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Douglas Potter and Denis Keeling

The effects of exercise and circadian rhythms on memory function were explored in a group of shift workers (mean age 32 yrs). A variant of the Auditory-Verbal Learning Test was used to test memory for word lists at 9:30 a.m. and 12:30, 3:30, and 6:30 p.m. in a repeated-measures design. Without exercise there was clear evidence of a circadian rhythm in memory performance, with peak performance occurring at 12:30 and poorest performance at 3:30. A brisk 10-min walk followed by a 15- to 30-min recovery period resulted in significant improvement in memory recall at all time periods except 12:30. The results of the AVLT task suggest an improvement in both working memory and long-term memory performance. Rhythmic changes in serotonin, epinephrine, norepinephrine, and acetylcholine levels all affect cortical arousal and cognitive function. Exercise may have resulted in altered levels of these neurotransmitters, increased glucose, oxygen, or nutrient levels, or from temporary changes in growth hormone or brain-derived neurotropic factor levels resulting in increased synaptogenesis and neurogenesis. The physiological basis of this temporary improvement in memory remains to be determined, but this simple behavioral intervention may have widespread application in improving memory function in all sections of the population including children and the elderly.

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David P. Looney, Mark J. Buller, Andrei V. Gribok, Jayme L. Leger, Adam W. Potter, William V. Rumpler, William J. Tharion, Alexander P. Welles, Karl E. Friedl and Reed W. Hoyt

) such as solely heart rate ( Buller et al., 2013 ). While the majority of estimation methods for CT have focused on stressed environments during exercise conditions, resting CT modeling is particularly valuable for research and clinical purposes including circadian rhythm monitoring. Circadian rhythm

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Michael J. Zurawlew, Jessica A. Mee and Neil P. Walsh

passive heat acclimation on core temperature circadian rhythm and thermoregulatory responses was examined in a series of investigations in rats 11 , 12 and then in humans. 10 Six adult men and women heat acclimated via 9 or 10 daily 4-hour passive heat exposures commencing in the afternoon (46°C and 20

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Francisco J. Amaro-Gahete, Lucas Jurado-Fasoli, Alejandro R. Triviño, Guillermo Sanchez-Delgado, Alejandro De-la-O, Jørn W. Helge and Jonatan R. Ruiz

. 2015 ; 45 : 37 – 56 . doi:10.1007/s40279-014-0246-y 10.1007/s40279-014-0246-y 25164465 7. Drust B , Waterhouse J , Atkinson G , Edwards B , Reilly T . Circadian rhythms in sports performance—an update . Chronobiol Int . 2005 ; 22 : 21 – 44 . PubMed ID: 15865319 doi:10.1081/CBI

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Chris Brogden, Kelly Marrin, Richard Page and Matt Greig

of movement screening is fundamental to the subsequent design of prehabilitation and injury management strategies. Circadian rhythm is a term used to describe variations in many human physiological variables 8 and factors influencing athletic performance, relative to time of day. 9 , 10 It has been

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Thorlene Egerton, Jorunn L. Helbostad, Dorthe Stensvold and Sebastien F.M. Chastin

Fatigue has been associated with reductions in daily activity of older people. Summary measures of daily physical activity provide limited understanding of how fatigue affects physical activity behavior. This study examined the hour-by-hour energy expenditure estimated from accelerometry data to provide insight into physical activity behaviors of older people experiencing fatigue. Fatigued participants were matched to ‘not fatigued’ participants by age, sex, and BMI. Each group consisted of 86 people with a mean age 73.8 years (SD 2.0), BMI 26.5 kg⋅m–2 (SD 3.9) and 61% female. The phase-space plot, constructed to express rate of change of average vertical axis counts per hour as a time series, showed fatigued participants deviated from the not fatigued participants during the morning period, when hour-by-hour activity was increasing. Older people who feel fatigued have a different morning activity pattern, which appears to lead to the lower overall levels of physical activity.

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Daniel Liebzeit, Cynthia Phelan, Chooza Moon, Roger Brown and Lisa Bratzke

The purpose of this investigation is to examine differences in rest-activity patterns and sleep characteristics in older adults with heart failure (HF) and healthy older adults. The sample included older adults with HF (n = 20) and a reference group of healthy older adults (n = 20). Traditional cosinor analysis was used to assess three parameters of rest–activity from wrist actigraphy data: amplitude (range of activity), mesor (mean activity), and acrophase (time of peak activity). Traditional sleep characteristics were also determined from actigraphy data: total sleep time (TST), sleep latency (SL), sleep efficiency (SE), and wake after sleep onset (WASO). The HF group demonstrated significantly lower mesor and amplitude than the reference group (p < .01). The HF group had significantly greater TST (p < .01), but the groups had similar SE, SL, and WASO. Despite similar sleep characteristics to healthy older adults, overall rest–activity patterns were significantly dampened in those with HF.

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Tzai-Li Li and Michael Gleeson

This study compared immunoendocrine responses to a single bout of prolonged cycling at different times of day and to a 2nd bout of cycling at the same intensity on the same day. In a counterbalanced design, 8 men participated in 3 experimental trials separated by at least 4 d. In the afternoon exercise-only trial, subjects cycled for 2 h at 60% VO2max starting at 14:00. In the other 2 trials, subjects performed either 2 bouts of cycling at 60% VO2max for 2 h (starting at 09:00 and 14:00) or a separate resting trial. The single bout of prolonged exercise performed in the afternoon induced a larger neutrophilia and monocy-tosis than the identical bout of morning exercise, possibly the result of reduced carbohydrate availability and the circadian rhythm in cortisol levels. The 2nd prolonged exercise bout caused greater immunoendocrine responses but lower plasma glucose levels and neutrophil function compared with the 1st bout.

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Lara A. Carlson, Kaylee M. Pobocik, Michael A. Lawrence, Daniel A. Brazeau and Alexander J. Koch

Melatonin’s response to exercise in athletes is important to understand to implement best training practices for promoting sleep. Melatonin (N-acetyl-5-methoxytryptamine) is known to influence the sleep–wake cycle, 8 and its secretion by the pinealocytes influences the circadian rhythm. 8 – 10 Melatonin

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:// for more information. May 28 to June 1, 2019, Orlando, FL, USA The 66th annual meeting of the American College of Sports Medicine (ACSM) will be held in conjunction with the 10th World Congress on Exercise is Medicine and the World Congress on the Basic Science of Exercise, Circadian Rhythms and Sleep