A Comparison of Capillary, Venous, and Salivary Cortisol Sampling after Intense Exercise

in International Journal of Sports Physiology and Performance
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Venipuncture is expensive, invasive, and impractical for many sport-science and clinical-based settings. Salivary free cortisol is often cited as a noninvasive practical alternative. However, when cortisol concentrations exceed the corticosteroid-binding globulin (CBG) point of 500 nmol/L, a lack of agreement between salivary and venous blood cortisol has been found. Alternatively, capillary blood may present a minimally invasive, cost-effective, and practical surrogate for determining cortisol concentration.

Purpose:

The aim of this study was to determine whether cortisol concentrations sampled from capillary blood and saliva accurately reflect those found in venous blood across a large range of concentrations after intense exercise.

Methods:

Eleven healthy aerobically trained male subjects were recruited. Capillary, salivary, and venous blood samples were collected before and after (immediately and 5, 10, 15, and 20 min after) a treadmill VO2 max test.

Results:

Capillary and venous concentrations increased at a similar rate after exercise (Cohen d.14–.33), increasing up to 15 min postexercise before a decline was seen. Salivary cortisol values increased at a slower rate than venous and capillary cortisol but continued to increase 15 min postexercise (Cohen d .19–.47 and .09–.72, respectively).

Conclusions:

Capillary cortisol accurately reflects concentrations assayed from venous blood across a range of values below and above the CBG binding point. Capillary sampling provides a minimally invasive, cost-effective, practical surrogate for assessment of hypothalamic-pituitary-gland function.

Fryer is with the School of Sport and Exercise, University of Gloucestershire, Gloucester, UK. Dickson is with the School of Sport and Physical Education; Scarrott, the Mathematic and Statistics Dept; and Draper, the School of Sport and Physical Education, University of Canterbury, Christchurch, New Zealand. Hillier is with the Anaesthesia Dept, Northampton General Hospital, Cliftonville, UK. Stoner is with the School of Sport and Exercise, Massey University, Wellington, New Zealand. Address author correspondence to Simon Fryer at sfryer@glos.ac.uk.