Workout Wednesday: Why Are My Muscles So Darn Sore After That Workout?

Last week, after returning to the SRC from a solid month of no gym access that caused me to rely on bodyweight exercises and a treadmill, I had the brilliant idea to hop straight back into my favorite group fitness class: lower body conditioning. This class is always a challenging one, but there were nearly 100 people there this time and it was fairly obvious that we were all struggling after the break. After 45 minutes of so many squats and lunges that I quickly lost count, my legs felt like two overcooked noodles as I picked up my backpack and wobbled down the stairs.

Within twenty minutes, I had cooled down and my legs were feeling almost back to normal. By the next morning, my leg muscles were felt tight and slightly sore, but I made it through the day without noticing the soreness too much. By the second morning, I could barely walk as I waddled and cringed my way across the house getting ready for class. Let me just say that you never really notice the subtle inclines and all of the many staircases on campus very much until every step reminds you of every single squat and lunge you did two days earlier.

So why were my legs so extremely sore?

This kind of achy, sore feeling after a workout has an official name: delayed onset muscle soreness, or DOMS. While many mechanisms work together to cause this soreness, they are not all well understood. The best-understood cause of muscle soreness is simply that strenuous exercise causes microscopic tears in the muscle, leading to inflammation and soreness as part of the healing process.

The eccentric phase of exercise may be particularly responsible for these tiny tears. This is the phase where the muscles are lengthening, so if you were doing bicep curls with a dumbbell, the action of lowering your had back down to the starting position would be the eccentric phase of the exercise. This phase of the exercises puts more load and strain on your muscles, leading to the micro-tears.

Often, you might hear people say that soreness comes from lactic acid build-up in the muscles. While lactic acid is a by-product of your body’s metabolism during exercise, the lactate is cleared from your system naturally in less than an hour, usually, and is not the cause of your muscle soreness later.

 How long does the soreness usually last?


Photo from

Most people experience peak soreness 24-72 hours after an exercise session when it’s something that they haven’t done in a while, if they are new to exercise, or if they greatly increase the weight load of the exercise compared to what they usually do. The good news is that after one bout of terrible soreness, like the one I experienced last week, you should feel back to normal in 3-5 days and the same workout isn’t likely to make you nearly as sore again if you continue to do it regularly. If you feel sharp pain WHILE you’re exercising or if your soreness doesn’t go away after five days of resting your muscles, you may need to consult a doctor to see if the pain is due to an injury and not just general soreness.

What else should I know about exercise-induced muscle soreness?

  • While studies have shown that medicines like Tylenol or ibuprofen may help with the pain, the results aren’t definite and they don’t help your muscles recover or heal more quickly.
  • If you’re not sore after a workout, it doesn’t mean that your workout was too easy or that it wasn’t “good enough.” The level of soreness is simply related to your level of muscle adaptation to that particular exercise, as well as your genetics.
  • While stretching, warming up and cooling down are still super important for keeping you safe during exercise, they have not been shown to reduce DOMS.
  • The micro-tears are not bad for your muscles, they are simply a natural consequence of tough exercise and they heal themselves naturally and strengthen your muscles in the process.

How can I recover more quickly from my DOMS?

Unfortunately, there is no definite way to make your soreness dissipate more quickly. No vitamin, mineral, or herbal supplements have been researched and proven effective for specifically treating DOMS, and you should ask a doctor before taking them. Massaging the muscles by hand or with a foam roll may be your best bet, because even though it is painful at the time, it increases blood flow to the muscles and may help them heal a little more quickly. There is no guarantee of what will work for you because every person’s body is different, but I usually feel a little better after a hot shower and after massaging the sorest spots.

Muscle soreness from exercise is a badge that some wear with pride and others, including myself, just try to minimize and get it to pass as quickly as possible. If you came running to work out with Campus Rec last week during “Spring Into Fitness,” and you were left as sore as I was, don’t be scared away! The worst has passed and your muscles are better prepared for your next workout, so come back to work out with Campus Rec during this chilly four-day week and be proud of the hard work your soreness represents!


Workout Wednesday blog posts are written by UNC Campus Recreation. Each Wednesday we swap blog posts with the Tar Heel 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


Why are Your Muscles Sore After a Workout? 22 July, 2015. Greatist.

Yu, Christine. No Pain, No Gain? 5 Myths About Muscle Soreness. 17 July, 2014. Daily Burn.

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