Back To CourseNMTA Physical Education: Practice & Study Guide
22 chapters | 160 lessons
As a member, you'll also get unlimited access to over 70,000 lessons in math, English, science, history, and more. Plus, get practice tests, quizzes, and personalized coaching to help you succeed.Free 5-day trial
Dr. Baker has a doctorate in podiatric medicine and practiced medicine in both the hospital and private practice atmosphere.
Sally Slim is an average 35-year-old female, with average 35-year-old female problems! She joined a gym a year ago with the goal of losing 35 pounds. She planned to reach this goal with a balanced diet of about 1400 calories daily and a cardio workout at least four days a week.
After nine months, Sally weighed 20 pounds less than when she started. Yay Sally Slim! But then she hit a plateau. Over the last three months she has maintained her new exercise and eating regimen, but hasn't been able to shed even one more pound, much less those last 15. She decided to contact her friend, the personal trainer Stevie Strong.
Stevie explained to Sally that performing the same exercises week after week puts you at risk for exactly what she's experiencing: a weight-loss plateau. He explained that our bodies adapt to an exercise that's repeated over and over; eventually, continuing this amount of exercise will only maintain the current fitness level. Stevie said that in order to continue to change our bodies, we must introduce them to new challenges. He recommended that Sally change her exercise regimen from doing the same cardio workout every week to including progressive resistance training in her routine.
Progressive resistance training (or PRT), is a style of strength training exercise that involves the utilization of resistance and something called the overload principle. The overload principle defines a solution to the problem of our bodies adapting to one particular exercise due to constant repetition. The principle states that in order to see ongoing training benefits, the load placed on our bodies via exercise must continue to be increased as our bodies adapt to the current load. Now that Sally gets the picture of the overload principle, she wants to know, what does resistance have to do with it?
For our discussion here, resistance can be defined as an external load or force that is used against our bodies for the purpose of causing muscle contraction. Stevie Strong explains that by combining the overload principle and the load, or resistance, muscular strength and size are increased. Put a slightly different way, progressive resistance training is top-notch for helping people burn more calories (and thereby losing weight) as well as strengthening muscles, joints, and even bones for better overall health and fitness. In progressive resistance training, the resistance against our bodies, usually via a loading source such as weights, is cautiously and steadily increased to balance with strength increases as the training exercise advances.
Must you always use weights in progressive resistance training? The short answer is: No. But there's a longer answer, and it has to do with the three different types of progressive resistance training: isotonic, isokinetic, and isometric. Some involve the use of objects, such as weights, and some do not.
Isotonic exercise is the most common type of progressive resistance exercise. It's also the type of exercise that Sally Slim is looking for. Why? The results from isotonic exercise are both weight loss and an improvement in overall fitness level.
Isotonic exercise stimulates movement of a particular part of the body through a full range of motion (caused by the shortening and lengthening of muscles) via variable resistance from equipment. The resultant movement is not at a constant speed, but instead at a variable or changing speed. More simply put, isotonic exercises entail the conditioning of a particular group of muscles via variable resistance caused from lifting a weighted object.
The resistance is variable in isotonic exercises because the production of force by the muscle being worked is not the same throughout the range of motion with a fixed load such as a weight. Because resistance throughout a muscle's range of motion is necessary for isotonic exercises to be performed, this type of workout requires equipment. These can include free weights, dumbbells, or a kettle ball.
When the overload principle is applied to isotonic exercise, the amount of weight of the resistance is steadily increased as the body adapts to the previous weight. When performing isotonic exercises, care must be taken to use proper form and technique as injury can occur if this exercise is not executed accurately. And beware: isotonic exercises have the potential to cause muscle soreness!
By contrast, isokinetic exercise stimulates movement of a particular part of the body through a full range of motion (caused by the shortening and lengthening of muscles) via a machine or apparatus with a constant, controlled speed. Since the resistance is provided by a machine with a constant speed, the speed of the muscle contraction remains the same throughout the muscle's range of motion. The difference in the outcome between isotonic and isokinetic exercise has to do with the overload principle.
Remember in isotonic exercise, when the overload principle was applied, the weight of resistance had to be increased? Well, in isokinetic exercise, when the overload principle is applied, the speed of resistance must be increased. Isokinetic exercise tends to be safer than isotonic exercise, and the participating individual is less likely to experience soreness.
Isometric exercise does not stimulate movement - it is static - where force is employed against an immovable object. In isometric exercise, the muscle or muscle groups still contract, but they don't have a noticeable change in length, and the associated joint does not move, which means they don't go through a range of motion.
If Sally were to press against a wall with her legs, the muscles in her legs would contract, but it would be impossible for them to move because the wall won't move! This is an example of an isometric exercise. The key thing to remember is that with isometric exercise, no movement is performed.
As we saw, isotonic and isokinetic exercises both build muscle strength. The purpose of isometric exercise is, by contrast, to maintain muscle strength. This type of exercise is commonly used in a rehabilitative setting for an individual that has suffered some type of condition, such as a stroke, to try to avoid muscle atrophy or muscle degradation. Isometric exercises are typically safe, with no resultant soreness, because no joint motion or change in muscle length occurs.
Progressive resistance exercise is a type of exercise that can be used in combination with other types of workouts to avoid hitting a weight-loss plateau. This type of exercise involves two main factors: resistance and the overload principle. Resistance can be defined as an external load or force that is used against our bodies for the purpose of causing muscle contraction, while the overload principle is the idea that the load placed on our bodies via exercise must continue to be increased as our bodies adapt to the current load.
There are three main types of progressive resistance exercise: isotonic, isokinetic, and isometric exercise. In isotonic exercise, a muscle group is put through a full range of motion via the use of an external load with the speed throughout the range of motion constantly changing. In isokinetic exercise, a muscle group is put through a full range of motion via the use of an apparatus-induced resistance, with the speed throughout the range of motion remaining constant. In isometric exercise, resistance is employed against an immovable object and the associated muscle(s) do contract but no range of motion is experienced.
To unlock this lesson you must be a Study.com Member.
Create your account
Did you know… We have over 95 college courses that prepare you to earn credit by exam that is accepted by over 2,000 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.
To learn more, visit our Earning Credit Page
Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.
Back To CourseNMTA Physical Education: Practice & Study Guide
22 chapters | 160 lessons
Next LessonStrategies for Developing Correct Posture