Guest Post: Sorry, but Science Says Running is Good for You, Not Bad

When my friend Sol from told me that he and his colleague Skip were working on a post examining the science behind some of the anti-running claims making the rounds of the blogosphere lately, I was excited to feature it here on my blog. I have a lot of friends and readers who will be very interested in their interpretation. Be sure to check out their website too, they offer some of the most sound, evidence based health and fitness information I’ve found on the internet. Enjoy! ~Go Kaleo

Why Women Should Not Run. Run and You’ll Only Die Tired. One Running Shoe in the Grave. Just a sampling of the anti-cardio articles we’ve seen in the past year.

Low-intensity steady-state (LISS) cardio has gotten a bad rap. Somewhere along the line, being fit and healthy got redefined to exclude endurance work. Long and steady cardio is now the height of boredom, a waste of time, and ' worse yet ' the antithesis of “gains.” No longer do we need to log endless miles to burn off stubborn fat (regardless of whether you enjoy cardio or not).

Hyperbolic? Not if you’ve read the plethora of anti-cardio articles these days.

Recently, an article titled Why Women Should Not Run, by John Kiefer, has been making the rounds. The article casts a damning light on steady state-cardio, seemingly with plenty of science to back it up. People see the high citation count, and immediately think that the assertions made must be true. Unfortunately, the citations it contains rarely relate to the statements that are made. Taking very specific studies and converting them into heavily generalized statements, the article is a testament to the lazy and sensationalistic “science-based fitness” that is currently running amok on the Internet.

“Why Women Should Not Run”

Before we get into claims and citations, there’s an underlying source of confusion throughout this article. The title is generalized to all women, and the author sets up a familiar example that could be applicable to many women: his friend “Jessica.” Jessica’s story is certainly one many women can relate to, or is at least something nearly everyone has seen or can envision.

However, as the article progresses we begin moving further and further away from this situation. The author mentions physique competitors and their coaches and portrays them as the source of his ire. As we move to the end of the piece, it focuses on binging, post-contest figure athletes. While this situation will be relevant to a few women, we’ve certainly moved a long way from the generality set up by the title and opening anecdote.

Speaking of binging, this brings up another area where this article is lacking ' dietary control. The author goes to great lengths to set up cardio as a metabolism-halting, fat-gaining nightmare, yet never mentions the effect (or lack thereof) of one’s diet on this process. This highlights the possibility the author may be overstating the relative influence of LISS on the issue. If that’s the case, it’s ironic given the author’s previous writing against “exercise-only” weight-loss plans. To quote from the piece: “Succinctly: Exercise alone does not cause significant weight loss.”

Finally, the last general weakness comes from how the author quantifies the problem. Words like “over-prescribed,” “too much,” and “excessive” appear throughout this article to describe the amount of cardio these women are doing. It should go without saying, but “too much” is never a good amount of anything. In fact, it’s inherently a bad amount ' too much water can kill you! What amount of cardio does the author use to highlight how much is actually too much? One to three months of 20+ hours per week. That’s three hours a day, every day. Done at a reasonable pace of 12 min/mile this equates to at least 100 miles/week. Unfortunately, the author provides no basis for the establishment of this threshold. No doubt there are women out there that log that much time, but how well does this relate back to our prototypical “Jessica?”

How many women do you know who log an average of 3 hours of cardio every day? If you do know one, is she fat?

Somehow, the anecdotal woman is a figure competitor and does 3+ hours of cardio every day.


“Science Wants You to Stop Running”

A main premise of this article is that too much cardio slows the body’s metabolism, especially in women. The author supports this claim with his first collection of citations:

the most detrimental effect of [steady-state] training'one that applies specifically to women: Studies'both clinical and observational'make a compelling case that too much cardio can impair the production of the thyroid hormone T3, its effectiveness and metabolism[1-11], particularly when accompanied by caloric restriction, an all too common practice.

In the first incarnation of this article the author took a much more hard-nosed approach on this idea, but softened the language due to initial critiques. Unfortunately, the current language is still misleading. We’re about to get science-heavy as we investigate these citations.

Five of the eleven citations used here to support steady-state training’s detrimental effects specifically in women relied solely on male subjects [4, 5, 8, 9, 10], and two of those used rats [8, 9]. A sixth looked at mixed subjects [3], though still weighted heavily toward males. When making claims about a specific population, we want studies that use subjects that match the target group as closely as possible. When sex differences exist, we cannot use male subjects to validate processes and outcomes occurring in women. If we ignore this error though and take the group of citations as a whole, it still portrays a very different picture than the one the author is attempting to paint.

