Author(s): STRØM SOLLI, G., YAMASHITA, D., MUJIKA, I. , Institution: NORD UNIVERSITY, Country: NORWAY, Abstract-ID: 1940

INTRODUCTION:
Sports science typically relies on group designs comparing experimental and control groups or pre- and post-intervention results. However, in elite sports, the focus shifts to individual adaptation rather than group averages. Single-subject or case-study designs offer valuable insights into long-term development of training and physiology that larger sample sizes cannot capture [1]. Therefore, this narrative review aims to provide a comprehensive overview of case studies on the long-term development of world-class and elite athletes in Olympic and Paralympic sports, advancing the field by identifying trends, highlighting knowledge gaps, and guiding methodological improvements.
METHODS:
A systematic search of ScienceDirect, PubMed, and SPORTDiscus identified case studies on world-class or elite athletes (Tier 5 or 4, McKay et al., [2]) that provided long-term data (>2 years) on training characteristics or physiological performance factors in Olympic or Paralympic sports.
RESULTS:
Twenty-six peer-reviewed studies met the inclusion criteria, covering nine sports including running (6 studies), triathlon (5), rowing (3), biathlon (2), swimming (2), tennis (2), cross-country skiing (2), cycling (1), and Nordic combined (1). Athletes from 8 countries were included, with the majority from Norway (9), Spain (6), and the United Kingdom (4). The studies included 29 athletes, with limited data on female (31%), Paralympic (14%), and non-endurance athletes (8%). The mean study duration was 7.1 ± 4.6 years.

Of the included studies, 23 reported long-term training data, showing a 10-438% increase in annual training volume over 2-17 years, with varying trends in training intensity distribution. Fourteen studies examined physiological performance, with eight reporting VO₂max increases of 4-42% over 2-11 years, while three documented declines of 4-17% post-retirement. Twelve studies analyzed submaximal performance indicators, showing power output or velocity at threshold values (VT2, LT, or 4 mmol) increased by 13-101% over 2-11 years. The percentage of VO₂peak at different threshold values remained stable or increased by up to 13 %-points. Only two studies reported data on efficiency/economy, showing a decline of 9% and 14% in VO₂ at similar submaximal speeds over 4-11 years, respectively.
CONCLUSION:
This review summarizes available evidence on long-term development of training and physiology in world-class or elite athletes. Detected knowledge gaps include long-term data on female and para-athletes, as well as training in specialized environments like heat and altitude. Developing better frameworks for reporting long-term training data on world-class and elite athletes (e.g., intensity distribution and exercise modes) represent key areas for methodological improvement.

References
1. Mujika I et al., (2025) Writing high-quality case studies in sport science. IJSPP
2. McKay AKA et al., (2022) Defining Training and Performance Caliber: A Participant Classification Framework. IJSPP