Have you ever heard people debating which type of exercise you should do? One says, “You need to do cardio for heart health!” while another may say, “Forget cardio! You have to build your muscles!” Actually, the type of physical activity or activities you should choose depends largely on what your training goals are. For example, if your main goal is to increase your fitness and your endurance capacity, your training should be “aerobic” in nature—meaning using oxygen—and involve your large-muscle groups performing rhythmic, prolonged activities like walking, running, swimming, cycling, rowing, inline skating, and cross-country skiing. By way of contrast, “anaerobic” activities are done without oxygen, meaning that the fuels your body uses are processed without the need for oxygen. By nature, these latter activities are more intense and not sustainable for more than a minute or two. They include sprinting, power sports (e.g., hitting a baseball), and strength training. Activities like heavy, “anaerobic” resistance training do not increase your endurance (“cardio” or “aerobic”) capacity, but do enhance muscular strength and muscular endurance (which is different from overall endurance) and prevent the loss of lean muscle mass that normally occurs with aging and disuse.
What does it matter which type of training you do?
Likely, the answer is that you should do some of both. Gains in your muscle mass from either type of training can increase your daily caloric needs, help you manage your weight, and improve your insulin sensitivity and blood glucose control. However, to achieve optimal cardiovascular fitness, your exercise program must include an aerobic component, whereas to preserve your muscle mass and strength, you should do some regular sprint or resistance training.
For optimal improvements in your aerobic fitness, you’ll need to do exercise of either moderate or vigorous intensity. Vigorous activities should challenge you, resulting in rapid breathing and a greatly elevated heart rate. Some examples are race walking, jogging or running, water jogging, bicycling uphill, gardening with a shovel, or playing competitive sports like soccer or lacrosse. Moderate-intensity activities still make you feel as if you’re exerting yourself, but your breathing will be less labored and your pace slower. Such activities include brisk walking, swimming at a moderate pace, or bicycling on level terrain.
Intensity and duration of exercise are interrelated. Usually when you’re doing higher-intensity exercise, you can’t keep going as long as you can during lower-intensity activities, but the greater overload that the harder exercise provides leads to more gains in fitness. If your goal is weight loss, doing an activity at a lower intensity for a longer duration also works. In either case, you need to consider your initial fitness level, exercise goals, diabetes-related complications, and personal preferences. If your workouts are too hard to start, you may stop doing them because of injuries or loss of motivation.
Luckily, if you can’t maintain a higher intensity at first, you can increase your fitness by doing intervals. Studies have shown that you can experience fitness gains from doing only six to eight minutes of harder exercise a week. When walking, speed up slightly for a short distance (such as between two light poles or mailboxes) before slowing back down to your original pace. Include these short, faster intervals occasionally and slowly lengthen the intervals so that they last two to five minutes at a time. The same principle applies to almost every kind of exercise that you do, from walking to cycling to gardening. Over the course of several weeks, you will be able to move faster and sustain a quicker pace for longer. You can also break up your aerobic activity into smaller bouts during the day—as long as you are active at least 10 minutes at a time—and achieve almost the same fitness gains.
In addition, you will definitely benefit from working on maintaining or increasing your muscular strength and endurance at least two days each week. Muscle-strengthening activities include a progressive weight-training program, weight-bearing calisthenics, stair climbing, and similar resistance exercises that use the major muscle groups. Ideally, you should do 8 to 10 exercises using your major muscle groups (in the upper body, thighs, and torso) on two or more nonconsecutive days a week. Some examples of traditional strength-training exercises are overhead (military) press, bench press, biceps and triceps curls, leg presses, leg extensions and curls, calf raises, and abdominal crunches. Your strength gains will be maximized by doing 8 to 12 repetitions of at least 8 to 10 exercises and doing two to three sets to the point of fatigue.
If you are a novice at resistance work, you can start out with lighter weights or more flexible resistance bands that enable you to complete one or two sets of 12 to 15 repetitions on each exercise, but use enough weight or resistance to feel fatigued by the end of the last set. Although focusing on more reps using lower weights increases muscular endurance, lifting a greater resistance for fewer reps generally produces greater gains in muscular strength and size, which is your ultimate goal—that is, to have more muscle mass that will require extra calories even at rest, increase your resting metabolism, and improve your insulin action.
There is no right or wrong way to resistance train. You can vary between easy days, when you do more reps with lighter weights, and hard days, when you lift heavier weights fewer times. The only resistance-training principles that you absolutely need to follow are to work a particular area of your body (i.e., upper body) no more frequently than every other day and to train muscles with opposite actions on a joint equally, such as the biceps and triceps muscles of your upper arm or the quadriceps and hamstring muscles of your thigh. The last point to keep in mind is that if you stop overloading your muscles, your strength gains will reach a plateau or start to reverse, so you’ll have to increase the weight or resistance. If you resistance train correctly, your workouts will never feel any easier, but you’ll know that you’re getting stronger because you can lift more weight.
The Impact on Your Blood Glucose
One last point to keep in mind is that although moderate aerobic workouts usually cause your blood sugars to decrease while you’re doing them, anaerobic or other intense work can cause them to rise instead due to an exaggerated release of glucose-raising hormones. However, even if a workout raises your blood glucose level temporarily, over a longer period of time (2-3 hours), the residual effects of the exercise will bring your blood sugar back down while replacing the carbs in your muscles. Intense work uses up muscle glycogen faster, which can help keep your insulin action higher over the following day or two.
My favorite way to approach fitness is simply to do a variety of activities, including both aerobic and anaerobic ones on the same or different days. Doing so allows you to get the benefits of both types of training and surely will make your diabetes management and fitness levels better in the long run.