Your Exercise Prescription is Ready for Pick Up
Personalized physical activity interventions could help individuals with diabetes manage, treat and even reverse disease
Tim Allerton, a postdoctoral researcher at Pennington Biomedical Research Center, has envisioned a new approach to treating and managing diabetes: personalized exercise prescriptions. Imagine going into your doctor and walking out with a prescription for a personalized workout regimen that you could “fill” at a local exercise physiology lab. Allerton hopes to study how personalized exercise prescriptions might help patients with type 1 diabetes better manage their blood sugar.
Allerton believes that individualized exercise prescriptions as well as in-person patient engagement with exercise physiologists (and at-home engagement via mobile apps) could help diabetics manage and even reverse disease symptoms. Studying the individual factors that determine how exercise impacts blood sugar control, across many diabetic patients, could also help researchers and healthcare providers better assess which patients respond to which types of exercise regimens.
“Cardiovascular disease is the leading cause of disease in patients with type 1 diabetes. However, only 20% of T1D patients report meeting the recommended threshold of 150 minutes of exercise per week. Recently, Riddell et al. (2017) published a consensus statement in The Lancet regarding exercise in the management of T1D. The authors call for an individualized approach to exercise. Both the American Diabetes Association (ADA) and the Juvenile Diabetes Research Foundation (JDRF) recommend nearly daily exercise with individualized focus.” — Tim Allerton
Exercise management in type 1 diabetes: a consensus statement
Type 1 diabetes is a challenging condition to manage for various physiological and behavioural reasons. Regular…
We asked Tim to tell us more about how exercise impacts diabetes symptoms and disease, and how exercise physiology is entering the fields of diabetes care, metabolism and precision health.
LifeOmic: Can you tell us more about the rationale behind helping to manage diabetes with exercise prescriptions?
Tim: The results from large randomized control trials such as the Diabetes Prevention Program brought to light the importance of exercise for the prevention of diabetes. Other studies like the Health Benefits of Aerobic and Resistance Training in Individuals With Type 2 Diabetes (HART-D) study (conducted at Pennington Biomedical Research Center) have been instrumental in determining that both aerobic and resistance training are critical for improved chronic glucose control in people with type 2 diabetes. These studies and many others are what comprise the rationale for prescribing exercise for people with pre-diabetes and type 2 diabetes.
The knowledge that exercise works as a “drug” and can improve cardiovascular, metabolic, musckuloskelal and mental health has promted the Exercise is Medicine initiative, supported by the American College of Sports Medicine (ACSM).
LifeOmic: What is an exercise prescription? How are different patient populations using or benefiting from exercise physiology and exercise prescriptions?
Tim: Similar to any prescription you might get for a pharmaceutical drug to treat a medical condition, an exercise prescription has a dose (characterized by intensity, percent of heart rate for aerobic exercise or percent of maximal amount that can be lifted for resistance training), and frequency. An exercise prescription will also include a recommended duration for the particular exercise. Depending on the health status and mobility of the person, recommendations for type of exercise will vary.
Ideally, an exercise prescription should be designed to meet an individual’s health and fitness goals.
The exercise prescription is not a new concept. The ACSM has been publishing guidelines on exercise prescriptions since 1975. However, since that time the number of people in the United States diagnosed with type 2 diabetes has increased from ~1.5 million to well over the 23 million according to the CDC.
Louisiana currently has a prevalence of 12% for type 2 diabetes. The national prevalence for all diabetes is around 10%. Louisiana doesn’t really utilize exercise prescriptions to the degree that it should, considering the incredible financial burden of this chronic disease. Louisiana is also the only state that provides licenses for clinical exercise physiologists.
Exercise prescriptions differ based on the health condition being treated. For example, prescriptions would be different for patients with type 2 diabetes as compared to patients with multiple sclerosis. The pathogenesis of the disease and prevailing symptoms must all be considered when making an exercise prescription.
Another important consideration is the medication(s) that the patient has been prescribed. Drugs such as beta blockers block the beta adrenergic response to epinephrine to control blood pressure. However, that is also a mechanism by which heart rate is increased during exercise. Patients taking this class of medication have a reduced (by approximately 10%) heart rate response to exercise. Therefore, prescribing exercise intensity (e.g. percent of heart rate reserve) based on age-related formulas will result in an inappropriate intensity level for these patients.
Unfortunately, there is very little data regarding how people should exercise on certain medications. This is partially why I am interested in personalizing ExRx. Currently, exercise prescriptions don’t routinely take into account prescription drug (maybe they should be — we just don’t know.)
Exercise prescriptions aren’t provided in a vacuum. Rather, clinical studies provide data to describe the outcomes of exercise interventions for both safety and efficacy.
LifeOmic: What is an exercise physiologist? What kind of work and research does this involve?
