CYCLING: IMPACTS ON REGULATION AND DEFENSE SYSTEMS – A REVIEW OF NERVOUS, HORMONAL, AND IMMUNOLOGICAL ADAPTATIONS

Abstract

Cycling is widely practiced as a sport, leisure activity, and means of transportation. This narrative review synthesized evidence on its effects on the nervous, endocrine, and immune systems. PubMed/MEDLINE, Scopus, and Web of Science were searched for publications from January 2015 to June 2026 by combining cycling-related terms with descriptors for the three systems. After title, abstract, and full-text screening, 59 publications were included in the qualitative synthesis. Findings indicate that cycling may benefit mood, well-being, and executive functions, particularly when protocols are regular and tailored to the population. Moderate- to high-intensity exercise elicits acute cortisol and testosterone responses, whereas training may attenuate the hormonal response to the same stimulus. Regular practice is associated with enhanced immune surveillance and a lower population risk of infection; however, high training loads combined with inadequate recovery, sleep, or energy availability may increase clinical vulnerability. Transient post-exercise leukocyte changes should not, in isolation, be interpreted as immunosuppression. Cycling therefore has health-promotion potential when prescription accounts for context, exercise dose, clinical status, and recovery.