The author’s citations highlight that there are responders and non-responders to exercise-induced declines in T3 levels (10 responders to 7 non-responders) [1]. So this problem of reduced T3 does not necessarily manifest in all women all the time. After the initial decline at the start of training seasons, T3 levels started to trend back towards baseline [1, 2]. Others report no change in T3 levels at all [3, 5], in direct contradiction to the author’s claim.

The citations state that T3 may initially decline, but it returns back to baseline. It is an adaptive response, not a permanent one.

The studies most relevant to this issue [6, 7] showed that it was not cardio alone ' either low or high intensities ' that impacted T3 levels, but rather an issue of energy availability. To quote the researchers:

“Neither the volume nor the intensity of exercise had any effect on T3 levels beyond the impact of the energy cost of exercise on energy availability.” [6]

And again:

“the results of this experiment suggest that exercising women may be able to prevent or to reverse [thyroid-related] reproductive disorders through dietary reform without reducing either the volume or the intensity of their exercise regimen.” [6]

In a follow-up study [7], the same authors determined a threshold level of energy availability below which T3 levels start to be affected, namely within the range of 19-25 calories per kilogram of lean body mass per day. The authors even propose a scenario where a woman similar to their subjects could inadvertently create such a situation: by reducing her energy intake by 450 calories per day while performing aerobic exercise equivalent to running 5 miles a day. Not an extreme situation.

The studies themselves found that that it was energy availability, not cardio per se, that impacted T3 levels.

However, what none of these sources show is steady-state cardio having a detrimental effect to weight-loss efforts, even in the presence of decreased T3 levels. To quote the authors of the first citation:

“Between the (') responder and non-responder rowers, there were no significant differences in physical characteristics, training history, performance times, or hydration status' Furthermore, the changes observed in the (') responder rowers for fT3, TSH and leptin were not significantly correlated with changes in body mass, percentage body fat or hydration status over the course of the study.” [1]

The author seems to think this is irrelevant, as he continues to paint a bleak picture by blasting out another twenty citations on T3, from its cellular effects to its role in fat loss. Yet these citations only illustrate the mechanics and influence of T3. They say nothing of its real-world effects on weight loss when steady-state cardio and caloric deficits are paired.

To be fair, there is clearly something going on with T3 here, and it does act in various roles throughout the body. But nothing the author has cited has identified anything to support the idea that cardio sabotages weight loss by decreasing T3 levels, even in the face of a caloric deficit.

The citations used not only showed no long-term decrease in T3 due to exercise, they also showed no negative impact on weight even if T3 was decreased.


“We Were Not Designed For This”

In the next section, the author continues with the supposed ill effects of steady-state cardio. Leaving T3 behind, we are now told that traditional cardio work alters the way your body burns fat; where muscles’ ability to burn fat is compromised, and the body takes extraordinary measures to preserve fat stores.

Training consistently at 65 percent or more of your max heart rate adapts your body to save as much body fat as possible. After regular training, fat cells stop releasing fat the way they once did during moderate-intensity activities[32-33]. Energy from body fat stores also decreases by 30 percent[34-35].

Papers 32-34 are all investigating the acute changes in the mechanics of fuel substrate utilization during exercise at differing levels of VO2max.

If you are not familiar with this idea, as the intensity of exercise increases the body tends to rely less on fat as the primary fuel source, and more on carbohydrate sources. The cited papers are investigating how this acute shift occurs and what factors mediate it. This is a normal physiological process.

Citation 35 shows the changes in substrate use after 12 weeks of endurance training. That study did indeed find that after twelve weeks of training, body fat stores were relied upon less to provide fuel for exercise ' 30% less as correctly noted in the author’s article. However, this decrease is taken completely out of context.

Before the 12 weeks of training, the subjects did a pre-test. What the scientists found was that the test exercise (90-120 minutes of cycling at 63% VO2max) utilized carbohydrate sources to fuel 60% of the effort. The remaining 40% came from body fat stores (17%) and from fatty acids stored within the exercised muscles (23%). After the twelve weeks of training, the same test was retaken, and the researchers found that carbohydrate usage declined to 40% of fuel needs and body fat stores down to 13%. To make up the difference, intramuscular fatty acids provided nearly half of the energy requirements at 47%. The study basically found that carbohydrate usage dropped 33%, body fat storage usage dropped 28%, but intramuscular fatty acid usage went up 113%! This effect appears to be a normal adaptation to endurance training (1, 2, 3).

However, all the above effects are observed during exercise. Shifts in substrate utilization during an exercise bout are not as important relative to one’s caloric deficit for long-term weight loss goals (4, 5, 6). Endurance exercise does not induce fat loss on its own. It is used to create or augment a caloric deficit which then creates the desired fat loss.

Endurance training appears to increase the amount of total fatty acids burned during a moderate intensity bout of exercise.


