This article thoroughly summarizes scientific research on the question of strength training frequency and volume, and it is a rare example of near-consensus in exercise science. There is actually minimal controversy here, believe it or not: 20+ years of research has made it quite clear that most people train more often than they need to, because strength training can be a more efficient form of exercise than you thought. (And now cardio, too.)
This is vital knowledge for people who hate the gym but need to spend some time there for injury rehabilitation, or as a prescription for disease prevention. It also matters to the legions of people who might be willing to develop a gym habit — and get all the health benefits — if they felt confident that a single visit per week was adequate. This information will convince you of that, and could save you thousands of dollars and countless unnecessary hours at the gym over the next few years.
This knowledge is virtually useless for people who like lifting weights and want to maximize their results. For those people and those goals, none of this is of much interest.
Warning! Please do not use this article as an excuse for not exercising. That’s not the point! Strength training is still a valuable form of exercise that requires an investment of your time and energy — less than you probably thought (which is pretty neat) but still an investment! Sorry, this information does not get you off the exercise hook. If you want that, please read 20 Reasons Why Going To The Gym Is A Huge Waste Of Time … actually just 20 short videos of hilarious exercise misfortune like this one, my favourite:
One day I was in the gym and an impressively built middle-aged man was working his triceps on the bench next to me. He was “hyooge,” but his barbells were so big that they were almost tipping him off the bench. It was one of the most awesome displays of lifting power I’d ever seen up close, and when he finished his set I chuckled and said, “I hope I’ll be able to do that someday.” There was a comic absurdity to this, since what he was lifting was literally a good bit heavier than I am (I am hobbit-like at 5'4"). His reply was quiet and delivered with a sad grin:
“And someday I hope I won’t feel like I have to.”
Pretty deep for the gym.
And there’s real hope for that guy. Anyone at all serious about the gym will log a lot of hours there. Even dabblers will probably turn up at least twice per week to beat on the same muscle group, usually three times — any less and they think they aren’t even trying. The conventional wisdom and the popular behaviour is to abuse a muscle group at least twice per week, in sets of three.
But 20 years of research — and especially the last 10 — have shown that less is not (much) less and that many people can probably get surprisingly good results with fewer and shorter visits to the gym. (Miss Piggy was right: less is not more, not in this situation.1 But it’s not much less.) The same may well also be more generally true of many other aspects of exercise. For instance, you can also probably get away with much shorter workouts of all kinds.
This is not a complicated article. In fact, it is little more than a list of the persuasive scientific experiments that have shown that less frequent strength training is probably very nearly as good as more. Nothing is carved in stone, but it’s a safe conclusion. Quite a few experts have critiqued this article, but none have really disputed it’s main point. So Read ‘em and … celebrate?
Less is not more. More is more!
— Miss Piggy
Five stars! This book reads like one of my own: science translated into practice. I learned more from this book than I have from any other book I can think of in years. The mind-blowing factor is high. Many myths well-busted.amazon.com
The authors of Body by Science, Doug McGuff and John Little, introduced me to this idea. When I read their myth-busting book, I was skeptical of many of their claims, despite the evidence they presented. I had a particularly hard time believing the claim that training frequency could be significantly reduced with minimal sacrifice in results. I read scientific papers every day and I have a finely-tuned and well-trained B.S. detector. My fear was that, if I did check their work, I would find that they were “cherry picking” — citing only scientific evidence supporting their point and ignoring conflicting evidence. So I went looking.
They weren’t cherry-picking. Not on this topic, anyway; there are definitely some other problems with the book.2
The evidence that lower training frequency is effective, or at least not much less effective, seems to be adequate. McGuff and Little cited 4 studies and I (easily) found 5 more, and scanned several others. The results were clear in every case, and I found no studies contradicting their position. Every available experiment shows basically the same thing: across the board, low frequency training got the same or at least surprisingly good results as higher frequency. All are cited below, with links. The evidence is not strong. None of the experiments were statistically “powerful” enough, but it is pretty consistent and encouraging.
Note, of course, that someone might well heed this evidence and still train 3 times per week … but rotating between different muscle groups. However, most people can probably achieve most or many of their strength training goals without such zealousness.
In 1988, Graves et al3 studied 50 men and women accustomed to strength training and tested them on 12 weeks of reduced training frequency, going from 2 or 3 days per week to 0, 1 or 2 days per week. Those reduced to zero lost strength as expected (about 70% over the 12 weeks), but for those who merely reduced their frequency? No loss at all.
