What is Muscle Atrophy?
Muscle atrophy is a term used to describe the loss of muscle. Atrophy may occur from injury, starvation, disease, bed rest, nerve damage, and other health-related issues. To understand how our bodies could be affected by experiencing muscle atrophy we need to think of how we rely on our muscles. The muscular system provides strength, endurance in movement, stabilization, and protection. Muscles are able to contract and relax, moving or stabilizing the joints they cross. If atrophy has occurred then the motion that would normally happen at the joint would be compromised. This would mean less strength and endurance during the movement, along with potentially less stabilization around the joints crossed. Atrophy can leave our bodies at a higher risk of injury due to lack of neural control of muscles that would normally be responsible for stabilizing and coordinating movement.
Is it Size or Strength?
When muscle atrophy occurs, do we lose just muscle size or do we lose strength as well? To answer this we need to know what occurs in the body when size and strength are gained.
Hypertrophy is the growth of skeletal muscle fibers in response to overcoming force from high volumes of tension. It occurs when muscle cells regenerate from progressive resistance training programs (1). Hypertrophy can also be described as an increase in the cross-sectional area of the muscle. This result is from an increase in the size and number of myofibrils per muscle cell, as well as an increase in structurally-related muscle tissue, such as ligaments and tendons along with an increase in stored nutrients and enzymes in the muscle fibers to break down and resynthesize ATP (1). The muscles also store more ATP and CP. This process helps in activities that involve strength, power and speed (2). With this increase in muscle mass other soft tissue will be more tolerable to higher amounts of stress without damage (3-5). Muscle atrophy would reverse these hypertrophy benefits. This muscle loss would result in loss in strength, stabilization of skeletal structure, and durability of resisting forces from opposing tension.
Hypertrophy can occur without major increases in strength, but there has also been shown a correlation of increases in strength as well as in the cross-sectional area of muscle (6). Premier Global NASM notes that strength is the ability of the neuromuscular system to produce internal tension in order to overcome an external load (1). The ability to gain strength can occur without dramatically increasing size. Gaining strength but not size directly relates to changes in the nervous system. This increase is from the coordination of muscles during weight training exercise — an increase in synchronization, recruitment, and firing of motor units (2).
There are variables that come into play to determine if you are going to gain size or maximal strength. By lifting heavy loads, keeping lower repetitions (1-5), having longer rest periods (3-5 min.), and nourishing your body without having a caloric surplus you’ll have the ability to improve strength with little to no gain in size (1).
If muscle atrophy occurs for individuals that have trained more for strength over size, they will still suffer from the same losses that one would from training for size. There would be a loss of strength, loss of neuromuscular coordination, a loss of endurance, and an increase in injury risk. Muscle atrophy isn’t just about losing size, it will also be a loss in strength.
Does muscle turn to fat if you don’t work out?
For years the urban legend that muscle turns to fat has been on the minds of many. The conversations regarding this concept have reverberated through the rows of exercise machines and the walls of locker rooms. It’s time to let this urban legend and gym rat campfire ghost story finally go away.
As we dive into the subject of muscle atrophy, many think if you lose muscle that it has to go somewhere, so it must turn into fat. When muscle atrophy occurs it is most often from lack of activity for an extended period of time. As protein degradation exceeds protein resynthesis your muscles are shrinking and your metabolism is likely requiring less calories to support the muscle. If you are losing muscle and you seem to be increasing body fat, it is most often due to a caloric surplus from not moving as much and consuming too many calories. This shift seems to be why people have assumed that muscle turns to fat.
By not regularly strength training and not having a proper nutrition plan in place, there is a much greater chance of body fat increasing. This is not because your muscle turned to fat, it’s because the ideal environment was created for fat stores to grow, and the worst opportunity for muscle to develop.
Minimum needed to maintain strength (and size)?
The concept of bare minimum work to maintain size and strength is challenging because of how complex our bodies truly are. Ideally, if we were nourishing our bodies properly with the right quality and quantity of what we needed, were handling stress well, keeping in proper homeostasis and all other systems were running well, the average person may maintain their body’s strength and size with just 2 to 3 resistance training workouts a week. (Don’t forget to include cardio training as part of your overall fitness routine!)
The problem that happens is that we do not live in the perfect scenario to keep ourselves in a maintenance phase. Many factors become challenges. This includes hitting a plateau, meaning if your body is no longer receiving the increased stimulus it once received from your workouts, you may not experience the same benefits you once did. If stress has increased in your life, cortisol levels may hinder your ability to maintain your strength and size. If sleep is compromised, this could also impact your progress.