Tim: An exercise physiologist is a certified healthcare professional with a degree (usually a masters degree) in exercise physiology, kinesiology, exercise science, etc. An exercise physiologist is trained in conducting and interpreting exercise and fitness testing and prescribing exercise to both healthy people and those with numerous health conditions.
Exercise physiologists often conduct research and work in wellness centers, hospitals, gyms or in corporate health.
Do you see exercise as an important element in the prevention and treatment of disease, and want to motivate people to…
The study of exercise physiology spans from sports performance to every aspect of health through the lens of exercise. The classical studies in exercise physiology involved studying cardiovascular and skeletal muscle physiology and biochemistry to understand how different exercises of different intensities change energy consumption. Today, exercise physiology has built on those findings and as a field is now exploring changes in gene regulation, metabolites, immune cell function, etc. in nearly all tissues (adipose, liver, brain, etc.) as a function of physical activity.
LifeOmic: Can you tell us more about your research on exercise as an intervention for diabetes?
Tim: I am generally interested in how acute and habitual exercise effects our ability to metabolize macronutrients from food (metabolic flexibility). Metabolic inflexibility is common in people with diabetes, both type 1 and 2, and obesity. The work I conducted during my Ph.D. was centered around how long a single bout of high intensity interval training can have an effect on metabolic flexibility. In other words, what is the half-life of HIIT?
The other aspect of my research as a postdoctoral fellow in the Botanicals Dietary Supplements Research Center at Pennington Biomedical involves exploring how botanical extracts and other natural products can improve metabolic health. I am currently conducting a preclinical experiment on the potential synergy between a botanical extract of Russian tarragon and exercise.
LifeOmic: What exercise programs might a type 1 diabetic or someone at risk for diabetes practice for greatest effectiveness in disease management or prevention? How does this depend on the individual? What might a personalized exercise plan look like?
Tim: The current exercise recommendations for people with type 1 diabetes (T1D) are similar to recommendations for the general population: 150 minutes per week of moderate to vigorous physical activity. This physical activity can be any “rhythmic” exercise, such as walking, running, cycling, rowing, or stair climbing, that gets your heart rate up to the prescribed level. In general, more exercise is associated with greater improvements for those with T1D.
There is a tremendous amount of trial and error that goes on with T1D and exercise. A safe and effective exercise program would likely involve aerobic-type exercise most days of the week, with no more than two consecutive days between exercise sessions. Resistance training and high intensity interval training have also been shown to be beneficial and safe in people with T1D. Interestingly, these more intense but shorter duration exercise approaches have been shown to improve cardiovascular and metabolic health with fewer incidences of post-exercise hypoglycemia. Such exercise approaches may be HIIT regimens, for example workouts that entail some sprinting. In fact, some studies have experimented with a single sprint at the end of a workout for people with T1D in an attempt to prevent post-exercise hypoglycemia.
“Both trained and untrained individuals with type 1 diabetes typically require an increased carbohydrate intake or an insulin dose reduction, or both, before commencing aerobic exercise. During predominantly anaerobic activities such as sprinting, and during a high intensity interval training session, circulating insulin concentrations do not decrease as markedly as in purely aerobic activities, in part because the duration of activity is typically shorter. … High intensity interval sprint training promotes the increased oxidative capacity of skeletal muscle in type 1 diabetes and attenuates the rates of glycogen breakdown, which might, in theory, protect against hypoglycaemia after exercise.” — Riddell et al. 2017
A personalized exercise prescription starts off with basic guidelines for health and fitness, but also factors in a patient’s exercise preference and time constraints. We can make adjustments to the prescription if adherence, safety or efficacy of the prescribed physical activity are not satisfactory. Insulin use and carbohydrate intake are highly important factors to take into account for a safe and effective personalized exercise prescription.
“Fear of hypoglycemia often deters T1D patients from exercise. Considering the complexity of T1D and the physiological response to exercise, that is unique to T1D patients, the adoption of an exercise regiment can be burdensome.” — Tim Allerton.
LifeOmic: How can exercise improve diabetes symptoms and blood sugar control? Do diabetics need to modify their medicine with exercise? What are the molecular mechanisms behind blood sugar control and exercise?
When glucose in present in our bodies, a transporter protein called glucose transporter 4 (GLUT4) translocates from the inside of our cells to the cell surface to facilitate the transport of glucose into tissues such as muscle and fat. This occurs during insulin stimulation, for example after a meal. Once inside the cell, glucose can be oxidized or converted into glycogen for storage.
A major determinant of insulin sensitivity is the ability for glucose to be converted into glycogen (stored glucose) in the skeletal muscle. Glycogen is one of the primary fuel sources for skeletal muscle during exercise, and can become quickly depleted during high intensity exercise.
We often see an improvement in glucose control, or a decrease in insulin resistance, following exercise. This improvement in glucose control is related to muscle glycogen levels.
