Damage, Inc.

Damage, Inc.
Is muscle damage necessary for muscle growth?

We've all experienced it, the intense muscle pain from delayed onset muscle soreness (DOMS) that comes on a day or two after an intense workout.

Those new to working out are particularly susceptible to DOMS because their muscles are not accustomed to the strain that the weight places on their weak muscles. But you may have noticed that as your training became more and more consistent, those days of not being able to comb your hair, or walk up a flight a stairs without difficulty due to severe DOMS have gotten few and far between. These days you really have to train like a maniac to get just the slightest DOMS in your pecs or biceps.

Some of you may be worried about this lack of muscle soreness with your training.

Maybe you're not doing it right. After all, if you've read anything about muscle growth you know that muscles grow by being damaged and then rebuilt bigger and stronger than they originally were. Right? While muscle damage does definitely lead to muscle growth and strength gains, there is some debate over whether or not it's absolutely critical for long-term muscle growth. Get out your microscopes. In this article, I'll take you deep into the muscle cells to look at how a muscle grows and investigate whether or not muscle damage is completely critical for muscle growth.

There is a lot of research that's been done on muscle damage and its effects on muscle hypertrophy.

In fact, we know a lot about the processes involved in muscle damage and how they influence muscle growth. Muscle damage can happen from mechanical or chemical stress. Here is a brief and simple rundown on what we currently know about it.

Muscle damage from mechanical stress usually occurs when lifting heavy weight.

In simple terms, muscle fibers contract by a ratchet mechanism. A specific protein called myosin connects to another protein actin, and pulls the actin closer. Thousands and thousands of actin and myosin connections are occurring in each muscle fiber when you lift a weight. This action shortens the muscle and is basically how a muscle contracts to lift a weight.

Consider the shortening of your biceps muscles as your arms flex at the elbows to curl a barbell.

Then when you lower the weight back down, the muscle must lengthen. To do this the myosin allows the actin to slide back to its original position and then it disconnects. However, when the weight is extremely heavy, the muscle fiber often cannot resist the weight back down and the force of the weight literally tears the myosin right off of the actin. This shearing force also damages other critical structures of the muscle fiber.

Even when you're not using heavy weight, similar muscle damage can occur.

When the muscles become fatigued from performing too many reps, again they have difficulty resisting the weight when the muscle fiber is lengthening. And again, the actin and myosin are forcibly ripped apart, causing damage.

This type of damage is similar to a wound that you get anywhere on your body.

And immediately following the damage ensues an inflammatory response that eventually leads to healing of the muscle fiber, but even bigger and stronger than it previously was. This inflammatory response is a long cascade of events involving many different white blood cells, cellular signaling messengers, chemicals, fluid, growth factors, and special cells known as satellite cells.

Once damage happens, the first cells to arrive on the scene are neutrophils.

These specialized white blood cells secrete chemicals, such as enzymes and toxic chemicals, that further break down the damaged tissue. Following on the heels of the neutrophils are another type of white blood cells, macrophages. Once the tissues are adequately decomposed, the neutrophils and macrophages literally consume them and remove them from the site in an effort to clear it out and prepare for the makeover. Think of this as if your house caught fire. You would have to rip out all of the damaged structure, appliances and furniture before you could rebuild and replace them. While all this breaking down and gobbling up is going on within the muscle cell, large amounts of fluid are filling it up, as well as the surrounding area, causing swelling.

Muscle damage can also happen from chemical stress within the muscle fibers.

During exercise, especially aerobic exercise, such as cardio, or during high rep sets, when you are using more oxygen, reactive oxygen species (ROS) or free radicals form. These ROS can damage muscle fibers and instigate a similar cascade as mechanical damage discussed above. There is even some belief that the high acidity levels that develop inside muscle cells during intense workouts can damage muscle fibers.

Regardless of whether the damage is mechanical or chemical, there are several ways that muscle damage leads to increased muscle growth.