To this end, your body sets into motion a series of reactions that make it difficult for muscle to burn fat at all[36-41]. Instead of burning body fat, your body takes extraordinary measures to retain it.

The first sentence is in direct contradiction to the previous sources given. Citation 35 found a 100% increase in fat use in muscles. Here again, papers 36-41 are investigating the pathways involved in fat metabolism and its use a fuel substrate. None of these sources show a link between endurance training and the muscles’ ability to burn fat beyond the normal transition to rely more heavily on carbohydrate oxidation as exercise intensity increases. The bold claim that the body takes “extraordinary measures” to retain body fat goes uncited.

The primary citation for cardio making it “difficult for muscle to burn fat” actually showed a 100% increase in fat usage in muscles.


The most critical statement, “instead of burning body fat, your body takes extraordinary measures to retain it” goes unsupported.


That’s not all. You can still lose muscle mass. Too much steady-state cardio actually triggers the loss of muscle[42-45].

The competing effects of muscular hypertrophy and endurance training are well researched. Simply put, you can’t be a top-tier bodybuilder and a top-tier endurance athlete. Just looking at real-world athletes will highlight this fact without the need to get into the underlying molecular processes, to say nothing of the time requirements. However, the choice of citations here is odd.

Paper 42 is a case study on a woman who ran 4500 miles across Canada over the course of 112 days (equivalent to 1.5 marathons a day). She did indeed lose lean body mass (LBM ' which includes more than just muscle mass), nearly 7 lbs worth. She also lost just less than 30 lbs of fat. Averaging 8 hours of running a day, for almost three months, on a 1000 calorie/day deficit, this woman is doing everything the author is ranting against. Yet, amazingly she managed to lose a considerable amount of fat even though she must surely be below the T3 threshold established earlier. It’s unfortunate her thyroid levels were not also monitored.

In paper 43, the freshman rowers did lose 2 lb of LBM over the course of six months with ad libitum food intake. However, the World Championship Rowers studied alongside them showed no changes in LBM.

The subjects in paper 44 increased muscle mass after the 5-week training protocol.

Paper 45 did not include exercise, steady state or otherwise. It did, however, find decreased T3 and increased urinary nitrogen excretion in subjects that consumed a diet that only had 2% carbohydrate content for eleven days. Subjects consuming diets with 85% and 44% did not experience these changes. How that is relevant is unknown.

The claim made was “steady-state cardio yields a loss in LBM,” yet these papers either directly contradict the author’s main premise or challenge the inevitability of muscle loss from cardio.

What follows is another dump of citations blaming increased cortisol for muscle loss, name-dropping myostatin, and then leaping to decreased bone density because of all this muscle mass runners are supposedly losing. If that’s not a slippery slope, it certainly sets one up:

And long term health? Out the window, as well. Your percentage of muscle mass is an independent indicator of health[65]. You’ll lose muscle, lose bone, and lose health. Awesome, right?

Let this one sink in a bit. According to the author, running is detrimental to your long-term health because of all the running-induced muscle loss (even though his previous citations contradicted that claim). Forget about all the known benefits of endurance training; it seems the only thing that matters is muscle. The possibility that endurance running can help in other facets of health are not even considered. Without a doubt, lean tissue can be an indicator of overall health status, but health is not necessarily solely dependent on lean tissue. Furthermore, the author makes no distinction between the lean tissue and strength levels of endurance-trained individuals to their sedentary counterparts, the latter being the population these sort of epidemiological studies are based upon.

When sewn together, these phenomena coordinate a symphony of fat gain for most female competitors after figure contests. After a month'or three'of 20-plus hours of cardio per week, fat burning hits astonishing lows, and fat cells await an onslaught of calories to store[66-72].

There is no need to invoke aggrandized ideas about the detriments of steady-state cardio to explain the propensity of female figure competitors to gain fat after a contest. These women have spent the previous weeks and months training intensely and dieting down to unsustainable levels of body fat. Post-contest is typically a recovery period where training is dialed back, and dietary controls are slackened. Moving less and eating more isn’t exactly a novel scenario when it comes to fat gain.

Figure competitors diet down to unsustainably low body fat levels for competitive edge, not health. Rebounding to higher levels is healthy and even necessary. Previous running sessions are not to blame.


The worst thing imaginable in this state would be to eat whatever you wanted, whenever you wanted. The combination of elevated insulin and cortisol would make you fat, and it would also create new fat cells so you could become even fatter[73-80.]

So this state (extremely lean, extremely stressed) is not a good place to be in to start binging. How does this relate to Jessica or “why women should not run?” This section seems to summarize more as “don’t overtrain and overeat.”

