Have you ever noticed that your muscles look larger and more defined after a session of resistance training? It’s not your imagination. This phenomenon has a name. It’s called “transient hypertrophy.” Transient hypertrophy simply means your muscles look larger due to swelling and tissue edema. When you stress your muscles through resistance training, assuming you use a weight that’s challenging enough, fluid builds up in the spaces between muscle fibers, making the muscles appear larger in size. This type of muscle “growth” usually only lasts a few hours and isn’t associated with an increase in strength. You may look a little “stronger” but that’s about it.
Transient Hypertrophy versus Actual Hypertrophy: How The Two Differ
Transient hypertrophy from tissue swelling is quite distinct from true muscle hypertrophy that causes muscles to enlarge on a more permanent basis, or at least as long as you keep training. “True” muscle hypertrophy comes from an increase in the size of the myofibrils that make up muscle cells. Myofibrils are the contractile fibers made up of thick and thin filaments that extend along the length of the muscle. These thin and thick filaments called actin and myosin increase in size and number in response to training. It’s this increase in the size of the myofibrils that causes you to become stronger. It also leads to a small increase in muscle size.
The other reason muscles hypertrophy or enlarge is through an increase in the tissue that surrounds the muscle fibers called the sarcoplasm. Sarcoplasm is made up of non-contractile elements like fluid and connective tissue. “Sarcoplasmic hypertrophy” leads to an increase in muscle size without an increase in strength since strength gains come from enlargement of contractile muscle elements. So, two distinct types of hypertrophy occur when you progressively overload a muscle – an increase in the size of the contractile elements, leading to greater strength and smaller increases in size, and sarcoplasmic hypertrophy, which leads to an increase in size but not strength.
Do Muscle Cells Increase in Number with Resistance Training?
Most muscle growth is a result of hypertrophy or enlargement of muscle fibers – not an increase in the number of muscle fibers, also known as hyperplasia. There’s not a lot of evidence that hyperplasia plays a role in muscle growth in humans, although it appears to occur in some animals. Some experts believe hyperplasia can occur under certain conditions and that some pre-existing muscle fibers may split into two fibers in response to training but it’s not clear if this actually happens and under what conditions it occurs.
Why Does Strength Increase Before Muscle Size?
You may experience improvements in strength early in a resistance training program, sometimes as soon as two weeks. The muscle size hasn’t changed, so why are you stronger? It’s related to how your nervous system adapts to strength-training. Early in training, your nervous system adapts by recruiting more motor units so that more muscle fibers are activated when you lift a weight. Therefore, you may experience improvements in strength before your muscle fibers and the surrounding connective tissue and fluid (sarcomere) have increased in size. So you can become stronger without seeing an actual increase in the size of the muscle.
The Bottom Line?
The bad news? That “pumped up” look isn’t true muscle hypertrophy, but keep working at it and you’ll be one step closer to having more permanent muscle definition.
References:
The Journal of Cell Biology, 156 (4), 751–60.
IDEA Fitness Journal, Volume 8, Number 11. November 2011.
Journal of Strength and Conditioning Research, 24 (10), 2857–72.
Related Articles By Cathe:
Are Some People Non-Responders to Strength Training?
Can You Build Muscle Strength Without Increasing Muscle Mass?
Exactly What Is Muscle Memory?
Does Stretching Boost Muscle Hypertrophy?
Can You Build Strength Lifting Lighter Weights?
Can You Build Muscle Size Through Aerobic Exercise?
Is Muscle Damage Necessary for Muscle Growth?
Related Cathe Friedrich Workout DVDs:
STS Strength 90 Day Workout Program
All of Cathe’s Strength & Toning Workout DVDs
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Lower Body Workouts
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