One-third of US adults have above normal blood glucose levels (BG), which is a major risk factor for type 2 diabetes (T2B). Exercise has a direct effect on BG levels, measuring BG levels pre and post workout for both aquatic and land exercise will show a change on BG levels. Aquatic treadmill (ATM) training is a form of exercise previously shown to offer similar improvements in cardiovascular fitness as land treadmill (LTM) training with the added benefit of greater improvements in some BG and vascular health measures.
However, it is unclear whether ATM or LTM exercise causes a more favorable BG response. The role of exercise intensity on BG levels is also uncertain in these circumstances. Because ATM is an expensive piece of equipment to use for the general population an adjustment has been made to account for this circumstance. Participants, rather than using an ATM will be instead aqua jogging at a moderate and vigorous intensity. The purpose of this study is to determine the effects of both aqua jogging and LTM exercise performed at moderate and vigorous intensities on prediabetic adults.
This study will have a significant impact in determining the optimal exercise prescription for managing BG levels and CV health, especially for individuals with weight limitations preventing LTM exercise participation.
The Principal Investigator (PI) requests a spring 2018 salary. Spring release will allow for the PI to analyze data, prepare manuscripts for publication, and prepare conference presentations. In addition to the fall session, it is estimated that the PI will spend at least 20 hours per week on data collection, subject recruitment, and subject screening.
Other Salaries ($300)
$300 is being requested for lifeguard wages. This will account for approximately 20 hours at $15/hour. Hired lifeguards will be needed when utilizing the Pioneer Hall pool outside of normal recreation hours.
Supply Purchase ($310)
$780 is being requested for supply purchases. This funding will be used for any equipment that is needed for the glucose analysis and testing. Glucose pack ($110 x 1), buffer ($50 x 1 bag), calibrator ($50 x 1 bottles), gloves ($10 x 1 box), storage vials ($40 x 1 box), needles ($25 x 1 pack), vacutainers ($25 x 1 pack)
$3500 is being requested for pool rental at Pioneer Hall ($75/hour x 20 subjects). This funding will be used to rent the appropriate number of lanes in the deep end of the pool at $75 per hour. The pool will be utilized when the participants are exercising in the pool for the study. $2000 is also being requested for participant compensation ($100 x 20 subjects) allowing for incentive for more participants in the form of $100 visa gift cards.
Environment / Resources
Research will be conducted in Pioneer Hall at Texas Women’s University in both the lab as well as the indoor pool area that is also located in Pioneer Hall. Equipment that is available to be used are as followed: Quinton Tm65 Treadmill, stethoscope, Polar FT2 Heart Rate Monitor Watch, Polar T31 Heart Rate Monitor, blood pressure cuff, YSI2900 glucose analyzer, and indoor pool. The project will benefit from the participant population of pre-diabetic subjects as well as collaborative arrangements between the indoor pool area and kinesiology department.
Objectives & Specific Aims
The objective of the proposed project is to determine the effects of both aquatic (aqua jogging) and land (treadmill walking/running) exercise sessions performed at both moderate and vigorous intensities on blood glucose levels on pre-diabetic adults.
Specific Aim 1: Determine the effect of exercise mode (aqua jogging or land treadmill walking/running) on blood glucose levels.
Specific Aim 2: Determine the effect of exercise intensity (moderate or vigorous) on blood glucose levels.
Specific Aim 3: Determine if there is any interaction between exercise mode and intensity on blood glucose levels.
Pre-diabetes, or elevated blood sugar levels, is a major risk factor for cardiovascular disease, which is the leading cause of death among U.S. adults (Albright 2000). Exercise is perceived to be beneficial for controlling glycemic levels and promotion of weight loss for patients with T2D (Boulé 2001). With over a 100- million U.S. adults struggling with abnormal blood sugar levels, research findings will lead to a better understanding and exercise prescription for the diabetic population. “Although these findings reveal some progress in diabetes management and prevention, there are still too many Americans with diabetes and prediabetes’ said CDC Director Brenda Fitzgerald, M.D.”(CDC Newsroom 2018).
ATM exercise is an innovative exercise mode that incorporates both resistance and aerobic exercise (Bressel 2014). It has been used in numerous studies that include obese animals such as cats and dogs as well as humans. Underwater training, such as aqua yoga, has been shown to have a lower impact on joints and other areas that are sensitive to high impact exercise (Brody 2009). The hydrostatic pressure from the water submersion has been shown to have unique cardiovascular effects both at rest (Haffor et al. 1991; Risch et al. 1978) and during exercise (Christie et al. 1990; Connelly et al. 1990): such as increased venous return, increased stroke volume and cardiac output, and reduced heart rates for a given exercise intensity. Recent data suggests that the environment of ATM exercise may acutely improve vascular function and vascular activity, as indicated by augmented flow-mediated dilation (Joubert 2015). ATM exercise will allow for less weighted impact on those areas as well as keeping a heart rate relative to the study.
