Triathletes keep borrowing FTP protocols from cycling and wondering why their run falls apart. The bike numbers look good on TrainingPeaks. The Tuesday threshold session is crushed. Then Saturday's long run turns into a survival shuffle and Sunday's brick is a disaster.
The problem isn't FTP training itself. FTP still sets the ceiling for your 70.3 and Ironman bike splits, and raising it is one of the highest-leverage things you can do. The problem is that triathletes are running programmes designed for athletes who don't run 40km a week.
This article lays out the specific differences — volume, recovery, placement, testing — and what to change so FTP work builds your bike without breaking your run.
Why FTP still matters (more than ever) for triathletes
FTP — functional threshold power, roughly the highest power you can hold for around an hour — is the single most useful number in triathlon bike training. Your 70.3 bike pace typically sits at 76-82% of FTP. Your Ironman pace sits at 68-75%. Raise the ceiling, and the floor moves with it.
Dan Lorang, former head of performance at Red Bull-Bora-Hansgrohe and long-time coach to Jan Frodeno and Gustav Iden, has been explicit on the Roadman Cycling Podcast that long-course performance is built on threshold and sub-threshold work. His athletes don't abandon FTP training when they move to Ironman distance. They refine how it's delivered.
The mistake triathletes make is treating FTP as either irrelevant ("I only need endurance for Ironman") or as the only thing that matters ("if I can just get to 4.5 w/kg"). Both are wrong. FTP is a ceiling-setter. Your race performance depends on what percentage of that ceiling you can hold while running a marathon afterwards.
Use a FTP zones calculator to anchor your training zones to the current number, and retest every 8-12 weeks.
How cyclists train FTP — and why it breaks triathletes
A structured cyclist build might look like this: Tuesday 2x20 at FTP, Thursday 3x12 at sweet spot, Saturday long ride with over-unders, Sunday endurance. That's three quality sessions, 12-16 hours on the bike, with easy days genuinely easy. Recovery is protected because nothing else is competing for it.
Drop that programme onto a triathlete running 40-60km per week and swimming three times, and within four weeks something breaks. Usually it's the run — stiff, slow, injury-prone. Sometimes it's sleep. Sometimes it's the immune system.
The interference effect is real. Prof. Stephen Seiler's research on concurrent endurance training shows that high-intensity sessions in one modality suppress adaptation in another when they're stacked without recovery. The signalling pathways compete. Cyclists don't face this because they only stress one modality.
There's also the mechanical side. Running creates eccentric muscle damage the bike doesn't. A cyclist's legs recover from Tuesday's threshold work by Thursday. A triathlete's legs, carrying residual damage from Saturday's long run, don't.
So the cyclist protocol isn't wrong — it's just designed for a different athlete. What works is keeping the intent of FTP training (progressive overload at or near threshold) and modifying the delivery.
Volume modifications
The first change is cutting total bike volume and reducing quality bike sessions from three to two per week. A cyclist can absorb 12-16 hours; most age-group triathletes building toward 70.3 or Ironman sit at 8-11 hours on the bike when run and swim are factored in.
Within that reduced envelope, the two quality sessions should do specific jobs. Session one is threshold: 2x20 minutes at FTP, or 4x8 at 102-105%, or 3x15 with short recoveries. Session two is sub-threshold volume: 3x20 or 2x30 at 88-94% of FTP, which builds the aerobic engine without the same recovery cost.
Everything else on the bike is Zone 2. Not "moderate". Not "comfortable-hard". Genuine Zone 2, where nasal breathing is possible and conversation is easy. This is where Seiler's polarised model earns its keep for triathletes — it concentrates stress in two weekly sessions and keeps the rest of the week restorative.
The temptation to add a third FTP session because "the pros do it" should be resisted unless you're a full-time athlete with no job, no kids, and a masseuse. Your third bike session is your long run's recovery day.
Total weekly Training Stress Score from the bike for most age-group triathletes in build phase sits around 450-600. Pure cyclists at the same fitness level might accumulate 700-900. The difference is what keeps your run intact.
Recovery modifications
Cyclists can do hard-easy-hard across 48-hour windows. Triathletes generally cannot. The recovery windows have to stretch, and the easy days have to be genuinely easy across all three disciplines.
The rule I use with triathlon bike coaching athletes is 36 hours minimum between a hard bike session and a hard run session, in either direction. Tuesday FTP intervals into Thursday track session? Fine. Tuesday FTP into Wednesday threshold run? That's how injuries happen.
Sleep matters more for triathletes than for single-sport cyclists because total stress is higher. Eight hours is a training variable, not a lifestyle preference. Tim Spector's work at ZOE on metabolic recovery reinforces what every sports scientist already knows — under-fuelled, under-slept athletes adapt poorly regardless of how good the session design is.
Recovery weeks should also come more often. A cyclist might run a 3:1 loading pattern (three weeks build, one week recover). Most triathletes do better on 2:1, especially in the final 12 weeks before an A race. The cumulative fatigue from three disciplines builds faster than the bike-only equivalent.
Monitor morning heart rate variability if you have the tools, or just track resting heart rate and subjective feel. If RHR is elevated 5+ beats for two consecutive mornings, the threshold session becomes Zone 2. Non-negotiable.
Session placement around swim and run
Placement is where most triathlon bike programmes fall apart. The session design can be perfect and the week still implode because the sessions landed on the wrong days.
Here's a working template for a triathlete doing two hard bike sessions, two hard runs, and three swims. Monday: swim + easy spin or full rest. Tuesday: FTP bike intervals. Wednesday: easy run + swim. Thursday: key run session (threshold or VO2). Friday: sub-threshold bike + swim. Saturday: long run early, short Z2 bike later or rest. Sunday: long ride with optional short brick run.
Notice what's happening. The Tuesday FTP session is 48 hours from the Thursday hard run. The Friday sub-threshold is 24 hours from the Saturday long run, but it's sub-threshold, not threshold — the recovery cost is lower. The Sunday long ride follows the long run, not precedes it.
The common error is putting the long run the day after the long ride. It feels logical — "brick-adjacent training". In practice, the long ride trashes the legs enough that Sunday's run becomes junk mileage at best and injury risk at worst. Run fresh, ride tired. Not the other way around.
Swim sessions slot in around the bike and run work without much interference. Swimming is the lowest-cost modality for leg recovery and often helps flush the legs after a hard bike day.
Testing FTP as a triathlete
FTP testing protocol is the same as for cyclists — 20-minute all-out effort with 95% of average power taken as FTP, or a ramp test. What changes is scheduling.
Testing 24-48 hours after a long run will underestimate your true FTP by 5-15 watts because of residual neuromuscular fatigue. Schedule the test during a deload week when run volume is reduced by 30-40%, or put a full rest day before it.
Retest every 8-12 weeks. More often and you're chasing noise. Less often and your training zones drift out of date. Dan Bigham, former UCI Hour Record holder, has made the point on the podcast that the number itself matters less than the consistency of how you produce it — same warm-up, same time of day, same nutrition, same fatigue state.
Record the context every time: hours of sleep, hours run that week, where you are in the training block. Two FTP tests with the same number but very different context tell very different stories.
If your FTP isn't moving across a 12-week block despite consistent training, the first thing to check isn't the bike programme. It's whether run load has crept up, sleep has dropped, or fuelling is inadequate. FTP plateaus in triathletes are usually recovery problems disguised as training problems.
Start with one change this week: move your hardest bike session to at least 36 hours from your hardest run session. If that single adjustment is all you make, your next FTP test will tell you it was worth it.
