Many lifters know what recovery means, but they don’t truly grasp the severity of the relationship between fatigue and muscle growth. Recovery can be defined as a restoration of physiological systems to baseline before further overloading a muscle again. Muscle growth occurs during recovery! If you are not recovering between workouts, don’t expect to make significant gains in muscle growth or strength


  •       Deloads are essential for reducing fatigue, enhancing recovery, and allowing for super-compensation.·
  • There are two types of fatigue: Central fatigue (brain) and peripheral fatigue (muscle).
  •       Compound movements can cause greater central fatigue than single-joint exercises.
  •       Athletes with more Type II fibers experience greater fatigue and are more likely to overtrain with high volume.
  •       Building muscle is highly individualized; some people recover faster and slower than others.
  •       Deloads are essential for reducing fatigue, enhancing recovery, and allowing for super-compensation.


Several tests have been suggested to monitor fatigue, such as psychological test, RPE and RIR, blood hormone testing (i.e., monitoring testosterone, IGF-1, cortisol, etc.), EMG testing to measure neuromuscular contractions, and performance tests (i.e., jumping height, sprint performance). Of all the tests used, performance tests via sprinting ability and jumping height were the most widely used and effective ways to monitor fatigue.

The article mentioned monitoring jump height is an easy way to monitor neuromuscular fatigue throughout a season. Although most lifters rarely do these types of tests, measuring workout performance can be used to monitor neuromuscular fatigue. If your reps and strength are consistently going down and exertion levels are high, it is a good time to take a deload. Monitoring performance is the best way to gauge your training level and how hard you can keep adding volume/load, etc. (18)


As mentioned in the article below, a drop in performance is the single best metric to gauge performance. If your strength levels are dropping, it’s time to rest more. What about if you use “feeling ready to train” to base your training on? Researchers had subjects perform 8 sets of 10 reps at 70% of a 1RM. This is a typical high-volume bodybuilding style workout. The researchers had the subjects complete a questionnaire 24, 48, and 72 hours later.

The questionnaire consisted of a 0-10 recovery scale with 0 being “Very poorly recovered, extremely tired” and 10 being “Very well recovered, highly energetic.” The researchers also had study subjects perform a vertical jump. A vertical jump is a great test to measure peak power; if your vertical jump goes down, it indicates not being fully recovered. They also measured barbell velocity in the squat, a measure of power. The goal was to see if how lifters “felt” was indicative of monitoring recovery. The study results found that how a person felt was correlated with their recovery following a high-volume resistance exercise for 72 hours after exercise.


One interesting finding was that how the subjects felt after exercise was highly variable and sometimes unrelated to their recovery. Some people reported feeling tired and reported a low recovery score but did well on test measures for power. Some subjects reported similar recovery ratings, but their performance outcomes were drastically different. For example, two subjects reported similar recovery ratings, but one had a ~40% decrease in barbell velocity (i.e., worse recovery), whereas another person had a ~10% decrease in barbell velocity. (i.e., better recovery).

Two lifters reported they felt a certain way and had ranked the same recovery number, but one was not fully recovered, and the other was recovered. The author suggested that how a person felt after exercise was related to recovery, but you can’t use this exclusively because of the large individual responses. (19)

deload week deload deloading WHAT how to deload deload workout deload meaning


Many lifters know what recovery means, but they don’t truly grasp the severity of the relationship between fatigue and muscle growth. Recovery can be defined as a restoration of physiological systems to baseline before further overloading a muscle again. Muscle growth occurs during recovery! If you are not recovering between workouts, don’t expect to make significant gains in muscle growth or strength. One study found that constantly stimulating a muscle without sufficient rest increased oxidative stress (i.e., cellular stress) and suppressed increases in protein synthesis rates after exercise.[1]

Remember, building muscle is a function of increasing protein synthesis while minimizing protein breakdown. If you are constantly breaking down muscle, you are not growing! Your body will eventually become overly fatigued by continuous exercise if you don’t take a break or deload. For example, one study found that biceps growth was lower with 27 weekly sets compared to 18 sets.