A major player in this glucose control response to exercise is AMPK. This cellular energy regulator detects changes in the AMP/ATP ratio. When glycogen levels are reduced during and following exercise, AMPK increases in activity, prompting key signaling proteins in the insulin signaling pathway to increase muscle glucose uptake by increasing the trafficking of the GLUT4 transporter protein to the cell surface.
Consistent exercise, especially glycogen-reducing exercise (think high reps during resistance training), helps diabetics reduce their circulating blood glucose by transporting and storing that glucose in the muscle as glycogen.
Patients with diabetes who are on insulin or insulin secretagogues drugs (sulfonylureas) need to be aware of post-exercise hypoglycemia. Since exercise has the ability to increase muscle glucose uptake, independent of insulin, adding exogenous insulin or increasing insulin secretion with medications has an additive effect and can drop glucose levels dangerously low when combined with exercise.
“In type 1 diabetes, the glycaemic responses to exercise are influenced by the location of insulin delivery, the amount of insulin in the circulation, the blood glucose concentration before exercise, the composition of the last meal or snack, as well as the intensity and duration of the activity.” — Riddel et al. 2017
LifeOmic: What do you find helps people adopt and maintain physical activity regimens? Can mobile apps help?
I think technology is going to become only more important as time goes on. Mobile apps and other technologies are great ways for researchers to track health behaviors and physiological responses to interventions like exercise, but having a patient adopt a particular technology long term is a challenge. Pairing technology with a human component, like an engaged healthcare provider, an exercise physiologist, or a social networking component, appears to be important in long-term adherence to mobile health platforms.
Based on previous research in this field, providing a great app does not always improve healthcare outcome long term. However, pairing that app with a healthcare professional (like an exercise physiologist) is a strategy that provides a more convenient platform for people to engage with healthcare and fitness professionals.
LifeOmic: What does your average day look like?
Tim: I am typically up early to account for my commute from New Orleans to Baton Rouge, so it’s coffee and out the door! I like to get my administrative work done first thing in the morning, so I’m usually returning emails and making checklists for the day.
Depending on the current project, I usually will spend the middle part of my day doing cell-based experiments, animal work, analyzing my human clinical data, or meeting with my mentor (Dr. Jackie Stephens).
I try to read a few scientific research papers I am interested in or do some writing for a manuscript or grant I am preparing with some afternoon coffee. I almost always go to the gym when I get home. Depending on the amount of time I have, I will fit a workout into that time. I usually do a some short of resistance training or a high intensity interval workout. I find having a flexible approach to exercise helps with consistency.
After my workout, I’m back home getting dinner ready or helping my two boys (who are 5 and 7 years old) with their homework, but in the summer it’s baseball practice and games!
LifeOmic: Can you tell us a bit more about your efforts to start a precision medicine program for exercise in type 1 diabetics?
My interest in a precision exercise prescription for T1D comes from my 10 years of experience as a clinical exercise physiologist. Throughout the years I have worked with many adolescents and adults with T1D and T2D. One of the benefits of working with people for many years is that you can collect data on a personal level and track progress over time. As a part of my practice, I conducted metabolic and fitness testing that allowed me to make adjustments to individuals’ exercise prescriptions, which improved long-term adherence to exercise and typically improved glucose control. Cloud technologies and apps that can track exercise and glucose control are valuable resources that we can use to start to develop personalized exercise prescriptions. Scientific research often reports the mean response to a treatment such as exercise. However, we need to acknowledge the tremendous diversity in individual responses to a single bout of exercise and exercise training. Identifying trends to real-world exercise conditions and then adjusting the prescription accordingly is, in my mind, a powerful method to personalize exercise as medicine.
“A sound understanding of the physiology of different forms of exercise and the variables that can influence glycaemia during exercise and sport should underpin the implementation of safe and effective glycaemic management strategies. For aerobic exercise, reductions in insulin administration before the activity … can help ameliorate the risk of hypoglycaemia, as can increasing carbohydrate intake… For anaerobic exercise, conservative insulin dose corrections might be required, although this too might increase the risk of nocturnal hypoglycaemia, particularly if the exercise is performed late in the day. In all instances, additional vigilance around glucose monitoring is needed before, during, and after the physical activity.” — Riddel et al. 2017
LifeOmic: In addition to exercise, what else can patients with diabetes do to manage symptoms or prevent disease or complications?
Tim: As healthcare providers and researchers, we need to start thinking outside of the box. I think some of the recent work on intermittent fasting and time-restricted feeding is promising, highlighting new strategies for improving metabolic health. Improving sleep quality has gained a greater appreciation in recent years, and sleep interventions could really make a dent in metabolic control or lack thereof.
Other practices like mindfulness and mediation are complimentary approaches that have been shown to reduce stress and could also really benefit those with diabetes.
Patients with diabetes and their physicians need to openly explore these options in addition the standards of care. I think technology can help track how these approaches work in the real world.