By: Chris Vann, MS, BS, CSCS
What is the practicality of completing a light (e.g., low volume and/or low intensity) session or a series of light sessions during a training cycle? My good friend, Dr. Cody Haun, discussed the importance of load and mentioned some implications of recoverability in “The Importance of Load During Resistance Training: Part 2”. In this article, I will discuss “deloading” and how it affects recoverability and performance. I will also discuss some physiological data that support the implementation of a deload, and briefly describe how to structure one. My operational definition of a deload in this post is a series of light sessions designed to reduce fatigue through a logical reduction in volume, intensity, or both. In general, a deload lasts the span of a week, or a “microcycle” (~4-10 days). A deload, as mentioned above, allows for a reduction in fatigue. Let’s unpack this a bit more. Fatigue is a result of overloading training sessions and is cumulative in nature (over time its effects are additive). Fatigue, herein, refers to a reduced capacity to produce force.
Fatigue is a multifactorial physiological process involving multiple body systems. Considering this, fatigue can be subdivided into different durations and categories dependent on the body system in reference (more on this below). When fatigue has accumulated to a sufficient degree, one generally experiences alterations in the recruitment patterns of motor units affecting technical execution of movement patterns, altered hormonal ratios, and a decreased desire to train. Another consequence of overloading training sessions is damage to connective and muscle tissue structure. Both tissues require time to repair and grow, with connective tissue requiring longer durations as connective tissues receive a low blood supply, while still requiring substrates for repair and growth. On the other hand, muscle tissue is fed a direct supply of blood via capillaries, and, for this reason, recovers quicker from overloading training. Dr. Mike Israetel et al. describe the conceptual timelines of these factors in the text “Scientific Principles of Strength Training”. These conceptual timelines are redrawn below.
The optimization of a training cycle, whether it be purely for aesthetic purposes or for increases in athletic performance, should take into account the aforementioned data. Conceptually, fatigue masks fitness. As we train and incur fatigue, performance temporarily decreases. Plisk and Stone describe this relationship in greater detail. Assuming progressive overload (accomplished through increasing intensity, volume, and/or frequency of training), a mesocycle is designed to accumulate fitness. As a result, each microcycle within a block of training would result in more fatigue and further decrements in performance over the course of time. However, with proper use of deloading paradigms, fatigue can be reduced and can result in increased performance for successive mesocycles. This is illustrated below.
Over time, to reduce fatigue further, a period of active recovery may be warranted involving longer than a microcycle in duration. Or, in the case of a competition or athletic event, a taper and peaking cycle is beneficial to drop as much fatigue as possible in order to optimize performance in a given athletic endeavor.
As overload is applied and fatigue is incurred over the course of a training cycle, glycogen stores (storage form of carbohydrates in muscle) important for the effective contraction of muscle tissue tend to be significantly reduced, resting blood hormone (chemical messengers) levels can be altered, and/or alterations in the nervous system can result in a decreased ability to produce force. Training can result in acute reductions of muscle glycogen which may result in a glycogen deficit that limits your ability to productively train at a sufficient intensity or volume to continue to stimulate adaptation, particularly without attention to proper nutritional strategies. Delayed onset muscle soreness (DOMS), which can occur from high-volume and/or high-intensity training (particularly when involving a large number of eccentric muscle actions), limits the ability to resynthesize glycogen stores, as shown by Costill et al. Glycogen is the preferred fuel source for high-volume, high-intensity training which was discussed in “Why You Should Care About Macronutrients”. Since it is relatively slow to fully replete, it is logical to program light days or a deload to facilitate an increased blood flow to specific musculature and allow adequate time for glycogen to return to baseline levels or “supercompensate” (increase beyond prior storage levels), before undertaking additional overloading training.
Blood hormone levels are also altered during overloading training. Izquierdo et al. performed a 7-week periodized study showing that, after the training period, resting serum testosterone increased in concentration. During voluminous training, however, Kraemer et al. reported decreases in serum testosterone, serum Insulin-like Growth Factor-1 (IGF-1), and an increase in serum cortisol. Kraemer et al highlighted this was particularly noticeable after a period of functional overreaching (a logical yet novel increase in training stress designed to elicit a certain adaptive response). These hormones are important to consider due to their implications on the eventual, adaptive response to resistance training. IGF-1 is involved in stimulating the synthesis of muscle proteins via the Akt-mTOR pathway, as discussed by Bond. Testosterone, when bound to the androgen receptor, can also stimulate this pathway in skeletal muscle resulting in increased muscle protein synthesis. Cortisol, however, seems to increase the rate of protein degradation and shunt the synthesis of proteins. Given this information, it is logical to allow a period of time to recover the endocrine system. This seems to occur after a period of reduced training stress for between 7-14 days.
Overloading training results in connective and muscle tissue damage. Muscle and connective tissues suffer microtrauma (minor tears and fraying) from training as a result of heavy loading. This damage is magnified during eccentric muscle actions. These tissues are malleable and change morphologically as a result of training in order to accommodate these demands, but this process requires time. Deloading periodically allows time for these tissues to regenerate and adapt while reducing the likelihood of severe tissue injury.
As a result of muscle and connective tissue microtrauma, an inflammatory response results in the release of cytokines which aid to signal the repair of tissue. As a part of this response, as discussed by Calle et al., local inflammation can cause a potential decrease in muscle protein synthesis as a result of increased activation of AMP-kinase activity stimulated from the cytokine Interleukin-6 (IL-6). MacDonald et al., similarly states that in the presence of low glycogen levels, IL-6 can signal AMP-k which can temporarily block the activation of the AkT/mTOR pathway discussed above. Central nervous system (CNS) fatigue from resistance training can result partly from this increase in cytokine production. Smith indicates that cytokines communicate with the CNS and, at high enough levels, can result in a feeling of sickness or an excessive feeling of fatigue. This is typically seen during a combination of both high-volume and high-intensity training, where damage to tissue can be relatively high. Further, these feelings of fatigue or being sick can decrease one’s desire to train and increases one’s desire for sleep. Periods of lighter training makes sense when evaluating this information in an effort to continue training at a high level long term and not reach an overtrained state, which could cost several weeks to several months of productive training as recovery occurs.
Simply, a deload week should involve a notable decrease in training volume and intensity, with the specifics being determined by the nature of training in the weeks prior. Practically, volume and intensity, or perceived effort, should be decreased by ~50%, on average, and training should resemble what many would refer to as “active recovery”. Similar movement patterns should occur so that blood flow distribution is specific to the tissues needing it the most. I am actively researching deloading strategies from a study involving extreme volumes of resistance training in young men hopefully to be published soon. Preliminary data indicate that deloading is a powerful fatigue management tool and can augment adaptations to training.
Thanks for reading and please let me know if you have any questions.
Chris Vann, MS, CSCS
-APLYFT Science Consultant