Triathlon Training: What Is Zone 5 / VO2 Max?
SUMMARY:
Zone 5 — around 93–100% of max heart rate, 106–120% of FTP and above 105% of CSS swim speed (RPE 9–10). It feels very hard, short and explosive. Zone 5 boosts your maximum oxygen uptake, increases speed, power and sharpens your ability to surge, climb and finish strong across all three disciplines.
What is VO2 Training?
Triathlon training isn’t just about long endurance sessions. High-intensity efforts play a crucial role in getting faster and stronger.
One of the most powerful tools in a triathlete’s training plan is Zone 5 training. VO2 max training is all about pushing the body’s maximum oxygen uptake—the ability to deliver oxygen to working muscles efficiently.
The higher the VO2 max, the better an athlete can sustain fast paces and high-intensity efforts. These workouts are short, tough and designed to increase speed, improve aerobic power and build race-day resilience.
Training Zone Guidelines for VO2 Max / Zone 5
These efforts are very hard, pushing the heart, lungs and muscles to their peak. They’re short, intense and designed to increase speed, power and resilience across all three triathlon disciplines.
Use the following guidelines to set your Zone 5 training intensity:
Heart Rate: 93–100% of max HR
FTP (Bike): 106–120% of FTP
CSS (Swim): Above 105% of CSS pace
RPE: 9–10
VO2 sessions typically involve short intervals (1-5 minutes) at a hard but controlled pace, followed by recovery periods to maintain quality and consistency. Check your heart rate and FTP zones with FLJUGA’s free calculators.
Why VO2 Training is Important for Triathletes
Boosts Speed and Power
High-intensity intervals develop stronger, more efficient muscles, translating to faster swim, bike, and run speeds.
Improves Fatigue Resistance
Training at a high effort teaches the body to clear lactate more efficiently, delaying fatigue and allowing athletes to push harder for longer.
Enhances Race-Day Performance
VO2 max training prepares triathletes for sustained high-effort sections of a race, such as surging on the bike, attacking hills, or finishing strong in the final sprint.
How to Incorporate VO2 Training into a Triathlon Plan
Cycling VO2 Workout Example
Warm-up: 15 minutes easy spinning
Main Set: 5 x 3 minutes @ Zone 5 - 3-minute easy recovery between efforts
Cooldown: 10 minutes easy spinning
Running VO2 Workout Example
Warm-up: 10-15 minutes easy jogging
Main Set: 6 x 2 minutes @ Zone 5 - 2-minute jog recovery between efforts
Cooldown: 10 minutes easy running
Swimming VO2 Workout Example
Warm-up: 400m easy swim + drills
Main Set: 8 x 100m @ Zone 5 - 20-30 seconds rest between reps
Cooldown: 200m easy swim
When should I avoid VO2 max training?
VO2 sessions are high stress and high reward—but they’re not always the right choice. Avoid VO2 training if you’re recovering from injury, feeling deeply fatigued or in a high-volume training block where recovery is limited. These workouts place significant strain on your nervous system, muscles and cardiovascular load. If you’re not feeling sharp, prioritise easier aerobic work until your body is ready to absorb intensity again.
Hold off on VO2 max work if:
You’re still in the early stages of base-building
You’re recovering from injury or illness
Your aerobic conditioning isn’t yet solid
You’re not sleeping well or under high stress
This is a high-impact training tool. Use it strategically to build fitness—not to chase exhaustion.
Where Zone 5 Fits in a Balanced Week
Think of Zone 5 as a peak, not a pillar. It’s there to sharpen—not carry—the week.
Try this simple rhythm:
Use Tuesday or Thursday for Zone 5 efforts—run or bike, depending on your block
Follow with a low-intensity day or recovery swim
Keep endurance and bricks for the weekend
Never combine Zone 5 with threshold or long sets on the same day
The key: place your Zone 5 sessions when you're fresh, focused, and ready to go all in.
Mini FAQ: VO2 Training in Triathlon
What is VO2 training in triathlon?
VO2 training targets your body’s maximum oxygen uptake through short, high-intensity intervals. It improves aerobic capacity, power and endurance by working near max effort across swim, bike, and run.
Why is VO2 training important for triathletes?
Improving your VO2 max helps you race faster by boosting the amount of oxygen your muscles can use during intense efforts—especially beneficial in bike climbs, surges, and race finishes.
How often should triathletes do VO2 workouts?
Most triathletes benefit from 1–2 VO2-focused sessions per week during specific training phases, with careful recovery in between.
What do VO2 training sessions look like?
Typical VO2 workouts include intervals like 4–6 x 3 minutes at 95–100% of max effort with equal rest, or sets of 30-second to 2-minute hard efforts on the bike or run.
When should I include VO2 training in my triathlon plan?
VO2 work is most effective during the build phase of training (after a base period) and before a taper to peak your race performance.
Final Thoughts
VO2 max training is an essential part of triathlon preparation, increasing speed, endurance, and high-intensity performance. Athletes develop the ability to race harder, recover faster, and sustain higher speeds when it matters most. Incorporating well-structured VO2 workouts into training builds power, efficiency, and resilience, giving triathletes the edge they need on race day.
Are you ready to push past your limits and make VO2 training a game-changer in your triathlon plan?
Always consult with a medical professional or certified coach before beginning any new training program. The information provided is for educational purposes only and is not a substitute for personalized advice.
