Almudena F. Vaquero

Saliva Composition and Exercise

Little attention has been directed toward identifying the changes which occur in salivary composition in response to exercise. To address this, our article first refers to the main aspects of salivary gland physiology. A knowledge of the neural control of salivary secretion is especially important for the understanding of the effects of exertion on salivary secretion. Both salivary output and composition depend on the activity of the autonomic nervous system and any modification of this activity can be observed indirectly by alterations in the salivary excretion.The effects of physical activity (with reference to factors such as exercise intensity and duration, or type of exercise protocol) on salivary composition are then considered. Exercise might indeed induce changes in several salivary components such as immunoglobulins, hormones, lactate, proteins and electrolytes. Saliva composition might therefore be used as an alternative noninvasive indicator of the response of the different body tissues and systems to physical exertion.In this respect, the response of salivary amylase and salivary electrolytes to incremental levels of exercise is of particular interest. Beyond a certain intensity of exercise, and coinciding with the accumulation of blood lactate (anaerobic threshold or AT), a ’saliva threshold’ (Tsa) does indeed exist. Tsa is the point during exercise at which the levels of salivary α-amylase and electrolytes (especially Na+) also begin to rise above baseline levels. The occurrence of the 2 thresholds (AT and Tsa) might, in turn, be attributable to the same underlying mechanism, that of increased adrenal sympathetic activity at high exercise intensities.

Anaerobic threshold in children: determination from saliva analysis in field tests

The purpose of this study was to determine the anaerobic threshold of children by the analysis of saliva collected during field tests. A group of 25 children (mean age, 10.5 years) performed an incremental exercise test on a track, consisting of 4-min stages at increasing running velocities. Before each test (at rest) and at the end of each stage, both blood (via finger pricks) and saliva samples (for measurement of salivary concentrations of Na+ and Cl−) were collected to determine lactate threshold (Th1a-) and saliva threshold (Thsa), respectively. There were no significant differences between values of Th1a- and Thsa when expressed either as running velocity [mean Th1a-, 10.73 (SD 1.96) km · h−1; mean Thsa, 10.89 (SD 1.69) km · h−1] or heart rate [Th1a-, 182(SD 14) beats · min−1 Thsa 183 (SD 11) beats · min−1]. In addition, correlations between Thsa and Th1a were high, when both values were expressed as running velocity in kilometres per hour (r = 0.89;P < 0.001), or heart rate in beats per minute (r = 0.90;P < 0.001). In conclusion, these findings suggested that saliva analysis would be a valid method for anaerobic threshold determination in field tests.