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Why Exercise Intensity Matters

why-exercise-intensity-matters

Introduction

Let me paint the picture for you. Your friend talks about how they’re doing everything right because they’re lifting all the time, eating the right food, and taking the right supplements. They tell you that their lifting sessions are super intense because they lift for two-three hours a day, and they’re drenched in sweat by the end.

When you ask them what rep range they are lifting in, they tell you that they do super sets, giant sets, strips sets. Every set is to failure, and they’re getting 20+ reps per set.

Did you pick up on what was wrong with this scenario? What your friend is not doing is lifting intense enough.

The definition of intensity between the well-educated lifter and the common gym bro is different.

By definition, exercise intensity is the amount of energy a person exerts while training relative to the exercise being performed1. To make this easier to understand, let’s discuss it in terms of lifting weights. The intensity of lifting is the amount of weight lifted relative to your one repetition max, what we call 1RM. So, if you can bench press 100 pounds, 60% intensity would be 60 pounds.

Why Intensity Matters

From the last example we talked about the friend that says they lift with intensity, but doing reps of 20+, is where intensity becomes a problem. It’s common for bodybuilders to put restraints on the number of repetitions they do depending on their goal. You have probably heard that if you want to lift for strength, lift in the 3-5 repetition range, for hypertrophy the 8-12 repetition range.

What is not commonly talked about is the intensity (amount of weight) you should lift in these repetition ranges.

Lifting in the 3-5 rep range, with longer rest periods, and multiple sets will increase strength. Lifting in the 8-12 repetition range with shorter rest periods (30-90 seconds) will increase both strength and hypertrophy2.

Strength is best optimized when training with low repetitions and heavier weight. Yet, it’s not out of the question to gain both strength and size using high repetitions2,3,4. This brings us to a concept known as the repetition continuum.

The repetition continuum is a concept where lifting heavyweight leads to gains in strength and lifting lighter weight leads to strength endurance5.

Generally, heavyweight is greater than 85% of your 1RM and lighter weight is 40-60% of your 1RM. The anomaly to this theory is training for hypertrophy. As said before, hypertrophy can occur when training in most repetition ranges. This is also contingent on age, training experience, training style (failure vs non-failure), and volume.

What is the best intensity to train?

The best training intensity is contingent on your goal and various other factors including age, training experience, training style, and total volume.

When you hear someone say, “this is the intensity you should train at to build muscle,” is untrue and irresponsible.

I am going to breakdown each of these variables in more detail for you to gain a better understanding of how you should be training and the best practices for you goal.

Intensity, Age & Experience

Training age can mean one of two things including your physical age and/or how long you have been training.

Younger people tend to respond well to all types of training whether it be heavy, moderate, or light loads6,7,8. Older people (>45 years) respond well to low intensity training with blood flow restriction when high intensity training is not a choice due to age or injury9.

But, young athletes also respond well to blood flow restriction training10.

Intensity & Training Type

Exercise intensity also plays a role in the type of training you do. Super sets or giant sets with >85% 1RM are possible, but not recommended.

High intensity training like this can cause injury, especially when performing quickly. In addition, high intensity training may cause a phenomena known as central fatigue.

Central fatigue occurs when it’s difficult for the brain to send adequate signal to the muscles to perform a lift. When lifting heavy, one uses larger, high threshold motor units, which require not only muscular energy but also cognitive energy to activate the muscle. As exercise intensity increases, larger motor units are recruited to move the weight resulting in greater neural drive to the muscle.

Therefore, frequent high intensity training may require longer periods of recovery between training sessions to reduce central fatigue.

The take home message is that training intensity should be varied from light to moderate to heavy.

High intensity training also results in greater muscle damage. One topic we have not discussed, but I will introduce, is contraction type.

Under normal circumstances in the gym we use concentric training. Concentric training is where we shorten the muscle. An example would be biceps curls. When you lift the weight, you are shortening the muscle.

Conversely, lowering the weight is the eccentric part of the lift. When we train strictly eccentrically, we are able to lift (lower) more weight. To properly do this, a partner would need to help you lift the weight so you can lift it eccentrically.

Eccentric training can cause high amounts of muscle damage, which, if not given enough time to recover, may result in greater central fatigue11.