When diet is finally discussed, the examples given could only be classified as binging. The dietary protocol accompanying the observed rapid fat gain is described as 4000 calories of “gluttony,” “feeding frenzy,” and “devastation” ' yet the author is still pointing the finger at excessive cardio.

“Science” by Citations

For some reason, many fitness writers tend to see the world in a binary of only black or white. There is no gray, there is no compromise. This bull-headed approach to fitness advice is overly restrictive and misleading. Absolutes are rarely valid in this field.

Thyroid hormones can vary significantly between people and even within an individual (7, 8). Even if depressed levels are found, the condition could present no symptoms and there is no agreement on appropriate methods of treatment (9, 10). The author’s own citations show we cannot lay the blame for declining levels (if and when they occur) on steady-state cardio alone, and even then, declining levels do not necessarily halt or reverse fat loss efforts. And it’s not only low-to-moderate intensity steady-steady cardio that affects your thyroid. High-intensity intervals have been shown to acutely decrease thyroid levels more than steady-state cardio (11, 12) and weight training isn’t completely off the hook either (13, 14).

Yes, running has been shown to decrease total lean body mass, but it’s also been shown to simultaneously increase lean mass in the limbs (15), and has been shown to have no effect (16) or even a protective effect (17) on age-related muscle loss. And while running may lose out to weight training for increasing bone density, it has been shown to improve it nonetheless (18, 19, 20, 21) and to outperform cycling and swimming (22, 23).

Meanwhile, improvements in health parameters (reduced blood pressure [24], increased insulin sensitivity [25], reduced liver fat [26], improved vasodilation [27], telomere protection [28], etc.) abound from regular endurance work that actually tend to result in reduced mortality rates (29, 30, 31).

That being said, there is some emerging evidence that you can do too much endurance training. Going overboard with steady-state cardio can lead one to the point of diminishing returns or even outright health detriments (32, 33, 34). People that generally engage in this level of endurance work, however, are rarely in it for the health aspect. Typically, sports performance is their ultimate goal, and often increasing one’s performance or ability in any sport comes at a detriment to overall health. This is the same situation figure competitors fall under.

Unfortunately, “too much” steady-state work has yet to be quantified, but it is safe to say that it is significantly higher than zero. For general health and fitness, moderate amounts of steady-state training can have a place in any comprehensive workout or training routine. It can complement and potentially enhance other aspects of one’s training (15, 35, 36, 37). That said, endurance training may detract from sport-specific goals, so each person needs to program their training accordingly. Despite many fitness writers’ claims to the contrary, there is no one-size-fits-all program that is optimal for everyone and their myriad goals or preferences.

And don’t forget that your dietary approach is integral to the success of your training. If fat loss if your goal but your diet is not in sync with that outcome, you will inevitably fail. The author used to espouse this himself, but seems to have forgotten it during the writing of his anti-cardio rant.

There is ample evidence that steady-state cardio has a plethora of health benefits. We’ve provided relevant citations above.


So is running bad for women?

In the end, the anecdotes and 79 citations in this article (one was listed twice) are a smoke screen to hide the precarious claim the author makes: that cardio above a walk or below a sprint is bad for you (especially if you are a woman). That women are destroying their metabolisms, losing muscle and bone mass, holding onto ' if not adding ' fat, and dying earlier from decreased health. Yet the evidence presented was poor and does not support the claims made. Fear-based marketing may get page views and sell your ebook, but the amount of sensationalism used was appalling. We would not expect to apply the physical/dietary habits of NFL players to the general male population, so why is it acceptable to do so for women and professional figure athletes?

It’s damning enough that the citations, when not outright contradicting the assertions made, seem to be cherry-picked papers and spurious links between mechanisms with all the blame being laid on cardio. Beyond that, the extreme example of 20+ hours

of cardio per week combined with binge eating is given to characterize the problem plaguing “Jessicas” in gyms across the nation, as if these two approaches are one and the same.

If anything should be taken away from John Kiefer’s article, it has little to do with running. What should be learned from this article is that a string of numbers after a claim does not automatically make it true. As a reader you should always check up on an author’s sources and come to your own conclusions after you’ve judged the evidence for yourself. If you were looking for an echo chamber to confirm your anti-endurance opinions, then the article was exactly what you wanted. But why mislead readers with contradicting or tangential citations? Why talk in certainties when none exist? Why use small, unrepresentative populations to generalize to the average woman?

Only the author can answer these questions.

