It’s All Been A Big Fat Lie

You’ve been lied to. Cheated.



Ladies, I’m talking to you. Specifically the one’s walking into fitness studios and group exercise classes looking to secure the holy trinity of female training – long, lean and tone muscle. Because, as I will describe below, what you are doing when you bust through those doors and curl and lunge to the beat is the exact opposite. That’s right, the structure of those fitness classes that are designed to make you look like Gwyneth Paltrow or a runway model or insert your related pop culture stick figure here, in reality, use many of the same principles as champion bodybuilders.

What in the name of Nicole Richie is going on, you ask. You don’t want to look like a bulky bodybuilder, you say. Well, allow me to explain the principles behind increasing muscle mass and how these protocols are used in many of your favorite boutique studios.

A Little Bit of Exercise Science

I don’t want to bore you with the science-y stuff but it’s important in understanding the underlying concept. But I’ll keep it super brief and not that technical.

“Hypertrophy” is the act of building muscle. A muscle can grow or it can shrink but there is no way to specifically make a muscle longer or leaner or more or less tone. How your muscle looks on your skeleton is really only affected by two things. The first is genetics. How long your bones are, the length relationship between muscle bellies and tendons, insertion points – these determine what your muscularity will look like on your frame. Sadly, these things are entirely out of your control barring surgery that would be way too insane to even consider. The second factor is your body fat percentage. People with lower body fat percentage overall will have more of their muscle on display as there is less fat covering it. This second factor is mainly in your control as a combination of diet, training, sleep, stress management and other lifestyle factors play an integral part in how much body fat one has. That’s the good news. The bad news is that if your muscle bellies are  full and your bones are short you are never going to look “long and lean” regardless of how low your body fat percentage is. You can still look amazing, but if your goal is to look like Giselle but in reality you are 5 foot one with short limbs, it ain’t gonna happen. Don’t blame me, blame your parents.

OK, so we know that a muscle grows or shrinks and you cannot control how long or lean it appears. And we can reveal more of our muscle mass with lower body fat percentage via good lifestyle habits. Great, we are on the same page. So, what exactly causes a muscle to grow? How do you maximize hypertrophy? Why are my legs getting (gasp!) bigger when I’m spinning at Spirit Cycle 4 times per week? Excellent questions. Let’s dive in.

The Factors Of Muscle Growth

Muscles need a few key things to maximize growth. Quite frankly, a muscle will grow under any kind of stress but there are certain factors that allow for maximal muscle growth. Again, this is a simplified version as this is a blog post and not a master’s level exercise physiology textbook. Factor number one is volume. Volume is simply the amount of work being done for a specific muscle group. For muscle size to increase you want a lot of volume per specific muscle group per training session. This is why bodybuilders tend to train specific body parts in a day (say, back and biceps) rather than do total body workouts every time they go into the gym. Everyone will react differently but 10 to 20 sets per body part is a good starting point. Secondly, you need to establish time under tension – usually between 40 and 60 seconds per set. All this means is that you want the muscle to either flex, extend or contract for that length of time before resting. Sets of 3 or 5 or 6 reps doesn’t usually do add up as, unless you are moving very slowly, the reps are completed before adequate time under tension is achieved. The last factor is metabolic stress, meaning that the muscle should not be completely recovered between sets. This is usually managed in terms of rest periods with the standard hypertrophy protocols calling for anywhere from 30 to 75 seconds between sets.

Finally, and this is outside the realm of just mass building, any resistance programming needs to incorporate something called progressive overload. To elicit any type of training response you need to start with a weight that will challenge the muscular system and systematically gets harder over time. How it gets harder is up to the person programming the workout. You can add more weight, more reps, same number of reps in a shorter time domain, shorten the rest along with dozens of other strategies that increase demand from week to week or session to session.

Phew, we made it through the technical stuff and hopefully you now have a decent understanding how to best utilize training variables if muscle building is your goal. But what if muscle building isn’t your goal? What if you just want to “tone up” and lose some body fat? You’d certainly bypass the free weight area of your gym where boys in the muscle tees with the armpits slit down to the bottom hem roam and head straight to your spin studio or boot camp or butt blaster power hour class, right? Well, let’s examine what actually happens in these classes.

Your Fitness Class And You

On one end of the spectrum you have what I call “pink dumbbell” classes such as Tracy Anderson Method, ModelFit and Skinny Bitch Collective to name but three that have actually made me insane enough that I’m willing to call them out specifically. These types of classes violate that last principle that I mentioned above – progressive overload. Essentially these classes use such low resistance (dumbbells of less than 5 pounds or strictly bodyweight) that they are below the threshold of eliciting an actual training effect. Sure, the running around in a circle while holding hands or punching each other’s butts or doing triceps kickbacks while holding a couple of paperclips in your hands will make you sweaty and might make your muscles burn but unless you are so detrained that holding a couple of pounds truly overloads your system, you are not going to get a result from it.

