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Circadian Phase-Shifting Effects of Bright Light, Exercise, and Bright Light + Exercise.

Youngstedt SD, Kline CE, Elliott JA, Zielinski MR, Devlin TM, Moore TA - J Circadian Rhythms (2016)

Bottom Line: In a within-subjects, counterbalanced design, 6 young adults completed each of three 2.5-day protocols.Participants followed a 3-h ultra-short sleep-wake cycle, involving wakefulness in dim light for 2h, followed by attempted sleep in darkness for 1 h, repeated throughout each protocol.Shifts in the 6-sulphatoxymelatonin (aMT6s) cosine acrophase from baseline to post-treatment were compared between treatments.

View Article: PubMed Central - HTML - PubMed

Affiliation: College of Nursing and Health Innovation and College of Health Solutions, Arizona State University, Phoenix, AZ, US; Phoenix VA Health Care System, Phoenix, AZ, US.

ABSTRACT
Limited research has compared the circadian phase-shifting effects of bright light and exercise and additive effects of these stimuli. The aim of this study was to compare the phase-delaying effects of late night bright light, late night exercise, and late evening bright light followed by early morning exercise. In a within-subjects, counterbalanced design, 6 young adults completed each of three 2.5-day protocols. Participants followed a 3-h ultra-short sleep-wake cycle, involving wakefulness in dim light for 2h, followed by attempted sleep in darkness for 1 h, repeated throughout each protocol. On night 2 of each protocol, participants received either (1) bright light alone (5,000 lux) from 2210-2340 h, (2) treadmill exercise alone from 2210-2340 h, or (3) bright light (2210-2340 h) followed by exercise from 0410-0540 h. Urine was collected every 90 min. Shifts in the 6-sulphatoxymelatonin (aMT6s) cosine acrophase from baseline to post-treatment were compared between treatments. Analyses revealed a significant additive phase-delaying effect of bright light + exercise (80.8 ± 11.6 [SD] min) compared with exercise alone (47.3 ± 21.6 min), and a similar phase delay following bright light alone (56.6 ± 15.2 min) and exercise alone administered for the same duration and at the same time of night. Thus, the data suggest that late night bright light followed by early morning exercise can have an additive circadian phase-shifting effect.

No MeSH data available.


Related in: MedlinePlus

24-h rhythms of aMT6s Excretion at baseline and after treatment. Individual urinary 6-sulphatoxymelatonin data (aMT6s) were averaged into 90-min bins, normalized to percent of peak, and group means (+/– SEM, N = 6) plotted on a 12 noon to 12 noon axis to yield synchronized 24-h profiles representing rhythm timing and waveform at baseline (●) and post-treatment (ο). Color-filled rectangles represent the timing of light and exercise stimuli (light: yellow; exercise: blue). Color filled diamonds underneath the curves represent mean acrophase times before (green) and after (red) treatment. ANOVAs for the normalized 90-min time series (panels A,B,C) underscored robust 24-h rhythmicity [p’s < 0.001] and confirmed a significant phase shift (interaction) for the Light + Exercise treatment, but not for the other treatments.
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Figure 2: 24-h rhythms of aMT6s Excretion at baseline and after treatment. Individual urinary 6-sulphatoxymelatonin data (aMT6s) were averaged into 90-min bins, normalized to percent of peak, and group means (+/– SEM, N = 6) plotted on a 12 noon to 12 noon axis to yield synchronized 24-h profiles representing rhythm timing and waveform at baseline (●) and post-treatment (ο). Color-filled rectangles represent the timing of light and exercise stimuli (light: yellow; exercise: blue). Color filled diamonds underneath the curves represent mean acrophase times before (green) and after (red) treatment. ANOVAs for the normalized 90-min time series (panels A,B,C) underscored robust 24-h rhythmicity [p’s < 0.001] and confirmed a significant phase shift (interaction) for the Light + Exercise treatment, but not for the other treatments.

Mentions: To further explore shifts across all participants, we created 90-min bins of averaged aMT6s ng/h time series data for all subjects and normalized each time series to the peak aMT6s excretion (ng/h) (Figure 2). ANOVA was then used to explore whether there were shifts in these normalized data.


