WORKOUT TIMERS
Norwegian 4×4 interval timer
Four 4-minute intervals at 85 to 95% of maximum heart rate, with 3 easy minutes between them
The 4×4 comes from researchers in Trondheim, Norway, who used it in trials with healthy runners, heart patients and older adults 1,2,3. It’s four intervals of 4 minutes at a hard but steady effort, with 3 minutes of easy movement between them, after a warm-up.
How hard is hard?
In the trials, the intervals were done at 85 to 95% of maximum heart rate, which most people describe as hard enough that talking is difficult, and the recovery at about 70% 1,2. Heart rate takes a minute or two to climb, so the first part of each interval feels easier than the end.
| Age | Max HR | Intervals, 85 to 95% | Recovery, about 70% |
|---|---|---|---|
| 30 | 187 bpm | 159 to 178 bpm | 131 bpm |
| 40 | 180 bpm | 153 to 171 bpm | 126 bpm |
| 50 | 173 bpm | 147 to 164 bpm | 121 bpm |
| 60 | 166 bpm | 141 to 158 bpm | 116 bpm |
| 70 | 159 bpm | 135 to 151 bpm | 111 bpm |
What the research found
Key study
4×4 intervals beat steady running for VO2max
- Training study
- Moderately trained men
- 8 weeks
Three sessions a week of 4×4 intervals at 90 to 95% of maximum heart rate improved VO2max by about 7%, more than long slow running or running at the lactate threshold, which didn’t change it significantly.
Source 1In a five-year trial with about 1,500 people in their 70s, two weekly sessions of 4×4 intervals were safe, and the group that did them had the lowest death rate, although the difference from a group following the usual activity guidelines wasn’t statistically significant 3.
How to set it up in Cero
- Create a new simple timer: high intensity 4:00, low intensity 3:00, sets 4.
- Add a 10-minute warm-up and a 5-minute cool down.
- Turn on Adaptive HR and set its warning targets, so Cero tells you when an interval is too easy or too hard.
- Run it on your Apple Watch to follow your heart rate on your wrist, on any machine or outdoors.
Sources
- Helgerud J, Høydal K, Wang E, et al. Aerobic High-Intensity Intervals Improve VO2max More Than Moderate Training. Med Sci Sports Exerc. 2007;39(4):665-671. doi.org/10.1249/mss.0b013e3180304570
- Wisløff U, Støylen A, Loennechen JP, et al. Superior Cardiovascular Effect of Aerobic Interval Training Versus Moderate Continuous Training in Heart Failure Patients. Circulation. 2007;115(24):3086-3094. doi.org/10.1161/CIRCULATIONAHA.106.675041
- Stensvold D, Viken H, Steinshamn SL, et al. Effect of exercise training for five years on all cause mortality in older adults: the Generation 100 study, randomised controlled trial. BMJ. 2020;371:m3485. doi.org/10.1136/bmj.m3485
- Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol. 2001;37(1):153-156. doi.org/10.1016/S0735-1097(00)01054-8
YOUR NEXT SESSION STARTS HERE
Bring the effort.
We’ll keep the time.
Cero is free to download for iPhone, iPad and Apple Watch.
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Cero is a timer, not a medical device. If you’re new to hard exercise, are pregnant or have a health condition, check with your doctor first, and stop if you feel unwell.