VO₂-max training often sparks debate in the triathlon world. Should you go long and grind out 8-minute reps? Or keep it sharp with short, punchy 30/15s? If you want to race faster, especially at Olympic and half-distance events, VO₂ intervals need a to form part of your training. But which type is best for you?
In this article, we’ll break down why VO₂ work matters for triathletes, explore proven interval formats across swim, bike, and run, and weigh the pros and cons of long vs short intervals. You’ll also find practical tips on when to schedule these sessions and how to progress them safely.
Why VO₂ Training Matters in Triathlon
Your VO₂-max is your aerobic ceiling the maximum rate at which your body can consume and use oxygen during exercise. Boosting this metric improves overall endurance performance because:
- It increases the size of your aerobic “engine.”
- It enhances your ability to sustain high percentages of that engine during racing.
- It provides a strong stimulus for adaptations in the heart, lungs, and muscles.
For triathletes juggling three sports, VO₂ work delivers a big return on investment. You’re short on time, and VO₂ intervals let you target the upper limits of aerobic capacity in as little as 20–30 minutes of hard effort.
How VO₂ Sessions Work
The goal isn’t just to “go hard” it’s to accumulate as much time as possible near 90–95% of your VO₂-max. The two big levers you can pull:
- Interval Duration: Long reps mean more continuous time at VO₂-max; short reps let you reach high oxygen uptake repeatedly without the mental grind.
- Recovery Length: Short recoveries keep your oxygen consumption elevated between efforts, stacking more quality time.
Across swim, bike, and run, VO₂ sessions look different. Running VO₂ pace is faster than bike VO₂ power because running generally elicits higher VO₂ values. That’s why we prescribe discipline-specific zones: power (bike), pace (run/swim), or % of HRmax.
Best VO₂ Interval Formats for Triathletes
Below are four proven structures you can rotate through in your season. Each has a specific role.
1. Long Intervals (4–8 minutes)
When to use: Great for half-Iron and Ironman builds or when you need durability at high intensity.
- Bike Example: 4 × 8 min at your best repeatable power (~108–112% FTP), 2–3 min easy spin.
- Run Example: 4–6 × 4–5 min at ~95–100% of VO₂ pace, 2–3 min jog recovery.
- Swim Example: 8–10 × 100m at ~400m pace with 20–30 sec rest.
Why it works: These sessions pile on continuous time at VO₂-max, improving aerobic capacity and lactate clearance. The downside? They’re mentally and physically taxing so you have to be careful when you schedule them within the overall training cycle.
2. Classic Intervals (3–5 minutes)
When to use: Your bread-and-butter VO₂ workout simple and effective for Olympic-distance prep.
- Bike: 5 × 3–5 min at 115–120% FTP, 3–4 min recovery.
- Run: 6 × 3 min at 3k–5k pace, 2–3 min jog.
Why it works: Easier to pace than 8-minute reps, but still enough duration to hit the VO₂ zone. This is often the first VO₂ workout athletes add after a base phase.
3. Tabata Intervals (30/15 or 30/30)
When to use: When you want a huge VO₂ stimulus without the mental grind or during bike-heavy blocks.
- Bike: 3 sets of 13 × 30s hard (≈120% FTP) / 15s float (50–60% FTP), 3 min easy between sets.
- Run: 2–3 × 10 min blocks of 30s fast / 30s float, 3 min jog between blocks.
Why it works: Frequent “on” efforts prevent oxygen uptake from dropping too much, letting you accumulate VO₂ time quickly. Be careful running these too aggressively as there’s an injury risk, a good mitigation is to do these uphill on the run.
4. Over/Under Intervals
When to use: Late in the build when you want to sharpen VO₂ capacity and practice pacing under fatigue.
- Bike Example: 4 × (2 min at 105–110% FTP + 1 min at 95–100% FTP), repeated for 4–5 cycles, 5 min recovery between sets.
Why it works: Mimics the stochastic nature of racing surging over threshold and recovering without fully backing off.
Long vs Short VO₂ Intervals: Pros and Cons
| Interval Type | Pros | Cons |
| Long (4–8 min) | Maximum sustained VO₂ time; great aerobic adaptations | Very taxing; requires precise pacing |
| Classic (3–5 min) | Balanced stimulus; simple to program | Slightly less VO₂ time than shuttles |
| Tabata | High VO₂ time with manageable RPE | Risk of going too hard; injury risk in run |
| Over/Under | Builds lactate tolerance & race realism | Less pure VO₂ stimulus |
Which should you choose?
- Long intervals suit long-course triathletes looking for durability.
- Short intervals (like 30/15) are great for bike VO₂ work and time efficiency.
- Classic intervals are your all-round option for Olympic-distance racing.
Swim, Bike, Run Practical Tips
- Swim: Use paddles sparingly on VO₂ sets to protect shoulders; focus on stroke rate control with a tempo trainer.
- Bike: Use ERG mode cautiously if you can’t hold power late in the set, lower the target and maintain cadence.
- Run: Warm up thoroughly; avoid VO₂ sets the day after a long run; run VO₂ sessions on flat or slightly uphill terrain to reduce impact.
The Bottom Line
VO₂ intervals aren’t just for cyclists they’re a critical piece of a well-rounded triathlon build. Whether you choose long, grinding 8-minute efforts or fast, fiery 30/15s, the best protocol depends on your race goals, injury history, and time availability. Rotate between formats, progress gradually, and always respect recovery.
Coach Jack