Strength values for subjects who reduced training to 2 and 1 days/week were not significantly different …. These data suggest that muscular strength can be maintained for up to 12 weeks with reduced training frequency.
In 1990, Graves led another study,4 larger and more rigorous, focussing on lumbar strength in 112 adults, and testing a wider range of frequencies: everything from 3 workouts per week to one workout every other week. Every training frequency produced results, though somewhat less at the lowest frequency. But results were basically identical for training 1, 2 or 3 times per week!
These data indicate that a training frequency as low as 1X/week provides an effective training stimulus for the development of lumbar extension strength.
Which is actually an understatement, because the data showed that training even every 2 weeks still produced respectable results — an average 26% increase in strength when exercising one sixth as frequently as the 3X/week group who got a 40% gain.
In 1996, DeRenne5 put 21 teenaged athletes through 12 weeks of pre-season strength training at three times per week, and then continued for another 12 weeks at reduced frequencies. As with Graves et al above, stopping altogether resulted in lost strength, but even training once per week was sufficient to maintain strength.
…for pubescent male athletes, a 1-day-a-week maintenance program is sufficient to retain strength during the competitive season.
In 1999, Taaffe et al studied strength training frequency in a few dozen healthy older adults, aged 65 to 79 years6 — remember, strength training is not just for bodybuilders! Training consisted of “three sets of eight exercises targeting major muscle groups of the upper and lower body, at 80% of one-repetition maximum (1-RM) for eight repetitions,” which would be a pretty decent regimen for a young person as well. They were divided into groups training 1, 2, or 3 days per week. They all did well. They all got equally stronger.
A program of once or twice weekly resistance exercise achieves muscle strength gains similar to 3 days per week training in older adults.
In 2000, McLester et al studied experienced recreational weight trainers,7 producing the only data I could find that showed that more frequent training produced more results. The finding is not accurately reported in Body by Science, due to what appears to be a case of mistaken identity — summarizing the wrong paper.8 Fortunately, the study does show that reduced training frequency is still surprisingly effective: it produced about 60% of the strength gains from training three times more often, while maintaining overall training volume, i.e. one long workout to three shorter ones.9
The findings suggest that a higher frequency of resistance training, even when volume is held constant, produces superior gains in 1RM. However, training only 1 day per week was an effective means of increasing strength, even in experienced recreational weight trainers.
So less was less here … but not a lot less, and that is pretty important. I imagine that a great many people would happily sacrifice some of their progress in exchange for reclaiming two trips to the gym each week.
In 2007, DiFrancisco-Donoghue et al tested 18 older adults in two groups for several weeks.10 Half of them trained twice per week, the other half once. Once again, they found no difference at all.
One set of exercises performed once weekly to muscle fatigue improved strength as well as twice a week in the older adult. Our results provide information that will assist in designing strength-training programmes that are more time and cost efficient in producing health and fitness benefits for older adults.
Also in 2007, Burt et al compared “strength differences between 2 groups of untrained women, who performed a single set of the leg press exercise once or twice per week.”11 There was no difference in their results.
These results indicate that performing a single set of the leg press once or twice per week results in statistically similar strength gains in untrained women.
Both groups increased lean tissue mass (2.2%), squat strength (28%), and bench press strength (22-30%) with training (p < 0.05), with no other differences. These results suggest that the volume of resistance training may be more important than frequency in developing muscle mass and strength in men and women initiating a resistance training program.
And still in 2007 — apparently there hasn’t been any new research of this type in three years — Wernbom et al analyzed data in many studies about the effect of frequency, intensity and volume of training.14 They found “insufficient evidence for the superiority of any mode and/or type of muscle action over other modes and types of training.” In other words, results were pretty good and roughly equal across the board, regardless of how regimen variables were tweaked — both lower and higher frequency, intensity and volume were effective.
All of this data is remarkably consistent. I simply could not find any research showing that twice as often is twice as good, let alone three times as often being three times as good. How strange for me — studying health care for injuries and pain problems, the research is never unanimous. For that matter, exercise research doesn’t generally seem to be unanimous either. This is most unusual!
