Intensity (in-ten’si-te) n. 1.Exceptionally great effect, concentration, or force. 2. Degree:strength. Or in other words: How much do you want it? Intensity can come from your heart and soul and it can come from your muscles. High intensity with weights leads to intense exercise sessions. Some women, maybe even you, have always done the same exercises with the same weight for the same number of repetitions and wonder why they don’t see results. C’mon girl, it’s time to get intense – intense about your exercise program and how you’re going to perform it. Follow this advice to determine how much weight you should lift and the benefits of pushing yourself to the limit in the gym.

Basic Principles
There are some basic principles of weight training that make programs effective. Progressively overloading the muscles by adding weight and/or reps and sets is an essential ingredient. Exercise frequency, or how many days per week you’re lifting, is another. Related to exercise frequency is an important variable called recovery or rest. Recovery is how much rest you’ll need between sets, exercises, and training sessions. But perhaps the most crucial principle of weight training programs is intensity. Intensity, also referred to as load, is estimated as a percentage of the 1 RM (repetitions maximum) or any RM for a certain exercise (1). A 1 RM is how much weight you can lift for 1 repetition – that’s 100% intensity. A 6 RM for any exercise is how much weight you can lift for 6 repetitions to failure. This means you can perform 6 reps with perfect form and maximum effort and absolutely cannot complete another rep or even come close to trying. Another way to quantify intensity is to measure it as a percentage of the 1 RM. So if your 1 RM in the squat is 135 lbs (100% intensity), at 70% intensity you’ll be lifting 94.5 lbs. But of course, you can lift that weight for more than 1 repetition, right? So how do you decide how much weight to lift and for how many repetitions and sets?

Determining Intensity
Many scientific studies have examined the RM formulas to determine the best way to assign training loads. However, the overall conclusion is that any formula should be used as a guideline for an estimate only, and not an absolute truth (2). Some of the many drawbacks in the formulas are that they are geared towards men, they are based on free weight exercises (bench press, back squat, and power clean), machine exercises will yield more repetitions, they aren’t based on multiple sets, and exercises that involve smaller muscle areas will yield less repetitions. So what’s a girl to do? Use the tables (sidebar) to determine approximate weights for your training program, diligently keep a training record, and be flexible. There are some hard rules that you can adhere to, though. Heavy resistance (85-100% of the 1 RM) is used for strength and power, moderate resistance (75 - 85% of the 1 RM) is needed for muscular hypertrophy (increasing muscle size), and light resistance (65% - 75% of the 1 RM) is used to gain muscular endurance. Typically, heavy resistance is categorized in the 3-5 RM range and requires 4-5 sets with a 3-4 minute rest between sets. Moderate resistance is considered 8-10 RM and requires 3-4 sets with a 2-minute rest between sets. Light resistance is a weight that can be lifted for 12-15 RM, in 3-4 sets, with a 1-minute rest between sets. As you can see, the heavier the weight is, the less repetitions you can perform, and the more time you’ll need to rest in between sets. Lifting heavy weights also feels more “intense” than lifting lighter weights. Don’t confuse working hard with working long, though. As a matter of fact, the opposite is true. If you are working with an appropriate amount of intensity on a “Heavy” workout day, your actual working time will be shorter than on a “Light or “Moderate” day. However, your rest periods will be longer, so the total session time will probably be about the same.

