High-intensity interval training (HIIT) has gained attention for its potential to improve health outcomes across various conditions. Thus, the aim of the study was to summarize studies on HIIT to understand its effects on various health outcomes. We conducted an umbrella review of systematic reviews and meta-analyses. PubMed, Cochrane Database of Systematic Reviews, EMBASE, Scopus, CINAHL, and Web of Science were searched for relevant articles. The experimental group was subjected to HIIT with or without treatment, while the control group comprised individuals who underwent alternative forms of training or were non-exercisers. Included studies were systematically analyzed for effects of HIIT and cardiovascular, respiratory, metabolic, neurological, gastrointestinal, immunological, and survival-related outcomes. Of 336 identified systematic reviews, 133 were included in the final analysis. HIIT was found to confer significant physiological benefits, including improvements in body composition, cardiovascular and metabolic parameters, and mental health outcomes. Studies demonstrated the efficacy of HIIT across diverse patient populations, with comparable or superior effects to moderate-intensity continuous training in conditions such as diabetes, cardiovascular diseases, neurological, oncologic, and pain-related disorders. Our review highlights the potential of HIIT as a time-efficient intervention for improving health outcomes and managing chronic diseases. However, interpretation of the results should be performed cautiously due to the heterogeneity observed. High-intensity interval training shows promise as an effective strategy for managing chronic diseases among diverse patient populations. Future research should focus on refining HIIT protocols and elucidating their long-term effects and sustainability.

The purpose of this review is to describe the impact of endurance and strength physical training on the cardiovascular system by reviewing the molecular signaling pathways, which plays a key role in different muscle adaptations, and the cardiac changes in terms of metabolic and cardiac remodeling, and hemodynamics. In response to endurance-exercise, multiple signaling pathways, including Ca2+-dependent pathways, reactive oxygen species (ROS), AMP-dependent protein kinase (AMPK), and mitogen activated protein kinases (p38 MAPK), are involved in the regulation of peroxisome-proliferator-activated receptor-γ coactivator-1α (PGC-1α), which controls the mitochondrial biogenesis. Strength training increases the insulin-like growth factor (IGF-1) which initiates the phosphatidylinositol 3-kinase (PI3-k)-(AKT)-(mTOR) signaling cascade, resulting in the synthesis of proteins and the muscle hypertrophy. In addition to the well-documented changes in skeletal muscle, a critical component of the response to exercise training is the dynamic cardiac remodeling, which is classified as either pathological or physiological depending on triggers.

Athletes require careful evaluation by specialized physicians to obtain eligibility for sport. In this context, electrocardiogram can be helpful to recognize patterns associated with heart disease that put the athletes at high risk of sudden cardiac death and may interdict participation in sports. On the other hand, adaptation to exercise may induce structural remodeling of the cardiac structures that results into electrocardiographic changes that are not associated with an increased risk of adverse events during exercise. Clearly, a correct interpretation of a resting 12-lead electrocardiogram is essential to differentiate athletes at risk of sudden cardiac death who must be prohibited from agonistic sports from those with physiologic changes who should be reassured and declared eligible for sport activities. Interpretation of the athlete’s ECG has evolved over the past 15 years, and in this chapter, we provide a brief review of current evidence regarding the electrocardiographic findings considered normal and abnormal in athletes based on the latest international recommendations.