Published August 11, 2026 03:05AM
Joining a gym after years of working out at home is a humbling experience. Don’t get me wrong, I knew how to exercise. What I did not know was how to walk into a room full of equipment and make a single decision about what to do with any of it. After ten minutes of inclined treadmill walking (which is my workout of choice when I want to pretend I look as if I know what I’m doing), I grabbed my things and left the gym so abruptly that I abandoned my car keys on the machine
After speed-walking to my car, I plopped in the driver’s seat, grabbed my phone, and opened Instagram. I searched for “gym routines,” saved a dozen or so videos, and came back the next day with something resembling a plan. Nearly every trainer on social media, regardless of equipment, background, or follower count, was prescribing the same thing: three sets of ten reps. The interesting part is that they all seemed to chant three sets of ten reps with the quiet authority of someone who has never once been asked to explain themselves.
With the help of exercise physiologists and digging into the science, I landed upon an answer to the question I kept asking myself when I got back into the gym: How many sets and reps should I be doing? Here’s what I found out
An Army Doctor’s Protocol Led to Our Obsession with Strength Training
Thomas DeLorme, an Army doctor, is responsible for bringing the three-sets-of-ten-reps protocol to the world
DeLorme, born in 1917, grew up in Birmingham, Alabama. At age 15, he was bedridden for four months with rheumatic fever (a painful illness that causes inflammation in the joints), and he shrank to 140 pounds. He spent that time reading medical textbooks alongside issues of Strength and Health magazine. He rebuilt his body through weightlifting, against the advice of his doctors who insisted that he rest, and went on to study medicine. In 1944, he began his official duties as a physician at Gardiner General Army Hospital in Chicago, Illinois, where he specialized in orthopedics.
Bed Rest, According to Doctors of the Time, Was Better Than Exercise
The standard approach to rehabilitation at the time was cautious to the point of passivity. Heat therapy and exercises with light or zero resistance (with lots of reps) were typical, but medical professionals said nothing was better for recovery than rest
Soldiers could be prescribed bed rest for between six and nine months, which meant not having enough beds for hospital newcomers. One doctor, William Brady, who published a newspaper column during that era, vehemently disapproved of weightlifting, stating: “Extreme effort is not desirable in any kind of physical training nor is it good for the heart.” Though strength training for soldiers was normal, it was not common among those in the medical field. But DeLorme knew firsthand that strength training can rehabilitate people post-injury.
When Sergeant Walter Easley came to him after surgeons had told him his knee would never fully recover from a parachute-jumping injury, DeLorme suggested the complete opposite of what had been the recovery norm: adding resistance to exercises
DeLorme built a primitive weight-training gym at Gardiner. Leg extensions looked like repeatedly lifting the legs while wearing iron boots, and leg curls were done with a handmade pulley system. DeLorme advised Easley to perform seven sets of ten reps with the maximum weight he could manage and then bump up the weights once he mastered the previous weight. Rinse and repeat. After just one month, Easley reported larger quads and no pain around the knee. Word of his recovery got out, and others were eager to put DeLorme’s protocol to the test.
How 3 Sets of 10 Reps Became Cemented in the Fitness World
In 1948, DeLorme named his program “Progressive Resistance Exercise,” a phrasing coined by his wife. Then, both he and another doctor, Arthur Watkins, reduced the recommended number of seven sets of ten reps to three sets of ten reps. Why? After testing out fewer sets with patients, they found that seven sets was too ambitious and that three sets allowed people to take on heavier loads, thus building strength and bigger muscles faster. The first set was meant to be performed at a weight that’s 50 percent of the person’s ten-rep maximum (10RM), the second at 75 percent of 10RM, and the third set at 100 percent of 10RM. (As a real-world example, if the heaviest weight you can lift for ten reps with good form is 50 pounds, you would lift 25 pounds in set one, around 38 pounds in set two, and then 50 pounds in the final set.)
DeLorme and Watkins’ 1951 textbook titled Progressive Resistance Exercise, Technique and Medical Application spread the three-sets-of-ten-reps protocol into physical therapy, coaching, and eventually every gym in the country
What Made 3 Sets of 10 Reps Stick?
Physical fitness culture historian Conor Heffernan describes in his blog Physical Culture Study the attachment to three sets of ten as “quasi-religious,” noting that rep ranges almost universally resolve to round numbers divisible by two. “When was the last time you heard someone promote four sets of eleven reps?” he wrote in an article about the origins of the three-sets-of-ten-reps routine
Tom Holland, an exercise physiologist with more than 30 years in the fitness industry, has a direct answer for why three sets of ten reps had such staying power in the fitness world. “Three sets of ten is simple and easy to remember,” he told Outside. At some point, the prescription stopped needing a reason to exist
Is 3 Sets of 10 Reps Really the Magic Formula We Think It Is?
Greg Nuckols, an exercise physiologist and the founder of the coaching program Stronger by Science, reviewed the literature comparing low, moderate, and high-rep training on muscle growth and arrived at a conclusion that undermines the whole premise: “There’s simply not a very big difference in muscle growth when comparing different rep ranges,” Nuckols wrote in a blog post on his website about muscle hypertrophy. Muscle growth is driven by two mechanisms, according to Nuckols. The first is mechanical tension from heavier loads with fewer reps, and the second is metabolic stress from lighter loads with more reps. Both work.
That said, the recipe of three sets of ten reps isn’t quite necessary for muscle growth. “DeLorme would have found similar success using 2×15 or 4×8 protocols with adequate resistance,” Holland told me
A 2019 study published in the journal Medicine and Science in Sports and Exercise compared resistance-trained men performing one, three, and five sets per exercise. More sets produced more muscle growth, but gains in strength were not much different between groups. In other words, more sets can get you bulkier, but that doesn’t inherently equate to more strength. The implication is that if getting stronger is your goal, you may be able to test out a number of set-and-reps combos that align with your preferences.
“In my experience, the average person doing the three-by-ten method does not work hard enough to see the strength and hypertrophy results they seek,” Holland said. Most choose weights that are too light out of fear of getting bulky, or too heavy driven by ego. Either way, the ratio falls short
According to Holland, the three-by-ten formula isn’t magic; strength comes from progressively placing stress on the muscles. The best strategy isn’t focusing on the number of sets or reps, but rather what happens during each rep
“Very few exercisers understand the importance of muscular time under tension,” Holland told Outside. “That’s what overloads the muscle and truly drives adaptation. Most people let gravity and momentum do the work on the lowering phase, yet the eccentric contraction is where much of the muscle damage and subsequent adaptation occurs.” So, if you’re working out and your reps are pretty lazy, you probably won’t see the results you’re looking for
Why Are We Still Doing 3 Sets of 10 Reps?
There are a couple of reasons why many of us are still adhering to three sets of ten reps when we enter a gym
“The fitness industry loves to take legitimate exercise science concepts and turn them into watered-down programs and overly simplistic marketing messages,” Holland said. “It happened with 10,000 steps, Tabata training, the fat-burning zone, the three-sets-of-ten-reps protocol and more. For the vast majority of exercisers, the focus should be on lifting moderate weight more slowly, exactly what DeLorme was trying to achieve with his wounded soldiers almost 80 years ago.”
DeLorme revised his recommendation down from seven sets to three when the evidence told him to. He would likely have kept making new recommendations. Turns out the question I was asking myself in that parking lot wasn’t the right one, because the number was never the point
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