article 2024 14 pages Morning versus Nocturnal Heart Rate and Heart Rate Variability Responses to Intensified Training in Recreational Runners Olli-Pekka Nuuttila, Heikki Kyröläinen, Veli-Pekka Kokkonen, Arja Uusitalo JournalSports Medicine - OpenDOI10.1186/s40798-024-00779-5Publication typeOriginal ResearchPopulationrecreational runners View on DOI ↗