Thanks for checking out BetterBaseline! As mentioned, all of the calculations that run the backend of the app are based on a number of peer-reviewed medical papers that provide evidence for the one line suggestions that BetterBaseline provides. Most of the time, the best health decisions to make at any given time are easy, and through the help of these papers and talking with medical professionals, I was able to build an algorithm that takes all of this into account.

If you’d like to help improve BetterBaseline: what metrics do you personally use to decide whether to train hard or rest? I'm genuinely curious whether people are doing this intuitively or tracking it. Let me know in Instagram comments!

HRV & Autonomic Nervous System

  1. Task Force of the European Society of Cardiology & North American Society of Pacing and Electrophysiology (1996). Heart rate variability: standards of measurement, physiological interpretation and clinical use. Circulation, 93(5).
  2. Plews, D.J., et al. (2013). Heart rate variability in elite triathletes, is variation in variability the key to effective training? A case comparison. European Journal of Applied Physiology.
  3. Buchheit, M. (2014). Monitoring training status with HR measures: do all roads lead to Rome? Frontiers in Physiology.
  4. Flatt, A.A. & Esco, M.R. (2015). Smartphone-derived heart-rate variability to assess recovery and training adaptation in collegiate female soccer players. Journal of Sports & Human Performance.
  5. Kiviniemi, A.M. et al. (2007). Endurance performance and heart rate variability. International Journal of Sports Medicine.
  6. Shaffer, F. & Ginsberg, J.P. (2017). An overview of heart rate variability metrics and norms. Frontiers in Public Health.
  7. Naranjo-Orellana, J. et al. (2015). A new method for the assessment of autonomic balance. Frontiers in Physiology.
  8. Düking, P. et al. (2021). HRV-guided training systematic review. Journal of Science and Medicine in Sport.
  9. Nuuttila, O.P. et al. (2022). Individualized endurance training based on recovery and training status. Medicine & Science in Sports & Exercise.
  10. Kubios HRV (2024). PNS and SNS indexes methodology. kubios.com/blog.
  11. PMC12485039 (2025). HRV + RHR + wellbeing combined training guidance. PubMed Central.
  12. PMC12367097 (2025). Oura vs WHOOP vs Garmin nocturnal HRV/RHR validation. PubMed Central.

Resting Heart Rate & Overtraining

  1. Achten, J. & Jeukendrup, A.E. (2003). Heart rate monitoring: applications and limitations. Sports Medicine.
  2. Jeukendrup, A.E. et al. (1992). Physiological changes in male competitive cyclists after two weeks of intensified training. International Journal of Sports Medicine.
  3. PubMed ID 27442738. Increased morning heart rate in runners: a valid sign of overtraining?