Circadian Phase-Shifting Effects of Bright Light, Exercise, and Bright Light + Exercise.

Youngstedt SD, Kline CE, Elliott JA, Zielinski MR, Devlin TM, Moore TA - J Circadian Rhythms (2016)

24-h rhythms of aMT6s Excretion at baseline and after treatment. Individual urinary 6-sulphatoxymelatonin data (aMT6s) were averaged into 90-min bins, normalized to percent of peak, and group means (+/– SEM, N = 6) plotted on a 12 noon to 12 noon axis to yield synchronized 24-h profiles representing rhythm timing and waveform at baseline (●) and post-treatment (ο). Color-filled rectangles represent the timing of light and exercise stimuli (light: yellow; exercise: blue). Color filled diamonds underneath the curves represent mean acrophase times before (green) and after (red) treatment. ANOVAs for the normalized 90-min time series (panels A,B,C) underscored robust 24-h rhythmicity [p’s < 0.001] and confirmed a significant phase shift (interaction) for the Light + Exercise treatment, but not for the other treatments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834751&req=5

Figure 2: 24-h rhythms of aMT6s Excretion at baseline and after treatment. Individual urinary 6-sulphatoxymelatonin data (aMT6s) were averaged into 90-min bins, normalized to percent of peak, and group means (+/– SEM, N = 6) plotted on a 12 noon to 12 noon axis to yield synchronized 24-h profiles representing rhythm timing and waveform at baseline (●) and post-treatment (ο). Color-filled rectangles represent the timing of light and exercise stimuli (light: yellow; exercise: blue). Color filled diamonds underneath the curves represent mean acrophase times before (green) and after (red) treatment. ANOVAs for the normalized 90-min time series (panels A,B,C) underscored robust 24-h rhythmicity [p’s < 0.001] and confirmed a significant phase shift (interaction) for the Light + Exercise treatment, but not for the other treatments.
Mentions: To further explore shifts across all participants, we created 90-min bins of averaged aMT6s ng/h time series data for all subjects and normalized each time series to the peak aMT6s excretion (ng/h) (Figure 2). ANOVA was then used to explore whether there were shifts in these normalized data.

Bottom Line: In a within-subjects, counterbalanced design, 6 young adults completed each of three 2.5-day protocols.Participants followed a 3-h ultra-short sleep-wake cycle, involving wakefulness in dim light for 2h, followed by attempted sleep in darkness for 1 h, repeated throughout each protocol.Shifts in the 6-sulphatoxymelatonin (aMT6s) cosine acrophase from baseline to post-treatment were compared between treatments.

View Article: PubMed Central - HTML - PubMed

Affiliation: College of Nursing and Health Innovation and College of Health Solutions, Arizona State University, Phoenix, AZ, US; Phoenix VA Health Care System, Phoenix, AZ, US.

ABSTRACT
Limited research has compared the circadian phase-shifting effects of bright light and exercise and additive effects of these stimuli. The aim of this study was to compare the phase-delaying effects of late night bright light, late night exercise, and late evening bright light followed by early morning exercise. In a within-subjects, counterbalanced design, 6 young adults completed each of three 2.5-day protocols. Participants followed a 3-h ultra-short sleep-wake cycle, involving wakefulness in dim light for 2h, followed by attempted sleep in darkness for 1 h, repeated throughout each protocol. On night 2 of each protocol, participants received either (1) bright light alone (5,000 lux) from 2210-2340 h, (2) treadmill exercise alone from 2210-2340 h, or (3) bright light (2210-2340 h) followed by exercise from 0410-0540 h. Urine was collected every 90 min. Shifts in the 6-sulphatoxymelatonin (aMT6s) cosine acrophase from baseline to post-treatment were compared between treatments. Analyses revealed a significant additive phase-delaying effect of bright light + exercise (80.8 ± 11.6 [SD] min) compared with exercise alone (47.3 ± 21.6 min), and a similar phase delay following bright light alone (56.6 ± 15.2 min) and exercise alone administered for the same duration and at the same time of night. Thus, the data suggest that late night bright light followed by early morning exercise can have an additive circadian phase-shifting effect.

No MeSH data available.


Related in: MedlinePlus