Once the damaged tissue has been cleaned up and removed, it's time to rebuild the house, er muscle cell. The macrophages that helped to clean up and remove the damaged tissue also secrete chemicals that attract cytokines and growth factors, such as interleukin-6, (IL-6), IL-7, IL-8, IL-10, IL-15, and fibroblast growth factor (FGF), to name a few. These all play a small, but critical role in numerous processes that eventually lead to the activation and growth of satellite cells. Satellite cells are specialized muscle stem cells. These cells sit dormant in a muscle, but then migrate to the area of damage bringing their nuclei into the muscle cell. The satellite cells fuse into the existing muscle fiber, typically becoming one cell, but now with more nuclei. Since the nuclei of muscle cells are the headquarters where muscle building originates, the more nuclei that a muscle cell contains, the bigger and stronger it can grow. And over time the muscle grows bigger and stronger.

Satellite cells are the real critical factor in how big a muscle can get.

Studies confirm that weight-trained subjects with greater muscle mass have more nuclei per muscle fiber/cell. The higher nuclei content has also been shown to be responsible for the phenomenon known as "muscle memory", where a previously trained person can rebuild muscle that they lost faster than someone who never had the muscle mass to begin with. That's because the extra nuclei build up more muscle protein quicker than can occur with fewer nuclei.

As discussed in my previous articles on growth factors: click on the links below to read these two articles.



insulin-like growth factor-I (IGF-I) also plays a critical role in damage-influenced muscle growth. Locally expressed IGF-I in muscle tissue helps to activate the satellite cells, enhance their fusion into existing muscle cells, and promote their growth. Even the ROS that are known to cause muscle damage may play a role in enhancing muscle growth after the storm. Just one of the few ways ROS do so is by enhancing IGF-I's actions.

The cell swelling that comes with the inflammation from damaged muscle can also help encourage muscle growth.

When a muscle cell fills with fluid, it places a stretch on the muscle cell membrane. This stretch signals the cell to increase the size and strength of its structure to prevent the swelling from literally popping the cell. To do so, the muscle cell increases muscle protein synthesis and simultaneously decreases muscle protein breakdown. This is one reason why supplements such as creatine, taurine, and glutamine, which can pull more fluid into the muscle cells can help to increase long-term muscle growth.

Clearly muscle damage is a good thing when it comes to building muscle.

After all, the only way to maximize muscle size is to increase the number of nuclei in the muscle cells to as many as possible. Yet causing muscle damage is a difficult thing the more training experience you have.

Bodybuilders with at least a few years of consistent training under their belt can tell you that they rarely get sore unless they really take on severely intense training with unique intensity techniques that they haven't done in a while.

That's because the muscle builds up a protective mechanism against muscle damage. Exercise scientists refer to this as the "repeated bout effect". Although scientists are unsure of precisely why this happens, the fact is that once you damage a muscle fiber, it is next to impossible to damage it again, at least for several months.

Luckily muscle cells have more than one trick up their sleeve to grow.

In addition to adding new nuclei to damaged muscle fibers, muscle also grows by increasing the amount of protein it contains. A muscle is composed primarily of protein. At least the structural components of it are. So another way that muscle grows is by synthesizing more muscle protein, through a process termed muscle protein synthesis.

Muscle protein synthesis is the build up of muscle protein one amino acid at a time.

This takes place in and around the nuclei of the muscle cell. In the nuclei, the DNA house the genes which encode the sequence of each specific protein a muscle contains. When the nuclei receive a signal to activate certain genes to build more protein, it replicates the sequence of the proteins with messenger RNA (mRNA). The mRNA then leaves the nuclei and single amino acids are brought together to form a long chain that makes up the protein that builds up the muscle. Of course, this is a very simplified recount of what actually takes place.

One major way that the nuclei receive the signal to activate genes and synthesize more muscle protein is from working out.

