The Effect of Long Distance Running on the Pattern of Production of Salivary Cortisol on Rest Days

Abstract

INTRODUCTIONCortisol is a glucocorticoid synthesized from cholesterol by the zona fasciculate of the adrenal cortex and is controlled by way of a negative feedback pathway within the hypothalamic‐pituitary‐adrenal (HPA) system. HPA axis receives strong circadian input and plays an essential role in the regulation of stress responses. Cortisol spikes in the morning upon waking up, and then decreases throughout the day, but exercise modifies this pattern of production. Physical exercise activates HPA axis to maintain proper blood glucose levels during these times of energy expenditure. According to previous studies endurance‐trained athletes possess a significantly higher level of circulating cortisol than power trained athletes immediately after exercise. Cortisol is known to have debilitating effects on factors related to bone mineral density (BMD). Consequently, the chronic increase in cortisol in long‐distance runners can lead to adverse effects such as decreased BMD and can contribute to stress fractures. The purpose of this study is to evaluate cortisol levels during days of rest to determine the possible change in the pattern of cortisol production stimulated by repetitive prolonged previous exposure to the physical activity rather than actual stimulus.METHODSMissouri Southern State University (MSSU) Institutional Review Board approval was gained before data collection. A participant group was gathered including 12 males from the men’s cross‐country team at MSSU in the fall of 2019. Participants completed a demographic questionnaire stating the number of hours per week actively participating in sport specified workouts, average hours of sleep per night, and a list of supplements being consumed. Participants gave saliva samples within pre‐determined time intervals before, during, and after their workouts as well as during the same times during days of rest. Samples were collected on two training days and one rest day a week on three separate weeks for a total of 27 samples per athlete. In addition to saliva samples, a stress assessment was filled out by every athlete each day of collection. All samples were placed in a freezer at 0 degrees Celsius until collections were completed and analyzed. Samples were evaluated via ELISA by a competitive immunoenzymatic colorimetric method for the quantitative determination of cortisol concentration. ELISA absorptions were analyzed with linear regression to calculate cortisol concentrations.CONCLUSIONThe result of this study will assist in a better understanding of the hypothalamic‐pituitary‐adrenal axis function. Furthermore, while allowing the endurance‐trained athlete to efficiently and properly recover, it will aid in reducing the risk of injury and overtraining syndrome.