Overtraining and Functional Overreaching

Table of Contents

  1. Overtraining and the Immune System
  2. Factors Stressing the Immune System
  3. Warning Signs and Symptoms of Overtraining
  4. Immunological Findings in Overtraining
  5. Strategies to Minimize Infection Risk
  6. References
  7. One-Minute-Paper Topics

1 Overtraining and the Immune System

Particularly strenuous exertions such as marathon competitions and prolonged, exhaustive exercise increase the risk of developing upper respiratory tract infections in the following weeks. High training volumes in the endurance range of more than 100 running kilometers per week also carry the risk of increased susceptibility to infection. Excessively frequent training in the anaerobic zone can lead to overtraining syndrome (Nieman 1994; Urhausen et al. 1995; Puta et al. 2026).

2 Factors Stressing the Immune System

  • Insufficient physical and psychological recovery
  • Excessive training volumes and duration
  • Too frequent anaerobic training (e.g., HIIT)
  • Infections, premature return after infections, allergies
  • Altitude stays
  • Psychological distress
  • Malnutrition or unbalanced diet
  • Insufficient sleep duration, sleep quality, and irregularity
  • Insufficient consideration of the female menstrual cycle

3 Warning Signs and Symptoms of Overtraining

Warning signs can be divided into four categories:

Individual performance aspects: Decline in athletic performance, premature training cessation, reduced exercise tolerance, decreased muscular strength, coordination difficulties.

Cardiovascular and muscular aspects: Altered resting heart rate (up to approximately 10 beats), altered blood pressure, muscle soreness, decreased body fat percentage.

Psychological aspects: Concentration and sleep disturbances, chronic fatigue, loss of appetite, depressive behavior, loss of motivation, emotional instability, competition anxiety.

Immunological aspects: Recurrent excessive upper respiratory tract infections (> 5 per year), gastrointestinal disturbances (Purvis et al. 2010; Gleeson 2002; Puta et al. 2026).

4 Immunological Findings in Overtraining

No substantial influence on immune cell concentrations through overloading training has been demonstrated to date. However, impaired function of neutrophils and monocytes was observed during intensified training phases. This reduced defense capacity was completely restored after a 2-week recovery phase (Gabriel and Kindermann 1997b; Puta et al. 2026).

5 Strategies to Minimize Infection Risk

Avoidance of very long training sessions (> 2 h), reduction of psychological stress, monitoring of mood and stress, adequate sleep duration (approximately 8 h), avoidance of extreme diets, minimization of contact with sick individuals, knowledge and implementation of hygiene rules, carbohydrate supplementation to attenuate exercise-induced proinflammatory immune regulation (Puta et al. 2026; Nieman 1998a, b).

References

  • Gabriel H, Kindermann W (1997b) Training and immune system. Dtsch Z Sportmed 48(Suppl):1-8.
  • Gleeson M (2002) Biochemical and immunological markers of over-training. J Sports Sci Med 1:31-41.
  • Nieman DC (1994) Exercise, upper respiratory tract infection, and the immune system. Med Sci Sports Exerc 26(2):128-139.
  • Nieman DC et al. (1998a, b) Carbohydrate and cytokine response to heavy exertion. Med Sci Sports Exerc.
  • Puta C, Haunhorst S, Gabriel HHW (2026) Sport und Immunsystem. In: Wonisch M et al. (eds) Kompendium der Sportmedizin. Springer.
  • Purvis D et al. (2010) Physiological and psychological fatigue in extreme conditions. PM R 2(5):438-441.
  • Urhausen A et al. (1995) Blood hormones as markers of training stress and overtraining. Sports Med 20(4):251-276.

One-Minute-Paper Topics

A One-Minute-Paper (OMP) is a short, focused prompt that students answer in ~60 seconds at the end of a session to consolidate learning, surface misconceptions, and provide formative feedback. When answering, be concise, specific, and use terminology from today’s session.

  1. Define functional overreaching, non-functional overreaching, and overtraining syndrome in one sentence each.
  2. What is the typical recovery timeline that distinguishes these three states?
  3. Name three performance-related warning signs of overtraining.
  4. Which cardiovascular markers can shift in athletes approaching overtraining?
  5. How do mood disturbances fit into the diagnostic picture of overtraining syndrome?
  6. List two immunological changes typically observed in chronically overreached athletes.
  7. Why is overtraining considered a diagnosis of exclusion?
  8. Explain the role of the HPA axis in chronic training stress.
  9. Which laboratory tests would you order to rule out endocrine causes of fatigue in an athlete?
  10. How does sleep quality interact with training load and immune function?
  11. Why are adolescent athletes considered particularly vulnerable to overreaching?
  12. Describe one evidence-based strategy to minimise infection risk during high-load training blocks.
  13. How does nutrition (especially carbohydrate availability) modulate the immune response to heavy training?
  14. What role does psychological stress play in the development of overtraining syndrome?
  15. Which monitoring tools (subjective and objective) would you implement in a season plan?
  16. What was the most actionable insight from today’s lecture for your own practice?
  17. Which concept from today’s lecture do you find most difficult to apply?
  18. Why is self-reported wellness data still considered the gold standard despite its subjectivity?
  19. Give one example of how overtraining and Long COVID/ME-CFS can be clinically confused.
  20. What is one open research question about overtraining that you would like to explore?