Steady-state cardio has been shown numerous times to have many health benefits leading to decreased mortality risks. Sure, “too much” (so far quantified only as “long term and excessive” amounts typically used by competitive, extreme distance athletes) is not good for you and can be detrimental to general health and fitness goals. But for all the Jessicas out there, moderate amounts can easily be included in a well-rounded routine to complement fat loss goals or general health pursuits.
That said, steady-state cardio is not a requirement. If someone doesn’t want to do it or doesn’t like it, there are other alternatives that can be used. What this all boils down to is this: If you enjoy running and feel it benefits you and your training, and aligns with your goals' then keep on running.

When reading the actual scientific papers referenced by John Kiefer, there was actually no evidence that the cardio that the average “Jessica” partakes in has any detrimental effects; if anything, there is a vast amount of scientific evidence that it is helpful.

Skip Bouma and Sol Orwell contribute to, where they help make sense of scientific research across health and fitness.

80 thoughts on “Guest Post: Sorry, but Science Says Running is Good for You, Not Bad

  1. I always wanted to run…to fly along in the great outdoors. But at 47 my joints just weren’t up to it. Then I discovered roller derby. Now for cardio I skate outdoors along the river..get up a good speed too (avg 8-10km/h) No impact and I feel like I’m flying…except when I fall. hahaha

    • Fellow derby girl here! I use running for endurance training so that I feel I can actually get through practice. Healing up from an injury, but so far, so good. I just have to give you a shout-out because I love, love, love derby chicks. Props for being a badass!

      • Hey :). I despise cardio. Outdoor skates I LOVE. Derby has brought back my love of exercise!

  2. I think, that running is a perfect sport for healthy life. You can be in the nature and do what you love to do – run. Nice guest post, thx for reading. '?

  3. Thank you, Amber, you did it again (make me happy, that is :-)). I am a distance runner (1500m-5000m), already a “master” (I am turning 35 years this summer. I love my sport. I am not doing this to lose weight. I love fast intervals on the track and slower jogs, alone to clear my mind, enjoy nature or in company to chat. I love competetions, all this makes me feel good. I complement with a good amount of heavy lifting…and yet, all this talk about how this is bad for me has drawn away some of the pleasure. There is this voice in my head telling me all this will make me sick, burned out and fat…Thank you for dedicating a long blogpost to the issue, especially if you are a strength athlete and have no reason to defend cardio. You are a honest person and a critical thinker, much, much needed!

  4. It also does look at the WHY, i have clients who LOVE running. why tell someone to stop doing something they love and which mentally they find relaxing and de stresses them'?

    Every aspect of health and fitness has its place…..

  5. Thank you for writing this….I been a runner for over 20 yes. And recently when I started reading all this post about not been good for me. I got a bit sad because this is a sport I enjoy doing not for weight loss but because I am good on going long distance and because it keeps me connected with my sister that died of cancer and she was my running buddy/my friend. One thing i know I need to do is more strength training…any advice for a ultra runner?
    Thank you!

    • Stength training would benefit you greatly … very important to activate glutes and hanstrings properly and having strong hips, so that when you are running your not compensating in way that could cause injury long term.

      • thank you Phillip!….i noticed that when i first started running i used to lift weights, do yoga and i felt good, of course iam not 20 yrs old now but i dont lift anymore and i have noticed the difference, had one injury and dont want anymore. i know i need to strenght train and eat a bit more. since my goal is to do my 2nd ultra next year on January.

        • Yes calorie intake is very important … if you dial in your calories and refueling and add in some strength training you will feel so much better.

  6. Running daily. Feel Great. That’s enough for me! xo Deb
    PS Have Sol Write more often, he’s kinda smart. And handsome too.

  7. I read the original article and was so stoked to find out that I didn’t *have* to run in order to be healthy – but I sure am glad to see the scientific breakdown behind some of those claims. I am working on losing weight slowly right now, with biking and strength training, but once I’m at a more comfortable spot with my body I’m looking forward to trying to run again!

  8. I’m not a runner. In fact, the only time you’ll see me run is if I see a snake or something or someone is chasing me. However, I’m a swimmer and don’t feel like always focusing on “what’s the best I can do today in the shortest time to lose weight/burn calories, etc.” There is something to be said for the nice mile swim. I love interval days, but my brain and body sometimes need that long swim to get ready for the day or unwind from the day, depending on when I go. I think we have become so focused on macros and maximum heart rates and fat grams and calories that we forget to eat healthy food and be active for the sake of feeling good. I know people who are competing need to take things more seriously than this, and my road to better health is a bit winding, but I’m getting there. I imagine running is for runners is what swimming is to me, and if you enjoy it, do it!

  9. I’m 51 and have been running since 1977 or so, there was a stretch where I couldn’t run because I had become sedentary and fat, been running again for 4 years now and even if a study concluded running was certain death I wouldn’t give it up. You can have my running shoes when you pry them off my cold, dead feet.