This suggests that after 18 sets, the fatigue response was too great, and no further training could stimulate muscle growth.[2] As mentioned previously, this is an example of junk volume in which further sets than required are no longer are conducive to muscle growth.


Everyone has a different genetic ability to recover from exercise; therefore, each person’s workout program should be unique to that person. Also, your ability to recuperate is highly dependent on your diet. A recent review of 17 studies found that physical performance can be maintained when consuming a ketogenic diet compared with carbohydrate diets. However, the current evidence does not support an ergogenic effect of consuming a ketogenic diet.[3]

If you are not gaining muscle over the course of your training, the workout stress is too high, and you are not taking sufficient rest to recover between workouts. Conversely, your workout stress may be too low, and you are not stimulating the muscle enough to enhance muscle growth, or you are not consuming enough calories, not sleeping enough, etc.

The Importance of Sleep

Many people are quick to neglect the optimal amount of sleep they need for muscle growth. A 2017 study of over 10,125 university students found that those who slept less than 6 hours had poorer strength than those who slept 7-8 hours.[4] A single night of sleep loss can increase cortisol by 24%, reduce testosterone by 24%, and reduce protein synthesis by 18%.[5] Researchers found that when subjects slept 1 hour less a night for five days resulted in a substantial loss of muscle compared to a group that was allowed a normal sleep pattern.[6]

deload week deload deloading WHAT how to deload deload workout deload meaning


Most people don’t know this, but different types of fatigue can occur during exercise: central and peripheral fatigue. Resistance exercise can cause both central and peripheral fatigue.[7] For an excellent review on the role of muscle growth and fatigue, one should read Chris Beardsley’s book: Hypertrophy: Muscle fiber growth caused by mechanical tension.[8]

Central fatigue or systemic fatigue is most associated with aerobic exercise; it is associated with the brain and spinal cord. If your brain is fatigued, you will have problems performing a maximal contraction. Ever watch a long-distance runner in the last few miles? You may notice that he has coordination problems; this is an example of central fatigue.


Psychological fatigue from the daily stressors of life can also affect performance. Studies have found that when subjects had to perform complex math equations before squats, there was a decrease in the training volume they could perform.[9]

This was also found when people used social media before exercise; this also reduced exercise performance compared to a control group.[10] This is just an example of how mental fatigue can impair weightlifting performance.

“Central fatigue can affect not only exercised muscles but also others that were resting. ”

— Halperin et al. 2014 (22,23)


Peripheral fatigue or local fatigue during exercise results in metabolic accumulation in muscles such as lactate, calcium, etc. Metabolic stress from high-intensity exercise and muscle damage causes central and peripheral fatigue. Also, training to complete muscular failure results in more peripheral fatigue and may cause more muscle damage.[11] Single-leg exercises elicit greater peripheral fatigue than double-leg exercises.

For example, single-leg extensions resulted in greater peripheral fatigue than double-leg extensions.[12] Most people think heavy weight, high-intensity exercise causes more central fatigue, but low-intensity, high-volume exercise causes greater central fatigue.[13] In this study, researchers compared training with 20% of a 1RM and 80% of a 1RM to failure in both men and women.

Central fatigue was greater for both men and women with the 20% contraction to failure than the 80%. If you have ever done a squat for >30 reps, you know it is extremely taxing on the body. It’s also been found that compound movements can cause greater central fatigue than single-joint exercises, so performing compound movements first can ensure that you maximize your workouts.[14]


Fatigue must be managed during exercise to increase workout volume. It’s well documented that high volume training to failure results in prolonged recuperation time between workouts and exacerbates muscle damage. One of the primary symptoms of overtraining/overreaching is reduced strength and fatigue. This likely occurs partly due to central nervous system fatigue-reducing muscle force output.

“Central fatigue, which can last for days and is linked to peripheral factors such as muscle damage and can affect both exercised and non-exercised muscles, could be interesting to consider when programming resistance training variables such as load, exercise selection, range of motion, or exercise order.”

