Exercise for Better Bones - Day or Night?

Inclusion Criteria

• •Postmenopausal women within 1-10 yr after menopause
• •BMI 18.5-29.9 kg/m2
• •Healthy as determined by a screening physical examination and blood chemistry related to thyroid, liver, kidney, and lipid profile within normal range
• •No osteoporosis as determined by dual energy x-ray absorptiometry (DEXA) scan at femoral neck or total spinal region
• •No regular exercise for more than 30 minutes a day on more than 2 days a week and no physically active employment, such as maintenance and repair or delivery worker
• •No regular use of medications known to interfere with calcium and bone metabolism from 6 weeks prior to the study to the end of study such as medications for heartburn, reflux, H2 blockers, diuretics, etc. such as antacids, Maalox, Pepcid AC, Nexium, Diuril, etc.
• •Weight stable (within 5 lbs change) for at least 3 months prior to the start of the study
• •Willing to maintain usual lifestyle and activities including the same wake-sleep schedule (go to sleep between 10:00 p.m. and midnight with an average 6-8 hours of sleep time)
• •Refrain from the use of alcohol and nicotine (for example, cigarettes, cigars, and e-cigarettes) for the length of the study
• •Able and willing to perform moderate intensity exercise without contraindications as determined by the Physical Activity Readiness Questionnaire
• •Willing and able to stop any nutritional supplements including vitamin D supplements and calcium-containing medications (for instance, calcium-carbonate antacids)
• •Willing not to use tanning booths during the study or not to travel to locations with a tropical climate two weeks prior to the study or during the washout period