So why do so many of the girls standing next to you at ModelFit look like models? They walked in looking that way. In fact, and I do actually have some insider information on this, many of these types of classes recruit women who already have this look or, in some cases, only allow women who already look like this in the class. The benefit of this is simple, many people will convince themselves that if they are around people who look a specific way, they will convince themselves that they are doing what it takes to also look that way. And there is some benefit to hanging around aspirational people. But when the training principles are just not sound you are never going to get the desired effect, regardless of how much you want it to be true or how hot the girls in the class next to you are.

Are there any benefits to this type of class? The activity will likely release some hormones that make you feel good. You will likely burn some extra calories though not nearly enough to be significant. You may make a new friend but you are probably just as likely to walk out being envious of the genetics of the 22-year old next to you whose parents were clearly David Beckham and a giraffe.

This may be a good time to interject this caveat: if you are doing any of classes mentioned in this post strictly for recreation or because you enjoy it or the way it makes you feel, by all means do not stop going. I walked by a Zumba class at the YMCA one time and there were a bunch of older women dancing around and having a ball in there. It was great to watch and I would never want to rob or talk anyone out of what they love doing. In fact, so many of us do way to little of what is fun or joyous. Just have the appropriate expectations – this is recreation, not training.

Now that I’ve quickly cleansed my soul, let’s take a look at the next level of fitness marketed towards the female population – classes that actually do use some form of overload.

Spin Class and Boot Camp and HIIT, Oh My!

Spin, boot camps, high intensity interval training, butt blaster classes, 30-minute circuit training boutiques, all of these modalities for the most part utilize some level of resistance that is significant enough that, while likely not nearly optimal, does use a system of increasing load from either week to week or exercise to exercise.

“You used the 8 pound weights for your lunges last week? How about grabbing the 10s this week?”

“Give me one and a half turns on the resistance!”

These are common things you hear coming through the headset of your favorite fitness instructor during these types of classes. And while you will ultimately run out of viable options for increasing resistance after a few weeks or months in the class when you are new you’ll likely use heavier weights or get in more reps every time you walk in through the studio doors.

Progressive overload? Check.

Now there are so many of these classes that it is difficult to make blanket statements about all of them but the vast, vast majority of the time they will have you doing a set of an exercise for a high number of reps and often in the time domains for hypertrophy that we discussed earlier. For example, performing a set of lunges on one leg for one minute before switching over to the other leg for a minute. Or, in the case of spin, cranking up the torque for a one-minute interval before bringing it back down. Sound familiar?

Time under tension that promotes hypertrophy? Check!

Spin classes have you repeating the same motion with the same muscle groups for about 45 minutes (save for that nice break in the middle of the class where you burn out the connective tissue in your shoulder with a 6-lb body bar for 5 minutes). Butt Blaster and Leg Burner classes will have you working on the same body part for the entirety of the class. And, as discussed before, most bodybuilding style training focuses on one or two body parts per workout in order to get the requisite amount of work in to spur muscle growth.

High amounts of volume per body part? Check!

How many of these classes have you taking longer rest periods that promote full muscle recovery before attacking the muscle group again? Better question, how many of these classes even give you a long enough break to grab a drink of water? This level of metabolic demand does not only increase your heart rate, it also increases muscle breakdown and ultimately the need for muscle repair. And you know how a muscle repairs itself? By getting bigger.

Incomplete rest periods? Yes, ma’am!

So as you can see, high volume, lots of time under tension and limited rest periods/increased metabolic demand – all the hallmarks of building muscle – are present in your favorite group ex classes. The one’s you are specifically going to because you don’t want to get “big and bulky” by lifting weights. Someone call Alanis Morrisette because there’s definitely some irony going on here.

What are the holes in the argument? There are a few. The overload in these classes, even the one’s that use them, is limited. You usually top out the weights you use quickly – often after a few sessions – and your progress usually stalls there. Many women, particularly in places like New York City where we are located, way under eat and simply don’t have the nutritional resources to add slabs of muscle. Bodybuilders tend to use a lot of variety to attack muscle groups from different angles and with different levels of mechanical tension. Something like spin just uses one exercise over and over again. Finally there’s training frequency – people chasing hypertrophy usually train 5 or 6 days per week – and at the highest level you cannot discount the use of anabolic steroids. However there are enough factors present in these classes that you will likely see some muscle growth from them.

And let me go on record as saying that we think this is a good thing. You should want to build muscle as it’s hugely beneficial to your health, life and longevity. But we know that most women are not looking for localized muscle hypertrophy (i.e. bigger legs) yet so many of them train in ways that are promoting exactly that.

This all begs the question of how you should train to get the body that you want if not by these traditional means. We’ve written several posts on this very topic here and here and this blog post is closing in on being as long as Les Miserables so we’re not going to get into all that here. But next time you’re sweating it out in your Booty Pump class or spinning your heart out to the latest inspirational Arianna Grande song just keep in mind that your training may be a little closer to Arnold’s than to Adrianna Lima’s.