I’m going to come at this in a kind of roundabout fashion. Bear with me. (Or don’t. I won’t mind.)

It starts like this: A week or so ago I put my hands on my hips and noticed a large muscle I’d never noticed before. I got out my copy of Strength Training Anatomy, and identified the muscle in question as my gluteus medius.

The glute med stabilizes the hip during gait (important for walking and running). It abducts the leg (important for dancers, I suppose, and anyone stepping sideways). It also inwardly rotates the leg (important for martial artists for kicking, and no doubt other things). That all makes sense. It’s an awfully big muscle to not be important for many things.

Still, I’d never given it much thought. I certainly hadn’t been designing my workout routines to build a bigger gluteus medius.

For a few minutes I was thinking, “Really? My glute med is where I’m seeing hypertrophy? Not my pecs. Not my biceps. Not my traps. Not my quads. Not my lats. Not my rectus abdominis. Not even my gluteus maximus. Nope. The gluteus medius.”

Once I got past that, I started to wonder what I had done that had caused my glute med to blow up in size, and the only thing that came to mind was kettlebell swings.

Now, at one level this makes perfect sense. In fact, the Tim Ferriss post that introduced me to kettlebells and the kettlebell swing made specific reference to exactly this effect:

In four weeks, he took his then-girlfriend, an ethnic Chinese with a surfboardlike profile, to being voted one of the top-10 sexiest girls out of 39,000 students at the University of Auckland. . . . Other female students constantly asked her how she’d lifted her glutes so high up her hamstrings.

https://tim.blog/2011/01/08/kettlebell-swing/

Building this muscle, at the top of the pelvis, just above the gluteus maximus, would produce exactly that effect: making your glutes look higher, as much it made them look bigger.

So the fact that kettlebell swings hit the glute med shouldn’t have been unexpected. But I was nevertheless surprised that I got so much hypertrophy out of the effort I was putting in. I suppose it could be something special about the glute med (or about my glute med—my lifetime movement history somehow priming my muscle to be ready to explode with growth), but I doubt it. I think it was the kettlebell swings, and there was really only one thing different about my kettlebell swing workouts as opposed to my other workouts: reps.

Once I gave it some thought, I realized that I should not have been as surprised as I was. This result of high reps is pretty well known. For example, Adam Sinicki, AKA The Bioneer has an excellent discussion of this in a post on bodyweight training that he wrote for people trying to put together a home exercise program during the pandemic.

My kettlebell swing workouts, drawing from Tim Ferriss’s suggested workout, were originally 3×25 swings, formerly with the 45 lb kettlebell in the fitness room, more recently with the 53 lb kettlebell I bought as soon as they became available again after the pandemic-related disappearance of all sorts of home workout equipment. I’ve started adding a 4th set to that workout, so a total of 100 swings, once or twice a week.

Despite having only a passing interest in making my muscles bigger (as opposed to making them stronger), I am intrigued by this effect. Maybe doing 100 reps is some sort of magic for producing hypertrophy.

I’ve reached the point where I can crank out a respectable number of push ups, but I’m not doing 75–100 reps. And for most of the other exercises I’m doing (in particular, dips and pull-ups), I’m working very close to my one-rep maximum—which is exactly the recommended protocol for building strength. For building size though, there are reasons to think that higher rep counts make good sense.

A lot of different factors go into making muscles bigger. You can make your muscle fibers bigger (myofibrillar hypertrophy). Maybe you can grow new muscles fibers (hyperplasia)—evidence is mixed. You can also add to other stuff in and around your muscle cells—glycogen stores, additional capillaries, supporting tissues, etc. (sarcoplasmic hypertrophy). These things will make your muscles bigger without necessarily making them any stronger (although they should increase your endurance).

My kettlebell swings, I suspect, mostly work through that last mechanism. (Although, to the extent that I do fatigue my glutes, I should get some amount of myofibrillar hypertrophy as well.)

Sarcoplasmic hypertrophy is the increase of sarcoplasm in the muscle cells. Sarcoplasm is to a muscle cell what cytoplasm is to any other cell but contains glycosomes, myoglobin and oxygen binding protein in high amounts (as well as calcium). . . . Whatever is going on, the fact remains that lifting heavy makes you stronger and lifting a little lighter and for reps makes you bigger.

https://www.thebioneer.com/an-introduction-to-powerbuilding-how-to-train-for-size-and-strength-simultaneously/

I continue to think that strength ought to be my main goal for lifting. Lifting for size seems to be about aesthetics, which is fine, but not important. But these past couple of years I keep coming back to thinking of my father, who is suffering from sarcopenia and becoming increasingly frail. And each time I do, I become all the more determined to add another few pounds of muscle as insurance against sarcopenia when I’m his age.

The success of my kettlebell workout in building the size of my glute med makes me think maybe I should go for 75–100 reps of a few other exercises. I’m within striking distance on push ups—I recently did 4×12 reps, so 3×25 isn’t that far off. I’m rather further away on inverted rows—I think the best I’ve done is 3×8 reps—but inverted rows are quite adjustable in terms of how hard they are. I’m sure there’s a ring height and foot position combination such that I could get close to 3×25 reps.

Maybe the result of those changes would be similar ballooning up of my pecs and lats. It seems, at least, to be worth a try.