You Might Actually Weigh More After Working Out. Here's Why

You've been slaying your workouts like the warrior you always wanted to be. But when you peel off your sweaty clothes and step on the scale, eager to see the results of all of those calories you've burned, you get a startling and unpleasant surprise: you weigh more now than you did before you went beast mode. Wait, what? This injustice is enough to make you want to throw in the gym towel and retreat back to your comfy couch.

In fact, there's a scientific explanation for why you might weigh more immediately after a workout. And the good news is, it's most likely temporary. "A person's scale mass is a combination of muscle, fat, bone, the brain and neural tract, connective tissue, blood, lymph, intestinal gas, urine, and the air that we carry in our lungs. Immediately after a workout routine, the percentage of mass in each of these categories can shift as much as 15%," clinical exercise physiologist Jeffrey A. Dolgan explained to Shape.

You've pumped up the volume

Blood volume might not be the first thing you think about when you're planning your workout, but it's vital to success. As a 2007 study in the American Journal of Medical Science put it, increased blood volume means more liquid in the body. This, in turn, makes it easier for your body to keep cool while you're pushing hard.

The journal goes on to say that increased blood volume also means an increase in "cardiac stability". This might be cold comfort when you're staring down the climbing numbers on the scale. But in the long run this means your heart will respond better during workouts, improving your performance.

But, like the swollen sore feeling after beating your personal rep best, this increased blood volume is temporary. The journal states that blood volume returns to normal after a "relative period of inactivity" — which means any weight it adds to the scale will drop off too.

Muscles make waves

Of course, extra post-workout pounds can't all be blamed on blood volume. Several other factors come into play as well — one of which is something you might have already heard around the gym. Muscle, they say, weighs more than fat.

This might sound like wishful thinking, but Cleveland Clinic says that it's true. It takes roughly a month for new, lean muscle mass to develop. But once it does, it will bump up the number on the scale a little bit. The Clinic warns that this new muscle usually appears during downward weight trends, and people may mistake it for a setback. But it's actually a good thing. Not only is the new weight lean muscle rather than fat, but (as Mayo Clinic points out) the more muscle mass someone has, the more calories they burn each day.

Using those new muscles might also trigger a bit of weight gain, too. The Cleveland Clinic also states that muscles require glycogen as energy. In order for them to absorb it, the glycogen has to bond with water. Add the two together, and you may experience an increase in water retention just after a workout. But like the others, this weight spike will fade over time.

Internal protections activated

You know how your muscles just feel heavier when they're sore? Well, they may actually be heavier due to something called delayed onset muscle soreness, or DOMS, in which your muscles get damaged during weight training. This leads to inflammation that registers on the scale as weight gain (per VeryWellFit). This swelling (and the extra pounds that come with it) can last for a few days, and it's actually your body trying to protect and defend the sore tissue so that you can heal faster (via SparkPeople).

But don't worry — once the pain starts to subside, you should see the few extra pounds you put on disappear. And then some. "As your muscles become more accustomed to the exercise and more efficient, however, they begin to need less glycogen to maintain the same level of energy output," Cleveland Clinic's doctor of physical therapy Gary Calabrese explained. "Thus, your water retention becomes less, so your weight will start to go down."