Intensity & Volume

If you refer to the table from above, you’ll notice the more weight you lift, the fewer reps you can do. This is where the concept of volume presents itself. When lifting at lower intensity, you have the ability to lift more volume.

You can easily perform 3 sets of 10 repetitions compared to 6 sets of 3 repetitions.

Doing the math of someone squatting 185 pounds (70% 1RM) for 30 reps (3 sets x 10 repetitions), the total volume is 5550 pounds. However, if that same person were to lift 240 pounds (90% 1RM) for 18 repetitions, the total volume would be 4320 pounds. Even though they lifted heavier weight, their total volume was lighter.

Their training style is conducive of strength, but not necessarily hypertrophy because volume is lower and volume is a primary driver of muscle growth.

Intensity Conclusions

Many mistake how “intense” they trained based on how much they were sweating during their training session. Yet, intensity is a misunderstood concept for building muscle. Intensity is the amount of weight you are lifting relative to a one repetition maximum. Higher intensity training is generally used to increase strength whereas lower intensity training is generally used to increase hypertrophy or strength endurance. Using the right intensity for your goal is the one of the quickest ways to making gains in gym and reaching your goal.

References

  1. Mann, T., Lamberts, R. P., & Lambert, M. I. (2013). Methods of prescribing relative exercise intensity: physiological and practical considerations. Sports medicine, 43(7), 613-625.
  2. Campos, G. E., Luecke, T. J., Wendeln, H. K., Toma, K., Hagerman, F. C., Murray, T. F., … & Staron, R. S. (2002). Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones. European journal of applied physiology, 88(1-2), 50-60.
  3. Ogasawara, R., Loenneke, J. P., Thiebaud, R. S., & Abe, T. (2013). Low-load bench press training to fatigue results in muscle hypertrophy similar to high-load bench press training. International Journal of Clinical Medicine, 4(02), 114.
  4. Schoenfeld, B. J., Peterson, M. D., Ogborn, D., Contreras, B., & Sonmez, G. T. (2015). Effects of low-vs. high-load resistance training on muscle strength and hypertrophy in well-trained men. The Journal of Strength & Conditioning Research, 29(10), 2954-2963.
  5. https://www.strengthandconditioningresearch.com/perspectives/strength-endurance-continuum/
  6. Aagaard, P., & Andersen, J. L. (1998). Correlation between contractile strength and myosin heavy chain isoform composition in human skeletal muscle. Medicine and science in sports and exercise, 30(8), 1217-1222.
  7. Schoenfeld, B. J., Peterson, M. D., Ogborn, D., Contreras, B., & Sonmez, G. T. (2015). Effects of low-vs. high-load resistance training on muscle strength and hypertrophy in well-trained men. The Journal of Strength & Conditioning Research, 29(10), 2954-2963.
  8. Ogasawara, R., Loenneke, J. P., Thiebaud, R. S., & Abe, T. (2013). Low-load bench press training to fatigue results in muscle hypertrophy similar to high-load bench press training. International Journal of Clinical Medicine, 4(02), 114.
  9. Vechin, F. C., Libardi, C. A., Conceição, M. S., Damas, F. R., Lixandrão, M. E., Berton, R. P., … & Ugrinowitsch, C. (2015). Comparisons between low-intensity resistance training with blood flow restriction and high-intensity resistance training on quadriceps muscle mass and strength in elderly. The Journal of Strength & Conditioning Research, 29(4), 1071-1076.
  10. Yasuda, T., Ogasawara, R., Sakamaki, M., Ozaki, H., Sato, Y., & Abe, T. (2011). Combined effects of low-intensity blood flow restriction training and high-intensity resistance training on muscle strength and size. European journal of applied physiology, 111(10), 2525-2533.
  11. Proske, U., & Morgan, D. L. (2001). Muscle damage from eccentric exercise: mechanism, mechanical signs, adaptation and clinical applications. The Journal of physiology, 537(2), 333-345.
About the author

Andy (The Performance Chef) has a passion for not only food. But also optimizing health and pushing the boundaries of human potential. A chef by trade, he has at trained a bachelor’s degree in culinary nutrition, master’s degree in nutrition & exercise science. And is a doctoral candidate in health & human performance.

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