Sports Medicine: Just the Facts

184 SECTION 3 • MEDICAL PROBLEMS IN THE ATHLETE

• Chronic exercise: Repeated exercise-induced release
  of PRL may result in menstrual cycle alterations
  (McCardle, Katch, and Katch, 1991).

POSTERIORPITUITARYHORMONES ANDEXERCISE

A. Oxytocin

• Endurance exercise/chronic exercise:Graded exer-
  cise to exhaustion in professional cyclists did not
  result in any response to plasma oxytocin levels
  (Chicharro et al, 2001).
  •Pathways of oxytocin from the hypothalamus to the
  brain stem restrain the tachycardic response in trained
  individuals without compromising cardiac output or
  circulatory demand during exercise (Michelini,
  2001).


• Six weeks of high intensity exercise decreased oxy-
  tocin levels in rats; this may be a result of overtrain-
  ing (Peijie et al, 2003).

B. Vasopressin

• Endurance exercise/chronic exercise:Following a
  1-h continuous cycling session at both 5 a.m. and 5 p.m.,
  vasopressin levels were significantly higher with both
  exercise sessions.
  
  
  1. Levels were significantly greater with the a.m. ses-
     sion versus the p.m. session.
  
  
  2. This difference between sessions persisted through
     1-h recovery period (Zhao et al, 2003; abstract).
  
  
  
  


• Ninety minutes of exercise at 60% peak VO 2 in
  untrained individuals significantly increased plasma
  vasopressin.
  
  
  • When plasma volume was expanded as with
    endurance training, this increase in vasopressin was
    blunted during exercise (Roy et al, 2001).
    •Two female ultradistance triathletes who experienced
    hyponatremia and increases in plasma volume failed
    to show any change in vasopressin levels from pre- to
    postevent (Speedy et al, 2000).
    •Takmata and coworkers (2000) found that exercise
    increases vasopressin.
    
    
    • Correlated with increased osmolality.
    
    
    • Dynamic running in rats increased vasopressin levels
      in the ventral and dorsal portions of the brain stem.
      
      
      • Contributes to heart rate’s (HR’s) response to
        increased circulatory demand with exercise
        (Michelini and Morris, 1999).
        •Following two treadmill tests (100% VO2maxand 90%
        VO2max), plasma vasopressin significantly increased in
        an intensity-dependent manner.
      
      
      • Higher values were found in women versus men
        (Deuster et al, 1998).
      
      
      
      
    
    
    
    
  
  
  
  

ADRENALCORTEXHORMONES ANDEXERCISE

A. Cortisol

• Endurance exercise:Cortisol levels increase acutely
  in middle-aged, postmenopausal women following
  exhaustive exercise.
  
  
  • Those who reported “low vigour” had lower cortisol
    responses than those who did not (Pompe van der
    et al,2001).
  
  
  
  


• High intensity exercise of short duration (<15 min)
  results in peak cortisol levels immediately after activity
  (Consitt et al, 2002).


• Acute cortisol increases with endurance activity returns
  to baseline levels within hours of activity cessation.
  •Viro et al (2001) revealed variable results in regard to
  cortisol levels following a 2-h exercise session.
  
  
  • High responders increased their performance in a
    1 minanaerobic test.
    •Low responders decreased their performance in the
    anaerobic test.
  
  
  
  


• Resistance exercise: Following 8 weeks of heavy
  resistance training (3 sets of 6–12 RM with 2-min rest;
  2 days/week), cortisol significantly increases above
  preexercise values (Kraemer et al, 1997).
  
  
  1. Men experienced increased values at weeks 1, 6,
     and 8.
  
  
  2. Women experienced increased values at weeks 6
     and 8.
  
  
  
  

TABLE 32-2 Posterior Pituitary Hormones

GLAND HORMONE CONTROL ACTION ENDURANCE RESISTANCE CHRONIC

Posterior Oxytocin Hypothalamic Stimulate uterine Conflicting; no change, controls Unknown Unknown
pituitary neurons muscles and breasts for ex-induced tachycardia;
may effect other hormone
secretions
Vasopress in Hypothalamic Controls water excretion; Increased effect;increased Unknown Possibly blunted
(ADH) neurons blood volume; blood water reabsorption by during exercise
osmolality; attenuates kidney as a result of itself; training
the inhibitory effect of result of sweating; results in
glucoorticoidson CRH conserves fluids; BP and increased plasma
release of ACTH HR control; intensity volume
related; circadian influence