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3 Things to Know About Muscle Fiber Type and Exercise3 Things to Know About Muscle Fiber Type and Exercise


muscle fiber types and exercise

There are two main groups of muscle fibers -- slow-twitch (Type I, aerobic) and fast-twitch (Type II, anaerobic). Slow-twitch muscle fibers are efficient at using oxygen to produce energy for endurance activities (e.g., distance running). Fast-twitch fibers support short bursts of strength or speed (e.g., sprinting), and fatigue much faster than slow-twitch fibers.

Genetics determine your fiber type.

The average person is born with 50% slow-twitch fibers and 50% fast-twitch fibers, but the specific ratio for each individual is determined by genetics. Additionally, some muscles contain more of one type due to their role in body movement. For example, the muscles of the core, which are responsible for holding you upright and maintaining posture, are largely made up of slow-twitch fibers making them resistant to fatigue.

Training may do little to change your fiber type.

Your prominent muscle fiber type can predict how well you perform in endurance versus anaerobic activities. Research is mixed regarding how much fiber type can be changed through training to improve performance. Many muscle fibers show characteristics of both slow-twitch and fast-twitch (often called hybrid fibers). It appears that these hybrid fibers can be trained to favor either fast-twitch or slow-twitch, but a fiber changing completely from one type to another is not likely. Elite athletes have as much as 80% of one fiber type, but its difficult to assess how much of this is due to training as opposed to genetic makeup.

Fiber type changes with age.

Age-related muscle loss becomes evident about the age of 50. Research shows that slow-twitch fibers are more resistant to this decline, and decreases often do not occur until the age of 60. Regular resistance training increases strength and grows both types of muscle fibers, which helps to combat age-related muscle loss.

Don’t be overly concerned with muscle fiber type when selecting an activity. A 50/50 mix of muscle fibers is a good thing because it allows you to perform a variety of activities well, increasing your enjoyment. Choosing an activity that you enjoy remains the key to sticking with an exercise program.

Benefits of Weight Training for Weight LossBenefits of Weight Training for Weight Loss


Benefits of Weight Training for Weight Loss

Minimize muscle loss.

For many people, a desire for weight loss has resulted in extreme measures. A drastic reduction in calories can cause a loss of lean muscle mass, but regular strength training helps to repair this damage. When you include strength training while consuming a healthy amount of calories and protein, you can build muscle mass and reduce further muscle loss.

Boost fat loss.

Studies conducted by strength training expert, Wayne Westcott, PhD., show that women who performed strength training exercises two to three times per week for eight weeks gained 1.75 pounds of muscle, but lost 3.5 pounds of fat.

The stronger you are, the more you can do.

The stronger you are, the more efficiently you can perform day-to-day activities. Improved strength also allows you to work harder during workouts which results in more total calories burned for weight loss.

The truths and myths of boosting metabolism.

The extra calories burned from increasing muscle isn’t as high as once believed, but the boost is still worth the effort. It was once thought that each pound of muscle burned up to 50 extra calories per day. While it is still a topic of debate, many researchers believe that a pound of muscle actually burns somewhere between 7 to 15 extra calories per day. It’s estimated that a pound of fat burns 2 to 3 calories.

According to the American Council on Exercise, most individuals gain 3 to 5 pounds of muscle after 3 to 4 months of strength training. Let’s say you replace 3 pounds of fat with 3 pounds of muscle. Using the estimate that 1 pound of muscle burns 10 calories and 1 pound of fat burns 3 calories, you will burn 21 extra calories a day. In a year, this results in losing over 2 pounds. While this is a small number, considering the many benefits of weight training, this added bonus certainly doesn’t hurt.

Health Benefits vs. Risks of ExerciseHealth Benefits vs. Risks of Exercise


Health Benefits vs. Risks of Exercise

Exercise can help you reach your fitness goals but, if overdone, it can also cause physical problems. Learn how to enjoy the health benefits of exercise while also staying safe.

Disease Risk

Regular exercise has a positive effect on many of the body’s systems, and can reduce the risk for chronic disease.

Regular exercise can:

  • Decrease the risk for type II diabetes by improving insulin sensitivity.
  • Reduce triglyceride levels and increase good (HDL) cholesterol levels.
  • Reduce the risk for heart disease by lowering resting blood pressure.

Studies suggest that people who engage in moderate exercise 5 times per week are 50 times less likely to suffer a cardiac event.

When paired with a decrease in body weight, regular exercise can also play a part in decreasing total cholesterol and bad (LDL) cholesterol.

Muscles and Bones

Research shows that adults lose one to two percent of muscle mass starting at age 50. This loss results in a reduced metabolic rate. Regular exercise, specifically strength training, helps to slow this loss by building muscle.

Weight-bearing physical activity (such as jogging, tennis, and strength training) provide the impact necessary to stimulate bone growth and improve bone health, which reduces the risk for fractures later in life.

