Why Spin Class Slims Thighs, not Bulks Them

Celebrity fitness trainer Tracy Anderson told Redbook Magazine that spinning can make thighs get bigger, but here’s why she’s so very wrong.

Have you been avoiding spin classes after reading what Tracy Anderson, a celebrity trainer, said what they can do to one’s thighs?

By the time you’re done reading this, you’ll be convinced that spinning is one of the best exercises for making your thighs (and whole body) slimmer, trimmer, tighter and fitter!

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Tracy Anderson’s Comments About Spin Class and Big Thighs: Analysis

#1. She has been quoted: “I have women who come into my office after spinning exclusively for six months, wondering why they can’t fit into their jeans.”

The spinning is merely an association with the increased girth; this doesn’t prove cause and effect.

Can we rule out that these women weren’t eating more because they were spinning—a phenomenon known as “entitlement eating”?

After grinding out a spin class for a full hour, some participants may end up eating more—not just consciously, but subconsciously—because they figure they could get away with it, after having burned so many calories spinning. But they may overcompensate and thus gain body fat over several months.

It would be quite interesting to take a spin class participant’s body composition and body weight, then after they exclusively spin for six months, take it again and see if there’s a shift in fat to muscle ratio.

#2. Tracy Anderson has stated, “It bulks the thigh and butt muscles.”

This is physiologically impossible. When a muscle “bulks,” this is called hypertrophy, what every bodybuilder dreams of. Men, who have about 10 times more testosterone than do women, often struggle to bulk their thighs up, performing very heavy squats, deadlifts, and leg presses.

Spinning, by stark contrast, involves extremely light resistance. In fact, the resistance is so light, that you’re able to sustain the pedaling for 30 minutes or more. Can you imagine performing 225-pound squats nonstop for 30 minutes?

There are many men who can perform eight repetitions with 225 pounds across their back—yet hardly have bulky thighs or a huge butt. This is because bulking up is hard to do—even for men.

Heavy strength training recruits fast twitch muscle fiber, which has the potential to increase in size.

Spinning is not strength training. It’s aerobic (cardio) exercise. Cardio exercise cannot bulk you up, even if it’s grueling. Ever see a long-distance runner with bulky thighs?

Endurance-based movement (which spinning is) recruits slow-twitch muscle fiber. Slow-twitch never increases in size. If it did, marathon runners would have mammoth thighs and a beastly butt.

#3. “You develop mass by working these same muscles over and over,” insists Tracy Anderson. The “over and over” approach will sabotage muscle-building efforts. Aerobic exercise is done “over and over,” and again, muscle building enthusiasts make gains in the weight lifting area, not the cardio machine area

If you can do something over and over, this means the intensity or resistance isn’t heavy enough to qualify as muscle building; it’s aerobic, endurance-based. Otherwise, lifting just your arms above your head over and over should build giant shoulders.

You’ll be hard-pressed to find a bodybuilder who claims he or she got their bulky, muscled-up quadriceps and gluteus maximus from months of spin classes or other “over and over” cardio. Bodybuilding competitors will tell you the top exercises for building the legs are the squat, deadlift and leg press—and with very heavy weight. Aerobics won’t even make the list.

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Embrace Spin Classes!

Usually, a woman who believes her thighs are too muscular turns out to have excess body fat in this location, as determined by a caliper reading. The body fat masquerades as muscle because it doesn’t jiggle. But fat and muscle are not the same. A body fat analysis with skinfold calipers will tell the true story.

Spinning burns a high rate of calories and will force the body to raid fat reserves for performance as well as recovery energy. Coupled with proper nutrition and controlled portions, spinning will make legs with excess fat smaller, not bigger. And it will make already-trim legs tighter and shapelier.

Spin classes are ideal for self-conscious individuals because everyone works out in the same physical position: sitting on a bike and pedaling; nobody stands out.

Final Thoughts

Bulking requires heavy strength training that engages fast-twitch muscle fiber. Fast-twitch fiber is designed for short bursts of significant force. With sufficient training, fast-twitch fiber grows in size.

Spinning and other cardio routines of a “steady state” nature (continuous pacing) tap into slow-twitch fiber, which is designed for long duration exercise. Slow-twitch fiber does not get bigger.

Though some spin routines involve brief explosive bursts of pedaling, this high-intensity phase does not bulk the thighs. If it did, spin classes would be full of bodybuilders. Tracy Anderson misses the boat on this one.

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