"N-of-1"-Study: A concept of acute and chronic stress research using the example of ballroom dancing.

Athletes often report on heightened stress, higher disease susceptibility, and a deterioration in mood and performance throughout periods of high training load and competitions. This paper presents a single-case study combining different research approaches to monitor the dynamic, idiosyncratic responses to competitive stress in elite sports using the example of professional ballroom dancing. Throughout an 8-month period (313 data points), one international-level female dancer provided data on mood, stress, and fatigue. In parallel, she collected saliva samples for the assessment of cortisol (sCort) and alpha-amylase (sAA). A hair strand was collected every 3 months to examine cumulative cortisol secretion. As expected, perceived stress was related to a reduction in well-being. On a daily basis, sCort predicted lower fatigue. In addition, tournaments resulted in a 3-fold and a 2-fold increase in sCort and sAA, respectively, and there was a pronounced drop in hair cortisol in the aftermath of a surgery-related break from dancing. We confirm competitive ballroom dancing to constitute a major stressor with immediate and prolonged consequences for self-reported well-being and biological stress markers. Single-case studies offer much potential for the observation of complex dynamic associations. In a next step, this approach will also become relevant when evaluating the efficacy of preventive and therapeutic interventions on an individual level.