Both the mechanical stress from the weight being lifted and the chemical stress produced inside the muscle from generating energy to contract, activate genes to increase muscle protein synthesis. Numerous chemicals and biochemical pathways are involved in creating these signals, but some of the major players include: mTOR (mmammalian target of rapamycin), MAPK (mitogen-activated protein kinase), testosterone, growth hormone, IGF-I, cytokines, and insulin.

As long as adequate amino acids are supplied to the muscles during and after the workout (hence, be sure to get in your pre and postworkout shakes), muscle protein synthesis following workouts will produce significant increases in muscle growth.

Yet, muscle protein synthesis from one nuclei can only produce so much muscle growth. So the best strategy is to not only train to maximize muscle protein synthesis, but to also increase muscle cell nuclei number. With more muscle cell nuclei you get greater muscle protein synthesis in each muscle cell and that leads to the greatest muscle growth.

So how do you maximize both muscle protein sythesis and muscle cell nuclei content when muscle damage becomes more and more difficult to achieve with the more training experience you gain?

See my strategies below.

The key to continually growing despite a greater difficulty in incurring muscle damage is to cycle your training to induce muscle damage through a number of different training techniques and utilize techniques to encourage greater muscle protein synthesis.

Try using these steps below in your long-term training plan to keep on growing, and growing, and growing...

Step 1: Get Negative – Perform one workout for each muscle group that involves negative rep training. To do this choose weight that is about 20% greater than the amount you can lift normally for one rep. Have a spotter assist you on the positive. Do 3-4 exercises per muscle group. Do 1-2 sets of 3-5 negative reps (resist the negative rep for about 3-5 seconds) for each exercise. Follow the negative rep sets of each exercise with 2 sets of regular reps for 3-6 reps. Do this work out just once every 2-3 months. Repeating it sooner won't offer much benefit due to the repeated bout effect.

Step 2: Lighten Up – The week following your negative rep training, keep weights light and reps high at about 15-20 per set. Not only do you want to train light because your muscles will be sore and weaker following the negative rep training, but the higher rep range will cause more metabolic stress in the muscle fibers, which will encourage greater muscle protein synthesis. You can repeat this week one or two more weeks in a row, if you prefer.

Step 3: Get Frequent – As discussed above, increasing muscle protein synthesis occurs by activating genes that encode for specific proteins in the muscle. Genes are turned on in the muscles trained, leading to higher protein synthesis and muscle growth. Some genes are turned on for only hours, others are turned on and stay on for several days. If you train a muscle group once per week then when you train you increase activity of these genes by a certain percent. By the time you train that muscle again a week later, the activity of those genes is back to previous levels. And when you train that muscle group again you increase the activity by about the same percent. If the normal resting level of gene activity was 0% and the activity increased by 100% after a workout, then each time you worked that muscle once a week you increased gene activity by 100%. But if you worked out before gene activity dropped to 0% you might be able to boost gene activity by more than 100%. Say you worked out again 2 days later and gene activity was still up to 50%. Training again, might allow you to increase that gene activity to 150%, which could lead to greater muscle growth. This is called the staircase effect. For 2-3 weeks, train each muscle group a minimum of twice per week and preferably 3 times per week. Your best bet is to use a two-day split that trains all the muscle groups over two workouts. Repeat the workouts three times each week. Of course, total sets per muscle group will have to drop to allow time to train so many muscle groups each workout. But remember that you will be hitting that muscle group again in two days. By the end of the week you would still have completed more total sets for t hat muscle group than you would have with the one workout per week.