  10. Great article! However, I have one minor issue. In discussing fat loss due to cardio, you lump together body fat storage usage and intramuscular fatty acid usage together under the category of fat loss. When it comes to figure competitors and those looking to lean out, these two sources of fat aren’t created equally, i.e. you wanted to lose body fat stores but you wanted to keep intramuscular fatty acid. I currently don’t have anything to back that up other than what’s in the recesses of my memory, but I was wondering if you could speak to that at all? Is losing intramuscular fatty acid a good thing?

    • Well if the figure competitor is resting the other 22 hours a day, and she is in a calorie deficit, where do you think the body is going to take fatty acids from to replace her muscular fatty acid stores?

      Her blood stream.

      Where is her blood stream going to get fatty acids from?

      Her body fat.

      So long as she maintains a caloric deficit she will lose bodyfat. She doesn’t have to burn it during her workout for it to wind up being used.

    • Hi, Frank.

      That’s a good point, but I cannot speak to the specific needs of figure athletes. I am fully prepared to concede that burning off intramuscular fatty acids may not be the best tactic for them.

      However, the reason we brought that issue up was to refute the assertion that steady-state cardio “makes it difficult for muscles to burn fat at all”. It most certainly doesn’t and the citations used as evidence that it does explicitly contradict that claim.

      Again, this may be detrimental to figure athlete needs (or it may not) but bringing it all together, is this concern something that should be generalized to all women?

  11. Outstanding article. Thanks for sharing. The authors made an excellent point about the high citation count convincing people that the claims were true, when they weren’t. It’s becoming a more and more common ploy, and it’s nice to see someone call it out.

    – Armi

  12. Pingback: Guest Post: Sorry, but Science Says Running is Good for You, Not Bad | Go Kaleo | Love2Lift

  13. I am not a runner. Nor do I do any form of endurance exercise. My workouts are a combination of power lifts, olympic lifts, and body weight. That being said I don’t think that running is harmful. But I also don’t think it is an optimal use of my time for my goals. I am 53 year old woman. My goals are to have my first 100 years of my life be usable '?

    For me this translates to maintaining/building muscle mass, avoiding bone loss, maintaining mobility, and maintaining metabolic health. Can running contribute to these goals? Sure. Will an hour spent running pay the same dividends as an hour spent doing body weight/free weight exercise? Nope, at least not if you lift heavy. I clean and jerk 80% of my body weight, deadlift twice my body weight, do 8 dead hang pull ups, etc. That being said, the best form of exercise is the one you will do.

    I also don’t think you need to do an endurance based activity for aerobic conditioning. Last year I was curious how long it would take me to jog 3 miles (I had not jogged/biked/swam/rowed in 20+ years). It took me 28 minutes.

    • I don’t worry about what kind of exercise is optimal or the best use of my time, there are 24 hours in a day and I spend at most 2 hours a day exercising, leaving 22 hours for everything else.

      I exercise based on what feels good. For me running feels good, lifting weights feels good, so I do them both.

      I never give a thought to the long-term health consequences of exercise, for all I know I am going to get run over by a truck this afternoon. In my experience attempting to control your future is an exercise in futility, you can only live in the present.

      • Same here! Also, I think what the original article may have been trying to say is overtraining and undereating = bad combo! but he just got a bit carried away with things lol.

  14. Amen! Thanks for writing this. I was so angered by the stupid “Why Women Shouldn’t Run” article. It made NO sense whatsoever. I am so tired of seeing and hear from others that what I do as a runner is bad. I am perfectly healthy, only getting healthier, improving my pace, getting leaner, and not getting injured. How can something that has literally transformed my life and my body be bad for me?

  15. I had just read about the article “Why Women Should Not Run” on MFP yesterday and believed it to be total tripe. I’m happy to see that there is scientific proof that agrees with my common sense. '?

  16. After two years of obsessive running, swimming, biking, and weightlifting, I was diagnosed with hypothyroidism at age 22. It never occurred to me that my activities could have contributed to it, but it doesn’t run in my family and I’m hearing more and more about a connection. A year ago you’d never be able to convince me that I blew out my thyroid with overtraining, but now I’m not so sure.

    • I think in many cases, overtraining is really a case of undereating. Certainly several of the studies Sol and Skip cited suggest that energy availability is the key to the body’s endocrine response.

      • you are right i noticed a difference in my running when i dont eat enough or rest, i have a friend who is a well known ultrarunner that has run the hardest ultra races all over the world and as far as i know she is strong and healthy and she is in her 40’s. She just finished and ultraironman….double the distance of a ironman, i think that is crazy but that is what she loves to do. maybe i should ask her that question?

