.