Zone 2 Training Gets All the Hype, But This 30-Minute Interval Method Built More VO2 Max in 3 Weeks Than 12 Weeks of Steady Cardio

Interval training has long been hailed as the secret weapon for building fitness faster.

But according to exercise physiologist Gomar, a senior scientist at ETH Zurich, most people are missing the nuance that makes all the difference.

In a recent YouTube video breaking down decades of sports science research, he revealed that not all intervals are created equal—and understanding which type to use can dramatically accelerate your gains in aerobic power, strength, and overall performance.

Here’s everything you need to know about training smarter with intervals.

Why Interval Training Works Better Than Steady-State Cardio

Interval training isn’t new, but its effectiveness is backed by robust science. Gomar explains that alternating hard work with rest allows your body to complete more quality volume in less time.

Decades of sport science research has shown that if you alternate periods of really hard work with periods of rest, this allows your body to do more quality volume, more quality work in less time.

He referenced a major overview study of 425 exercise trials comparing continuous training with interval training. The results? Sprint interval training (SIT) produced massive jumps in VO2 max within the first two to three weeks, then plateaued. High-intensity interval training (HIT), on the other hand, delivered sustained improvements over 12+ weeks.

Traditional endurance training showed gradual gains, primarily improving capillarization and long-term aerobic capacity. Each method has its place—but intervals offer faster returns for those seeking performance breakthroughs.

Understanding Training Zones: The Foundation of Smart Intervals

Gomar emphasizes that effective interval training hinges on hitting specific training zones, each triggering unique physiological adaptations.

He uses a five- to six-zone model based on percentage of maximum heart rate and lactate production. Lower zones rely primarily on aerobic energy systems, while higher zones demand anaerobic contributions from glycolysis and phosphocreatine stores.

But heart rate alone isn’t ideal. Gomar advocates for Functional Threshold Power (FTP)—the average power you can sustain for 20 minutes at maximum effort.

This metric provides a more accurate gauge of intensity across different training zones, especially for cyclists, rowers, and functional fitness athletes.

Zone 2 Training: Building Your Aerobic Base

Zone 2 work sits at around 75% of FTP and targets aerobic energy production with maximal fat oxidation. Sessions typically last 40 to 90 minutes with minimal rest—think 20:1 work-to-rest ratios or fully continuous effort.

Key adaptations include:

• Expanded mitochondrial density
• Improved fat oxidation capacity
• Increased capillary density around muscles
• Enhanced aerobic efficiency through upregulated Krebs cycle enzymes

For endurance athletes, Gomar suggests classic steady-state work: 60-minute runs or four rounds of six-minute intervals rotating between ski erg, rower, and bike.

Functional fitness athletes can accumulate 200-plus calories on an air bike at low intensity (RPE 3), breaking every two minutes for six alternating dumbbell clean-and-jerks and four easy burpees.

Threshold Training: Mastering Sustained Intensity

Threshold training targets Zone 4, hovering around 100% FTP with 30 to 50 minutes of total work time. Work-to-rest ratios shift to 5:1 or 10:1—think five to seven minutes on, one minute off.

This zone improves tolerance to sustained metabolic stress, training your body to buffer lactate and maintain power output near your lactate threshold.

This really improves your tolerance to sustained metabolic stress. It’s not just very short or very long at low intensity. It is at this medium to high intensity, but a sustained period of time.

An effective protocol: eight minutes on, one minute off on the rower at RPE 6-7 and 95-100% FTP.

For functional athletes, Gomar recommends three 10-minute AMRAPs with two-minute rests, cycling through 10 burpee pull-ups, 40 meters of walking lunges, and 15 light wall balls. The goal isn’t maximum rounds—it’s continuous movement at moderate intensity.

Why Most CrossFit Workouts Miss the Aerobic Mark

Gomar drops a bombshell for functional fitness enthusiasts: most AMRAPs don’t hit high aerobic energy production like you think.

He cites research on “Cindy”—a 20-minute AMRAP of five pull-ups, 10 push-ups, and 15 air squats. Despite athletes going all-out, they only reached 64% of VO2 max, placing them in moderate intensity territory.

Why? Functional movements involve high instant power demands and built-in rest periods, even during continuous work. Much of your energy comes from anaerobic sources.

To truly target aerobic systems in CrossFit-style training, choose low-skill, continuous movements at controlled intensity—not heavy, technical lifts with short rest intervals.

VO2 Max Training: Hitting Maximum Aerobic Capacity

VO2 max intervals push intensity to 110-130% of FTP in Zone 5. Total work time drops to 15-25 minutes with 2:1 or even 1:1 work-to-rest ratios.

These sessions feel brutal—RPE 8-9—and lactate climbs throughout. But they deliver powerful cardiovascular adaptations.

Gomar’s endurance example: four rounds of four minutes hard, two minutes easy (the famous Norwegian 4×4 protocol).

Functional athletes can program eight-minute intervals where they complete 10-15 air bike calories, 12 power snatches, 15 pull-ups, 15 wall balls, and 15 burpees over the bar—finishing in four to five minutes, then resting the remainder. Repeat for four rounds.

Really fun way of training. I like to do it as well. The harder they go, the more rest they have and you’re really hitting this high intensity, high aerobic fitness.

Sprint Interval Training: The Power Zone

Zone 6 encompasses everything above VO2 max—all-out sprints and explosive efforts lasting seconds to one minute. Total quality work? Just 10 minutes with 1:5 work-to-rest ratios.

These sessions improve:

• Phosphocreatine resynthesis for explosive repeat efforts
• Anaerobic glycolysis and lactate buffering
• Neuromuscular firing rate, recruiting maximum muscle fibers instantly

Classic example: five rounds of 30 seconds all-out on the air bike, resting four to five minutes between efforts.

Functional version: every four to five minutes for four rounds, complete 12 air bike calories (nine for women), 10 heavy wall balls, and 10 jumping lunges—taking 45-60 seconds, then recovering fully.

Balancing Intensity with Recovery

Gomar stresses that intensity manipulation isn’t just about adaptation—it’s about managing recovery.

Low-intensity Zone 2 work allows massive volume with minimal strain. You can train again the next day without issue. Threshold training offers moderate strain with manageable recovery demands. VO2 max and sprint intervals deliver powerful adaptations but require substantial recovery time.

Endurance athletes meticulously track FTP to avoid overtraining while maximizing physiological stress. Functional athletes should adopt similar precision rather than going hard every session.

Designing Your Interval Training Plan

Gomar’s ultimate guide breaks down like this:

• Zone 2: 40-90 minutes, 20:1 work-to-rest, aerobic base building
• Threshold: 30-50 minutes, 5:1 or 10:1 ratio, lactate tolerance
• VO2 Max: 15-25 minutes, 2:1 or 1:1 ratio, maximum aerobic power
• Sprint: 10 minutes total, 1:5 ratio, explosive power and neuromuscular adaptations

Rather than defaulting to max-effort AMRAPs or random MetCons, thoughtful programming across these zones yields faster gains and better recovery.

Gomar encourages athletes to get creative—using functional movements strategically to hit specific zones, not just grinding through high-intensity chaos.

The science is clear: smarter intervals beat harder, random efforts every time.