Most of the evidence above concerns training frequency — how often you go to the gym, how much time you allow for recovery between visits. Another factor is how much you do when you’re there: the question of sets. Do you do one set of leg presses? Two sets? (Red set, blue set?) Every set takes almost as long as the last. If you have to exercise everything three times, you’re going to be at the gym about three times as long. If you could get good results from one set, it would be a big deal. And you can.
When it comes to sets, more is better, but not by much … and that’s what matters for most non-bodybuilders.
In 2009 and 2010, James Krieger did nice meticulous reviews of set science for both muscle growth15 and strength.1617 Both reviews came to quite similar conclusions. For strength, Krieger evaluate eight tests of multiple sets versus one set of strength training, finding that more sets do have a greater effect, but not proportionately: Three sets do not have even double the effect of one, not even close.a clear case of diminishing returns. Three sets do not have even double the effect of one, not even close. Specifically, 2-3 sets are 40% better than just one,18 and only 20% more for 4-6 sets.
Krieger points out that “some authors have argued that a single set per exercise is all that is necessary for all populations and that further gains are not achieved by successive sets.” These results show the truth is in the middle, as it so often is: more sets probably are better, but nowhere near proportionate to the time and effort required. “If time is a limiting factor, then single sets can produce hypertrophy, but improvements may not be optimal.” Time is indeed a factor — a huge factor — for most people. More is better, but less is fine.
Reducing strength training frequency is only one knob you can fiddle with on the training dashboard. The less-is-not-less theme you see in the research above continues as you expand the search to other variables in strength training. In general, more-is-better is the official position of the American College of Sports Medicine (ACSM) … but they haven’t supported that position well.
In 1999, Ralph Carpinelli strongly criticized the ACSM’s position on strength training, accusing them of supporting their more-is-better recommendations with misleading and irrelevant evidence.19 It was quite harsh and a bit entertaining, if you like geeking on this sort of thing.
Is this the best evidence the American College of Sports Medicine and the National Strength and Conditioning Association can produce to substantiate their more-is-better philosophy? The NSCA is disingenuous at best, editorially incompetent at worst. Shame on the editors. Shame on the NSCA. Shame on the ACSM.
Zing! That was quite a while ago, but nothing much has improved since then, according to Carpinelli. In 2009 the ACSM published a new Position Stand, and Ralph Carpinelli wrote a new and better critique.20 It’s generally dry reading by necessity — refuting official positions published by major professional organizations requires tedious, thorough academic analysis — but the Discussion and Conclusions sections are, again, quite entertaining. After presenting numerous examples of the ACSM’s incredibly sloppy citing, Carpinelli fairly concludes:
Because ACSM Position Stands are so bereft of any science and apparently not open to criticism, there is very little expectation that the ACSM or its Position Stands will gain any respect from those who carefully read the studies and evaluate all the evidence. Readers can decide on the validity of the ACSM’s claims and recommendations and whether those claims and recommendations belong in a Position Stand supported by science or perhaps in an Opinion Statement supported by opinions.
Zing again! Carpinelli also discloses the rather sordid details of the ACSM’s reaction to his criticisms.21
But it gets better. My favourite excerpt from the conclusion is this excellent observation:
The complex resistance training recommendations … are based on the unsubstantiated opinion that the obsessive manipulation and specific combinations of training variables such as loading (amount of resistance), the number of repetitions, number of sets, interset rest intervals, repetition duration, time under load, frequency of exercise, modality of exercise, order of exercise, and exercise selection (single or multiple joint) results in significantly different specific outcomes. Most resistance training studies do not support that opinion.
If people were to assume that the ACSM’s recommendations in the Position Stand have any validity, they can actually calculate how many hours are required in the gym to attain or maintain the essential components of muscular fitness. Trainees would be required to spend a minimum of 20 hours per week performing resistance exercise; that is, approximately five hours a day four times per week.
This is really astute stuff. I do enjoy a good logical inconsistency, and this is a classic case of “you know there’s something wrong when.” Clearly people achieve results at the gym without following such a hyperbolic regimen. Obviously there is something wrong with official recommendations that require hopelessly impractical dedication to follow.
This reminds me of the common example of nutritional serving recommendations: has anyone ever looked at what you are supposed to eat without thinking, “Who could possibly eat that many servings of anything? If I was supposed to eat ice cream laced with heroine, I’m not sure I could cram down that much of it!”
