By: Igor Klibanov
As a fitness professional, you undoubtedly know how prevalent diabetes is, and you may even work with people who have it. However, what is currently taught is simply how to avoid making it worse. And any improvements that come in blood sugar control are simply a side effect of exercise. But what if there was a direct way to exercise specifically for better blood sugar control? What kind of impact would it have on your business?
Would you now be able to send a letter to your client’s doctor, explaining the scientific basis behind your recommendations? Would that help with medical referrals? Would you separate yourself from other trainers? Would you be able to carve a niche for yourself as the “medical exercise guru” of your community? I’ve done that, and you can too. So let’s jump in.
Do you have clients with diabetes? If so, you’ll want to read this article, because this is going to be the most thorough, detailed, and comprehensive article on the internet about how to exercise for people with diabetes.
A lot of our clients are diabetics. But within a few months of correct and proper personal training, their blood sugar levels are no longer high enough to be considered a diabetic. How do we do it? That’s exactly what we’ll discuss in this article: exercise for diabetes (plus a real-life case study, at the end of the article).
And it’s going to be as precise as a doctor’s prescription for medications. After all, when a doctor prescribes a medication, s/he tells you:
- The name of the medication
- The dosage
- Whether to take it with food, or away from food
- Whether to take it in the morning or the evening
But when a doctor recommends exercise, there’s not a lot of precision behind it. It’s missing such details as:
- The type (cardio, strength training, or stretching)
- Frequency (how many days per week)
- Intensity (low, medium, or high)
- Duration (how much time per exercise session)
And just as the doctor would not prescribe the same medication for different conditions, so too you shouldn’t do the same exercise for different conditions. What works for diabetes may not work for arthritis. What works for high blood pressure may not work for osteoporosis.
In here, we’re going to go into great detail on the exercise prescription for diabetes.
As with all of my “exercise prescription” articles, we need to start with a definition, so that we’re all on the same page.
Diabetes has a simple definition of “chronically high blood sugar.” And yes, I know that as a fitness professional, you probably know that diabetes is high blood sugar. But the question is “how high?”
There are a number of answers to that, which would qualify a person to be diagnosed as a “diabetic.”
- If fasting blood sugar is over 126 mg/dl (7.0 mmol/l), on 2 different measurements
- If HbA1C is over 6.5%. HbA1C is the average blood sugar over the last 3 months. This is in contrast to fasting blood sugar, which is just a snapshot during the moment when the blood was drawn.
- If blood sugar 2 hours after a meal, or after an oral glucose tolerance test is over 200 mg/dl (11.1 mmol/l)
Now yes, there are 2 major types of diabetes (and a few less common types), but the end result is the same: high blood sugar. This article will specifically refer to exercise for type 2 diabetes.
However, there’s also a step before diabetes, called “prediabetes.” The diagnostic criteria for that are:
- Fasting blood sugar between 110 mg/dl and 124 mg/dl (6.1 – 6.9 mmol/l).
- HbA1C is 6.0-6.4% (and in some laboratories, 5.5-6.4%)
- Blood sugar 2 hours after a meal, or after an oral glucose tolerance test is 140 mg/dl 198 mg/dl (7.8-11.0 mmol/l).
So now that we’re all on the same page in regards to what diabetes is, let’s talk about the details: how should you exercise for diabetes control?
Type of Exercise for Diabetes: Cardio or Strength Training?
What’s more effective for controlling blood sugar – cardio or strength training?
In one study, 62 diabetics were divided into 2 groups:
- Group 1 did strength training
- Group 2 was the control group (they didn’t exercise).
After 16 weeks of progressive strength training, group 1 lowered their HbA1C by 1.1% (from 8.7% to 7.6%). That’s HUGE. On par with the most common diabetic medication out there (Metformin). Though in this study, 72% of the people in group 1 were able to lower the dosage of their diabetes medications. Group 2 (not surprisingly) had no change in their HbA1C, and some of them actually increased the dosage of their medications.
Another study showed a reduction of about 1.3% in the group of people who did strength training (from 7.57%, to 6.23%).
As for cardio, one study found a similar reduction in HbA1C. Participants who did cardio lowered their HbA1C by 1.1% (from 8.9 to 7.8).
And most studies doing a head-to-head comparison of cardio vs. strength training find that both are more or less equally effective at lowering blood sugar.
But hey, why does it have to be one or the other – cardio OR strength training? Why can’t we do both? Why can’t we all just get along? 🙂
Well, most studies actually find that when cardio and strength training are combined, the results are better than the sum of their parts.
So it shouldn’t really be cardio OR strength training. It should be cardio AND strength training for good management of diabetes.
And the interesting thing is that all these improvements in blood sugar control happen without any changes in nutrition. That’s not to say that nutritional changes aren’t beneficial. They are. But in studies, researchers need to isolate 1 variable. If they change both exercise and nutrition, and blood sugar improves, it’s not known why it improved – exercise, or nutrition? And in all these studies, participants were never instructed on any nutritional changes.
Frequency of Exercise for Diabetes: How Many Days Per Week?
Unfortunately there are no studies that I’m aware of that directly compare different exercise frequencies to each other. However, in this study, strength training just twice per week was able to reduce fasting blood glucose by 7.1% over a period of 16 weeks.
In this study, cardio was done 3 times per week was able to lower blood glucose levels.
Though it should be noted that the American College of Sports Medicine recommends moderate intensity cardio on 5 days per week, or high-intensity cardio on 3 days per week. It also recommends strength training 2-3 days per week.
Duration of Exercise for Diabetes: For How Long Should You Exercise?
