Assessment of exercise-induced stress by automated measurement of salivary cortisol concentrations within the circadian rhythm in Japanese female long-distance runners

Abstract

Background: Overtraining syndrome, caused by prolonged excessive stress, results in reduced performance and cortisol responsiveness in athletes. It is necessary to collect saliva samples sequentially within circadian rhythm for assessing exercise stress by measuring cortisol concentrations, and automated cortisol measurements using electrochemiluminescence immunoassay (ECLIA) may be useful for measuring a large number of saliva samples. In this study, we evaluated the appropriate use of cortisol-based exercise stress assessment within the circadian rhythm, which may diagnose and prevent overtraining syndrome in athletes. Methods: We collected saliva and sera from 54 healthy participants and analyzed the correlation between salivary cortisol concentrations measured by ECLIA and enzyme-linked immunosorbent assay (ELISA) or serum cortisol analysis. We also collected saliva continuously from 12 female long-distance runners on 2 consecutive days involving different intensities and types of exercise early in the morning and in the afternoon and measured salivary cortisol concentrations using ECLIA. Each exercise intensity of runners was measured by running velocities, Borg Scale score, and rate of change in the pulse rate by exercise.

Exercise stress assessed by automated measurements of salivary testosterone and cortisol levels and testosterone/cortisol ratio within circadian rhythms in male long-distance runners

“…We collected saliva and serum samples for correlation analyses of the testosterone and cortisol concentrations from all runners at 7:00 before morning exercise and breakfast. Four weeks later, we collected salivary samples were collected sequentially from these runners on two consecutive days involving different intensities and types of training in the morning and evening during a training period su ciently removed from races, as previously described [8]. We divided the runners into two groups; a low-intensity exercise group and a high-intensity exercise group.…”

“…The runners in the high-intensity exercise group were subjected to the following exercise program: day 1, 12,000-m xed-distance speed running in the morning and interval training with seven sets of 1,000-m fast running and light jogging in the evening; day 2, 10,000-m xeddistance running in the morning and 15,000-m xed-distance running in the evening. The runners were allowed to drink drank enough water to avoid dehydration during these training sessions [8]. On both days, saliva samples were collected at eight time points: upon waking (05:00), before morning exercise (05:30), after morning exercise (07:00), before breakfast (07:30), before lunch (12:00), before evening exercise (16:00), after evening exercise (18:30), and before dinner (19:00), as previously described [8].…”

“…The runners were allowed to drink drank enough water to avoid dehydration during these training sessions [8]. On both days, saliva samples were collected at eight time points: upon waking (05:00), before morning exercise (05:30), after morning exercise (07:00), before breakfast (07:30), before lunch (12:00), before evening exercise (16:00), after evening exercise (18:30), and before dinner (19:00), as previously described [8].…”

“…The resting pulse rates at wakeup time and the maximum pulse rates during each exercise session were measured using the wearable devices. The distance and duration of running during each exercise session were was measured, and the running velocity was calculated as the distance divided by the duration (m/min), as previously described [8]. The Borg Scale [11] was used to determine the rating of perceived exertion of the runners after exercise.…”

“…This monitoring requires sequential sampling within circadian rhythms throughout days with different exercise training intensities and the e cient measurement of a large number of such samples. We previously reported that sequential saliva sampling and automated electrochemiluminescence immunoassay (ECLIA)-based salivary cortisol measurements made it possible to detect the circadian rhythm and to compare the stress induced by different intensities of endurance exercise at the same time on different days in female long-distance runners [8]. By contrast, there have been no reports of similar saliva sampling and automated measurements of testosterone for assessing exercise stress in male athletes.…”