It is well-established that aerobic exercise training is beneficial in maintaining cardiovascular health and regulating BG levels. Less is known regarding the acute effect of various modes and intensities of exercise on cardiovascular health markers. ATM exercise is a novel form of exercise that has been previously shown to offer similar gains in cardiovascular fitness as land treadmill training but with the added benefit of reduced BG level activity (Joubert 2018). Furthermore, an acute ATM exercise session may elicit a greater post-exercise hypoglycemic response in addition to improving vascular function. Should the reduction in BG levels following aquatic exercise persist in the following day, this would further justify the efficacy of prescribing aquatic exercise for the promotion of cardiovascular health and management of BG levels.
Because not all individuals can exercise safely or comfortably on a normal land treadmill due to orthopedic or body weight limitations, comparing the relative efficacy of aquatic activity as a potentially superior, or at least equally beneficial, alternative mode of aerobic exercise is important. While other non-impact aerobic exercise, such as cycling, would be an option for these individuals as well, cycling on land does not elicit the same cardiovascular responses caused by the hydrostatic pressure exerted by water submersion.
However, much of the research indicating the unique cardiovascular stimulus and benefits of upright aquatic activity has focused on ATM exercise. Because of the cost-prohibitive nature and limited access to aquatic treadmills, this study seeks to expand the findings of previous research by exploring the physiological impact of aqua jogging on BG levels. Aqua jogging only requires access to a body of water to run in place and is a more traditional, easily accessible form of upright aquatic exercise.
Given that one-third of the population is pre-diabetic or has T2D (CDC Newsroom 2018) and that exercise is one option to attenuate elevated glycemia levels, examining the BG levels response to aquatic and land exercise, in addition to the effect of exercise intensity, will result in a greater understanding of the vascular health benefits and unique physiological changes elicited by exercise (Connelly 1990). These findings will help to better target cardiovascular exercise prescriptions for promoting cardiovascular health and regulating BG levels.
The results regarding the impact of exercise mode and intensity on BG levels will justify further research to identify the potential physiological mechanisms (glucose-inhibition, arterial stiffness, blood markers, etc.) behind such changes. This future research would have the potential for further grant funding from organizations such as the American College of Sports Medicine, American Heart Association, and the National Institutes of Health.
A total of 20 pre-diabetic (fasting blood sugar levels from 100-125 mg/dL) adults between the ages of 18 and 65 who are not currently taking anti-diabetic medication will be recruited to complete the study. Subjects must be apparently healthy, physically untrained, and be defined as low or moderate risk according to American College of Sports Medicine guidelines to be accepted into the study.
Following an initial blood sugar screening to determine pre-diabetic status, subjects will report to the lab on 10 separate occasions over the course of approximately 4-5 weeks. The 10 visits will consist of 4 different exercise sessions, a controlled sedentary session, and a day after each session to remeasure the BG levels for comparison. The order of each visit will be randomized, except each session that follows the corresponding day prior. There will be a 2-7 day delay between sessions. The 4 exercise sessions will include the following combinations of exercise mode and intensity: aquatic-moderate intensity, aquatic-high intensity, land-moderate intensity, land-high intensity. All aquatic sessions will be performed by aqua jogging in the deep end of a pool with the assistance of a flotation belt. Land exercise sessions will be performed on a treadmill and include a combination of walking at an incline or jogging.
Exercise intensity will be measured by heart rate monitors. For the moderate intensity exercise sessions, subjects will exercise within 5 beats per minute of their calculated 55% heart rate reserve for 30 minutes. For the vigorous intensity exercise sessions, subjects will exercise within 5 beats per minute of their calculated 80% heart rate reserve for 20 minutes. This combination of intensity and duration will result in equivalent overall volumes of exercise so that energy expenditure between the sessions will be similar and the impact of exercise mode and intensity can be assessed.
For each session, subjects will report to the laboratory at the same time of day (~6:30-7:00 am). Subjects will report to the lab having fasted for at least 8 hours and having abstained from alcohol, caffeine, and nicotine for that same time period. Prior to each exercise session, BG levels will be measured following 10 minutes of seated rest. At the end of each exercise session, subjects will have their BG levels tested. Testing will be done on the non-dominant arm each session. Additionally, subjects will be asked to record their daily habits (i.e. walking time, stairs they take, any low intensity exercise) as well as their diets for the duration of the study. Participants will also be required to eat the same meal as their last meal of the day prior to the next research session.
Because this study will employ a cross-over design where all subjects will perform both modes and intensities of exercise, a 2 (mode: aquatic, land) x 2 (intensity: moderate, vigorous) repeated measures ANOVA will be used to determine significant main effects for exercise mode and intensity, as well as interaction between these two independent variables on BG levels. Paired sample t-tests will be used to determine the effect of the exercise sessions compared to the sedentary control session on blood glucose levels.