Effects of Progressive Intensity Exercise Training on Glycemic Control in Older Adults

The purpose of this study is to compare the effects of moderate versus vigorous intensity exercise training on glycemic control in older adults. Glycemic control will be assessed using an oral glucose tolerance test and continuous glucose monitors. In addition, the investigaotrs will investigate whether engaging in an exercise training program elicits changes in sedentary behavior, non-exercise physical activity, sleep, and total daily energy expenditure.

Approximately 25% of older adults have type 2 diabetes mellitus, and almost 50% of older adults have prediabetes. Identifying strategies to prevent the progression of diabetes in this older adult population is imperative. One strategy that has shown promise is lifestyle modification. As adults age they also increase sedentary behavior, decrease physical activity, and have increased occurrence of sleep problems. The combination of these lifestyle factors are likely responsible for the decreases in glycemic control with aging. The American Diabetes Association recommends that prediabetic adults, including older adults, increase structured aerobic exercise and incidental (non-exercise) physical activity while decreasing sedentary behavior. It is emphasized that structured exercise is the most important of these recommendations. However, initiating an exercise routine, may unintentionally affect time spent sitting, non-exercise physical activity, and other lifestyle behaviors like sleep. These changes may attenuate or enhance the effects of exercise on glycemic control. This study will compare the effects of moderate and high intensity exercise on glycemic control, and determine whether changes in non-exercise physical activity, sitting time, and sleep are associated with the observed changes. Because of the increasing prevalence of diabetes with age, identifying the optimal exercise prescription to preserve glycemic control in older adults has important clinical implications.

Eligibility Criteria:
Inclusion Criteria:

* Age ≥60 to \<80 years upon study entry
* Body mass index ≥25.0 to \<35.0 kg/m2 as measured at the baseline screening visit
* HBA1c ≥ 5.7% to \<6.5% OR Fasting Glucose ≥ 100 to \<126 mg/dl as measured at the baseline screening visit.

Exclusion Criteria:

* History of metabolic, cardiac, or pulmonary disease that classifies the individual as high risk by the American College of Sports Medicine
* Participants with un-controlled hypertension and un-controlled thyroid disorders and are on medication for \<3 months.
* Resting systolic blood pressure \>160 mmHg or resting diastolic blood pressure \>100 mmHg will be exclusionary. At the baseline screening visit, an initial resting blood pressure measurement will be attained after the participant is seated at rest for 5 minutes. Subsequent resting blood pressure measurements can be taken at the baseline screening visit up to 3 times to determine eligibility. Subsequent measurements will be taken under the same conditions as the initial measurement with a minimum of 5 minutes between readings. If more than one reading is needed to determine eligibility, the average of all readings taken will be used.
* Thyroid dysfunction, defined as an ultrasensitive thyroid stimulating hormone (TSH) \<0.5 or \>5.0 mU/L; volunteers with abnormal TSH values will be re-considered for participation in the study after follow-up evaluation by the PCP with initiation or adjustment of thyroid hormone replacement.
* Self-reported chronic Inflammatory Disease (e.g., rheumatoid arthritis, lupus)
* Currently taking statins, hormone replacement therapy, prescribed sleep medications, or medications that may affect heart rate response to exercise (e.g., beta blockers)
* Participating in \>30 minutes of aerobic exercise/week during the past 3 months
* Inability to complete exercise test
* Sleep Apnea