A famous Scottish study was inspired by the same thing …
How much are you really getting out of that extra half hour on the StairMaster? Have you ever thought that conventional exercise regimens have a diminishing returns problem? That it seems to take an enormous amount of effort for relatively little additional benefit? How do you know how much is enough? “Lots” seems to be the idea everyone has: the more cardio, the better, as much you can possibly cram into your week. Frankly, it’s a logistical nightmare.
Buck up: this research should make it much easier to stick to your New Year’s resolutions.
The theme of efficiency in exercise has continued and expanded with new cardio science. It started with an excellent little Scottish experiment from 2009,22 which gave us startlingly “good news”, showing that it may be possible to get really fantastic bang for your cardio exercise buck. They found that only a few 30-second sprints on a stationary bike — intense but quick and only twice per week — may be nearly as effective at preventing disease as much more time-intensive traditional (cardio) exercise programs. In their words:
…we demonstrate for the first time that only a few minutes of high intensity interval exercise performed over two weeks is required to substantially improve both insulin action and glucose homeostasis in sedentary young males. This is both a physiologically important observation and potentially useful as it highlights a preventative intervention that could logically be implemented as an early strategy to prevent age related development of cardiovascular disease.
If true, it should change lives. And the researchers were well aware of this: they were inspired to do the research by the grim reality that the great majority of people will never make the kind of time for aerobic exercise that is officially recommended in most published guidelines. The study is noteworthy because the encouraging benefits could be halved and still be at least noteworthy: a surprising amount of benefit, for a surprisingly brief workout. The point is not that this research proves that sprints can replace tedious cardio — although that is a possibility — but that slow cardio has a diminishing returns problem: every minute on the StairMaster or trail is bestowing less benefit than the last.
I recommend listening to this short interview with researcher Dr. Jamie Timmons, an exercise biologist at Heriot-Watt University in Edinburgh. Listening is worthwhile for his Scottish accent alone:
Strength training is not just for bodybuilders. It has many health benefits — especially weight loss. Cruising into too-good-to-be-true territory? Not really, because it’s not crazy good: just a minor, nice perk.
Muscle mass is metabolically expensive. It costs a few calories per hour. More of it will modestly increase your basal metabolic rate (BMR) — your base rate of calorie burn. Reduced muscle mass and BMR with aging is one reason people tend to get fatter over the years. Dieting usually fails because it’s hard to sustain adequate calorie restriction to make up for that sluggish BMR, creating the “losing battle” effect: sure, you can always lose 10 pounds if you’re disciplined for three months … but you gain it back just as fast.
A higher BMR can help tip things back in your favour. And you can get a higher BMR by building some more muscle. And the whole point of this article is that it’s surprisingly easy to do that (to build muscle). Both the workouts themselves burn calories (though they do), and the extra muscle: about 5 for every pound of muscle every day, without any additional effort. That number is probably a fair bit bigger for recovering muscle. Muscle recovery is more metabolically expensive. Therefore, the more muscle you have, the more calories you will burn after working out.
There’s a common myth that every pound of muscle burn about 50–100 calories, which I carelessly repeated myself in early versions of this article.23 That number is much too high, and no one seems to be sure where it came from — just one of those things that gets passed around.
I’ll emphasize again: this is not a major factor. You would need a lot of muscle for it to make a major difference. Calorie restriction is still the trump factor in weight loss — the first thing you have to get right — but muscle mass is in the equation. Like compound interest, it adds up, and it’s a “free” bonus for doing something you should do for all kinds.
Body by Science does a good job of presenting all of this science as well.
What if it was just as good for your aerobic fitness to lift weights as to run? What if you could get an “aerobic” workout without doing aerobics? This unproved possibility is yet another reason to work with weights — even more bang for your buck, perhaps. If it’s even partially true, it builds that case that strength training is not just for bodybuilders.
A 2012 paper makes a detailed basic science case that relatively brief, intense doses of muscular training may actually be able to build cardiovascular fitness about as well as steady-state aerobic exercise (like, say, running).24 The idea is mostly supported by comparing what is known about physiological responses to these types of exercise (it’s not a report on the results of a controlled experiment directly comparing the two). It’s hardly a strong case.25
Actually, it’s quite a controversial idea that some exercise physiologists denigrate as a pet theory. Who’s pet? Why, the authors of this paper! Steele and McGuff are particularly well-known for their association with a strength training method, high-intensity training (HIT). Their conclusion here, if true, would obviously be great news for HIT — because it suggests that HIT is good for general fitness, not just bodybuilding. So the risk of bias is high.