— Carroll 2017 [20]


After exercise, direct damage to the muscle causes inflammation and prolongs muscle recovery time.[15] It has also been found that training to failure can contribute to overuse injuries. An individual’s muscle fiber types (i.e., fast twitch or slow twitch) can also determine whether they recuperate faster or slower. Athletes with more fast-twitch fibers are more likely to overtrain.


One study found that when athletes were exposed to an overtraining period, it caused some to overtrain while others did not. The athletes that experienced overtraining had more fast-twitch explosive fibers. Those athletes with more fast-twitch fibers will result in more fatigue than those with slow-twitch fibers. Athletes with more fast-twitch fibers demonstrated fatigue for a maximal 90-second exercise bout 5 hours after exercise, whereas athletes with slow-twitch fibers recovered 20 minutes after exercise.[16]


Athletes with more fast-twitch fibers will experience more fatigue than those with slow-twitch fibers. This suggests that your genetic makeup of fibers can determine whether you can handle a high-volume program or not. Remember, not all athletes respond to every workout the same; no cookie-cutter weight training program works for everyone.

As mentioned, not all muscle groups recover at the same rate. Slow-twitch fibers will recuperate at a faster rate than fast-twitch fibers. Therefore, you can train the calves, which comprise a high proportion of type I fibers, more frequently than a muscle group like the hamstrings, which consist primarily of type II fibers and take longer to recover. The calf soleus muscle is about 80% type I muscle fiber (i.e., soleus Type I fibers range from 64 to 100%). In contrast, the gastrocnemius and vastus lateralis muscles only contain 57% slow-twitch fibers (range 34–82%).[17]


As Dr. Mike Israetel of Renaissance Periodization has termed, a well-planned training cycle will have a high stimulus-to-fatigue ratio, placing high tension on the muscle without overly fatiguing the nervous system. An example of a high stimulus-to-fatigue ratio technique would be using the mind-muscle connection, actively squeezing the muscle with each rep, and stopping with 1-2 RIR. In contrast, going to failure each set results in a worse stimulus-to-fatigue ratio because you are causing excess fatigue with no added stimulation.

Another example of a worsening stimulus-to-fatigue ratio would be high rep squats with light weight. This generates extreme fatigue when squats performed with a heavier weight can achieve the same results with less fatigue stopping short of failure.

“Knowing that more training volume provoke more fatigue, studies demonstrate that more fatigue does not always cause more muscle growth. When training volume is equated, although reaching failure promotes greater fatigue than not training to failure, this does not always cause more muscle gains. Thus, taking fatigue as a greater stimulus is a great mistake.”

— Alix-Fages 2022 [21]


1.     Junya Takegaki et al., “Repeated Bouts of Resistance Exercise with Short Recovery Periods Activates MTOR Signaling, but Not Protein Synthesis, in Mouse Skeletal Muscle,” Physiological Reports 5, no. 22 (November 2017): e13515.

2.     Samuel R. Heaselgrave et al., “Dose-Response Relationship of Weekly Resistance—Training Volume and Frequency on Muscular Adaptations in Trained Men,” International Journal of Sports Physiology and Performance 14, no. 3 (March 1, 2019): 360–68.

3.     Murphy, N. E., Carrigan, C. T., & Margolis, L. M. (2021). High-Fat Ketogenic Diets and Physical Performance: A Systematic Review. Advances in nutrition (Bethesda, Md.), 12(1), 223–233.

4.     Yanbo Chen et al., “Relationship between Sleep and Muscle Strength among Chinese University Students: A Cross-Sectional Study,” Journal of Musculoskeletal & Neuronal Interactions 17, no. 4 (December 2017): 327–33.

5.     Séverine Lamon et al., “The Effect of Acute Sleep Deprivation on Skeletal Muscle Protein Synthesis and the Hormonal Environment,” Physiological Reports 9, no. 1 (January 5, 2021): e14660.

6.     Xuewen Wang et al., “Influence of Sleep Restriction on Weight Loss Outcomes Associated with Caloric Restriction,” Sleep 41, no. 5 (May 1, 2018).

7.     Adam Zając et al., “Central and Peripheral Fatigue During Resistance Exercise – A Critical Review,” Journal of Human Kinetics 49 (December 22, 2015): 159–69.


