Workout Wednesday: The Biological Basis of Bulk

Pop quiz: Joe weighs 150 lbs. and decides that he wants to start working out in the weight room on a regular basis to gain some muscle mass.  Through consistent work at his new routine, Joe gained thirty pounds of muscle! By what percentage did the number of Joe’s muscle cells increase?

Answer: Zero percent! When a person gains muscle mass, the number of muscle cells does not change, but the size of each of those muscle cells increases! How does this work?

bulkAs we know from experience, people gain muscle mass and strength by working out the muscles that they are targeting.  What is actually happening on a cellular level within each of the muscle cells of the body is the basis for gaining muscle mass, even though we don’t gain more muscle cells.  It all starts with trauma to the muscle; that is what exercise does, even healthy amounts of careful exercise cause small amounts of damage to the muscle. This damage activates a different type of cells called “satellite cells” to come to the aid of the damaged muscle cells in efforts to repair them. These satellite cells fuse to the muscle cells and create new strands of protein within the muscle cell, called myofibrils.  As this process is happening, it is still only happening in a single muscle cell, but that cell is accumulating more myofibrils and making existing myofibrils larger as they are repaired and this is what causes the muscle to grow in size. The extra muscle fiber can allow creation of more actin and myosin in muscle cells, which are the “contractile myofilaments” that contribute to muscle strength! (1).

Also, as you exercise muscles, the number of capillaries to that muscle increases, which allows more blood flow to that part of the body, and muscle cells develop more mitochondria due to regular exercise.  The mitochondria “convert chemical energy into energy the cells can use” (2). The increased amount of both capillaries and mitochondria in the muscle cells also contributes to the increase the size of the overall muscle. A good thing to know if you lift weights regularly is that high repetition sets are good for building up more mitochondria, so while low reps with high weight are also beneficial for increasing muscle size, adding sets of high reps with lower weight will also be good for increasing muscle strength. As with any exercise routine, it’s all about balance and variety. Regularly exercising a muscle also increases the ability of the muscle cells to store glycogen, which is the storage form of energy in the body and can be broken down and used within the muscle to provide energy for working muscle cells when they are exercised (2).

The scientific term for increasing muscle mass is “muscle hypertrophy.” Muscle hypertrophy is affected directly by hormone levels specific to each person’s body, and one main hormone affecting muscle hypertrophy is testosterone. Testosterone “can stimulate growth hormone responses in the pituitary, which enhances cellular amino acid uptake and protein synthesis in skeletal muscle” (2).  This is part of the reason that men typically gain muscle mass much more easily than women, because although both men and women have testosterone as a regulatory hormone in their bodies, the levels are much higher in men. Due to differences in other regulatory hormones, at the same BMI, a healthy women will also have a higher level of body fat than men because this is required for normal bodily processes and for women to be able to have children (3).

This is a pretty basic understanding of how muscles grow, but I found it really interesting! I also found this video illustrating the things that were explained above in what I thought was a fun and simple way! But whether you’re trying to bulk up or not, don’t worry about the fact that working out damages your muscle fibers—the repair process is completely normal and necessary and virtually all cells in our bodies need repair on a regular basis. Just make sure to maintain proper form and safety precautions when lifting weights to prevent unnecessary damage to joints and tendons, which are much, much harder to repair!

Workout Wednesday blog posts are written by UNC Campus Recreation staff members. Each Wednesday we’ll be swapping blog posts with the Tarheel Tone Up blog so that readers can view more diverse post topics that will benefit their health and wellness. Workout Wednesday blog posts can be found both here and on

Workout Wednesday: Five Health Benefits Of Regular Exercise That You Can’t Get From Good Nutrition Alone

by Emily Wheeler

On Tuesday, I talked about the health benefits of good nutrition that you can’t reap just from exercising regularly and, as promised, today we’re exploring the opposite topic: what are some of the heath benefits of exercising regularly that we can’t get simply from having healthy dietary habits?

1.   It not only reduces, but reverses the effects of stress on our bodies, and can help to lessen depression! If there is something that all college students have in common, I would have to say that it would be stress.  Even in this big bundle of diversity that we call UNC, we all have the common factor of stress, because there is most likely something in each of our lives that keeps us on edge, whether that thing is grades, our parents, money, or just figuring out what we’re doing with our lives.  Over time, stress can cause some wear and tear to our bodies, which translates into faster aging of our tissues as well as mental side effects, such as depression, which can then translate into more stress because it makes it even harder to overcome the thing that causes us stress! However, the good news is that a study from the University of California—San Francisco in 2010 showed that exercise can actually create a visible difference in the physical aging of and damage to our individual cells.  Stressed out women exercising for as little as 45 minutes a day for 3 days (only three days people! That’s the time between now and the blog I posted on Tuesday!) had cells that “showed fewer signs of aging compared to women who were stressed and inactive.” It is also proven to lessen depression by releasing chemicals in the brain that work to make us happier and more satisfied with our lives from a scientific perspective. Wrinkle cream? Try exercise instead.

