Exercise intensity is one of the most important variables in any workout, because if the intensity is not correct, your workout won’t have the intended effect. Exercising at the wrong intensity level is one of the most common mistakes people make and it should definitely be avoided, if you want to experience optimal results. Intensity seems like a fairly simple concept, as it typically refers to exercise difficulty, but intensity is a little more complicated than it first appears.
The problem with intensity is that it has multiple definitions and different ways of being measured, depending on the type of exercise being performed. For example, when designing resistance training workouts (e.g. lifting weights), intensity is measured differently than when designing a traditional aerobic workout (e.g. running). Therefore, if you want to design workouts to achieve specific goals, it is important to understand how intensity is used in different situations.
Exercise intensity is a measure of difficulty, but a workout can be difficult without being considered a high intensity workout. To give you a better idea of what I mean, let’s take a closer look at resistance training workouts. When training with weights or other types of resistance where you perform sets and reps of various exercises, intensity is determined by the amount of weight used during the set, not the perceived difficulty of the set.
More specifically, intensity is measured as the percentage of your one rep max (1RM). A 1RM represents the amount of weight you can lift one time with proper form and you will have a separate 1RM for every exercise in a workout. For example, if the greatest amount of weight you can lift during the bench press bench press one time is 100 pounds and you want to train at 80% intensity, then you would use 80 pounds during your bench press sets.
Safety Note: 1RM testing can be dangerous if not conducted properly. If you need to figure out your 1RM for program design purposes, be sure to have a qualified professional conduct the tests. Another option is to use a higher repetition test, such as a 10RM test (highest amount of weight you can lift 10 times) and then find a chart to predict your 1RM from that number.
High percentages of a 1RM are consider high intensity exercises and low percentages are considered low intensity exercises, regardless of the number of reps you complete during the set. This means that performing one rep at 90% of your 1RM is technically considered higher intensity training than performing 5 reps at 85% of your 1RM, although 5 reps at 85% is actually more difficult. Factors like reps, sets, tempo, and rest periods are not considered when determining the level of intensity of a resistance training workout, although they certainly affect the difficulty of your workout.
Honestly, for most people it is not too important to know their 1RM, as programs designed from 1RM testing are mainly used with competitive athletes. However, it is important to understand what it means when someone refers to the intensity of a resistance training exercise. With resistance training, intensity is just one of many variables used to determine the overall difficulty of a workout. Therefore, by itself, intensity is always reliable for predicting workout difficulty.
Traditional aerobic training (swimming, running, etc.) also uses percentages to signify the level of exercise intensity, but the percentages represent something completely different with resistance training. With aerobic training, intensity is expressed as a percentage of your maximal heart rate. In other words, the percentage is a measure of the cardiovascular demand of the exercise. Simply put, the higher your heart rate, the higher the intensity of the exercise.
Since higher heart rates correspond to higher levels of difficulty, the intensity of aerobic training workouts are more reflective of overall difficulty than the intensity level used to describe resistance training exercises. If you want to design an aerobic workout of a specific difficulty level, all you need to do is perform the exercise at the intensity (heart rate) that corresponds with your fitness goals. Unless you are a competitive athlete or need to improve very specific physiological characteristics, you do not have to factor in many variables, as you do with resistance training.
Even though resistance training and aerobic training measure intensity in different ways, they both use a specific physiological attribute to measure intensity. Resistance training uses muscular strength to quantify intensity and aerobic training uses heart rate. The important thing to note is both types of exercise use a measure that can be numerically quantified, so specific adjustments can be made to improve the effectiveness of each exercise or workout, which ultimately improves the results of your overall training program.
When most people refer to intensity, they mean to the general feeling of difficulty, as opposed to a specific physiological measurement. Describing intensity as the overall feeling of difficulty is also an acceptable definition of intensity and if you have very general goals, such as making any type of improvement in your fitness level, then using the general feeling of difficulty as your guide can be appropriate. However, if you have more specific goals, such as improving aerobic endurance, speed, muscular strength, etc., then your workouts need to be designed to match the intensity level required to stimulate each specific improvement.
There is no single workout that will improve every aspect of fitness simultaneously, so you have to decide which fitness attributes are most important to you. Multiple fitness attributes can be improved through your overall training program, but different attributes often need to be improved by performing different types of workouts. For example, training to improve aerobic endurance requires a drastically different workout design than training for maximal strength.
Understanding the different meanings and measures of intensity really comes into play when creating workouts to improve different aspects of fitness using the same type of exercise. For instance, if you perform resistance training workouts and you want to improve your maximal strength and muscular endurance, you need to train using different intensity levels (use different amounts of weight) for each task.
Training to improve maximal strength requires training with a high intensity (high percentage of 1RM), but you will not be able to perform many reps with the high amount of weight. When training for muscular endurance, you must perform a high numbers of reps, so a lower intensity weight must be used to achieve the desires results. It is important to note that though different intensities are used during each workout, both workouts may still feel equally challenging, depending on the other variables in the workout design.
If you want your workouts to result in specific improvements, it is important to have a way to quantify the intensity of your workouts. Not only will using numerical intensities help you figure out how to plan for your goals, but it also makes it easier to modify your program as your ability level and goals change over time. On the other hand, if you use the more general meaning of intensity and create workouts solely because they are a certain difficulty, then you won’t have nearly as much control over the type of results you get from your training program.
Intensity is a general concept to describe exercise difficulty, but by using the physiological numerical measures of intensity, you can take your training to the next level and really personalize your program to match your particular goals.