Why Your Muscles Look Bigger Right After a Workout


Cathe Friedrich doing a one arm dumbbell row working on her muscle pump

For many lifters, the goal of weight training is to build muscle strength and increase muscle size and definition. However, it’s hard to argue with the other health benefits that weight training offers. However, gains in muscle size, also known as hypertrophy, don’t come quickly or easily, especially for women. It takes consistent training and you need to challenge the muscles you’re working to do more than they’re accustomed to.

It usually takes at least 6 to 8 weeks of weight training to see an increase in muscle size. Depending upon training, age, genetics, and body type, it might happen more quickly for you or even slower. Yet, you might look in the mirror right after a workout and notice your muscles look larger. It’s too early for your muscles to have grown. Why do they LOOK bigger?

Don’t worry. It’s not your imagination. What you’re experiencing is commonly known as the “muscle pump.” When you lift weights, assuming you lift relatively heavy and do enough volume, blood flow increases to the muscles you’re working. One reason for the increased blood flow is the stress of training causes blood vessels to release more nitric oxide. In turn, nitric oxide opens blood vessels wider to bring more blood flow to the area. As blood vessels in the area become engorged with blood, fluid leaks from the vessels and the muscle swell slightly. This phenomenon is sometimes referred to as “transient hypertrophy.”

Transient hypertrophy, or the muscle pump, is fairly short-lived. Your muscles might appear larger for a few hours or even the rest of the day but it’s not permanent. The fluid will slowly be absorbed back into your bloodstream and your muscles will return to their previous size. Think of it as a preview of what you’ll get if you keep training, only with regular training, the muscle itself will actually grow in size and become stronger.

Can You Enhance the Muscle Pump?

Many serious bodybuilders love the temporary muscle pump they get and want to enhance it. Not only do they like the way their muscles look but they look the feeling of their muscles being engorged with fluid. Are there ways to increase the muscle pump?

Arnold Schwarzenegger was a big proponent of the muscle pump. As he points out, the best way to get it is to use moderate resistance and moderate reps, between 10 to 12 per set. Arnold believed that courting a close muscle-mind connection and focusing mentally on the muscle while doing a rep enhances the pump. In addition, slowing the tempo to place the muscle under tension longer is another way to maximize the muscle pump. When you reach the peak of the movement, hold the tension at the top and squeeze the muscle for a few seconds before bringing the weight back down.

Supersets for a Muscle Pump

More advanced training techniques, particularly supersets, forces more blood into the muscles to maximize the muscle pump. If you’re not familiar with supersets, there are two kinds: agonist and antagonist. With agonist supersets, you do two sets that work the same muscle group back to back with minimal rest between sets. For example, one set of biceps curls followed by a set of hammer curls. With antagonistic sets, you do one set of an exercise followed by an exercise that works the antagonistic muscle group. In the case of biceps curls, you’d work the triceps using an exercise like triceps kickbacks.

Agonist supersets, because you’re working the same muscle group with minimal rest between sets, reduces strength in the muscle group you’re working because you’re not giving the muscle time to recover before doing the second set. With antagonistic supersets, you don’t experience the same reduction in strength since one muscle group is recovering while you work the other.

Of the two, agonist supersets are best for creating a strong muscle pump since you’re really pounding the muscle fibers by not resting between sets. How to put this to work for you? Toward the end of your workout, do a few agonist supersets and see if your muscles don’t look bigger after your workout is over.

You’ll have more success getting a muscle pump focusing on isolation exercises that work a single muscle group rather than compound ones that work multiple muscle groups, like squats and deadlifts. With compound exercises, you have multiple muscle groups handling the stress you’re applying and that’s not as effective for creating a muscle pump.

Long-Term Muscle Growth

As you know, the muscle pump is only temporary. The real gains come from long term, chronic hypertrophy. Those are the muscle gains that don’t go away once you’ve finished. With chronic hypertrophy, the increases come from structural changes to the muscle and muscle fibers themselves rather than temporary swelling. In response to training, existing muscle fibers increase in size. If you could see inside a muscle fiber, you would see more myofibrils, the component inside muscle cells that house the contractile elements called myofilaments. Non-contractile elements in the sarcoplasm of the muscle cell also grow, a process called sarcoplasmic hypertrophy. These changes increase the size of the muscle without increasing strength. This is sometimes referred to as sarcoplasmic hypertrophy.

Unlike transient hypertrophy, or the muscle pump, these changes take weeks or even a few months to show up and they only happen if you stress your muscles beyond a certain threshold and do a high enough volume of training. In other words, muscles won’t grow if you do a few sets every day using light weights and don’t fatigue the muscles. You also need to supply your muscles with enough amino acid building blocks for them to repair and build muscle fibers.

The Bottom Line

The muscle pump gives you some immediate gratification but it doesn’t last, unlike the “real” muscle development you get after weeks of training. Enjoy it for the short time that it lasts and then keep working for the future gains to come!



Sports Fitness Advisor. “Hypertrophy in Human Muscle”

T Nation. “5 Things We Can Learn From Arnold About Building Muscle”

Bodybuilding.com. “8 Ways To Maximize Your Muscle Pump”

The Mystery of Skeletal Muscle Hypertrophy. Richard Joshua Hernandez, B.S. and Len Kravitz, Ph.D.


Related Articles By Cathe:

4 Common Mistakes Women Make When Training with Weights

5 Biggest Myths about Female Strength Training

Strength Training: Avoid These 5 Mistakes When Lifting Heavy


Related Cathe Friedrich Workout DVDs:

STS Strength 90 Day Workout Program

All of Cathe’s Strength & Toning Workout DVDs
Total Body Workouts
Lower Body Workouts
Upper Body Workouts


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