The effects of chronotype on measures of physical performance and stress reactivity

Boiling, Sophie Marie (2020). The effects of chronotype on measures of physical performance and stress reactivity. University of Birmingham. M.Sc.

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Abstract

Research has indicated that an individual’s chronotype can have significant effects on peak performance and stress reactivity across the day. However, there is limited research that investigates multiple measures of performance in conjunction with stress inducing tasks and their cortisol responses. Participants comprised of eighteen healthy individuals identified as early (n=10) and late chronotypes (n=8) from their responses to two chronometric questionnaires. The experimental trial consisted of three experimental sessions (08:00 hrs, 14:00 hrs and 20:00 hrs) each
separated by a week’s rest. Each session included two physical tasks (Maximal Isometric Grip Strength Manoeuvres and an Incremental Test to Volitional Exhaustion), one acute stress inducing task (Paced Auditory Serial Addition Task) and three salivary cortisol samples. Salivary cortisol samples following awakening were collected from each participant on the morning of the 14:00 hrs session. We found significant differences between chronotypes in both handgrip strength and VO2 max. PASAT performance was significantly greater when both chronotypes performed at their optimal time of day. Salivary cortisol increased following both a PASAT test and following high intensity exercise, irrespective of chronotype. Finally, cortisol awakening response occurred significantly earlier and was more pronounced in early chronotypes. Our results provide evidence to support the notion that chronotype a significant impact on peak performance times between chronotypes, however the difference in response to stressful tasks is minimal. Cortisol awakening response may be a better indicator of peak performance than the individual’s response to stress.

Type of Work:

Thesis (Masters by Research > M.Sc.)

Award Type:

Masters by Research > M.Sc.

Supervisor(s):