How Quickly You Lose Strength Gains
Every person that gets into strength training or an exercise regimen will eventually find themselves slightly paranoid about losing their progress. Maybe they have been hitting recent PR's lately and now they find themselves with a troubling injury or maybe they have gained several pounds of muscle over the last several months and find themselves without access to a gym for an extended amount of time. One of the main questions people have is how quickly do I lose my gains? For context for this article, we are focusing on strength training and its physiological effects during detraining specifically on strength and muscle mass.
First, it is important to review the physiological adaptations that occur from strength training to better understand the changes that occur following the cessation of strength training.
Effects of Strength Training
Strength training obviously increases strength, but there are several mechanisms that facilitate strength gains. For every sedentary person that starts strength training, there is a popular slogan used to describe the early stages. I am sure you have heard of “beginner gains” before. There is merit behind it. It is vital to view strength as a skill that you must learn and practice. During the initial weeks of training, neuromuscular efficiency is the predominate proponent of strength gains.
There is also the simple motor development of the movement itself, being able to perform a squat, for example, correctly and most efficiently is one of the best ways to improve strength early on. That comes with movement practice.
Without going too in-depth in it, force production is dictated in large part to the amount of motor units recruited. Motor units are made up of motor neurons and the muscle fibers that innervate it. When the motor unit is stimulated, the muscle fibers contract producing force. According to the Henneman’s size principle, smaller motor units are recruited first then the larger motor units depending on the load. These smaller motor units do not require as much stimulation and are slower yet more enduring than larger motor units that require more stimulation yet are the faster, higher force yielding muscle fibers.
There are two main ways motor units are recruited. Spatial recruitment is basically stimulating more motor units. The other is temporal recruitment which is essentially the increased frequency of neural stimulation. Both are used to increase force production.
Think about it this way. If you held an empty jug up, there are a fine amount of motor units that are needed to complete the task. The jug is not heavy, so you use the least amount of force needed to lift it up. The interesting thing is that even if you were not conscious of the amount of weight of the jug, your nervous system will still recruit the certain amount of motor units needed to complete the task. As I mentioned previously, smaller motor units are activated first because they do not require much stimulation. They also are more enduring which is why it feels like you could hold that jug up for a long time. Now what happens when water is poured into the jug and starts to become heavier? The increase in load increases neural stimulation to recruit more motor units, the larger motor units. These fibers can generate higher forces, but they are not as enduring as the smaller motor units which is why you cannot hold it up for as long.
The body essentially learns how to recruit more motor units more efficiently.
The other adaptations that occur are increases in muscle glycogen, bone density, and tensile strength.
Muscle glycogen is essentially fuel during exercise. The muscles need energy to contract and the glycogen levels provide that stored energy to meet that demand. The increase in muscle glycogen also increases water resulting in a larger cell size. They are perhaps the main reason muscles look fuller in the initial weeks of training. Real muscle hypertrophy takes time so that would mean that muscle glycogen plays a major role in muscle size early on.
Tensile strength is crucial for strength gains. Imagine a new lifter walks into a gym and tries to squat the same as his buddy who has been squatting for years. There are obviously defense mechanisms in place to avoid a disastrous injury, but the idea is still the same. In your mind, you would assume the weight would crush him. The muscles are obviously producing force, but they are attached to bones via tendons and bones are attached to other bones via ligaments. All these tissues grow and get stronger with strength training.
Bone density is one many people would not think about too often, but it is important to remember strength is a spectrum. Take someone with osteoporosis for example. Resistance exercise has been shown to maintain and increase bone strength by exerting mechanical load on the bones (Hong, 2018).
The most known effect of strength training is the increase in muscle mass, or muscle hypertrophy. This is an extraordinarily complex area and one we still are not fully knowledgeable about. However, there are three main mechanisms that are proposed for increasing muscle hypertrophy (Schoenfeld, 2010).
1) Mechanical Tension
2) Muscle Damage
3) Metabolic Stress
I do not necessarily want to breakdown those mechanisms in-depth right now, but it is important to know the proponents of muscle hypertrophy. The more important thing for this article is the adaptation in the muscle fibers.
When we lift something with adequate mechanical load, our muscle fibers must contract causing a breakdown in muscle proteins. The stretch in the muscle synthesizes a hormone called IGF-1 that increases molecules Akt and mTor that promote protein synthesis. This process is called translation.
When the protein synthesis is greater than the protein breakdown, muscle hypertrophy occurs. Therefore, adequate protein intake is required and why excessive muscle damage can be detrimental to your muscle gains.
There is a consensus that the increased capacity for translation for muscle protein synthesis is met with the addition of myonuclei (Adams, 2006). At the same time, there is a constant ratio between the amount of myonuclei and cross-sectional area of a muscle fiber. With the increase of myonuclei in the muscle fiber, the muscle fiber must grow. And thus, we have muscle hypertrophy.
