High-intensity interval training reduces burden of atrial fibrillation

Vegard Malmo’s PhD thesis shows that intensive aerobic exercise could have a role in both prevention and treatment of atrial fibrillation.


  1. Aerobic interval training reduces atrial fibrillation burden in the short term.
  2. Interval training prevents atrial fibrillation in middle-aged rats.
  3. Self-report is not an accurate method to identify cases of atrial fibrillation.


Thesis: Atrial fibrillation and exercise
Candidate: Vegard Malmo
Time: March 1 at 12:15
Place: St. Olavs hospital, Medical Technical Research Center: Auditorium MTA
Link to university website (in Norwegian)


(1) Patients with atrial fibrillation had far less fibrillation and fewer symptoms after 12 weeks of high-intensity interval training. The participants had atrial fibrillation for almost two hours every day the month before the exercise period. Afterwards, the burden was almost halved. Exercise also improved quality of life and the levels of several cardiovascular risk factors.

A total of 51 patients were randomized to interval training or a sedentary control group. The exercise period consisted of three weekly sessions of 4×4-minute high-intensity interval training. The burden of atrial fibrillation was measured with an implanted loop recorder.

(4) One single bout of maximal exercise reduces the burden of atrial fibrillation the following day. The study is based on the maximal exercise tests performed before and after the 12-week intervention period described above. After excluding patients without atrial fibrillation in the analyzed period, the mean time in atrial fibrillation was reduced from 15 % of the time the week before the baseline test to less than 3 % the day after. Similar improvements were seen in the non-exercising control group after the follow-up test.

(3) Aerobic interval training prevents susceptibility to atrial fibrillation in middle-aged rats. Sustained atrial fibrillation was not induced in any of the 14 rats who exercised for 16 weeks, compared to four of the eleven rats who did not exercise.

Malmo and co-workers compared middle-aged rats who exercised for 16 weeks with both young and middle-aged rates who did not exercise. After the exercise intervention, the middle-aged rats had the same aerobic fitness as young, sedentary rats. The researchers also examined the rat hearts, and found that exercise had increased the atrial conduction velocity, which could explain the reduced vulnerability to atrial fibrillation.

(2) Questionnaires should not be used alone to define cases of atrial fibrillation. Hospital discharge diagnosis are more valid, but if a high sensitivity is required primary care registries should also be included, according to Malmo’s results.

Atrial fibrillation was verified in 502 out of 16,000 included participants from the third wave of the HUNT study. Only half of them had reported atrial fibrillation in the survey. Moreover, patient journals from hospitals and general practitioners could only verify atrial fibrillation in 249 of the 376 participants with self-reported fibrillation.


(1) Malmo, V., Nes, B. M., Amundsen, B. H., Tjonna, A. E., Stoylen, A., Rossvoll, O.,  & Loennechen, J. P. (2016). Aerobic interval training reduces the burden of atrial fibrillation in the short term: a randomized trialCirculation133(5), 466-473.

(2) Malmo, V., Langhammer, A., Bønaa, K. H., Loennechen, J. P., & Ellekjaer, H. (2016). Validation of self-reported and hospital-diagnosed atrial fibrillation: the HUNT studyClinical epidemiology8, 185.

(3) Malmo, V., Kelly, A., Garten, K. S., Stolen, T., Rolim, N. P., Wisloff, U., Smith, G., & Loennechen, J. P. (2018). Aerobic interval training prevents age-dependent vulnerability to atrial fibrillation in rodentsFrontiers in physiology9, 206..

(4) Malmo, V., Nes, B. M., Amundsen, B. H., Tjønna, A. E., Støylen, A., Rossvoll, O., Wisløff, U., & Loennechen, J. P., Immediate reduction of atrial fibrillation burden after one bout of maximal exercise (Unpublished)

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