Step 4: Go Beyond Failure – You've already damaged your muscles with mechanical stress from negative rep training. That increased the nuclei content of your muscles. Then you used high rep training followed by high frequency training to increase the muscle protein synthesis from those nuclei. Going back to negative training won't likely provide further damage for another month or so. So how can you encourage a further increase in muscle nuclei content? With chemical muscle damage. Now is the time to truly exhaust your muscle fibers and take them to the point of true muscle failure and beyond. For the next 2-3 weeks keep reps in the sweet spot for muscle growth, 8-12 reps per set, and do 3-4 forced reps at the end of every working set. If you train alone, you can do forced reps on single limb exercises such as dumbbell concentration curls by assisting with the non-working arm. For bilateral exercises such as the bench press, use drop sets instead. Going past muscle failure will produce metabolic waste products that can lead to chemical-induced muscle damage and help to bring more nuclei into the muscle cells. Going past failure will also place mechanical stress and metabolic stress on the muscle fibers to increase growth through muscle protein synthesis.

To do forced reps – take the set to muscle failure, then have a partner (or your non-working limb) help you perform 3-4 more reps by supplying just enough help to get you through the rep.

To do drop sets – take the set to muscle failure, then immediately remove 20-30% of the weight and continue until reaching muscle failure again..

Step 5: Lighten Up Even More – Now that you've incurred some muscle damage through chemical means and hopefully increased your muscle nuclei content again, it's time to allow your muscles to recover and focus on boosting muscle protein synthesis. For the next 1-2 weeks keep your rep range at 25-30 per set. Several recent studies have shown that using a very light weight for very high reps increases muscle protein synthesis better than using very heavy weight for low reps.

Step 6: Periodize –For the next four weeks follow a workout schedule where you train each muscle group once per week and each week the weight gets heavier and reps get fewer. Consider using the rep ranges in my Micro Muscle eBook for each of the four weeks: week 1 = 12-15 reps, week 2 = 9-11 reps, week 3 = 6-8 reps, and week 4 = 3-5 reps. Weeks 1 and 2, and even week 3 will help to increase muscle protein synthesis. Weeks 3 and 4 work to maximize muscle strength, which is also important for encouraging muscle growth. The stronger you are the more overload you can place on a muscle. And that overload can help to increase muscle growth and it can increase muscle damage, leading to further muscle growth. This strength will be important when it's time to cause some mechanical damage again, as the more weight you can handle the more muscle damage you can incur. Feel free to follow the Micro Muscle program and repeat these four week cycles two more times.

Click here for the eBook page:


Step 7: Reduce Your Rest – Set a four-week training program that starts with rest at two minutes per set. Each week reduce rest periods by 30 seconds so that in week 4 you are resting just 30 seconds per week. A recent study found that subjects reducing their rest time between sets over an 8-week training period increased muscle mass better than those keeping their rest periods steady at 2 minutes. The constant dropping of rest between sets produces metabolic stress on the muscles, which encourages an increase in muscle protein synthesis. Like one of the key players in this strategy is locally produced IGF-I in the muscle fibers.

Step 8: Repeat – By now at least three months should have elapsed since you last trained with negative reps. The protection of the repeated bout effect should have elapsed and you can finally enjoy some negative-rep induced muscle damage, along with the DOMS and satisfaction of knowing that you're increase muscle nuclei content, and that is going to help you maximize your muscle growth.


Schoenfeld, B. Does exercise-induced muscle damage play a role in skeletal muscle hypertrophy? J Strength Cond Res, in press, 2012.

Tidball, J. G. Inflammatory processes in muscle injury and repair. Am. J. Physiol. Regul. Integr. Comp. Physiol. 288: 345-353, 2005.

Koh, T. J. and Pizza, F. X. Do inflammatory cells influence skeletal muscle hypertrophy? Front. Biosci. (Elite Ed) 1: 60-71, 2009.

Nielsen, A. R. and Pedersen, B. K. The biological roles of exercise-induced cytokines: IL-6, IL-8, and IL-15. Appl. Physiol. Nutr. Metab. 32: 833-839, 2007.

Quinn, L. S. Interleukin-15: a muscle-derived cytokine regulating fat-to-lean body composition. J. Anim. Sci. 86: E75-83, 2008.