Again, unfortunately there’s no good evidence doing head to head comparisons between different durations of exercise. However, most studies find a minimum effect at about 1000 calories per week. How long does it take to burn 1000 calories per week? It depends on both your client’s weight, and the intensity. But assuming moderate intensity, and being overweight, it would take somewhere in the 60-90 minute range. That’s 60-90 minutes per week, not per day.
That’s the minimum. But what’s the optimum? We don’t know the exact optimum, but the same study as earlier saw that diabetics achieved better blood sugar control on an expenditure of about 2000 calories per week. This translates to about 2-3 hours across a week (not a day) of moderate intensity physical activity.
Is 3000 calories better than 2000? Is there a point of diminishing returns, when more exercise doesn’t result in greater blood sugar control? Those are all good questions that unfortunately are still unanswered by the research.
Intensity of Exercise for Diabetes: How Hard Should You Exercise?
Intensity may be the single most important variable when it comes to improving blood glucose control in diabetics.
Most studies find that high intensity is superior to low or even moderate intensity when it comes to improving blood sugar levels. What’s high intensity? Typically, it’s over about 85% of the maximal heart rate. How do you calculate that? The theoretical maximal heart rate is 220 minus your age. So if your client is 60 years old, your theoretical maximum would be 160 beats per minute. 85% of 160 would be 136 beats per minute. But again, that’s the theoretical maximum. That maximum may be wrong for about 65% of the population, but it’s in the ballpark. To figure out your client’s true maximum heart rate is a fairly high-risk test that may not even be worth doing for someone just getting started. Suffice it to say that your client shouldn’t be able to put 3-4 words together without taking a breath.
In one study, participants were divided into 2 groups:
- Group 1: did continuous cardio
- Group 2: did interval training
In both cases, the calories burned were equal (so group 2 had a shorter duration, but obviously higher intensity). Despite the caloric expenditure being identical, the interval group had improved blood sugar control, compared to the continuous group.
One other study was able to replicate those results, and showed a similar outcome: that even when calories are matched between high intensity and lower intensity groups, the high intensity group exhibits better blood sugar control.
But that’s what’s optimal. Is it an all-or-nothing type of deal? Should you either do high intensity exercise, or it’s not worth doing? Far from it.
One study found blood sugar to improve at intensities of as low as 50% of maximal aerobic capacity, which translates to about 60% of maximal heart rate. So take our 60-year-old diabetic again. For this person, 60% of their maximal heart rate would be 96 beats per minute.
The effects of low intensity aren’t quite as pronounced as those of high intensity, but they’re sure better than sitting on your butt, doing nothing.
And what about strength training? What’s the right intensity of strength training? Again, unfortunately I’m not aware of any studies doing head-to-head comparisons of different intensities, but the studies using strength training to lower blood sugar use intensities ranging from 50% of the 1RM, up to 85%. How does that translate to “real world?” That is, you can use a weight that your client can lift about 7 or so times, and you can use a weight that your client can lift 30 or so times. So the range of what works is very wide. Though I do wish there was more research into what’s optimal.
How Does it Work?
So now we know what to do. For some people, that’s enough information. But some of us (the geeks) want to know how. How does exercise improve blood sugar control? There are a few ways:
- Glucose disposal. What does that mean? When blood sugar gets too high, your body wants to “dump it” out of the blood. But if you have type 2 diabetes, you also have insulin resistance. So although the body wants to dump that sugar out of the blood, other organs aren’t accepting it. But if you make your muscles work (through exercise), suddenly muscles will take the extra sugar from the blood, to use as energy.
- Insulin sensitivity. Whenever blood sugar rises, insulin also rises, to tell muscle cells (and others) to “open up the gates” and let the sugar out of the blood, and into the muscle cells. But if you’re insulin resistant, your cells don’t “hear” the message of insulin. It’s like you sitting at home, and someone is ringing your doorbell. But you don’t hear the doorbell. So you won’t let that person in your house. You need insulin in order to lower blood sugar, and you need the message of insulin to be “heard.” Fortunately, there’s one other way to decrease your blood sugar, without insulin. The technical term for it is “non-insulin-mediated glucose transport.”
That is, with the simple contraction of the muscles, transporters go from inside the cell to the surface of the cell, and create almost like a channel for blood sugar to flow from the blood and into the muscles. Again, this happens without the help of insulin.
- This next benefit is unique to strength training. Your body can store about 400-500 grams of sugar. That is split between the muscles, the liver, and the blood. The blood stores about 4-6 grams. The liver stores about 90-100 grams. And the muscles can store 300-400 grams. So the majority of sugar is stored in the muscles. But what happens when the muscles are atrophied from disuse, or the absence of strength training? They can’t store as much sugar. But increasing your muscle mass, even just a little bit, you’re able to control your blood sugar better.
A couple of years ago, I wrote an article about one of our clients, Mandy, who had been a type 2 diabetic for about 15 years before she came to see us. Her average blood sugar (HbA1C) was around 7.1%.
Within the first week of correct training, with one of our trainers, her blood sugar dropped to the 70-98mg/dl (3.9-5.5 mmol/l) range. This required a change in the dosing of her medications, which were adjusted with the help of her doctor, and after working out the changes, her blood sugar came up to what her doctor called an “acceptable” 112-116 mg/dl (6.2-6.5 mmol/l). Which essentially, is a non-diabetic range.
So if your diabetes is really bothering your client, maybe they:
- Don’t like being on medications
- Are afraid of the shorter lifespan that diabetics unfortunately suffer
- Are afraid of losing their vision, as a side effect of poorly controlling their blood sugar
- Are concerned about losing their memory, since Alzheimer’s is much more common in diabetics than in non-diabetics. They might not be able to recognize their spouse, kids, or grandkids.
- Don’t have the energy levels that they want
Fortunately, they can prevent either all of it, or at the very least, a lot of it. And as a fitness professional, you now have the tools, and the data to help them with that.