Impact of a 12-week high-intensity interval training intervention on cardiac structure and function after COVID-19 at 12-month follow-up.

In patients previously hospitalised for COVID-19, a 12-week high-intensity interval training (HIIT) intervention has previously been shown to increase left ventricular mass (LVM) immediately after the intervention. In the present study, we examined the effects of the same HIIT scheme on LVM, pulmonary diffusing capacity, symptom severity and functional capacity at 12-month follow-up. In this investigator-blinded, randomised controlled trial, 12 weeks of a supervised HIIT scheme (4 × 4 min, three times a week) was compared to standard care (control) in patients recently discharged from hospital due to COVID-19. At inclusion and at 12-month follow-up, LVM was assessed by cardiac magnetic resonance imaging (cMRI, primary outcome), while pulmonary diffusing capacity for carbon monoxide (D, secondary outcome) was examined by the single-breath method. Symptom severity and functional status were examined by the Post-COVID-19 Functional Scale (PCFS) and King's Brief Interstitial Lung Disease (KBILD) questionnaire score. Of the 28 patients assessed at baseline, 22 completed cMRI at 12-month follow-up (12.4 ± 0.6 months after inclusion). LVM was maintained in the HIIT but not the standard care group, with a mean between-group difference of 9.68 [95% CI: 1.72, 17.64] g (P = 0.0182). There was no differences in change from baseline to 12-month follow-up between groups in D % predicted (-2.45 [-11.25, 6.34]%; P = 0.578). PCFS and KBILD improved similarly in the two groups. In individuals previously hospitalised for COVID-19, a 12-week supervised HIIT scheme resulted in a preserved LVM at 12-month follow-up but did not affect pulmonary diffusing capacity or symptom severity.