Sore muscles – it’s not unusual to have muscle soreness when you’re just starting out or when you work out harder than your muscles are accustomed to. In fact, muscle soreness is almost universal when you first begin working out, although you can experience it anytime you expose your muscles to a level of stress they haven’t acclimated to. If you’ve ever increased the intensity or volume of your workout, you may have experienced soreness even though you do that exercise regularly.
This type of soreness, as you probably know, is called delayed onset muscle soreness, or DOMS, and it comes from stressing your muscles more than they’re accustomed to. Delayed onset muscle soreness usually appears between 24 and 48 hours after an exercise session and lasts about 72 hours, although it can linger for as long as a week. The theory is that DOMS is caused by microscopic tears in muscle fibers that elicit an inflammatory response.
On days when you experienced DOMS to the point even getting out of bed was uncomfortable, you might have reached for an ice pack, stretched, or taken an Advil. Unfortunately, none of these therapies are proven to work for DOMS. In fact, taking a non-steroidal anti-inflammatory, like Advil, may be detrimental. Some research suggests it reduces muscle growth by blocking the activity of the satellite cells involved in muscle hypertrophy.
Fortunately, after you’ve done a particular exercise for a while, you no longer experience soreness as your muscles adapt to the stress you place on them. This is referred to as the “repeated bout effect.” Simply put, repeated bouts of exercise reduces the impact that a particular exercise has on your muscles and you experience less muscle damage and soreness. Therefore, if you keep repeating a particular exercise, it will no longer cause you to feel sore unless you increase the intensity or volume you do.
The repeated bout effect mainly applies to eccentric exercise, the phase of an exercise when the muscle lengthens against resistance. The “downward” phase of a biceps curl is eccentric but so is running downhill. Research shows training that emphasizes the eccentric portion of an exercise produces the greatest amount of muscle damage and the most muscle soreness. Eccentric movements are also the ones that lead to the greatest potential for strength gains and muscle growth.
However, if you stop exercising for months and return to doing that same movement, your muscles will have to adapt to the stress all over again. The repeated bout effect doesn’t offer permanent protection against muscle soreness. Once your muscles adapt to the stimulus you place on them, you probably won’t experience delayed onset muscle soreness again unless you increase the volume or intensity of the exercise to create stress your muscles AREN’T accustomed to.
How long does the repeated bout effect protect you against muscle soreness? Surprisingly, quite a while. According to one study, up to 6 months even if you DON’T exercise.
What Causes This Type of Adaptation?
As much as we know the repeated bout effect is a real phenomenon, but no one knows exactly WHY it occurs. It’s a process of adaptation but it’s not clear where adaptation happens. Is it at the level of muscle cells, connective tissue or at the level of the brain and nervous system? It may involve adaptation, to some degree, at all of these levels.
What the Repeated Bout Effect Means for Muscle Growth
The repeated bout effect shows how your muscles adapt to exercise. That’s a good thing in terms of muscle soreness. It would be annoying if you got sore every time you worked out. On the other hand, the repeated bout effect also shows just how capable your body is of adapting to the forces you place on it. That, in turn, means you can’t keep doing the same movements using the same intensity and volume and expect for your muscles to grow and become stronger.
Is DOMS Correlated with Muscle Growth?
Do you judge how hard you worked based on how sore you are? In reality, there may not be a strong correlation between DOMS and muscle growth. Research suggests muscles can still grow even if you don’t experience post-workout soreness and stiffness. Don’t forget, lots of factors can influence how sore you feel after a workout that aren’t related to how hard you lifted. Even diet may have an impact. Certain foods and spices, including green tea, dark chocolate, omega-3s, turmeric, and tart cherry have an anti-inflammatory effect, which may reduce how sore you feel. So, don’t use post-workout soreness as the only indicator of how hard you’re working.
The Bottom Line
Now you know why you stop getting sore when you do an exercise over and over. Your body has a remarkable ability to adapt to the stress you place on it through the repeated bout effect. This ability to adapt also means you have to vary the movements you do and the intensity and volume to provide your muscles with a new stimulus to grow. So, don’t get complacent. Changing the intensity and volume of your workouts as well as the exercises you do is challenging for your body and keeps your workout from becoming stagnant.
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