Intensity or Resistance

The following is an exclusive excerpt from the book Strength Training, Second Edition, published by Human Kinetics. All text and images provided by Human Kinetics.

The amount of resistance used for a specific exercise is one of the key factors in any resistance training program. It is the major stimulus related to changes in strength and local muscular endurance. Higher intensity is important for strength development in all individuals, older and younger (Peterson et al. 2004, 2005, 2010).

One of the easiest methods for determining the right resistance for an exercise is to determine your RM—the specific resistance that allows you to perform only a specific number of repetitions. Typically, to determine RM, you can choose a single training RM target (e.g., 10RM) or choose an RM target training zone (e.g., 3-5RM); you then perform each exercise at different resistances until you meet this target. As your strength level changes over time for each lift, you can adjust the resistance so that you continue to hit your specified RM target or zone. Going to failure on every repetition can be stressful on the joints, but for optimal results you should make sure that the resistance you use places you within a targeted range of reps—for example, the resistance allows you to lift the weight for only 4 or 5 repetitions compared with 14 or 15 repetitions. The training outcome for these two resistances is quite different.

Another method for determining resistance for an exercise involves using a percentage of the 1RM for a lift. For example, if your 1RM for an exercise is 100 pounds (45.4 kg), lifting 80 percent of the 1RM would mean lifting 80 pounds (36.3 kg). This method requires you to regularly evaluate your maximal strength in the various lifts so that you can adjust the resistance appropriately as you get stronger. However, if you do not test your 1RM each week, especially when beginning a program, the resistance represented by the percentage of 1RM that you use in training will decrease as your strength increases; as a result, training intensity will be reduced. From a practical perspective, using a percentage of 1RM as the resistance for many exercises may not be efficient because of the amount of testing time required. Use of an RM target or RM target zone allows you to change resistance as necessary during training in order to stay at the RM target or within the RM target zone you’ve chosen.

Like other acute variables, the loading intensity a person chooses depends on his or her goals and training status (i.e., whether the person is a trained athlete or a sedentary individual). The intensity of the loading as a percentage of 1RM affects the number of repetitions that a person can perform at a given load or intensity. Ultimately, the number of repetitions you can perform at a given intensity or load determines the effects of training on strength development (Hoeger et al. 1990). It is important to note that the RM at a set percentage of the 1RM can vary between free weights and machines; more repetitions can be performed when the resistance is on a set, controlled path because no balance is required (Hoeger et al. 1990; Shimano et al. 2006). If an athlete lifting a specific percentage of the 1RM can lift only a specific number of repetitions, then lifting fewer repetitions without changing the resistance would mean that the athlete is using different motor units to perform the exercise. For instance, a low-intensity (light resistance), high-repetition workout protocol would effectively activate the Type I muscle fibers (those more suited to local muscular endurance) but would not adequately activate the Type II muscle fibers (the predominant muscle fibers responsible for maximal strength and hypertrophy gains). Thus, if you want to maximize strength gains, you should lift heavier loads and therefore perform fewer repetitions. If local muscular endurance is the goal, you should use a lighter load, which in turn allows a greater number of repetitions.

Whether you’re launching a lifting program or fine-tuning a serious training regimen, Strength Training will fill any knowledge void and correct the misconceptions to ensure proper technique, safety, and progressions. Multiple program options for specific machines, free weights, body weight, and other types of apparatus provide the flexibility to tailor your training to personal preferences or needs. It’s the authoritative guide from the world’s authority on strength training.. The book is available in bookstores everywhere, as well as online at the NSCA Store.