The purpose of weight training is to make your muscles stronger and larger. To achieve this, you have to place more stress on the muscles than they’re accustomed to creating muscle damage. Yet, you have to do this in a controlled manner to avoid injury or overtraining the muscles you’re working. In response to this controlled stress, muscles adapt and become larger and stronger to accommodate the additional burden placed on them.
We also know that when you lift hard, you damage muscle fibers. This damage consists of microscopic tears in the muscle fibers that make up the muscle and may involve injury to the contractile elements within the muscle fiber as well as the surrounding tissue, the connective tissue that surrounds each muscle fiber. In response to injury, some, but not all studies, suggest that inflammation ensues and inflammatory cells, like macrophages, flock to the damaged muscle tissue, in much the same way a cut or burn on the skin activates an inflammatory response. These inflammatory cells release chemicals called myokines that help ramp up the production of new muscle tissue.
The Role of Satellite Cells in Muscle Hypertrophy
Muscle cells also swell and take up more water in response to damage. But, that’s not all. Another group of cells is involved in repairing the damaged muscle tissue. These cells, called satellite cells, freely donate their nuclei to damaged muscle cells to help them repair. They can do this because, unlike most cells in the human body, satellite cells have more than one nucleus. Furthermore, the nucleus houses the DNA that codes for the proteins muscle cells need to repair properly. It’s this repair process that leads to hypertrophy or muscle growth. The nuclei from the satellite cells are donated toward making new myofibrils within muscle fibers and toward increasing the size of pre-existing ones. As the myofibrils, with their contractile elements, grow in size and number, the muscle becomes larger and stronger.
In reality, it’s a bit more complicated than this, as hormones and hormone-like factors, also play a role in muscle repair and hypertrophy. In fact, hormone-like factors help to activate the satellite cells. Some of the key players in this hormonal symphony are hepatocyte growth factor and fibroblast growth factor. But, some of the most important are insulin and insulin-like growth factor one, or IGF-1 as well as the anabolic hormone growth hormone. IGF-1 is released from tissues in response to growth hormone.
Once released, IGF-1 plays a key role in turning on one of the most important pathways for muscle protein synthesis, the mTOR pathway. Key activators of the mTOR pathway are IGF-1, resistance exercise, and amino acids from protein. That’s why getting enough protein is important for muscle growth. It appears that muscle tension alone can turn on the mT0R pathway, even in the absence of IGF-1.
Do You Need Muscle Damage to Get It to Hypertrophy?
One question is whether you need to damage the muscle to get it to grow or whether mechanical tension is enough. You subject your muscles to mechanical tension with every repetition of an exercise that you do. Is mechanical tension enough to induce muscle growth or do you also need to damage the muscle? It’s not as clear-cut as you might hope.
As you know, there are three main types of muscle contractions. Isometric contractions where you hold tension, but the joint angle or muscle tension doesn’t change. Concentric contractions are where the muscle shortens against resistance. An example is the upward movement of a biceps curl when you bring the weights toward your shoulders.
In contrast, eccentric contractions are where the muscle lengthens while holding tension. An example of an eccentric contraction is the downward phase of a biceps curl where your arms return to the resting position as you lower the weight in a controlled manner. Eccentric contractions create more muscle damage than concentric contractions – and most studies show that eccentric contractions lead to greater strength gains and muscle hypertrophy than concentric contractions.
For this reason, some experts believe that muscle damage is an important driver of muscle growth since eccentric lead to more damage AND more muscle hypertrophy. But, it’s not so clear-cut. Some studies suggest that concentric contractions may be as effective or even better for muscle growth, although these studies are the minority.
Why This Issue Matters
You might wonder why it matters whether muscle damage is a prerequisite for muscle hypertrophy. Some hardcore bodybuilders train their muscles super hard in the belief that muscle damage is the key trigger for muscle hypertrophy. In fact, blasting muscles to the point of feeling stiff and sore is almost a badge of honor. Some bodybuilders don’t feel like they’ve had an effective workout unless the train their muscles to the point of failure. Plus, muscle soreness is often used as a marker of muscle damage. But, based on research, soreness isn’t necessarily correlated with damage.
Plus, there are disadvantages to working a muscle to the point of soreness and stiffness. Training a muscle to the point of muscle damage reduces its force and power output and necessitates more recovery time. So, working the muscle to the point of exhaustion and soreness too often might be detrimental. At the very least, your muscles need more recovery time when you work them that hard. All in all, the verdict is still out about how important muscle damage is to changes in muscle size and you also have to consider the downsides of working your muscles too aggressively.
The Bottom Line
It’s not clear whether you need to damage a muscle to get it to hypertrophy. However, we do know that eccentric contractions create more muscle damage and also more effective for hypertrophying a muscle. So, emphasizing the eccentric portion of an exercise during some sessions may pay off with more growth as you become more advanced. But, don’t overdo it by pushing your muscles hard every time you train. That will only compromise your performance on your next workout and there’s no strong evidence that you need to do this to get your muscles to grow. However, occasionally blasting your muscles will shock them out of complacency and help you avoid reaching a plateau.
References:
J Strength Cond Res. 2012 May;26(5):1441-53. doi: 10.1519/JSC.0b013e31824f207e.
J Exp Biol. 2011 Feb 15;214(Pt 4):674-9. doi: 10.1242/jeb.050112.
Med. Sci. Sports Exerc. 27: 868-873, 1995.
J Strength Cond Res. 2012 May;26(5):1441-53. doi: 10.1519/JSC.0b013e31824f207e.
Physiological Reviews, Volume 84, 209-238. (2004)
Br J Pharmacol. 2008 Jun; 154(3): 557–568. Published online 2008 May 26. doi: 10.1038/bjp.2008.153.
The Mystery of Skeletal Muscle Hypertrophy. Richard Joshua Hernandez, B.S. and Len Kravitz, Ph.D.
Journal of Trainology 2012;1:36-44.
Related Articles:
Strength Training: 5 Rules for Training to Failure
What Does Research Show about Partial Reps vs. Full Reps for Strength Training?
The Repeated Bout Effect: Why You Don’t Always Get Sore When You Lift Weights
How Your Muscles Repair after a Workout and How It’s Linked with Hypertrophy
Related Cathe Friedrich Workout DVDs:
STS Strength 90 Day Workout Program
All of Cathe’s Strength & Toning Workout DVDs
Total Body Workouts
Lower Body Workouts
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