What are the different types of interval training?

The 8 main interval training methods are classic track intervals (400m to 1 mile repeats), tempo intervals (cruise intervals), fartlek, Tabata, HIIT, the Norwegian double threshold method, Billat 30/30 intervals, and pyramid intervals. They differ in work duration, rest duration, and intensity: short all-out methods like Tabata build top-end power in minimal time, while longer controlled methods like tempo intervals and the Norwegian method build the lactate threshold that drives half marathon and marathon performance.

What are the best interval training methods?

The best interval training methods for endurance athletes are classic track intervals (400m to 1 mile repeats at 5K effort) for VO2 max, tempo or cruise intervals for lactate threshold and marathon fitness, Billat 30/30s for accumulating time at VO2 max, and fartlek for beginners starting speedwork. For time-crunched general fitness, HIIT and Tabata deliver the most benefit per minute. Pick one or two methods that match your goal race and run them 1-2 times per week rather than sampling everything at once.

What is the most effective interval training method?

The most effective method depends on your goal. For VO2 max development, classic 800m repeats or Billat 30/30 intervals work best. For marathon fitness, tempo intervals (cruise intervals) are highest-leverage. For general fitness in minimal time, HIIT or Tabata deliver strong results. There is no single best method — match the protocol to your specific goal.

How many days per week should I do interval training?

Most runners and cyclists benefit from 1–2 interval sessions per week. More than two high-intensity sessions per week significantly increases injury and overtraining risk. Beginners should start with one session weekly. Advanced athletes can manage two sessions if the remainder of their training volume is easy aerobic work — the 80/20 principle (80% easy, 20% hard) holds true.

What is the difference between HIIT and interval training?

Interval training is the broader category — any training that alternates work and rest periods, regardless of intensity. HIIT is a specific subset that uses near-maximal efforts at 85–95% of maximum heart rate. All HIIT is interval training, but not all interval training is HIIT. Tempo intervals, for example, are interval training but not HIIT — they are performed at a sustainable comfortably hard effort, not near-maximum intensity.

What is fartlek training and who is it best for?

Fartlek is Swedish for "speed play" — unstructured intervals based on feel rather than a watch or measured distances. You alternate between faster and slower efforts based on terrain, landmarks, or how you feel. It is ideal for beginners starting speedwork (less intimidating than track intervals), trail runners navigating variable terrain, and all athletes in base-building phases who want a break from rigid structure.

Does Tabata actually work for runners and cyclists?

Yes — but only if you execute it at true maximum effort. The original Tabata research showed significant improvements in both aerobic and anaerobic capacity with the correct protocol (8 x 20 sec at 170% VO2 max / 10 sec rest). For runners and cyclists, Tabata is an excellent tool to boost sprint capacity and peak power. The caveat: most "Tabata" sessions in fitness classes are not done at maximum intensity and therefore produce different (lesser) results than the studied protocol.

What is the Norwegian double threshold method?

The Norwegian method uses two threshold training sessions per day, separated by 4–6 hours. Each session is multiple cruise intervals at exact lactate threshold effort (confirmed by portable lactate meters in elite settings). The method allows elite athletes to accumulate enormous threshold volume without the deep fatigue of VO2 max work. Recreational athletes can apply the principle with a single threshold session using perceived effort instead of lactate testing. Read our full Norwegian method guide for the complete breakdown.

How long should I rest between intervals?

Rest duration depends on the method. For short fast intervals (400m), rest 2–3 minutes. For 800m repeats, rest approximately equal to the work time (2–3 minutes). For tempo intervals, keep rest short (60–90 seconds) to sustain the threshold stimulus. For Tabata, rest is fixed at 10 seconds. For HIIT, rest equals or exceeds work time. The goal is arriving at each rep capable of completing it at target effort — not fully recovered, but functional.

Can beginners do interval training?

Yes — with the right method. Fartlek is the ideal starting point: no track, no watch required, just periodic speed surges within a regular run. Beginners should also have a base of 4–6 weeks of regular easy running before adding any formal speedwork to reduce injury risk. Start with 4–6 fartlek surges per run, then progress to more structured intervals over 4–6 weeks. Avoid Tabata and classic track intervals until you can run 3–4 days per week comfortably.