From the Guidelines
The Norwegian 4x4 interval training protocol is more effective for improving maximal oxygen uptake (VO2 max) compared to repeated 2 x 20 second sprints, due to its longer duration in the high-intensity zone, which creates greater cardiovascular stress and drives adaptations. The Norwegian 4x4 protocol consists of four 4-minute intervals at 85-95% of maximum heart rate with 3-minute recovery periods between intervals, typically performed 2-3 times per week 1. This protocol is recommended because it keeps individuals in the high-intensity zone for a longer total duration, creating greater cardiovascular stress that drives adaptations. In contrast, the Rehit protocol involves just two 20-second all-out sprints within a 10-minute session, making it significantly shorter but requiring absolute maximum effort during those brief sprints.
Key Considerations
- The physiological mechanism behind both protocols involves stressing the cardiovascular system to improve oxygen delivery and utilization, but the longer intervals in the Norwegian protocol create more sustained demand on both central (heart/lungs) and peripheral (muscle) adaptations 1.
- For beginners, starting with 2 sessions weekly of either protocol, allowing 48 hours between sessions for recovery, and gradually increasing frequency as fitness improves is recommended 1.
- The combination of endurance and strength training is probably the best strategy to treat peripheral muscle dysfunction, because it results in combined improvements in muscle strength and whole body endurance, without unduly increasing training time 1.
Protocol Details
- Norwegian 4x4: four 4-minute intervals at 85-95% of maximum heart rate with 3-minute recovery periods between intervals, typically performed 2-3 times per week.
- Rehit: two 20-second all-out sprints within a 10-minute session, making it significantly shorter but requiring absolute maximum effort during those brief sprints.
Evidence-Based Recommendation
Based on the most recent and highest quality study, the Norwegian 4x4 interval training protocol is the recommended choice for improving VO2 max, due to its ability to create greater cardiovascular stress and drive adaptations 1. However, if time is extremely limited, the Rehit protocol can still provide meaningful benefits with minimal time commitment.
From the Research
Comparison of Training Methods
The effectiveness of Norwegian 4x4 interval training versus repeated 2 x 20 second sprints for improving maximal oxygen uptake (VO2 max) can be compared based on existing research studies.
- Norwegian 4x4 interval training, also known as high-intensity aerobic interval training, has been shown to be effective in improving VO2 max in several studies 2, 3, 4.
- Repeated 2 x 20 second sprints, a form of sprint interval training, has also been studied, but the results suggest that it may not be as effective as high-intensity aerobic interval training for improving VO2 max 2, 3.
Key Findings
Some key findings from the studies include:
- A study published in the Scandinavian journal of medicine & science in sports found that high-intensity aerobic interval training (4x4 minutes at ~95% maximal aerobic speed) increased VO2 max more than sprint interval training (8x20 seconds at ~150% maximal aerobic speed) in well-trained men 2.
- A similar study published in the same journal found that high-intensity aerobic interval training was also superior to sprint interval training in improving VO2 max in well-trained women 3.
- Another study published in Medicine and science in sports and exercise found that high-intensity aerobic interval training (4x4 minutes at 90-95% maximal heart rate) increased VO2 max more than moderate training (70% maximal heart rate) in moderately trained men 4.
Training Protocol
The training protocol used in the studies varied, but the general format of high-intensity aerobic interval training involved:
- 4x4 minutes of high-intensity exercise at ~90-95% maximal aerobic speed or heart rate, followed by 3 minutes of active recovery at ~70% maximal heart rate 2, 3, 4.
- The sprint interval training protocol involved 8x20 seconds of all-out sprinting, followed by 10 seconds of passive recovery 2, 3.