Lowest perceived exertion in the late morning due to effects of the endogenous circadian system

Thosar, Saurabh S.; Herzig, Maya X.; Roberts, Sally; Berman, Alec M.; Clemons, Noal A.; McHill, Andrew W.; Bowles, Nicole; Morimoto, Miki; Butler, Matthew; Emens, Jonathan S.; Shea, Steven A.

doi:10.1136/bjsports-2018-099148

Cited by 9 publications

(8 citation statements)

References 5 publications

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“…The lower oxygen consumption upon exercise Late compared to Early suggests a better exercise efficiency in humans in the evening hours. This is in line with previous studies showing better exercise capacity in the evening than in the morning hours in humans (Drust et al, 2005;K€ u€ usmaa et al, 2016;Reilly and Waterhouse, 2009;Thosar et al, 2018).…”

Section: Daytime Variance In Exercise Capacity In Humanssupporting

confidence: 93%

“…The pervasive circadian control of metabolism raises the question of whether exercise performance exhibits daily variance. Hitherto, several human studies supported daily variance in exercise performance (Drust et al, 2005;K€ u€ usmaa et al, 2016;Reilly and Waterhouse, 2009;Thosar et al, 2018). Yet the circadian clock control and the associated time-and exercise-dependent molecular events are relatively unknown.…”

Section: Introductionmentioning

confidence: 96%

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Physiological and Molecular Dissection of Daily Variance in Exercise Capacity

et al. 2019

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Section: Daytime Variance In Exercise Capacity In Humanssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 96%

Physiological and Molecular Dissection of Daily Variance in Exercise Capacity

et al. 2019

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“…Light levels were Ͻ3 lux at the horizontal angle of gaze during scheduled wakefulness to prevent light-induced phase shifts of the circadian clock (28) and were Ͻ0.1 lux during scheduled sleep periods. The FD protocol consisted of a baseline 8-h sleep opportunity at the participant's habitual sleep time and a baseline day followed by 10 identical recurring 5-h 20-min sleep-wake cycles (2-h 40-min sleep opportunity and 2-h 40-min scheduled wakefulness) to desynchronize the behaviors from the endogenous circadian system (31). For the ten 5-h 20-min behavioral cycles there was a 2-h 40-min sleep opportunity, and then participants were gently awoken in a standardized fashion by use of a mild auditory stimulus.…”

Section: Methodsmentioning

confidence: 99%

Separate and interacting effects of the endogenous circadian system and behaviors on plasma aldosterone in humans

Thosar

Rueda

Berman

et al. 2019

American Journal of Physiology-Regulatory, Integrative and Comp

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Measurements of aldosterone for diagnosis of primary aldosteronism are usually made from blood sampled in the morning when aldosterone typically peaks. We tested the relative contributions and interacting influences of the circadian system, ongoing behaviors, and prior sleep to this morning peak in aldosterone. To determine circadian rhythmicity and separate effects of behaviors on aldosterone, 16 healthy participants completed a 5-day protocol in dim light while all behaviors ranging from sleep to exercise were standardized and scheduled evenly across the 24-h circadian period. In another experiment, to test the separate effects of prior nocturnal sleep or the inactivity that accompanies sleep on aldosterone, 10 healthy participants were studied across 2 nights: 1 with sleep and 1 with maintained wakefulness (randomized order). Plasma aldosterone was measured repeatedly in each experiment. Aldosterone had a significant endogenous rhythm ( P < 0.001), rising across the circadian night and peaking in the morning (~8 AM). Activity, including exercise, increased aldosterone, and different behaviors modulated aldosterone differently across the circadian cycle (circadian phase × behavior interaction; P < 0.001). In the second experiment, prior nocturnal sleep and prior rested wakefulness both increased plasma aldosterone ( P < 0.001) in the morning, to the same extent as the change in circadian phases between evening and morning. The morning increase in aldosterone is due to effects of the circadian system plus increased morning activities and not prior sleep or the inactivity accompanying sleep. These findings have implications for the time of and behaviors preceding measurement of aldosterone, especially under conditions of shift work and jet lag.

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“…Studies were approved by the institutional review board for human subject protection at Oregon Health and Science University, and all participants provided written informed consent. These data were collected as part of two larger studies on the effects of the circadian system, sleep, and activity on cardiovascular function in humans, of which a number of other measurements taken in protocol 1 ( Figure 1A ) have been reported ( Thosar et al, 2018b , 2019a , b ; Emens et al, 2020 ).…”

Section: Methodsmentioning

confidence: 99%

The circadian system modulates the cortisol awakening response in humans

Bowles

Thosar²,

Butler³

et al. 2022

Front. Neurosci.

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BackgroundIn humans, circulating cortisol usually peaks 30–60 min after awakening from nocturnal sleep, this is commonly referred to as the cortisol awakening response (CAR). We examined the extent to which the CAR is influenced by the circadian system, independent of behaviors including sleep.Materials and methodsWe examined the CAR in 34 adults (20 female) using two complementary multiday in-laboratory circadian protocols performed in dim light, throughout which behavioral factors were uniformly distributed across the 24-hour circadian cycle. Protocol 1 consisted of 10 identical consecutive 5-hour 20-minute sleep/wake cycles, and protocol 2 consisted of 5 identical consecutive 18-hour sleep/wake cycles. Salivary melatonin was used as the circadian phase marker (0° = dim light melatonin onset). During each sleep/wake cycle, salivary cortisol was measured upon scheduled awakening and 50-minutes later, with the change in cortisol defined as the CAR. Cosinor analyses were used to detect any significant circadian rhythmicity in the CAR. In secondary analyses, we adjusted the models for time awake before lights on, total sleep time, percent of rapid eye movement (REM) sleep, and percent of non-rapid eye movement (NREM) sleep.ResultsBoth protocols revealed a similar circadian rhythm in the CAR, with peaks occurring at a circadian phase corresponding to 3:40–3:45 a.m., with no detectable CAR during the circadian phases corresponding to the afternoon. In addition to the sinusoidal component of the circadian rhythm, total sleep time was also associated with the CAR for protocol 1. The percent of sleep spent in REM or NREM sleep were not associated with the CAR in either protocol.ConclusionOur results show that the CAR exhibits a robust circadian rhythm that persists even after adjusting for prior sleep. Presuming that the CAR optimizes physiological responses to the anticipated stressors related to awakening, these findings may have implications for shift workers who wake up at unusual circadian phases. A blunted CAR in shift workers upon awakening in the evening may result in diminished responses to stressors.

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Lowest perceived exertion in the late morning due to effects of the endogenous circadian system

Cited by 9 publications

References 5 publications

Physiological and Molecular Dissection of Daily Variance in Exercise Capacity

Physiological and Molecular Dissection of Daily Variance in Exercise Capacity

Separate and interacting effects of the endogenous circadian system and behaviors on plasma aldosterone in humans

The circadian system modulates the cortisol awakening response in humans

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