Almost any form of exercise will stimulate some degree of strength and muscle development. Unfortunately, misconceptions, myths, and misunderstandings plague the fitness industry, especially in regard to strength training. There is a huge attrition rate among those starting a strength training program primarily because most people are not taught the principles essential for a safe and effective program.

This article is part four of a five part series discussing the very important principles and guidelines of a safe and effective strength training program. This article discusses the amount of weight you should use and the number of repititions you should do for the results you desire. I'll also explain how to gradually increase the weight you use to stimulate further gains. The previous article, part three of this five part series, discussed the importance of proper lifting technique, exercising through the full range of motion, the proper exercise sequence, and the correct number of sets to do for what you're trying to achieve. The following exercise guidelines are extremely important for your safety and the effectiveness of your strength training program.

Relationship Between Resistance and Repetitions

It's important to understand the inverse relationship between exercise resistance and exercise repetitions. When exercising to the point of muscle fatigue, most people can complete about six repetitions with 85 percent of maximum resistance. "Maximum resistance" is the most weight you can lift one time, in good form. Most people can complete eight repetitions with 80 percent of maximum resistance, 10 repetitions with 75 percent of maximum resistance, and 12 repetitions with 70 percent of maximum resistance.

For most people (those seeking muscle strength and tone), 8-12 repetitions with 70-80 percent of maximum resistance is a sound training recommendation for strength and muscle development. Most people do not bother with finding their one repetition maximum for each lift to obtain the appropriate weight for each set of 8-12 repetitions. This would get pretty tedious especially when you are learning a new exercise

Really, the best and easiest way to figure out how much weight you should use on each lift is to begin by taking your best conservative guess. After you have warmed up by using a light weight for 12 or 20 reps, choose a weight for your next set that will challenge you for your goal number of repetitions. If you are not sure what that weight should be, choose a weight that is likely to be too light, rather than making the mistake of going too heavy and not reaching your desired number of repetitions. For example, say you are trying to decide the proper weight for a set of 12 repetitions on the Shoulder Press. Choose a light, conservative weight slightly heavier than your warm-up and do the set 12 times (repetitions or reps). When you come to your twelfth repetition, if you feel as though you can perform another repetition or two, while still using good form, you might as well do that (to further promote blood flow to the shoulder muscle). Since you know that the weight you chose was a little too light (your 12th repetition was not a challenge), next time choose a slightly heavier weight that will challenge you for all twelve repetitions, or whatever your goal number of repetitions happens to be.

Important Note: Your strength may gradually decline as you progress through your routine. For example, on your first set (after warm-up) of the Bench Press you did 12 reps with 150 pounds--this would force a good amount of blood and fatigue your chest muscles. If for your second set you're trying to figure out the appropriate weight for 10 reps, you may or may not want to slightly increase the weight. That is, 150 pounds might be a challenging weight for 10 reps because your muscles are a little fatigued from the first set. So, try to be intuitive and pick an appropriate weight based not only on the weight you used on the previous set, but also how fatigued your muscles feel.

It is important that the weight you choose for each set challenges you for all of your desired repetitions, whether the number is 6, 8, 10, or 12 repetitions. Similarly, if you choose a weight that does not allow you to perform all the desired repetitions in good form, do as many as you can and choose a lighter weight for the next set. It is a good idea to keep a record of the weights you use on each lift so that when you perform the same exercise at another workout you know what weight to use on each exercise set.

In general, if your goal is to get notably bigger and significantly stronger, you will want to do fewer reps with more weight, so 6-10 reps is a good target for you on most exercises. Sometimes, on exercises like the bench press and squats, even as low as 2 reps will be enough. If you are more concerned with creating muscle tone, your rep number should be in the range of 10-15. Most people's goal is a combination of muscle strength, size and tone; the target number for these folks should stay between 8-12 repetitions. Remember, however, that whether you are going for 6 reps or 15, always pick a weight that will challenge you for the full set.

Progressive Resistance

As your muscles adapt to a given exercise resistance (weight), that resistance must be gradually increased to stimulate further gains. The key to strength and muscle development is progressive resistance, which is also called "exercise progression," or "the overload principle." This is the gradual and continual addition of weight to the exercise over time, as the previous weights become too easy to lift, so that your muscles are continually forced to work harder and thus increase muscle strength, size and tone. For example, in the Front Shoulder Press you might start out pressing (lifting) 20 pounds. After two or three weeks you may find that pressing 20 pounds has become too easy, and that you can do more than your chosen number of repetitions with little or no difficulty. The progression principle demands that as soon as the weight you are using is no longer a challenge, you must raise it. You progressively increase the weight you use for a lift so that you continue to make gains in muscle tone, size, and strength. It is important that you increase the weight only if the previous weight is too light; increasing the weight to push yourself harder can result in poor form and definitely increases the risk of injury.

Please understand that an increase in repetitions is an increase in strength. Many people think strength gains are only obtained when they increase the weight. But if you have increased the number of repetitions you can do with good form, you have increased your strength and more than likely, your muscle size and tone as well.

Please check back for Part five, where I'll discuss exactly how to avoid the common mistake of overtraining. Until then, be sure to use the right amount of weight and number of repititions for each set you do so you can achieve the results you desire. Good luck, and enjoy all the wonderful benefits of strength training.

Chad Tackett is President of Global Health & Fitness. Learn how you can have your own personal online trainer, dietician and motivator at http://www.global-fitness.com