8.     Beardsley, C. Hypertrophy: Muscle fiber growth caused by mechanical tension. 2019

9.     “Mental Fatigue Reduces Training Volume in Resistance Exercise: A Cross-Over and Randomized Study – Victor Sabino de Queiros, Matheus Dantas, Leonardo de Sousa Fortes, Luiz Felipe Da Silva, Gilson Mendes Da Silva, Paulo Moreira Silva Dantas, Breno Guilherme de Araújo Tinôco Cabral, 2021,” accessed October 8, 2021.

10.  Leonardo Fortes et al., “Effects of Social Media on Smartphone Use before and during Velocity-Based Resistance Exercise on Cognitive Interference Control and Physiological Measures in Trained Adults,” Applied Neuropsychology: Adult, December 29, 2020.

11.  Jorge M. González-Hernández et al., “Resistance Training to Failure vs. Not to Failure: Acute and Delayed Markers of Mechanical, Neuromuscular, and Biochemical Fatigue,” Journal of Strength and Conditioning Research 35, no. 4 (April 1, 2021): 886–93.

12.  Matthew J. Rossman et al., “The Role of Active Muscle Mass in Determining the Magnitude of Peripheral Fatigue during Dynamic Exercise,” American Journal of Physiology. Regulatory, Integrative and Comparative Physiology 306, no. 12 (June 15, 2014): R934-940.

13.  Tejin Yoon et al., “Mechanisms of Fatigue Differ after Low- and High-Force Fatiguing Contractions in Men and Women,” Muscle & Nerve 36, no. 4 (October 2007): 515–24.

14.  Matthew J. Rossman et al., “The Role of Active Muscle Mass in Determining the Magnitude of Peripheral Fatigue during Dynamic Exercise,” American Journal of Physiology. Regulatory, Integrative and Comparative Physiology 306, no. 12 (June 15, 2014): R934-940.


15.  Arthur J. Cheng, Baptiste Jude, and Johanna T. Lanner, “Intramuscular Mechanisms of Overtraining,” Redox Biology 35 (August 2020): 101480.

16.  Eline Lievens et al., “Muscle Fiber Typology Substantially Influences Time to Recover from High-Intensity Exercise,” Journal of Applied Physiology 128, no. 3 (March 1, 2020): 648–59.

17.  Philip D. Gollnick et al., “Human Soleus Muscle: A Comparison of Fiber Composition and Enzyme Activities with Other Leg Muscles,” Pflügers Archiv 348, no. 3 (September 1, 1974): 247–55.

18. Alba-Jiménez, C.; Moreno-Doutres, D.; Peña, J. Trends Assessing Neuromuscular Fatigue in Team Sports: A Narrative Review. Sports 2022, 10, 33.

19. Tolusso, D. V., Dobbs, W. C., MacDonald, H. V., Winchester, L. J., Laurent, C. M., Fedewa, M. V., & Esco, M. R. (2022). The Validity of Perceived Recovery Status as a Marker of Daily Recovery Following a High-Volume Back-Squat Protocol, International Journal of Sports Physiology and Performance.

20. T. J. Carroll, J. L. Taylor, and S. C. Gandevia. Recovery of central and peripheral neuromuscular fatigue after exercise. Journal of Applied Physiology 2017 122:5, 1068-1076.

21. Alix-Fages, Carlos & Del Vecchio, Alessandro & Baz-Valle, Eneko & Santos-Concejero, Jordan & Balsalobre-Fernández, Carlos. (2022). The role of the neural stimulus in regulating skeletal muscle hypertrophy. European Journal of Applied Physiology.

22. Israel Halperin, Saied J. Aboodarda & David G. Behm (2014) Knee extension fatigue attenuates repeated force production of the elbow flexors, European Journal of Sport Science, 14:8, 823-829.

23. Halperin, Israel, CopithorneDavid, and BehmDavid G.. Unilateral isometric muscle fatigue decreases force production and activation of contralateral knee extensors but not elbow flexors. Applied Physiology, Nutrition, and Metabolism. 39(12): 1338-1344.

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