But biased opinions can be valid, and there’s nothing obviously wrong with this paper, except the . This is probably their boldest statement: “Identifying a particular modality of exercise as being ‘aerobic’ or ‘CV’ constitutes a misnomer. The extent that any modality of exercise produces CV fitness adaptations appears to be dependent primarily upon the intensity of the exercise.” That could be true, but perhaps a bit overconfident, there just isn’t much experimental data about this yet — they cite it, and acknowledge that it’s not much — and it does seem a little far-fetched that athletes who did only resistance training would stand a chance competing in an endurance event. But it is possible they would do better than we think. The biology does seem to support the claim, at least well enough to make it plausible and worth testing.
And, of course, the inevitable …
The scientific evidence is the only thing we should pay attention to. But we are emotional and irrational beings by nature, and we love a good story. Nothing persuades like a personal anecdote. So here’s mine:
After only four months of a decidedly minimalistic gym schedule — exercising as infrequently as once every 14-21 days! — my strength significantly increased, roughly 75% across the board. My chest press (bench press) strength has actually doubled. Doubled strength is a satisfying accomplishment, I gotta say. The only thing about my technique that was unusual was that my 20-minute sessions were certainly intense! I did my exercises to full, quivering failure each time, thoroughly exhausting the muscles with continuous loading at the highest weight I could possibly keep in the air for two minutes. This is high intensity training (HIT), as taught by McGuff and Little.
I was not a beginner when I started, and this was not low-hanging fruit that I picked. I am sort of an athlete, and I was already quite active and non-weak when I started this new approach. I had been tinkering with weight training off and on for years. It felt really strange — and yet good! — to stay away from the gym for up to three weeks at a time. It seemed almost impossible that it could work.
And yet I have never seen an increase like this! Less really was more … for me.
One of the strongest criticisms of the original version of this article was that I was exaggerating, and in fact I changed the title from “less is more” to “less is not less” in the days after publication (and then eventually I half back-tracked to the play on words, “less is more than enough”). Critics were correct that the evidence doesn’t really support my original, more sensational title. And yet now, ironically, I appear to actually be an example of “less is more.” I suspect that I have an unusually slow recovery time, and that higher training frequency for me is particularly counter-productive.
Perhaps you will also find that less gym actually gets you more — or at least not less!
McGuff and Little:
Obviously, you should not work out before recovery and full adaptation from the previous workout takes place — but how long is this, on average? We can share with you the average length of time that we have found to be most beneficial based on our own thirty-plus years of training, in addition to our experience in supervising in excess of 150,000 workouts and performing informal studies on the subject. Perhaps more significantly, we can also share with you the findings of exercise physiology studies regarding what happens as a result of a high-intensity workout stimulus being applied to the muscles and how long the recovery and overcompensation process typically takes.
… The muscle fibers build back to their preworkout size and then, if further time is allowed, will build up to a level that is greater than it was before the workout. The length of time required for the entire process to complete itself is dependent on the intensity of the workout stimulus and the corresponding damage to the muscle fibers. Typically, it falls in the neighborhood of five days (on the quick side of things) to six weeks.
What interested me there was that McGuff and Little considered 5 days to be “quick” — the very lowest end of the range!
They believe, based on experience and a little more evidence, that although the studies cited above show equal results, higher frequency can actually backfire over longer periods:
…even at best, the data suggest that if you train twice a week, the second workout isn’t doing anything positive [or not much] and serves only to waste your time. The reality is that by week twelve, had the study been carried out that long, you would have noted that not only were you wasting your time by performing a second weekly workout, but also you were actually starting to regress and would be unable to lift the same amount of weight for the same time-under-load (or repetition) ranges.
No controversy? Impossible! This is exercise science! There is always controversy. Predictably, within hours of publishing this article, a number of people had already raised objections — nothing too fiery, but objections nevertheless.
However, most of the objections concern evidence that shows that higher frequencies are “better,” confusing the idea of “what’s most effective” with “what’s most cost effective.” Indeed, studies like McLester et al do indeed show that “more is more,” as Miss Piggy would put it. But how much more? Diminishing returns may not matter much to a bodybuilder, but they matter very much to … nearly everyone else. (And even some bodybuilders, like the philosophical fellow in the story at the top of the article.)
That’s the story here. The diminishing returns are the story, and that lower frequencies are still effective — even if they aren’t optimal. That perspective may not matter to a bodybuilder, but matters very much to the masses!