Benefits of Increasing Intensity
Why spend your valuable time and money in the gym without getting the body that you deserve? After all, you work hard. Well, maybe not hard enough! If your weight lifting plan isn’t yielding increased strength, decreased body fat, and harder muscles, then you are probably doing something wrong. Many women shy away from challenging themselves with their weight training programs, but it is just these women who need to brave the new world of resistance training. Long gone are the days of “3 sets and 12 reps”. Science has proven that the most effective weight training programs are a well-designed mix of the essential components described previously. If you desire a strong, hard body, then performing exercises always in the “light resistance” range with 12-15 reps will not do the trick. You have to cycle in the heavy and moderate resistance weight to complete the puzzle.
Diane Vives, a certified strength and conditioning specialist and owner of Vives Training Systems in Austin, TX says that “incorporating intense work loads benefits women by creating exercises that require a high caloric demand, especially when using combination exercises and total body movements.” Not only will exercise in the high intensity zones burn calories, but it will also increase muscle size. But most women question whether lifting heavy will make them “too big”. Vives says that is a female client’s most common question. “Actually, she explains, “increased lean body mass (more muscle) aids in speeding our metabolism, which burns calories, and allows us to accomplish higher workloads, which burns even more calories. Since our natural female hormones can only take us so far, intensifying our workout is a huge bonus for women.”
Vives’ comments are backed with scientific fact. Fat is lazy. It doesn’t do anything except sit on the couch with the remote control and keep us warm. On the other hand, muscle is constantly at work. It generates and gives off heat and requires energy (calories) to do this. So the more muscle you can add to your body, the more calories you will burn – even when you are resting! And when it comes to losing fat, high intensity exercise can’t be beat. In a study to evaluate the effect of intensity of physical activity on body fatness and fat distribution on 1,366 women, it was found that the subjects who practiced vigorous activities on a regular basis had lower skinfold thicknesses and waist-to-hip ratios than those not performing high intensity exercise (3). Furthermore, the study suggested that the decrease in body fat wasn’t only the result of the high intensity exercise, but also the result of the participants eating less and gaining more muscle! If you are watching your calories, then high intensity workouts may help you even more. In addition to possibly decreasing your appetite, they will also provide you with the muscle to burn extra calories if an “extra calorie” situation arises – and it always does!

How and When to Increase Intensity
High intensity can only be achieved by increasing the load, the amount of weight lifted. You can psyche yourself up and believe that you are getting more intense, but the bottom line is how heavy you go. Your current condition, training background, and exercise history are important factors to consider before designing a high intensity program. Because a high intensity workout is very challenging, beginners should get a good base of strength before attempting one. In order to prevent overuse injuries, the frequency of high intensity exercise should be limited. Vives recommends high intensity work be performed only 3 times a week with 2 lighter workouts added in between. Some general rules to remember are that one day of rest between training a particular muscle group is good, but if muscle soreness persists, more rest is needed. An “active recovery” day of light aerobic exercise may also be used after a high intensity total body workout.
You probably already know what weight is close to your 10 RM. You’ve probably been doing it every day in the gym. But take a week with your current training program and record each weight that you can lift in each exercise for 10 reps. Try to pick weights that will challenge you to complete the 10th rep and use a spotter. To meet our goals of a lean, mean machine, our workouts should use heavy and moderate intensities mixed either throughout a particular session or during the week. You can split a body part into heavy and moderate exercises; for example, heavy bench presses, moderate cable crossovers, and heavy incline dumbbell presses. Or you can divide a workout week into a heavy day, rest day, moderate day, active recovery day, heavy day, and rest day. Just remember to cycle your body parts and exercises so they alternate between the heavy and moderate intensities. You don’t always want to squat heavy for 3-5 reps. For maximal muscle stimulation and injury prevention, you need moderate weights for 8-10 reps too.

Get Intense
“Lift heavy or go home” all of the guys in the gym say. Most women just go through the motions as though just being at the gym will make them stronger or more fit. It just isn’t so. You really have to challenge yourself with some heavy weights to realize your potential of a hard, strong body. Get off the leg press, go to the squat bar, and punch out 5 intense reps. Throw away your old misconceptions and start training with intensity. Your body and your attitude will never be the same!

References:
1. Fleck, S.J. and W.J. Kraemer, Designing Resistance Training Programs. 2nd ed. 1997, Champaign, IL: Human Kinetics.
2. Baechle, T.R. and R.W. Earle, eds. Essentials of Strength Training and Conditioning. 2nd ed. 2000, Human Kinetics: Champaign, IL.
3. Tremblay, A. and E. Doucet, Influence of intense physical activity on energy balance and body fatness. Proc Nutr Soc, 1999. 58(1): p. 99-105.