Timed Exercise Study

Study Overview
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Brief Summary
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The purpose of this study was to investigate the effect of timed exercise on human circadian rhythms. Subjects were randomized to 5 days of morning or evening treadmill exercise. A measure of internal circadian timing, or phase, was measured at baseline and following the exercise intervention. Change in circadian phase was compared between the morning and evening group.

Detailed Description
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This study investigated the effect of morning versus evening exercise on internal circadian timing, or phase. Young, sedentary subjects were recruited for this study. Baseline measures included anthropometric, body composition, cardiorespiratory fitness, chronotype, and circadian phase. Subjects were randomized to 5 consecutive days of morning or evening exercise. Thirty minutes of exercise was performed at the designated time and intensity was maintained at a heart rate corresponding with 70% peak VO2. The measure of circadian phase was salivary dim light melatonin onset, indicated by the time when saliva melatonin concentration exceeded 4pg/ml. Post-exercise circadian phase was measured the evening following the last day of exercise. Changes in circadian phase were compared between morning and evening groups.

Official Title
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Investigating the Effects of Timed Exercise on Human Circadian Rhythms

Conditions
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Circadian Timing - Exercise

Intervention / Treatment
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* Other: Morning Exercise
* Other: Evening Exercise


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: BMI 18.5-40.0 sedentary; <=2 hrs structured exercise weekly medication free (other than birth control) Exclusion Criteria: diagnosed conditions that would contraindicate safe participation in physical activity diagnosed psychiatric conditions night or rotating shift work 1-year prior to study travel across time zones within previous 4 weeks having children <2 years of age smoking

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Morning Exercise Group<br>Participants perform moderate exercise in the morning. | Other: Morning Exercise<br>* moderate intensity exercise (70% VO2 max) each morning for 5 days<br>|
| Experimental: Evening Exercise Group<br>Participants perform moderate exercise in the evening. | Other: Evening Exercise<br>* moderate intensity exercise (70% VO2 max) each evening for 5 days<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in onset (time) of melatonin secretion | Difference in onset (time at which salivary melatonin exceeds threshhold; 4pg/mL) from baseline to completion of exercise intervention. | baseline and following completion of exercise intervention (approximately 5 days) | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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circadian, phase shift, exercise