Myocardial infarction (MI) is a leading cause of death in developed countries, including Sweden. Standard treatment for patients after MI includes exercise-based cardiac rehabilitation which contributes to improved cardiovascular function and reduces the risk of hospital readmissions, new cardiovascular events and mortality. Thermotherapy may also have beneficial effects on cardiovascular disease by a reduction in inflammatory status and improved metabolism and vascular function. Given the well-documented effects of exercise training on cardiac rehabilitation and recent evidence that thermotherapy may improve cardiovascular function, we wish to investigate the effect of exercise combined with hot water immersion (HWI) in cardiac rehabilitation post-MI. This is a single-centre, randomized controlled clinical trial in patients with recent MI. Our aim is to investigate whether exercise training combined with HWI improves inflammatory and metabolic status, cardiovascular function as well as psychological well-being, compared with exercise training alone. Patients will be randomized 1:1 to an 8 week intervention with exercise training 2 times per week followed by 15 minutes of hot water immersion, or to a control group with exercise training alone. The primary endpoint is changes in the inflammatory marker interleukin (IL-) 6 between groups at 8 weeks. Secondary endpoints include other biomarkers of inflammation, metabolism, effects on cardiovascular function and psychological benefits. Secondary prevention after MI has improved during the last decades but readmissions and death following acute MI remain large health challenges. If HWI in addition to standard cardiac rehabilitation can lower inflammation more than standard therapy alone, and improve metabolic, cardiovascular and psychological status, it could be a cost-effective and safe complementary strategy for secondary prevention after MI, particularly for those with limited exercise capability.