The Insulin Sensitivity Using Aerobic Interval Conditioning

The Insulin Sensitivity using Aerobic Interval Conditioning (ISAIC) trial will compare traditional aerobic training (AER) to interval training (INT) in sedentary, overweight/obese men at risk for pre-diabetes. The investigators will randomly assign 42 individuals to 3 months of monitored exercise using a randomly assisgned design where participants will exercise under either AER or INT training conditions. The AER training condition will be consistent with "standard-of-care" recommendations. Exercise training will entail one 3-month blocks of either AER or INT. Training will consist of 1) a 1-month ramp up period, 2) 1-month of traditional aerobic training and 3) 1-month of either continued AER or INT.

It is currently estimated that type II diabetes (T2D) affects 5-8% of adults. Also recognized is a transitional group of individuals whose control of blood glucose is abnormal, but not yet considered diabetic. These individuals are classified as having pre-diabetes, which is defined as having impaired fasting glucose (IFG;fasting glucose 100-125 mg/dl), impaired glucose tolerance (IGT; post 2-h glucose load; 140-199 mg/dl) or both. This population represents a significant segment of the population as it is estimated that approximately 23% of Americans have pre-diabetes (IGT or IFG). Two unifying features associated with these metabolic impairments is a strong link to obesity and physical inactivity. Regular exercise positively influences IFG/IGT and obesity, and represents an important therapy for preventing the progression to T2D by enhancing several mechanisms of action including improved: glucose metabolism, muscle respiratory capacity, mitochondrial respiratory chain activity and ß-oxidation. Importantly, the dose of physical activity required to promote metabolic benefits appears to be obtainable for most individuals with as little as \~1000 kcal/w of aerobic activity.

While most exercise policy statement guidelines recommend that exercise be performed within an intensity ranging of 40-85% V02max, newer guidelines, such as the recently updated Physical Activity and Public Health Recommendations recognize that few studies have examined the effects of intensity, duration, or frequency of physical activity independent of their contribution to the total amount of physical activity. Accordingly, this writing group specifically recommended that, "based on recent data, there is some indication that vigorous-intensity activities may have greater benefit for reducing cardiovascular disease and premature mortality than moderate-intensity physical activity .... that much more work is needed is this area."

Eligibility Criteria:
Inclusion Criteria:

* Age 30 to 60 years, inclusive
* BMI greater than or equal to 25 - less than or equal to 35 kg/m2
* Waist circumference \>38"; Waist-to-Hip Ratio \>0.95 Sedentary Lifestvle
* Not physically active greater than or equal to 3 days/week-l for 20 min each time for the previous 6 months,
* Not participating in regular resistance exercise

Exclusion Criteria:

* Resting blood pressure greater than or equal to 160/100 mm Hg
* Triglycerides greater than or equal to 500 mg/dL
* Factors that may limit adherence to intervention or affect conduct of the trial such as lack of time, amount of travel, and/or work or family stressors
* Unable or willing to communicate with staff, to provide written informed consent, or accept the randomized assignment
* Failure to complete behavioral run-in and baseline testing
* Hospitalization for depression in the last 6 months
* Not physically capable of performing the exercise required of the study protocols
* Consuming \>14 alcoholic beverages per week
* Plans to be away \>4 weeks in the next 6 months
* Lack of support from primary health care provider or family members
* Signficant weight loss in the past year (\>20 kg) or current use of weight loss medications
* Current diagnsis of schizophrenia, or other psychotic disorders, or bipolar disorder
* Another member of household is a participant or staff member of the study.
* History of bariatric surgery within last 3 years,
* Other temporary intervening event, such as sick spouse, bereavement, or recent move.
* Other medical, psychiatric, or behavioral limitations that in the view of the principal investigator may interfere with study participation or the ability to follow the intervention protocol.
* Underlying diseases or conditions likely to limit lifespan and/or affect the safety of the intervention
* Cancers requiring treatment in the past 5 years, unless prognosis is excellent.
* Self-report HIV or tuberculosis.
* History or evidence of serious arrhythmias, cardiomyopathy, congestive heart failure, aortic aneurysm, or heart transplantation.
* Renal disease: currently receiving dialysis.
* Type I diabetes mellitus
* Type 2 diabetes mellitus, defined as:

Fasting plasma glucose levels greater than or equal to 26 mg/dL 2-hour postprandial Oral Glucose Tolerance Test results greater than or equal to 200 mg/dL

* Any other medical condition or disease that is life threatening or that can interfere with or be aggravated by exercise.
* Chronic obstructive lung disease, peripheral vascular disease or angina that limits ability to follow exercise protocol.
* Advanced neuropathy or retinopathy.
* Smoker or have used nicotine/tobacco products within the last 12 months.