Overtraining in athletes can occur when the training load is not adequately balanced with recovery periods. This can lead to functional overreaching, non-functional overreaching, or overtraining syndrome. The document discusses several hypotheses for the pathophysiology of overtraining, including central fatigue, oxidative stress, hypothalamic dysfunction, and increased cytokine levels. It notes that prevention through periodization of training and adequate rest is key to avoiding overtraining. More research is still needed to better understand and diagnose overtraining in athletes.

1. OVERTRANING IN ATHLETES
By Pathum Bandara

2. Background
• Athletes achieve performance increase by
gradually increasing training load
• Increased loads are tolerated only through
interspersed periods of training and recovery
• If the training intensity, duration, frequency
and recovery period are not carefully
managed athletes are at risk of been
overtrained.

4. Terminology
Functional overreaching (FO)

5. Non-functional overreaching (NFO)

6. Overtraining syndrome (OS)

7. Epidemiology
• One study found a NFO lifetime prevalence of 60% in elite
male and female runners, compared to 33% in non-elite
female runners.
• A multicentre, multi-country survey found that 35% of
adolescent swimmers had been overtrained at least once.
• Estimate of “staleness” were reported in 5% to 30% of
swimmers over a season and in 15% of British elite athletes.
• In a recent study of elite adolescent athletes, 30% reported
NFO at least once in their careers, averaging 2 episodes
lasting 4 weeks.
• Risk significantly increased in individual sports, low
physically demanding sports, females and elite athletes.

8. Symptoms of OTS
• Fatigue • Weight loss
• Depression • Lack of mental
• Bradycardia concentration
• Loss of motivation • Heavy, sore, stiff muscles
• Insomnia • Anxiety
• Irritability • Awakening unrefreshed
• Agitation • Increased exercise VO2
• Tachycardia • Decreased maximal
• Hypertension aerobic power
• Restlessness • Increased basal metabolic
• Anorexia rate
• Increased infection

9. Potential Triggers of OTS
• Increased training load without adequate recovery
• Monotony of training
• Excessive number of competitions
• Sleep disturbances
• Stressors including family life and occupational
• Previous illness
• Altitude exposure
• Heat injury episode
• Severe “bonk”

10. Glycogen Hypothesis
• Literature supports correlation between low
glycogen and decreased performance and
exercise induced fatigue
• However, no proven correlation between low
glycogen and overtrained athletes

11. Central Fatigue Hypothesis
Increased Increased
tryptophan serotonin and
uptake in the mood
brain symptoms
• Selective serotonin reuptake inhibitors
decreased performance
• Although, mood/fatigue are subjective and
influenced by many other factors

12. Glutamine Hypothesis
Increased
Decreased Immune
susceptibility
glutamine dysfunction
to infection
• Athletes are more susceptible to upper
respiratory tract infections after intense exercise
• However, glutamine supplementation does not
improve post-exercise impairment of immune
cells

13. Oxidative Stress Hypothesis
Excessive Muscle
oxidative damage
stress and fatigue
• Resting markers of oxidative stress are higher
in overtrained athletes and increase with
exercise
• Studies on this field have been small and
there are lack of clinically relevant research

14. Autonomic Nervous System Hypothesis
Decreased
Performance
sympathetic
inhibition, fatigue,
activation &
depression and
parasympathetic
bradycardia
dominance
• Decreased HR variability with awakening in
overtrained athletes suggest disruption of ANS
modulation

15. Hypothalamic Hypothesis
Dysregulation of
hypothalamus Many symptoms
and hormonal of OTS
axes
• Endurance athletes have activation of HPA-
axis compared with controls
• However, other factors can influence
HPA/HPG-axis activation

16. Cytokine Hypothesis

17. • Unified theory accounting for many symptoms of
OTS and “why” it develops
• May account for many effects suggested in above
hypothesis
• In contrast, there is lack of evidence supporting
increased cytokines in overtrained athletes
• Need more research to establish the relationship

18. Diagnosis
• Patient history demonstrating
– Decreased performance persisting despite weeks to month
recovery
– Disturbances in mood
– Lack of sign/symptoms or diagnosis of other possible
causes for underperformance
• Screening tests
– Comprehensive metabolic panel
– FBC, ESR, C-reactive protein, iron studies, creatine kinase
– Oxidative stress biomarkers and T cell activation
– Hormonal markers

19. Prevention: Note to Coaches
• Periodization of training • Promoting mental
• Tapering for competition toughness or resilience as
• Adjust training volume and buffer
intensity based on • Rest periods of greater
performance and mood than 6 hours between
• Ensure adequate calorie exercise bouts
intake and hydration • Avoid training following
• Ensure adequate infection, heat stroke,
carbohydrate ingestion periods of high stress
• Ensure adequate sleep • Avoid extreme
environmental conditions
• Utilize profile mood states
and alter training load

20. Future Directions
• Future studies should involve larger number of
elite competitive athletes and observations over
longer time intervals
• Animal model of overtraining could be used to
further hypothesis testing
• Fourier transform infrared spectroscopy
• Further investigation of psychomotor speed testing
as a means of diagnosing OTS

21. Conclusion
• OTS is a maladapted response to excessive
exercise when not matched with appropriate rest
• Many pathophysiologic hypothesis have been
proposed, where cytokine hypothesis appears to
be the strongest
• Differential diagnosis of FO, NFO and OTS is
challenging
• Prevention is the best cure
• Further research is essential to identify definite
causes and treatments

22. References
• Armstrong, L. & VanHeest, J. (2002). The unknown
mechanism of the overtraining syndrome. Sports Medicine,
185-209.
• Hollander, D. & Meyers, M. (1995). Psychological factors
associated with overtraining: Implications for youth sport
coaches. Journal of Sport Behaviour, 3-19.
• Kreher, J. & Schwartz, J. (2012). Overtraining syndrome: a
practical guide. Journal of Sports Health, 128-138.
• Urhausen, A. & Kindermann, W. (2002). Diagnosis of
overtraining: what tools do we have? Sports Medicine, 95-
102.