Knowing the bare minimum to maintain strength is good, but do not lose site that fitness programs need to progress, typically every 4 to 8 weeks. Another consideration is to also know your numbers in other aspects of fitness and health. Know your 1 repetition max (1 RM) for various exercises, your VO2 score for cardio and your body fat percentage as well. If you have access to metabolic testing and blood panels, these are also important to know. Being proactive is key to keeping your size and strength.
How long can you go before strength begins to decrease?
Studies have shown that within a week there are molecular signs of atrophy. Depending on the muscle group, the time varies, with lower body muscles showing signs of atrophy quicker (7-8).
What if looking to “debulk”?
For anyone wanting to “debulk” or reduce muscle size, look first at items that could give you clarity if that’s truly the goal. Losing muscle is actually a lot easier than losing fat and yet more difficult to gain back up. If you find out through monitoring your body fat percentage that you can stand to actually lose fat instead, my recommendation would be to focus efforts toward that goal.
If you truly need to reduce muscle mass, consider the healthiest ways possible to do so. Avoid workout styles that promote gaining muscle mass, and instead focus on ones that concentrate on strength or endurance. If following the Premier Global NASM OPT model, skip phase 3 (hypertrophy), and target the higher rep ranges for phases 1 and 2, and lower rep ranges in phases 4 and 5 with the appropriate training variables. Don’t forget to include cardio training as well.
Nutrition also plays a major role in “debulking.” You would benefit by being in a caloric deficit to lose the weight. During this time you would still want to eat as healthy as you can with meals that consist of all three macronutrients (protein, carbohydrates and fat).
Homeostasis is the balance of our sympathetic (flight or flight) system and parasympathetic (rest, restore and recover) system. To maximize results and improve performance these systems need to be balanced. Our muscles are similar in needing muscular homeostasis.
Exercise routines need to be progressive and challenging, but also allow for proper recovery. Assessments need to be given to ensure proper body mechanics during the exercises. If synergistic dominance is occurring muscles may no longer be participating in an ideal length tension relationship, which may result in atrophy of compensated muscles. By addressing these compensations and including the needed techniques to correct them the body can be brought back to moving with efficiency.
When I think of atrophy I think of the grim reaper for meat heads. As a fitness professional, atrophy is what we normally fight to avoid at all costs. Like many challenges we face in our pursuit of improving performance and getting healthier, it takes a whole life approach. Every aspect of your life plays a role in your success. By developing a positive relationship with physical activity and lifestyle behaviors, atrophy will hopefully be something you can help your clients (and yourself) avoid.
- Clark M, Lucett S, McGill E, Montel I, Sutton B. (editors). (2018) NASM Essentials of Personal Fitness Training (6th ed). Burlington, MA: Jones & Bartlett Learning.
- Boone, T. (2014) Introduction to Exercise Physiology. Burlington, MA, Jones & Bartlett Learning.
- Almstedt H, Canepa J, Ramirez D, & Shoepe T. (2011) Changes in bone mineral density in response to 24 weeks of resistance training in college-age men and women. J Strength Cond Res. 2011;25:1098–1103.
- Folland J & Williams A. (2007) The adaptations to strength training: Morphological and neurological contributions to increased strength. Sports medicine (Auckland, N.Z.). 37. 145-68.
- Hinton P, Nigh P, & Thyfault J. (2015) Effectiveness of resistance training or jumping-exercise to increase bone mineral density in men with low bone mass: A 12-month randomized, clinical trial. Bone. Oct;79:203-12. doi:10.1016/j.bone.2015.06.008.
- Maughan R, Watson J. & Weir J. (1983) Strength and cross-sectional area of human skeletal muscle. Journal of Physiology, 338:37-49.
- LeBlanc AD, Schneider VS, Evans HJ, et al. (1992) Regional changes in muscle mass following 17 weeks of bed rest. Journal of Applied Physiology. 1992;73:2172–2178.
- Salanova M, Gambara G, Moriggi M, Vasso M, Ungethuem U, Belavy D, Felsenberg D, Cerretelli P, Gelfi Cecilia, Blottner D. (2015). Vibration mechanosignals superimposed to resistive exercise result in baseline skeletal muscle transcriptome profiles following chronic disuse in bed rest. Scientific Reports. 5(5):17027. doi: 10.1038/srep17027.