The Best Muscle-Strengthening Exercise Program for Prediabetes
Regular muscle-strengthening exercise (MSE) training (examples: weight training, calisthenics, or use of resistance bands) is one of the most effective ways to manage blood glucose (sugar) for type 2 diabetes prevention (1,2). People with prediabetes have elevated blood glucose levels, but not high enough to be considered type 2 diabetes. Insulin resistance often leads to prediabetes and type 2 diabetes, and is a condition in which muscle, fat, and liver cells have difficulty in removing glucose from the bloodstream, and there are also issues with protein metabolism (3). This challenge with the body’s inability to optimally use glucose and protein is often due to damaged receptors on the surface of muscle, fat, or liver cells that are not properly interacting with the hormone, insulin (4). Regular MSE training improves insulin resistance by (a) activating a pathway for muscle and liver cells to transport glucose out of the blood and into the tissue without requiring insulin, (b) increasing muscle size which results in increased metabolism, (c) reducing belly fat, (d) and stimulating the storage of glucose in the muscle (glycogen) and (e) the creation of energy-generating organelles in the cell (mitochondria).
Our research team conducted the first systematic review and meta-analysis of its kind that looked at how effective regular MSE training for at least eight weeks is in improving blood glucose, lipids (fat in blood), and insulin, body fat percentage, and blood pressure in people at risk for type 2 diabetes, including those with prediabetes (1). We also tested which characteristics of the MSE programs were effective in improving these health indicators. Our study found that MSE improved blood glucose management (HbA1c and fasting blood glucose) and blood lipids (HDL-cholesterol, LDL-cholesterol, and triglycerides), and reduced body fat percentage. Even when beneficial dietary changes were made alongside the MSE training, the reductions in fasting blood glucose and triglyceride levels were similar compared to doing MSE training without changing diet at all. This article is going to focus on how to design a MSE program that has been scientifically demonstrated to enhance blood sugar management and other health markers in prediabetes. I summarize the program design in the video below.
Frequency. The first consideration for designing a MSE program for prediabetes is how often the individual should be exercising. The vast majority of studies included in our review (12/14 studies) used a MSE training frequency of three days per week working every major muscle group each session (1). Even though doing this type of exercise (full-body workout) two days a week can still reduce fasting glucose and insulin and improve insulin resistance (6), doing MSE three days per week may improve other areas of health to a greater degree, including body composition (muscle size, bone thickness, and body fat percentage) and blood lipids (7). For an optimal MSE program design, at least three days a week working every major muscle group each session is the way to go.
Intensity and repetitions. The next program design characteristic is intensity, which needs to be discussed alongside repetitions (reps). Intensity is often prescribed as a percentage of one-repetition maximum (1RM), which is the highest amount of weight that a person can lift with correct technique for one rep (8). Generally speaking, the lower the intensity, the more reps an individual can perform. Training intensity should be at least 60% of 1RM for 10-15 reps, but greater reductions in HbA1c may occur at higher intensities (75-100% of 1RM) (9). When using resistance bands or doing bodyweight MSE like push-ups or air squats, rating of perceived exertion may be a better way to prescribe intensity. Using Borg’s 6-20 rating of perceived exertion scale, intensity should be at least 15-18 which corresponds to intensity perceptions of hard - very hard (10).
Exercise modality. Selection of what type of MSE to program is another important consideration. MSE research interventions in people with prediabetes have mainly used free weights, machine weights, and resistance bands. In our review, the only interventions to show reductions in HbA1c or fasting blood glucose used free weights or elastic bands. However, in people with type 2 diabetes, use of machine weights has also resulted in the lowering of HbA1c (11). The current evidence suggests that in people with prediabetes, free weights and resistance bands can be used to lower HbA1c, but it is likely that machine weights can be useful when other program design elements are appropriate.
Exercise selection. Should you program multi-joint, single-joint, or a combination of these types of exercises for improving risk factors in people with prediabetes? Our review suggests that most exercises should be multi-joint (examples: back squat, bench press, or lat pull-down), but including single-joint exercises (examples: leg extension, lateral raise, or calf raise) can also be beneficial in improving blood glucose control. When considering increases in strength and muscle size, which are important for physical function and metabolism in prediabetes, long-term incorporation of multi-joint exercises rather than single-joint exercises is superior (12).
Rest periods. How long a person rests between sets is usually determined by the intensity of the exercise and training goals. For example, lower intensity training with a primary goal of increased muscle size will likely involve shorter rest periods compared to higher intensity training with a primary goal of increased muscle strength. Unfortunately, only a few studies in our review (3/14 studies) reported rest periods (1). Circuit training with 30 seconds between exercises and 60 seconds between circuits and conventional MSE training with 120 seconds of rest between exercises both resulted in improved glycemic control. Clearly more work needs to be done in this area before solid recommendations are available. Two minutes in between sets is appropriate in most cases if training at a 10-15 rep range with an intensity of at least 60%, but rest periods will need to be increased to at least three minutes as the intensity increases and the reps decrease (8).
Sets. All of the studies that measured blood glucose control included 2-3 sets per exercise, which is in alignment with American Diabetes Association recommendations for type 2 diabetes (1-3 sets) (13). Four studies included at least 52 total sets per week, while three studies included less than 52 total sets per week. However, there was an insufficient number of studies to run analyses on the number of weekly sets. This is relevant since more weekly sets is associated with greater increases in muscle size (14), providing a metabolic advantage in people with prediabetes. Additionally, a meta-analysis conducted by Ishiguro et al. (2015) found that including at least 21 sets per MSE training session resulted in greater improvements in glycemic control (14). Since our review was not able to determine the number of sets linked to improvements in glycemic health, including at least 21 sets per MSE training session and maintaining current (ADA) guidelines for type 2 diabetes at 1-3 sets per exercise makes sense.
Progression. Although we did not examine progression in our review, ADA guidelines (13) suggest starting at a moderate intensity, increasing intensity after the higher end of the rep range is reached, then increasing the number of sets followed by the number of days per week. For beginners, linear progression can be used for months, meaning the intensity of each exercise can be increased each exercise session or week before more advanced manipulation of training variables is needed (15).
Getting the MSE programming right is essential for reversing prediabetes and stopping its progression to type 2 diabetes. While the research in this area is young, we have a good starting point with the evidence at hand and greater understanding of the effects of MSE in type 2 diabetes. While MSE may be the most effective exercise modality for improving some areas of health in prediabetes, other training modalities like aerobic (cardio), balance, and flexibility training have additional benefits and should be incorporated into a well-rounded exercise program.
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