Obviously there are probably other studies out there, and probably some that don’t fit the pattern I found. Like the German study.27 The one that agrees with Miss Piggy: more is more, and proportionately so.
This article is hardly a comprehensive meta-analysis and doesn’t claim to be. I did a “casual” PubMed search. I checked the four studies cited by McGuff and Little, and then I checked the next five relevant, recent studies that I found — and all five had results that were strongly consistent, and strongly suggestive that “less is not less.” It took me many hours to read, summarize and present those findings. I stopped there. That was good enough for me, for now. I didn’t imagine for a moment that I’d found everything there was to find.
Reader Sven pointed out the German study. At first glance, it does seem to spoil that lovely scientific consensus. But look a little more closely and the German data is not so much at odds with the themes of this article, namely that the data still confirms that lower training frequencies will get the job done.
Still, if I had found this in my initial search, I probably would not have claimed that there was a scientific consensus. It clearly shows that more frequent workouts produced better strength and growth. Muscle mass gains were about twice as good with twice as many workouts. And strength benefitted even more: one session per week produced only a 2.7% gain, while 3 times per week got a whopping 12.8% increase — triple the gym time, but quadruple the benefit!
And yet the authors concluded that, “all groups showed significant gains in muscle mass with a tendency of better training results when doing two or three training sessions a week,” because they did. Even the once-a-weekers gained. Not a lot compared to the thrice-a-weekers, but some. Arguably enough for the average person. Would you say no to a 6.4% increase in muscle mass, achieved with a very reasonable investment? Many people would be delighted with that inexpensive result. What a bargain!
Even though this study does not confirm the “diminishing returns” problem, it does still confirm that you can make progress with a single visit to the gym each week — something many people just don’t believe. They assume that more is necessary for any gains. This German evidence debunks that, just like the evidence I’ve already cited, clearly showing that you’re going to get benefits even at low workout frequencies. Fast or slow, you’re going to get where you’re going.
In any case, it’s just one study. Perhaps they chose to study a strength training protocol that really does work much better at higher frequencies. There are so many variables! A main point of my article was to look for signs that McGuff and Little were cherry-picking the evidence to make a sensational point, and they do not seem to be. One study with different results does not change that, and cannot magically make all the other evidence go away.
(A single dissenting study doesn’t actually break scientific consensus anyway, since scientific consensus doesn’t require perfect unanimity, just a good strong majority.)
This information about training frequency contrasts starkly with the prevalent prescription habits of physiotherapists.
Physiotherapists are infamously prone to prescribing tediously unsustainable exercise regimens to their patients: many exercises to be performed frequently. I do not dispute that therapeutic exercise has an important role to play in rehabilitation (that’s a whole ‘nother topic). But there can be no doubt that there is a glaring conflict of interest for the many therapists who charge patients for supervised time in their office gymnasiums: their livelihood is directly affected by the training frequency that they recommend.
Patients routinely fail to stick to tedious physical therapy exercise prescriptions, and suffer much angst about it along the way. I spent many years in clinical practice watching patients struggle with such prescriptions. I even watched a perfect example of the problem unfold in my own house in the spring of 2010, when my wife was recovering from some (very) severe injuries while also fighting constant guilt that she wasn’t doing the exercises that we had paid handsomely to have prescribed. Even with a barrage of reassurances from me and her physiatrist that such exercise was probably not critical to her recovery, she still found it frustrating and anxiety-producing.
I’m sure I could have been much more reassuring if only I’d had the weight of all this training frequency evidence in hand then! Or for my entire career, for that matter.
I am a science writer, former massage therapist, and assistant editor of Science-Based Medicine. I have had my share of injuries and pain challenges as a runner and ultimate player. My wife and I live in downtown Vancouver, Canada. See my full bio and qualifications, or my blog, Writerly. You might run into me on Facebook and Google, but mostly Twitter.
This 2005 paper presents good evidence that there may be genetic differences between people that account for a surprisingly wide range of responses to strength training. In a fascinating radio interview about the paper (see Exorcizing Myths about Exercise), co-author Dr. Eric Hoffman says, “If we take two friends and enter them into a resistance training program, you could find that the one friend would trip all their muscle strength, whereas we have cases in the study of the other friend who either gains no strength, and we have some subjects that even lose a little strength.”BACK TO TEXT