If you're not already training prediabetic clients, current statistics indicate that it's only a matter of time until you are.
From 2005 to 2008, 35 percent of U.S. adults ages 20 years or older had prediabetes — and 50 percent of those were ages 65 years or older. If we apply this percentage to the 2010 U.S. population, an estimated 79 million Americans aged 20 or older have prediabetes (National Diabetes Statistics, 2011). The National Diabetes Information Clearinghouse (n.d.) predicts that that majority of these individuals will go on to develop type 2 diabetes within the next 10 years. Diabetes UK (2009) estimates that seven million people in the UK have prediabetes, and we see similar statistics for this growing condition worldwide.
Many studies in fitness literature support the idea that type 2 diabetes is preventable and that exercise is an important factor in reducing symptoms of prediabetes as well as the likelihood that it will progress to type 2 diabetes. As a fitness professional, you need to understand the basics of prediabetes and how you can help your prediabetic clients use their personal training sessions to safely reduce and even reverse their symptoms.
What is Prediabetes?
Prediabetic is the term used to define individuals with blood glucose levels that are slightly elevated. While their blood glucose levels are not yet high enough to be classified as having type 2 diabetes (T2D), these individuals are at higher risk to develop T2D over the next few years. T2D typically develops over time as the result of a decline in insulin sensitivity and a loss in beta cell function in the pancreas (Riddell and Fowles, 2010). Because of these pathological changes, there is a “prediabetes” period when circulating insulin levels are high (insulin resistance) and plasma glucose levels are slightly above normal.
The transition from prediabetes — characterized by impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) — to diabetes may take many years. Regardless, current estimates indicate that most individuals (perhaps up to 70%) with prediabetes eventually develop diabetes (Nathan et al., 2007). While the risk of a cardiovascular disease (CVD) event is modestly increased in the prediabetic state (Coutinho et al., 1999), the onset of type 2 diabetes brings significantly increases risk for CVD as well as for long-term complications affecting the eyes, kidneys, and nervous system.
Frequently Asked Questions by Personal Trainers About Working with Prediabetic Clients
What are the factors that put a client at higher risk of prediabetes (and therefore type 2 diabetes)?
Your client may be at risk of prediabetes (and ultimately type 2 diabetes) and should ask their doctor for a test if he or she is:
- white and over 40 years old
- or black or south Asian and over 25 years old
- and has one or more of the following risk factors:
- Has a close family member (parent or sibling) who has type 2 diabetes.
- Is overweight with a waistline 31.5 inches or over for women; 35 inches or over for South Asian men; 37 inches or over for white and black men.
- Has high blood pressure or a history of heart attack or stroke.
- Is an overweight woman with polycystic ovary syndrome.
- Is a woman who has had gestational diabetes (Albright et al., 2000).
At what point should I suggest that a client be checked for prediabetes?
It is recommended that you refer your personal training clients to a general practitioner if they mention any kind of symptom, even if they casually remark they have felt “wobbly/light headed/etc.” and they meet the criteria noted above. This may seem a little over the top, but in terms of client health, it’s better to err on the side of caution.
Are there liability factors for personal trainers working with prediabetic clients?
As long as you hold sufficient personal liability insurance and follow the correct pre-exercise health screening forms (like a Physical Activity Readiness Questionnaire (PAR-Q)), there are no specific liability factors beyond those that are expected of any qualified and insured personal trainer.
What type of medical clearance do I need to get from client’s doctor if prediabetes is suspected or diagnosed?
All the personal trainer needs is a letter from the general practitioner advising that physical exercise is beneficial to the client's heath, and that the client has no other medical conditions that may impair his or her ability to begin an exercise program.
What to Expect After a Prediabetes Diagnosis
A client who is newly diagnosed with prediabetes will probably have many questions, but typically the doctor should address those questions as part of a multidisciplinary care team, including diabetes specialist nurses, dieticians and diabetologists during the client's medical appointments. There should not be any limitations to exercise, but it may take some time for the client to get used to the idea of counting carbohydrates and watching dietary intake in general. The client may want to keep a daily diary outlining dietary intake and feelings before and after exercise.
It is unlikely that medications will be prescribed at this stage, although weight reduction medication such as Alli Orlistat (which reduces fat absorption in the gut, thereby reducing caloric intake) may be offered in certain limited cases.
Doctors will, however, routinely recommend lifestyle changes, including regular exercise. This is where personal training comes in.
Benefits of Exercise for Prediabetic Individuals
Numerous studies underscore the importance of long-term exercise programs for the treatment and prevention of prediabetes and diabetes.