Mental Wellbeing

Research has shown that both cardiovascular exercise and resistance training are equally effective at protecting against depression. Cardio is also linked to reduced anxiety. Other benefits include an improved ability to manage stress and improved sleep patterns.

Moderate vs. Vigorous

It is recommended to maintain moderate intensity activity for at least 30 min, 5 times or more per week OR to maintain vigorous intensity activity for at least 20 min, 3 times or more per week. Moderate intensity activities include brisk walking, recreational swimming, or bicycling. Vigorous activities are more intense (such as bicycling uphill or running). Use the "talk test" to determine your intensity level. If you can carry on a conversation while active, but you are working too hard to sing, then you are at a moderate intensity. If you are out-of-breath, you have moved into vigorous exercise.

How Much Is Too Much

The correct amount and intensity of exercise depends on your current fitness level. If you are sedentary, you can improve your health by adding even small amounts of exercise. However, the health benefits are gained in a linear-type progression, up to a state of moderate fitness. Beyond this point, health gains slow and they can eventually drop off due to over-training (refer to Figure 1).

Figure 1. The change in health benefit with increased physical fitness.

This shouldn’t discourage you from incorporating more vigorous exercise when you are ready. It simply stresses the importance of starting at an exercise duration and intensity that is right for you. As your strength and endurance builds, you can begin to challenge yourself with vigorous exercise.

People who occasionally jump into activities well-beyond their fitness level (known as Weekend Warriors) greatly increase their risks of physical injury and illnesses.

Don’t let these risks prevent you from starting a program. About 90 percent of heart attacks occur in a resting state, not during exercise. By selecting activities that match your current fitness level and by planning regular workouts, you can reap the benefits while reducing most risks associated with exercise.

5 Health Benefits of Water Exercise5 Health Benefits of Water Exercise


Health Benefits of Water Exercise

Easy On the Joints

When you are waist deep in the water, the body carries only 50 percent of your body weight. When the water is chest level, only 25 to 35 percent of your body weight is carried. Whether you are swimming laps or taking a deep-end aquatics class, water exercise gives your joints a break from the pounding that is common with other activities such as running, tennis, or kickboxing. It has also been shown to increase the use of joints and reduce joint pain in those with osteoarthritis.

Strength and Flexibility

Moving your body through the water, especially when swimming, requires that many joints extend through their full range of motion, improving flexibility. Water also provides about twelve times the resistance of air -- making it a challenging, yet gentle, way to improve strength.


During water exercise, the body is challenged to work much differently than when exercising on land, which makes it ideal for cross-training. When swimming, you challenge the respiratory system because you must gain better control of your breathing pattern (particularly as your breathing rate increases). Your muscles are also challenged in new ways as you move your limbs to stay afloat.

Beginners to Advanced

Beginning an exercise program for the first time or restarting after a long break can be intimidating. Water exercise provides a way to ease back into fitness while reducing stress on the knees and ankles. Your heart rate will stay elevated as you keep the body in motion to stay above water. Working in speed intervals and increasing the length of your exercise session will keep you challenged as you build your fitness level.

Weight Loss

In a 30-minute workout, a 150-pound person will burn 359 calories doing the breaststroke, and 279 calories with either moderate paced freestyle swimming or water jogging. Despite the calories burned, many research studies show that people who swim are at risk for gaining weight. This is because water exercise can increase appetite. The increase in hunger is attributed to the drop in body temperature that occurs during water exercise. Track your calorie intake to be sure you don’t eat more calories than your body needs to lose weight.

How to Rate Exercise IntensityHow to Rate Exercise Intensity


Rate Exercise Intensity

Experts recommend getting at least 150 minutes of moderate-intensity exercise each week for improved health. It is easy to count minutes, but how do you determine your intensity? Using the rate of perceived exertion scale or the simple talk-test will help ensure you reach moderate intensity without the need for high tech gadgets.

Rate of Perceived Exertion

The Borg Scale of Perceived Exertion assesses intensity through a rating of how hard you are working (Rate of Perceived Exertion - RPE). With this scale you assign a number to how you feel during exercise based on fatigue, breathing rate, effort, and discomfort.

Scale of 6 to 20: 6 is a rating of rest and 20 is a rating of very, very hard. A rating of 12 to 14 is considered moderate intensity.

Use the RPE scale at different points throughout your workout to determine if you need to push harder or ease up. And remember that you should rate yourself based on how you feel, not on how hard you think you should be working, nor by comparing yourself to others. Depending on fitness level, for the same activity, one person’s 2 can be another person’s 6.


Research confirms that the talk-test is a good method for judging your exercise intensity.

  • Low intensity: You can easily carry on a conversation during exercise without having to pause to catch your breath.
  • Moderate intensity: You can talk, but you are breathing more heavily and you need to take occasional breaks to catch your breath. The Centers for Disease Control and Prevention describe this as being able to talk, but not sing, during your workout.
  • Vigorous intensity: You can speak no more than a few words during your workout due to rapid breathing and an elevated heart rate.
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