30/30s, 30/15s, and 40/20s: The VO₂max Intervals Every Cyclist Should Use
30/30s, 30/15s, and 40/20s: The VO₂max Intervals Every Cyclist Should Use
VO₂max intervals are some of the most powerful tools in endurance training. Whether you race on the road, build FTP for long-distance rides, or want stronger running and cycling crossover fitness, structured high-intensity intervals help athletes unlock more speed, power, and resilience.
Three formats dominate endurance cycling training today: 30/30s, 30/15s, and 40/20s. These short, repeatable bursts elevate heart rate rapidly, increase oxygen uptake, and drive adaptations that improve aerobic capacity.
This guide breaks down what each interval format does, how to use them, and—most importantly—how to fuel them with the right sports nutrition for consistent high-intensity performance.
Why VO₂max Intervals Matter for Endurance Athletes
Athletes training for cycling, triathlon, or long-distance running all benefit from VO₂max work. These sessions:
• Improve the body’s ability to use oxygen efficiently
• Increase sustainable power and running speed
• Boost cardiovascular and metabolic capacity
• Build fatigue resistance for races and long training days
For athletes who care about performance, fuelling, and long-distance energy strategies, VO₂max intervals are an essential part of a well-built endurance training cycle.
Understanding the Intervals: 30/30s, 30/15s, and 40/20s
30/30s — The Classic 1:1 Format
Structure:
• 30 seconds “on” at 130–140% FTP
• 30 seconds “off” at 50–60% FTP
• For 8–10 minute sets
Why athletes love them:
30/30s allow you to accumulate a large amount of high-quality work without blowing up. They’re ideal for cyclists, triathletes, or runners cross-training on the bike who want controlled high-intensity volume.
Best for: Improving aerobic power in a sustainable, repeatable format.
30/15s — A Sharper, More Demanding Variation
Similar to 30/30s, but the recovery is cut in half.
• 30 seconds “on”
• 15 seconds “off”
These hit VO₂max faster and suit experienced cyclists with good pacing and air hunger tolerance.
40/20s — The 2:1 Work Ratio Power Builder
Structure:
• 40 seconds “on” at 120–130% FTP
• 20 seconds “off” at 50–60% FTP
• 8–10 minute sets
These intervals spike VO₂ quickly but allow just enough recovery to keep you in the zone. They are incredibly effective for developing high-end aerobic capacity and race-specific power.
Which Interval Is Best?
All three formats work—but the best one is the one you can repeat consistently.
• 40/20s often push athletes to a higher oxygen uptake peak.
• 30/30s deliver the most total quality work for many riders.
• 30/15s sit in the middle, demanding but manageable with practice.
The key is not one interval session—it’s week after week of consistency. That’s where the real endurance gains happen.
How to Fuel VO₂max Sessions for Maximum Power
Short-interval training demands fast, accessible energy. Under-fuelled athletes hit power targets early but fade, compromise technique, or fail to complete the session.
To maintain output and oxygen uptake, endurance athletes should use easily absorbed carbohydrates and electrolytes.
Pre-Session Fuel (15–20 minutes before)
Consume:
20–30g carbohydrates from:
• Energy gels
• Energy chews
• A small energy bar
• High-carb drink mix
This helps raise blood glucose for the first set and stabilises power.
During the Session
Sip carbohydrates + electrolytes between sets to maintain:
• Consistent power
• Steady oxygen uptake
• Better muscle recruitment
• Mental sharpness
This mirrors strategies used in long-distance running fuel plans, triathlon fuelling, and high-intensity cycling workouts.
Recommended Endurance Fuel Options
For natural, anti-doping tested sports fuel:
• Veloforte natural energy gels and chews
• Veloforte energy bars for pre-session carbs
• Neversecond C30 energy gels or drinks for precise 30g doses
• Pillar Performance Triple Magnesium post-session to support recovery and sleep quality
Using the right endurance sports nutrition keeps quality high across every interval rep.
Training Tips for Success
• Follow RPE 8–9/10—strong, repeatable, never chaotic.
• Aim for smooth power transitions.
• Start with fewer sets and build volume over 4–6 weeks.
• Prioritise hydration and electrolytes, especially on indoor sessions.
• Recover properly with carbohydrates and protein afterward.
When integrated into a structured endurance training plan, these VO₂max intervals accelerate progress and improve race-day readiness for cyclists, runners, and triathletes.
Final Takeaway
VO₂max work isn’t just for elite cyclists—it’s one of the most efficient ways for any endurance athlete to build fitness, speed, and resilience. Whether you choose 30/30s, 30/15s, or 40/20s, commit to consistency and smart fuelling.
Fuel well. Train with purpose. Build performance that lasts.