Serrano, A. L., et al. Interleukin-6 is an essential regulator of satellite cell-mediated skeletal muscle hypertrophy. Cell. Metab. 7: 33-44, 2008.

Aoi, W., et al. Oxidative stress and delayed-onset muscle damage after exercise. Free Radic Biol Med. 2004 Aug 15;37(4):480-7.

Handayaningsih, A., et al. Reactive oxygen species play an essential role in IGF-I signaling and IGF-I-induced myocyte hypertrophy in C2C12 myocytes. Endocrinology 152: 912-921, 2011.

Clarke, M.S. and Feeback, D. L. Mechanical load induces sarcoplasmic wounding and FGF release in differentiated human skeletal muscle cultures. FASEB J. 10: 502-509, 1996.

Bruusgaard, J. C., et al. Myonuclei acquired by overload exercise precede hypertrophy and are not lost on detraining. Proc Natl Acad Sci U S A. 2010 Aug 24;107(34):15111-6.

Dangott, B., et al. Dietary creatine monohydrate supplementation increases satellite cell mitotic activity during compensatory hypertrophy. Int. J. Sports Med. 21: 13-16, 2000.

Haussinger, D. The role of cellular hydration in the regulation of cell function. Biochem. J. 313 ( Pt 3): 697-710, 1996.

Lang, F. Mechanisms and significance of cell volume regulation. J. Am. Coll. Nutr. 26:613S-623S, 2007.

Low, S. Y., et al. Signaling elements involved in amino acid transport responses to altered muscle cell volume. FASEB J. 11: 1111-1117, 1997.

McHugh, M. P. Recent advances in the understanding of the repeated bout effect: the protective effect against muscle damage from a single bout of eccentric exercise. Scand. J. Med. Sci. Sports 13: 88-97, 2003.

Tee, J. C., et al. Metabolic consequences of exercise-induced muscle damage. Sports Med. 37: 827-836, 2007.

Goldspink, G. Gene expression in skeletal muscle. Biochem Soc Trans 30: 285–290, 2002.

Hornberger, T. A. and Chien, S. Mechanical stimuli and nutrients regulate rapamycin-sensitive signaling through distinct mecha- nisms in skeletal muscle. J Cell Biochem 97: 1207–1216, 2006.

Vandenburgh, H. H. Motion into mass: How does tension stimulate muscle growth? Med Sci Sport Exerc 19(5 Suppl.): S142–S149, 1987.

Rooney, K. J., et al. Fatigue contributes to the strength training stimulus. Med Sci Sport Exerc 26: 1160–1164, 1994.

Schott, J. et al. The role of metabolites in strength training. II. Short versus long isometric contractions. Eur J Appl Physiol 71: 337–341, 1995.

Smith,R. C. and Rutherford,O. M.Theroleofmetabolitesinstrength training. I. A comparison of eccentric and concentric contractions. Eur J Appl Physiol Occup Physiol 71: 332–336, 1995.

Schoenfeld, B. J. The mechanisms of muscle hypertrophy and their application to resistance training. J Strength Cond Res. 2010 Oct;24(10):2857-72.

Booth, F.W. and Neufer, P.D. Exercise controls gene expression. American Scientist. 93: 28-35, 2005.

Pilegaard, H., et al. Transcriptional regulation of gene expression in human skeletal muscle during recovery from exercise. American Journal of Physiology: Endocrinology and Me- tabolism 279:E806–E814, 2000.

Williams, R. S., and P. D. Neufer. 1996. Regulation of gene expression in skeletal muscle by contractile activity. In: Handbook of Physiology: Section 12: Integration of Motor, Circulatory, Re- spiratory, and Metabolic Control during Exercise, ed. L. B. Rowell and J. T. Shepherd. Oxford University Press: New York. pp. 1124–1150.

Souza-Junior, T. P., et al. Strength and hypertrophy responses to constant and decreasing rest intervals in trained men using creatine supplementation. Journal of the International Society of Sports Nutrition 2011, 8:17.


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