CHAPTER 38 • OVERTRAINING SYNDROME/CHRONIC FATIGUE 229- Overtraining:Maladaptive response to training from
extended overload with inadequate recovery resulting in
decrements of performance generally lasting >2 weeks.
It is manifested by increased fatigability, pronounce
vegetative somatic complaints, sleep disorder, altered
psychic excitability, overuse injuries, immune dysfunc-
tion, and some blood chemistry changes. Pathologic
Fatigue (Derman et al, 1997)
PHYSIOLOGIC CHANGES
WITH TRAINING
IMMUNOLOGIC
•Decreased salivary immunoglobulin A(IgA)
- Increased white blood cells (WBC), lymphocytes, nat-
ural killer cells, and poly morphonuclear cells(PMN)
activity
•Transient decrease in the T helper/T suppressor
(Th/Ts) ratio - Decreased serum glutamine
ENDOCRINE
- Increased testosterone proportional to exercise inten-
sity and muscle mass stimulating glycogen regenera-
tion and protein synthesis (Anabolism).
•Transient increased cortisol relative to the duration and
intensity of exercise. The stress response (Catabolism). - The ratio of free testosterone to cortisol(FTCR) rep-
resents the balance of catabolism and anabolism. A
30% decrease in this ratio may suggest inadequate
recovery or overreaching (Fry and Kraemer, 1997). - Norepinephrine increase preexercise (anticipation)
and early in exercise, stimulating lypolysis. - Epinephrine increase proportional to exercise intensity.
- Sex hormone binding globulin(SHBG) decreased pro-
duction with intense exercise. - Suppression of pulsatile secretion of gonadotropin
releasing factor(GnRH); probably affected by stress
and poor nutrition.
•Growth hormone peak secretion at night and with
exercise ~50% VO2max; blunted response with intense
exercise.
EPIDEMIOLOGY
•Overtraining affects 5–15% of elite athletes at any one
time and as much as two-thirds of runners during and
athletic career.
- It may be higher in amateur athletes.
- Seen more commonly in endurance events like swim-
ming, cycling, or running. Overtraining in power
lifters is probably different. - Susceptible athletes include highly motivated, goal-
oriented individuals, exercise programs designed by
the athletes themselves, those athletes that tend to be
focused, conventional, and conservative.
- Seen more commonly in endurance events like swim-
HYPOTHESES- Chronic glycogen depletion:A chronic nutritional
deficiency leading to chronic glycogen depletion with
peripheral muscle fatigue. Central fatigue is interre-
lated to changes in branched-chain amino acids, see
central fatigue hypothesis (Snyder, 1998). - Autonomic imbalance:An increase in sympathetic
activity form stress and overloaded target organs and
increased catabolism leading to decreased sympa-
thetic intrinsic activity. Chronically increased cate-
cholamine levels causes a receptor down regulation
and fatigue (Lehmann et al, 1998). - Central fatigue hypothesis:Peripheral fatigue and
nutrient depletion leading to the consumption of
branched-chain amino acids(BCAAs) with subse-
quent change in the BCAA to free Tryptophan ratio
(fTry) in the plasma. This change favors increased
transport of Try into the central nervous system. Try is
a precursor for serotonin 5-hydroxytryptamine(5HT)
which causes central fatigue (Gastman and Lehmann,
1997; Davis and Bailey, 1996). - Glutamine hypothesis (immune dysfunction):
Overload training leads to depressed glutamine produc-
tion from stressed muscle tissue. Glutamine deficiency
as well as acute exercise stress on the immune system
creates immunologic open windows leading to repeated
minor infections and systemic stress (Walsh et al, 1998). - Cytokine hypothesis:Incomplete recovery of locally
damage tissues with overload causing a local inflam-
matory response that becomes systemic with elevated
proinflammatory cytokines IL-1β, TNF-α, and IL-6.
These cytokines cause CNS fatigue (Smith, 2000).
CATEGORIES OF OVERTRAINING- Sympathetic overtraining:Probably represents early
overtraining. It is manifested by increased resting
heart rate(HR) and blood pressure, loss of appetite,
loss of lean body mass(LBM), irritability, sleep dis-
turbance, and fatigue (Fry and Kraemer, 1997). - Parasympathetic overtraining: Probably represents
more chronic, prolonged overtraining. It is manifested by
low resting HR and blood pressure, sleep disturbance,
depressed mood, and fatigue. (Fry and Kraemer,1997).