Research has shown that exercise leads to improvements in metabolic control, as measured by blood glucose or insulin sensitivity. However, the exercise should be of at least moderate intensity (55% to 65% HR max), as exercise of either low volume (Khan and Rupp, 1995) or low intensity (ADA, 2000) failed to elicit the same benefit. Regular exercise has consistently being shown to be effective in reducing very low density lipoprotein (VLDL), and therefore can contribute to a lower risk for coronary heart disease in physically active individuals compared to sedentary individuals. Exercise can be viewed as a drug-free approach to lowering high blood pressure (Mayo Clinic, n.d.). Aerobic exercise intensities between 40 to 70% HRR appears to reduce blood pressure as much as, if not more than, exercise at lower intensities (Fagard, 2001). Obesity significantly contributes to insulin resistance, and the majority (~80%) of people with T2D are obese at onset (Hornsby et al., 2003). Data suggest that exercise may enhance weight loss and, in particular, weight maintenance when used along with an appropriate calorie-controlled meal plan.
Exercise should be considered the cornerstone of diabetes care, alongside dietary control and medication. The American College of Sports Medicine (2003) cites numerous potential benefits to an exercise program for the individual with prediabetes:
- Improved blood glucose control. This reduces the risks of effects of hypo/hyperglycemia, therefore reduces the risk of further hospital admissions.
- Improved insulin sensitivity through reduced body fat. Muscles become insulin insensitive due to the accumulation of fat around them. A review by Goodpaster et al. (2008) suggests that increases in abdominal obesity and non-adipose tissue lipids within skeletal muscle can cause of insulin resistance. High intra-abdominal fat, especially around the pancreas, reduces the ability to secrete insulin, therefore increasing the workload of the beta cells of the pancreas. Over time these beta cells can wear out, which can lead to the individual's dependence on insulin injections. Obesity also causes stress in the endoplasmic reticulum (ER), a system of cell membranes found inside cells. This stress results in the suppression of the insulin receptors' signals, leading to insulin resistance. When combined with excess adipose tissue surrounding the muscle, insulin is unable to facilitate glucose transport across the cell membrane (Wilmore et al., 2008). Regular exercise can help reduce the storage of fat, thus allowing the easier passage of insulin into the muscle.
- Better cardiovascular health. Regular exercise for the prediabetic, as with the nondiabetic individual, decreases the risk of cardiovascular disease.
- Prevention of type 2 diabetes. The Diabetes Prevention Program examined the effect of weight loss and increased exercise on the development of T2D among men and women who had high blood sugar readings but who hadn't yet developed full diabetes. The group assigned to weight loss and exercise, showed 58 percent fewer cases of diabetes after almost three years than in the group assigned to usual care (ACSM, 2003).
Generally speaking, you should work with your prediabetic training clients as you would with non-diabetic clients. The only special measures the client should take, as detailed by Knowleer et al. (2002), are as follows:
- Ensure a source of carbohydrate is available during exercise (jelly babies, for example). This is a good practical idea as this kind of food product is easy to carry around in your bag, and is a quickly digestible source of carbohydrate that can be taken quickly should the client start to feel like he or she has low blood sugar.
- Practice good foot care by wearing proper shoes and cotton socks, and inspecting feet post-exercise. This is important to the prediabetic, and especially with progression to type 2 diabetes. Peripheral neuropathy (where one suffers from nerve damage to the extremities) can mean that wounds to the feet (such as sores) can develop into ulcerations, and ultimately lead to amputations of the foot or lower limbs. Peripheral neuropathy will often manifest itself after chronically poorly managed diabetes. The personal trainer can help ensure that the client regularly checks the condition of his or her feet, and get the appropriate treatment before any laceration or ulceration progresses.
- Carry medical identification. Should the client suffer a hypoglycemic event during exercise, it is easier for medical providers to access the client’s information and provide treatment with proper identification. Both the trainer’s and the health club’s records should be updated to reflect the client’s prediabetic status so that appropriate care and service can be provided.
Exercise Programming for Prediabetic Training Clients
Exercise programming for the prediabetic individual is similar to the nondiabetic individual (once the above considerations have been factored in). Table 1 gives an example of an aerobic and resistance training session that could be appropriate for a prediabetic client whose goal is weight loss. Aerobic training may be difficult for some individuals because of other comorbidities or obesity. For those individuals, resistance training may represent an attractive alternative (ACSM, 2009).
Table 1: A sample session for the target prediabetic client
- 10 min increasing intensity using selected CV equipment
- RPE 9 - 11
- 5 min cycle
- 5 min arm ergometer
Large muscle group activities
- 30 min cardiovascular exercise
- RPE 11 - 13
- 10 min stationary cycle
- 10 min cross trainer
- 10 min rowing machine
- Increase INTENSITY of exercise from RPE 11 – 13 to 13 - 15.
- Circuit of exercises using resistance machine exercising the major muscle groups (quads / pectorals / trapezius / deltoids)
- 10 to 12 reps of good form
- Leg press
- Seated chest press
- Seated row
- Shoulder press
- Hamstring curl
- For the beginner progress from 1 set of each exercise to 2.