      • You’re definitely on the right track. My undergrad was in physical activity and sport performance and we were taught that “Overtraining Syndrome” is more often than not a combination of both “Under-Nutrition” and “Under-Recovery” over an extended period of time.

        Athletic people tend to have a well-tuned intuitive sense of how much training stress their body can handle but not eating enough of the right nutrients and not getting sleep are easier mistakes for a person to make. You just have to stay up late for the newest episode of your favorite show, or get hit with a pile of life stress, while stubbornly keeping your training volume the same, and you will wind-up over-trained without any understanding why because you have your horseblinders on focusing only on training volume and not the whole life picture.

        There are many examples of elite athletes winding up with overtraining syndrome within a year of the death of a relative or breakdown of a significant relationship — with no change in their weekly training volume. These are people who are over-stressed and under-recovered, but not over-trained if all you looked at was their typical training volume one year to the next.

        It is still possible to over-train however and as someone over-reaches in their training, they also tend to lose their appetite and find it difficult to sleep, so these are natural indicators that a “back-off” period of about one to two weeks is necessary for the body to catch up.

        I have a friend who was a national-level biathlon competitor, now national-level mountain bike racer, who will train three weeks hard and take every fourth week off completely. His training volume during training weeks is insane, but he’s never had any issues with overtraining in the last 20 years.

    • I’m with you there, except I was overtraining (and subsequently undereating) for about 6 years. At 22, I’m now on thyroid medication to pick my sluggish metabolism back up. Wish someone had told me this could have happened long ago!

  17. This is my first time reading your blog and this article is amazing! YOU are amazing! Bookmarked!

  18. Yay, great post! I run a lot and sometimes have to skip leg workouts for them not to interfere with my run training, however, my legs are far from underdeveloped!
    Not to mention all of the other benefits running can have besides just burning fat '?

  19. What amazes me most (and I wish someone could elaborate on this) is that it is mentioned that running build muscle mass in the lower body (while overall muscle mass is decreased). So theoretically, when combined with a total body program, running should help in building muscle? All the negative stuff about endurance exercises is about how it contributes to muscle loss and that you cannot gain muscle with endurance exercise, so the findings about lower body muscle mass are quite a surprise, right?

    • As this article points out that this is true to some point. The real answer is that it depends. It depends on what your endurance regimen entails, i.e. what is endurance for you. For many endurance is the ability to run a few miles without stop at a moderate pace. For others this may mean they run 5 miles at a fairly intense pace. Yet others may call the 5 mile run a warm-up. So the real answer is that it depends. This holds true for many different types of endurance activities such as swimming, etc. It is really difficult smear generalities across the board. However, what will occur is that you will reach a homeostasis of muscle mass for a given endurance regimen as long as a complementary body program is part of that regimen.

  20. I’ve gravitated towards endurance training over the past few years, because I genuinely enjoy “going long”. I eat well to support my training and my energy levels are good, my skin is clear and I’m healthy – and in my 40s.

  21. I think a lot of this comes down to what’s important to you, and where your starting point is at. If you are a beginner and wanting to add muscle while losing fat any type cardio mixed with resistance training will do. But as you progress you will probably need to adjust.

    If running is fun for you, or if your goal is distance running on some level then by all means go get it! (although Tim Ferriss has some interesting tactics for this as well).

    All that said… almost anything can be put into a positive or negative light when used in comparison.

    I will admit I am a Kiefer follower… so have at me '?

  22. Thank you Go Kaleo & Sol for digging through the citations and providing the real information! When I first read that article back in the spring my jaw hit the floor. Fortunately for the author, the “comments” section was already closed (the majority of the replies coming from readers like me in a giant, collective *facepalm*.) As an avid runner, spin instructor, AND personal trainer, I can personally attest to the fact that a well-balance routine combined with a nutritious diet are what helps most of my clients – and has helped me – achieve optimal results. Thank you, also, for highlighting the importance of understanding specificity; that a power lifter can’t and won’t train for a marathon, and vice versa.

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  25. Awesome article in that you took the time to read the offending author’s citations and used the lack of relevance to debunk the personal opinion that he offered. This is something that is sorely missing in most fitness forums online and allows a lot of misinformation to go uncorrected.

    Did I miss something though? Where is the support for the title of the post ‘Sorry, science says running is good for you, not bad’?

    • Hi Joe,

      We have several of our own citations in the middle of piece showing the benefits of running (and a few showing the ill-effects of ‘too much’).

      Was there something else you were looking for?

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  27. I’m so confused… I took the time to read your article and after all that I’m unclear as to what your position is or what your point was ? Critics promoting an agenda are a dime a dozen… What makes your article any different ?

    “That too much of anything is bad for you” ?

