OVERTRANING IN ATHLETES

By Pathum Bandara

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.

Terminology

Functional overreaching (FO)

Non-functional overreaching (NFO)

Overtraining syndrome (OS)

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.

Symptoms of OTS

• Fatigue

• Depression

• Bradycardia

• Loss of motivation

• Insomnia

• Irritability

• Agitation

• Tachycardia

• Hypertension

• Restlessness

• Anorexia

• Weight loss

• Lack of mental concentration

• Heavy, sore, stiff muscles

• Anxiety

• Awakening unrefreshed

• Increased exercise VO2

• Decreased maximal aerobic power

• Increased basal metabolic rate

• Increased infection

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”

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

Central Fatigue Hypothesis

Increased tryptophan

uptake in the brain

Increased serotonin and

mood symptoms

• Selective serotonin reuptake inhibitors

decreased performance

• Although, mood/fatigue are subjective and

influenced by many other factors

Glutamine Hypothesis

Decreased glutamine

Immune dysfunction

Increased susceptibility 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

Oxidative Stress Hypothesis

Excessive oxidative

stress

Muscle damage

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

Autonomic Nervous System Hypothesis

Decreased sympathetic activation &

parasympathetic dominance

Performance inhibition, fatigue,

depression and bradycardia

• Decreased HR variability with awakening in

overtrained athletes suggest disruption of ANS

modulation

Hypothalamic Hypothesis

Dysregulation of hypothalamus and hormonal

axes

Many symptoms of OTS

• Endurance athletes have activation of HPA-

axis compared with controls

• However, other factors can influence

HPA/HPG-axis activation

Cytokine Hypothesis

• 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

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

Prevention: Note to Coaches

• Periodization of training

• Tapering for competition

• Adjust training volume and intensity based on performance and mood

• Ensure adequate calorie intake and hydration

• Ensure adequate carbohydrate ingestion

• Ensure adequate sleep

• Utilize profile mood states and alter training load

• Promoting mental toughness or resilience as buffer

• Rest periods of greater than 6 hours between exercise bouts

• Avoid training following infection, heat stroke, periods of high stress

• Avoid extreme environmental conditions

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

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

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.