- Further progression from machines to free weights (i.e. leg press to back squat).
- Static stretching off all major muscle groups.
- Perform 3 circuits of all stretches.
- Hold each stretch for 30 seconds.
- Seated or standing quadricep stretch
- Chest stretch (arms behind back, or using wall to aid stretch)
- Hold at the point of "slight discomfort." May need to push hips forward to accentuate quad stretch. Position of slight discomfort may change as the weeks progress.
Even moderate activity such as brisk walking for 2½ hours per week is capable of reducing the risk of diabetes by 66% in the prediabetic individual. Making this type of simple lifestyle modification can make a huge difference to your clients’ health and to their likelihood of avoiding type 2 diabetes altogether (Yaspelkis, 2006).
- ACSM. (2003). Exercise management for persons with chronic diseases and disabilities, 2nd Ed. Human Kinetics, Champaign, IL.
- Albright, A., Franz, M., Hornsby, G., Kriska, A., Marrero, D., Ullrich, I., et al. (2000). American College of Sports Medicine position stand: Exercise and type 2 diabetes. Medicine and Science in Sport and Exercise, 32: 1345-1360.
- American Diabetes Association. (2002 Jan). Diabetes Mellitus and Exercise. Diabetes Care 25(1).
- Brun, J.F., Bordenave, S., Mercier, J., Jaussent, A., Picot, M.C., Picot, M.C., et.al. (2008). Cost sparing effect of twice weekly targeted endurance training in type 2 diabetics: a one-year controlled randomized trial. Diabetes Metab 34: 258-265.
- Coutinho, M., Gerstein, H.C., Wang, Y. & Yusuf, S. (1999). The relationship between glucose and incident cardiovascular events: a meta-regression analysis of published data from 20 studies of 95,783 individuals followed for 12.4 years. Diabetes Care, 22: 233–240.
- Diabetes UK. (n.d.).What is prediabetes? Retrieved from http://www.diabetes.org.uk/Guide-to-diabetes/Introduction-to-diabetes/What_is_diabetes/Prediabetes/.
- Fagard, R. (2001). Exercise characteristics and the blood pressure response to dynamic physical training. Medicine and Science in Sports and Exercise, 33: S484-S492.
- Goodpaster, B.H. & Kelley, D.E. (2008) Chapter 5. Metabolic inflexibility and insulin resistance in Skeletal Muscle. In Hawley, J.A and Zierath, J.E. (Eds.) Physical Inactivity and Type 2 Diabetes - Therapeutic Effects and Mechanisms of Action. Human Kinetics, Champaign, IL.
- Hornsby Jr, W.G, and Albright, A.L. (2003). Chapter 21, Diabetes. In ACSM Exercise management for persons with chronic diseases and disabilities. 2nd Ed. Human Kinetics, Champaign, IL.
- Khan, S. & Rupp, J. (1995). The effect of exercise conditioning, diet, and drug therapy on glycosylated haemoglobin levels in type 2 (NIDDM) diabetics. Journal of Sports Medicine and Physical Fitness, 35: 281-288.
- Knowler W.C., Barrett-Connor E, Fowler SE, et al. (2002). Reduction in the incidence of type 2 diabetes with lifestyle intervention or Metformin. New England Journal Medicine, 346: 393-403.
- Mayo Clinic. (n.d.). A drug-free approach to lowering high blood pressure. Retrieved from http://www.mayoclinic.com/health/high-blood-pressure/HI00024. Accessed 3rd August 2011.
- Nathan, D.M, Davidson, M.B., DeFronzo, R.A., Heine, R.J., Henry, R.R., Pratley, R. et. al. (2007 Mar). Impaired Fasting Glucose and Impaired Glucose Tolerance. Implications for Care. Diabetes Care, 30 (3).
- National Diabetes Statistics. (2011). Retrieved from http://diabetes.niddk.nih.gov/dm/pubs/statistics/#Pre-diabetes. Accessed 5th September 2011.
- National Diabetes Information Clearinghouse (NDIC). (n.d.) Type 2 Diabetes and Pre-diabetes. http://diabetes.niddk.nih.gov/dm/pubs/preventionprogram/ accessed 5th September 2011.
- Riddell, M., and Fowles, J. (2010 Nov). How to treat prediabetes with exercise – effectively. Diabetes: 10 - 20.
- Wilmore, J.H., Costill, D.L. & Kenney, W.L. (2008). Physiology of Sport and Exercise, 4th Edition. Human Kinetics, Champaign, IL.
- World Health Organization/International Diabetes Federation. (2006). Definition and Diagnosis of Diabetes Mellitus and Intermediate Hyperglycaemia.
- Yaspelkis, B.B. 3rd. (2006). Resistance training improves insulin signalling and action in skeletal muscle. Exercise and Sport Science Reviews, 34: 42-46.