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3. The Specificity of Training Principle: This refers to the fact that only the muscle or muscle group you exercise will respond to the demands placed upon it. By regularly doing bicep curls, for example, the muscles involved (biceps) will become larger and stronger, but curls will have no effect on the muscles that are not being trained (such as your legs). Therefore, when strength training, it is important to strengthen all of the major muscle groups.
4. The Detraining Principle: After consistent strength training stops, you will eventually lose the strength that you built up. Without overload or maintenance, muscles will weaken in two weeks or less! This is the basis behind why individuals lose muscle mass as they age—because they are detraining by exercising less frequently.
How Much Strength Training Should You Do?
When considering the guidelines for aerobic exercise, keep the FITT principles in mind (Frequency, (Intensity, Time and Type).
Frequency: Number of strength training sessions per week Aim to train each muscle group at least two times per week, and up to three if you have the time or are more advanced. One day per week may help you maintain your current level of strength, but in most cases, it will not be enough to build muscle. It is important to rest 1-2 days in between working the same muscle(s) again. Rest days give the muscles time to repair themselves from small tears that occur during strength training, and this is how you get stronger. For example, if you do a full body routine on Monday, do not lift again until Wednesday or Thursday (1-2 days). If you decide to split up your strength training (due to time, schedule or personal preference), and do upper body exercises on Monday and lower body exercises on Tuesday, it’s okay to lift two days in a row—because you are working different muscles. You wouldn’t lift upper body again until Wednesday or Thursday, or lower body again until Thursday or Friday.
Intensity: How much weight or resistance you should lift This is a tricky one—and if you’re new to exercise, it will take some trial and error. The intensity of the resistance you lift should challenge you. It should be high enough that as you approach your last repetition, you feel muscle exhaustion. Exhaustion means your muscle is so tired that you can’t do another full repetition in good form. Many people do not lift to exhaustion, mostly because they don’t know that they are supposed to. They tend to just lift the number of reps that they have subscribed to and stop.
For example, if you are going to do 10 reps of biceps curls, don’t merely stop on that 10th rep if you haven’t reached muscle exhaustion. You could either continue doing reps until you do reach exhaustion, or take this as a sign that the weight you are lifting is too light. Increase your weight until you do feel exhausted on the 10th rep. How much weight/resistance you lift will work hand in hand with the number of reps you do (see Time below).
Time: Number of reps and sets you should do Going from the starting position, through the action and back to the starting position counts as one rep. Most people lift somewhere between 8 and 15 reps, which equals one set. Most people do 1-3 sets with rest in between each set.
How many reps should you do? Most experts recommend between 8 and 15 reps per set. If your goal is to build strength and muscle size, then aim for fewer reps (like 8-10). Because you are doing fewer reps, you will need a heavier weight to reach muscle exhaustion in each set, so that’s where the words “heavy weight, low reps” come from. If your goal is general fitness or endurance, then aim for more reps (like 10-15). Because you are doing so many, you’ll need a lighter weight.
No matter what your goal, be sure to lift resistance that is heavy enough to exhaust you at the end of your set. So, while you may be able to curl 20 pounds and feel exhaustion in 8 reps, you may only be able to lift 12 or 15 pounds if you are doing 15 reps.
The ideal number of sets has been debated about for years. A good rule of thumb is 1-3 sets. Research studies have shown that performing 2 sets is not significantly better than one. And performing 3 sets is not significantly better than doing 2. The only significant difference is between 1 and 3 sets. As long as you are working to the point of exhaustion, you can maintain and even build strength by doing only 1 set. But unless you are crunched for time, most beginners start with 2 sets of each exercise.
Make sure you rest 30-90 seconds between sets. You can use this time to stretch the muscle you are working and catch your breath or get a drink of water. The longer you rest, the more strength you will have to finish out your next set just as strongly as the previous one—which will aid in your strength development.