No pain, no gain, right? Well, not really. Turns out, it’s mostly in our heads that we should feel sore after a workout. The truth is, even if you’re sore after a workout that doesn’t necessarily mean that it was an effective or efficient session. And just because you aren’t sore, that doesn’t mean your workout wasn’t effective or efficient.

The human body is, after all, quite a complex thing. In other words, post-workout muscle soreness—or that lack thereof—might tell you something, but it certainly doesn’t tell you everything. What information you do gather, however, can help guide you toward a much more well-rounded fitness journey that has as much to do with what happens when you’re not exercising as when you are.

What Causes Muscle Soreness?

“Soreness is the result of structural damage to the proteins in your muscles, which then results in an inflammatory response in the muscles being used,” explains Phillip Vardiman, PhD, an athletic trainer and associate professor in the Department of Food, Nutrition, Dietetics, and Health at Kansas State University. “This inflammatory response is natural and aids in the healing process. With training, the body will adapt to the exercise—and its ability to perform that activity without pain.”

In other words, you were probably sore after the first few times you went for a run or clipped into your Peloton Bike. After a month or two, though, your legs felt fine, even after a tough workout, right? That’s because your body got used to it. Then when you tried, say, an upper body strength class, you probably developed soreness again.

“If you are exercising at a level you haven’t performed before, with a different technique, a new form or exercise position, or performing a new task or skill, that can result in soreness to the untrained or different muscles,” Vardiman explains. The soreness can happen right away, the next day, or even increase slowly over the next few days, an effect called delayed onset muscle soreness (DOMS). But it’s all essentially the same thing: Try a new exercise, expect soreness—but not forever.

So, If I’m Not Sore Is It Still a Good Workout?

Just because you're not sore after a workout doesn’t automatically mean it wasn’t an effective training session. If you push yourself hard during a workout and no soreness sets in, that means “your muscles have reached a training capacity to handle that volume of activity or amount of external load,” Vardiman says. In simpler terms: You’re killin’ it.

Vardiman also points out that soreness also has a lot to do with whether you’re getting the right amounts of sleep, nutrition, and hydration, and if you’re taking time to warm up and cool down (especially stretching). So, if you’re not sore after a strenuous workout, it could be because you’re doing everything right when you’re not working out.

Of course, this assumes that you’re mixing things up as an essential element of your routine. For example, maybe you’re doing indoor cycling three days of the week, rowing machine workouts for two, and also sprinkling in some upper and lower body strength classes a few days each week. If you just ride the Peloton Bike all the time, that’s great—any workout is better than none, especially if you love indoor cycling classes. But if you then try a core class or lift weights a couple of times each month, you will definitely feel sore after those sessions because they’re not activities your body is used to doing.

If I’m Not Sore Am I Still Building Muscle?

Believe it or not, soreness isn’t synonymous with building muscle. “You do not have to have muscle soreness to build muscle or increase your fitness level,” says Vardiman. You might feel tight or tired, but not particularly sore after you work out.

He points out that even if you’re increasing the frequency and difficulty of your workouts over time, you might not be very sore. “If you are increasing your exercise volume and load appropriately over time, you should have minimal levels of soreness compared to what is typically experienced during the start of a workout routine.” (Such as, say, the first month or so after you started running or indoor cycling for the first time.) “Your muscles have reached a training capacity to handle that volume of activity or amount of external load,” he says.

Why Am I Not Sore After a Workout?

From a physiological standpoint, the reason that post-workout soreness decreases over time is that your body is adapting in a couple of different ways. First, Vardiman explains, your body increases the amount of active proteins in your muscles—that’s just what it does in response to consistent activity. “Your body will also adapt through increased cardiovascular fitness,” he says, “allowing you to perform increased exercise bouts or volume without feeling the post-workout soreness or the burn from the lactic acid buildup.”

This isn’t a linear journey, however. Vardiman points out that “eccentric exercise” can bring soreness back like it’s five minutes after your first ride on a Peloton Bike. Eccentric exercise is the term for when your muscles are contracting, but go from a shortened position to a lengthened position—such as when you decide today’s the day to try running downhill for a bit. “Your quadriceps start in a shorter position and get longer as you descend,” he says. “If this is a repeated exercise or is a task completed with enough resistance, it can result in muscle damage,” or in layman’s terms, soreness.

It'd be a similar story if you love cycling, but then decide to try a Bike Bootcamp class, which incorporates strength training off of the Bike. “The different exercise recruits different muscles, and requires different contraction patterns that the body hasn’t had to perform before,” Vardiman says. “Once your body adapts to doing both, the occurrence of muscle soreness should decline—if you are taking care of yourself,” with stretching, nutrition, hydration, and rest.

The Takeaway

Soreness isn’t the sign of a superior workout. Mostly, it’s that you’re trying something new and different, and asking different muscle groups to wake up and join the party. Or, it’s that you didn’t take the time to stretch, take that extra sip of water, eat your veggies, and get a good night’s sleep.

In other words, soreness is a sign something’s either new or not quite right with your routine. Restore the balance in whatever way you need to, and you’ll build strength without experiencing much soreness.