2.     Hello muscle mass! Everyone knows that if you want to bulk up and add some extra muscle mass to your already schmexy body, all you have to do is walk around eating protein bars and drinking protein shakes and your muscles will just automatically start growing, right?  If you just agreed with that statement I’m going to find you and personally kick the protein bar out of your hand.  You have been warned.  In reality, they key to gaining muscle mass and simply becoming stronger is exercise, because although food provides the energy, you have to put that energy to good use in a way that can actually stimulate change in your body composition! This is why a mixture of cardio and strength exercises in your weekly routine is especially swell, because let’s not forget that our hearts are muscles too! Want stronger legs? Squats and lunges can target those muscles. Arms? Try out some dumbbells or even some barbells! There are muscle cut group fitness classes this semester that use both! The main idea: to strengthen a muscle, you have to use it and make it work more than it would on just any old regular day.

3.     Anyone care for a little extra euphoria? Those chemicals that I mentioned earlier as beneficial for reducing depression include serotonin, dopamine, and norepinephrine.  That runner’s high that you hear people talking about (even though I have quite a hard time finding it myself) really does exist, because the same chemicals are released in response to exercise as to many drugs that people take for the feeling of that “high” euphoria. Try out different times of the day to get in just 30 minutes to an hour of exercise, and see if it doesn’t leave both your body and mind feeling better afterward! Two days per week, I get up and exercise in the morning before my first class, because those are my longest days of class and I know that starting off my day with exercise keeps me more alert and in a better mood than if I just roll out of bed and lumber directly off to class.

4.     Fight the loss of brain function with age and help prevent the possible onset of Alzheimer’s. Many studies have been done in the past few years concerning Alzheimer’s disease and brain function, including memory, with age.  Although nothing has been proven to guarantee prevention of Alzheimer’s or brain function with age, one thing that has been proven to delay these events drastically is exercise.  It seems that not only does exercising regularly keep your body fit, but it can also serve to improve and maintain cognitive function, much like muscle function!  If you don’t think that this affects you, consider this quote from an article entitled “7 Mind-Blowing Benefits of Exercise”: “In 2000, Dutch researchers found that inactive men who were genetically prone to Alzheimer’s were four times more likely to develop the disease than those who carried the trait but worked out regularly.” You have the power to drastically reduce your chance of developing a devastating disease just by taking action now to keep yourself healthy and to protect you brain– why wouldn’t you do it?

5.     Be happier with what you see in the mirror. This one is not only related to the fact that those happy chemicals are floating around in your brain after you finish exercising, but it also relies on the fact that exercising naturally makes us proud of ourselves, because we got out and did something and used our bodies for good that day.  Even if not a single physical thing changes about your appearance, the act of doing exercise makes us feel more active and happy about doing something to improve ourselves, no matter how much you weigh and what you look like.  Food can also make us happy and eating well can make you feel better about yourself, but it’s just not quite the same as looking in a mirror at yourself and the sweat you just poured into the last hour and feeling the satisfaction of hard work well done.

6.    Get more done. (Bonus!) Stuck in the middle of writing a paper? Too tired to even start writing the paper? Getting away from the computer and doing some exercise might be the answer! Exercising increases blood flow to the brain, which can help to take away that sleepy feeling and make you feel prepared to work. Personally, long reading assignments for class tend to make me sleepy, but I’ve found that if I read while pedaling on a stationary bike at the gym then I feel much more awake and more likely to remember what I read! People who make time to exercise for just 30 minutes a day tend to be more productive than those who do not, which means that next time you think you have too much homework to squeeze time for exercise into your schedule, do yourself and favor and go exercise anyway; you might just be surprised at what you accomplish.

Pictures compliments of

Interested in the sources of this article and where the research references came from? Check out this US News health article on the 7 Mind Blowing Benefits of Exercise and this blog post entitled “13 Unexpected Benefits of Exercise.

Workout Wednesday blog posts are written by UNC Campus Recreation staff members. Each Wednesday we’ll be swapping blog posts with the Tarheel Tone Up blog so that readers can view more diverse post topics that will benefit their health and wellness. Workout Wednesday blog posts can be found both here and on