There are more effects from strength training such as a decrease in body fat and increased endurance from improved cardiovascular and metabolic efficiency, but the main objective of this article is for the effects of detraining on strength and muscle mass.
Effects of Detraining
The degree of losses is determined by the duration of the detraining period and training status.
Highly trained individuals are shown to maintain strength performance for up to four weeks of inactivity with the bulk of eccentric force and sport-specific power declining significantly faster. 1 RM strength for the bench press and back squat did not have significant affect after 14 days of detraining (Hortobayo, 1993). After 8 to 12 weeks strength is shown to drop about 7-12% (Mujka, 2001). While recreational men showed little change following 6 weeks of detraining (Kraemer, WJ, 2002).
The strength losses are initially due to neural implications. As I mentioned previously, neural stimulation of motor units is a major part of strength. Periods of detraining correlate with a decrease in average intramuscular EMG. The muscle glycogen that was increased due to training will decline rapidly within even a week after cessation of training. This muscle glycogen was the fuel for the muscle which could add to the weak, lethargic feeling someone has after not training for an extended period.
When it comes to muscle fiber changes, 14 days of detraining was shown to not effect muscle fiber type distribution (Hortobay, 1993). For longer periods of detraining such as 30 weeks that were done in a study of trained women, there was a 31% decline in maximal dynamic muscle strength along with a decline of 2% in Type I fiber cross-sectional area, a 10% decline in Type IIa fibers, and a 14% decline in Type IIx fibers (Staron, 1991). These findings show a larger decline in muscular strength relative to muscle atrophy. But as we have established before, muscle glycogen and water can affect the measurements of muscle size (Bone, 2016). This could make deducing raw muscle atrophy difficult in short to moderate detraining periods.
However, what we can deduce is the rapid decline in muscular strength and Type IIx fibers. This backs the theory that the losses during detraining periods are predominately neuromuscular and with the decline of neural stimulation, the Type IIx fibers that require high stimulation to activate are not as utilized. The “use it or lose it” mantra becomes evident in this scenario.
This same study also had a 6-week retraining period following the 30-week detraining period. After 6 weeks dynamic strength was quickly retained, and all fiber types returned to training levels (Staron, 1991). This retainment supports my notion that strength is more of a skill than a physical phenomenon due to “muscle memory” that is present in any motor skill. This could also support the theory that muscle losses were most likely due to the decrease in muscle glycogen and water within the muscle given the fast re-attainment because of increased muscle glycogen to normal training levels.
When it comes to even longer periods of detraining legit muscle atrophy can occur. After 7 months, powerlifters showed a decrease of 37% in all muscle fibers (Staron, 1981) while bodybuilders showed decreases in fat-free mass after 13.5 months of detraining (Häkkinen, 1986).
Conclusion
Regular training is needed to retain strength and muscle gains. However, it appears there is a grace period if you find yourself unable to exercise for an extended period. Aerobic capacity is the first thing to decline typically occurring within days. This is due to the changes in the cardiovascular and metabolic systems that optimize efficiency. Our main concern was strength and muscle mass. The initial losses in strength are from neural mechanisms but are retained quickly because of muscle memory. The losses in muscle are initially from the decline in muscle glycogen stores and water within the muscle cell. Muscle atrophy occurs after months of detraining.
It is also worth noting that there is no way to quantify the degree of strength training losses. There are many individual variables such as the duration, training status, and even genetic makeup that can affect the rate of muscle loss.
All the losses experienced from detraining are quickly retained back to training levels within weeks of retraining. The losses are also rarely below pretraining levels meaning there is a residual effect to strength training. In essence, once you have trained and you are stronger and more muscular, these adaptations become a part of you barring +6 months of any detraining.
Hopefully, this puts the mind at ease regarding losing strength gains if you find yourself unable to train for some time.
References:
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Bone, Julia & Ross, Megan & Tomcik, Kristyen & Jeacocke, Nikki & Hopkins, Will & Burke, Louise. (2016). Manipulation of Muscle Creatine and Glycogen Changes DXA Estimates of Body Composition. Medicine & Science in Sports & Exercise. 49. 1. 10.1249/MSS.0000000000001174.
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Hong, A. R., & Kim, S. W. (2018). Effects of Resistance Exercise on Bone Health. Endocrinology and metabolism (Seoul, Korea), 33(4), 435–444.
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Mujika, I, and Padilla, S. Muscular characteristics of detrainingin humans. Med Scr Sports Exerc 33:1297-1303, 2001
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Staron RS, Leonardi MJ, Karapondo DL, Malicky ES, Falkel JE, Hagerman FC, Hikida RS. Strength and skeletal muscle adaptations in heavy-resistance-trained women after detraining and retraining. J Appl Physiol (1985). 1991 Feb;70(2):631-40. doi: 10.1152/jappl.1991.70.2.631. PMID: 1827108.