    Anyways… This is the first time I’ve come across your site…. You seem a little obsessed with body image in the primary and optimal health as a secondary, which ( to me ) is a tail wag the dog perspective anyway !

      • Ok… Its important to know '? I’d initially thought this was a health based site, but if the focus is body image it sits more appropriately… Run till your hearts content – you look great '?

  28. I am so excited about this article. I have been searching for a response about this women shouldn’t run idea for a couple months. I will be putting on my minimalist running shoes this afternoon and running. It has been months since I stopped running because of hypothyriodism but I am now thinking I was under nourished even though I eat paleo. Thank you for this!!

  29. Excellent and well-researched response to poorly-written and downright dishonest newspaper/magazine articles.
    And they wonder why reading figures are going down the pan.

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  32. Thank You for FINALLY offering a “place” for real discussion!

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  34. There were a billion different ways to start the discussion.

    Starting with “women should not run,” and then backing it with a bunch of assertions that had citations that contradicted those very assertions is *not* the way to start a discussion.

    There was no provocative question. There was just a bunch of made up facts.

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  36. A fine critique, and while I appreciated the face that you did not stoop to ad hominems, it would be remiss of me not to point out the utter reprehensibility of this man abusing his “friend” in an internet article.

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  38. I don’t know anyone who ever said running isn’t good for the body and I have always thought it’s one of the best way to exercise and lose weight. Every weekend, especially in the morning, I make it a point that I run for at least an hour. It’s what gives me my strength.

  39. Thank you for taking the time to research this so thoroughly, and for writing this article. As a long-time distance runner I read the article you referred to and thought it was hooey, but didn’t have time to go to the trouble to flesh it out. Run on.

  40. So far I don’t think there is any clear indication that there is a threshold where if you exceed a certain number of miles run per week it is bad for you. Obviously there would have to be such a level somewhere–most of us would probably die if forced to run 500 miles per week.

    Alex Hutchinson at his Runner’s World blog had a good piece on this notion that excessive running ( meaning more than about 30 miles per week) is bad for you–I think it came out in November 2012, but I’m too lazy to look it up right now.

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  46. Thank you guys so much for taking the time to extrapolate the sources in the sensationalist article by Kiefer. I think the initial article was really in poor taste, as using a woman who is “sick” (thyroid problems) to begin with and whose personal goals (at least the ones projected by Kiefer) were not in line with necessarily every other women’s goals, don’t make his study applicable to the masses, but the dramatic and “edgy” title made people think it did. I’m a powerlifter. I’m a runner. A younger me would have bought in to this hype, but I’m way over fitness “gurus” being over dramatic.

  47. Oh man this is brilliant! Thanks Sol and GoKaleo ' this is exactly the sort of evidence based and non-alarmist information I’ve been looking for about concurrent cardio and strength training '?

  48. Sorry for commenting so long after this was posted. I just discovered the fantastic site that is Go Kaleo. I’d like to give a bit of a counter argument to this article.

    Why women shouldn’t run: Because it’s torture. It’s boring. It nearly destroyed my knees and did NOTHING to improve my body composition.

    Okay, that’s just why THIS woman shouldn’t run. Yet over and over again I told myself I HAD to run because it’s the gold standard of fitness and that’s what you do if you want to lose weight. Fit people run. So every time I told myself that I’d get back on a running program until the next time my left foot would be in agonizing pain or when my knees felt ouchy. When a bout of tendonitis got me and the MRI showed the cartilage wearing away, I ditched running for good. Currently I’m at my lowest weight I’ve been at for years thanks to a better effort to clean up my diet, a good weight training program, and a desire to make sure I truly enjoy as much of the exercise I do as possible.

    I wouldn’t want anyone to dismiss running based on my anecdotal experience. I do hope that my own story can at least inspire other who hate running to stop feeling *obliged* to run for health and fitness. So many articles out there say, “You hate running? I hated it too. Just keep doing it and you’ll love it.” I only ever loved running when I was finished with a run. I am never going to run again if someone isn’t chasing me. Running may be very good for you, but don’t feel that it’s the only exercise that’s good for you. You don’t have to do it.

    • Great article and a comment. While I appreciate that some people love running, just as much as I enjoy powerlifting, I think that there are far too many extreme opinions there at the moment. Love running? Run. Hate running? Don’t. At the end of the day, the real battles are being fought in the kitchen and exercise should be there to support it and make things easier. Saying that everyone should run is just as wrong as is claiming that women should only lift, and avoid cardio like the plague.

        • No, I don’t think that I expressed myself properly here. I meant the feeling many people seem to experience that ‘all the fit people, who run are so fit because they run therefore I should run too’- this is an extreme and I don’t agree with it, just as much as I disagree with making running the scapegoat. I loved the article '?

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