The flip flops discussion—are they healthy, are they not—seems to come up every year once the weather turns nice. There are wide-ranging opinions on the merits and pitfalls of flip flops for foot health, and many healthcare professionals possess strong views on this ubiquitous warm-weather footwear. In fact, the topic of flip flops often generates a lot of controversy, seemingly out of proportion with the somewhat unexceptional nature of this subject matter. In this article, we’d like to share our viewpoint and stance on flip flops and how this simple, stripped-down footwear option might contribute to or hinder foot health. So, are flip flops bad for your feet?
A Review of Healthy Footwear Design Features
Any conversation about flip flops and foot health should begin with a review of foot-healthy shoe design features. This criteria differs based on who you poll, but in our experience, we’ve found the following design features to be foot-health-positive: A completely flat support platform from heel to toe to encourage natural arch support, a flexible sole to encourage enhanced foot strength, and a wide toe box to encourage natural toe splay. We’ve also found that the less “technology” a shoe possesses, the better it is for the foot, because the foot—in almost all instances—is inherently strong and stable, if it’s allowed to function in the manner that nature intended. An additional feature we like to see in footwear is an open upper that allows the foot and toes to be exposed to light and air, as this helps promote a healthier environment for the foot. Obviously not all climates are conducive to this last design feature, but most regions can accommodate foot exposure for at least a portion of the year.
So, if we take each of these points into consideration, flip flops do indeed meet all of our criteria for what constitutes foot-healthy footwear. Flip flops, in most cases, and for most people, represent an opportunity to build foot strength and prevent a lot of the chronic foot problems that plague our shod society, although some caveats do exist (please see the section below entitled Where Problems Might Arise).
A Look at the Evidence
Digging into various online discussions and even the literature, it’s not difficult to find articles and even a few studies admonishing flip flops for being harmful footwear. But, as is so common in the world of laboratory research, you can also find studies that state the opposite. The seemingly equivocal nature of conventional research into this topic creates confusion for those interested in making the most informed decisions. The best thing any consumer or health advocate can do is to look at the current evidence (both experimental and empirical) and make the best possible decision based on all the available findings.
Let’s take a closer look at one of those studies that inadvertently landed on the side of flip flops. This study, supported by the National Institutes of Health, was conducted by Dr. Najia Shakoor and published in the journal Arthritis Care & Research. Shakoor’s study, entitled “The Effects of Common Footwear on Joint Loading in Osteoarthritis of the Knee,” examined the effects of several common shoe types on knee loading in subjects with osteoarthritis of the knee, including clogs, athletic “stability” shoes, flat walking shoes, and flip flops. The author states the following:
We know barefoot is good for your knee load from previous studies [please see our article entitled Footwear & Knee Osteoarthritis for more on this study]. Then we thought, do different shoes have different effects on the knee?
And so Shakoor and her team compared the above-mentioned shoes with going barefoot in terms of the amount of force upon the knee while walking. Here is what Shakoor had to say about the findings of her study:
The shoes that we intuitively recommend to our patients [with knee arthritis] and thought might be best—stability shoes and clogs—were associated with the highest load. Flat walking shoes, barefoot, and flip-flops were essentially the same in load on the knee. But clogs and stability shoes result in a 15% higher load.
Shakoor goes on to say this:
These are just initial studies, and it's too early to recommend [changes]. But several studies are suggesting that perhaps flat, flexible footwear may help decrease loads on the knee compared to footwear that is less flexible and has higher heels. Stability shoes have higher heels [than other athletic shoes]. We think it's the flatness and the flexibility that may provide the benefit.
This comment by Shakoor will resonate with those who are already familiar with Natural Footgear’s foot health philosophy. Other relevant articles we have published that relate to the topic of what constitutes a foot-healthy shoe include The Shoe Cushioning Myth, Definition of a Healthy Shoe, and What is Natural Arch Support?.
A Look at Real-World Evidence
Flip flops, in one form or another, have been a part of our human civilization for millennia. In our contemporary society, we tend to look to research studies to tell us what’s truthful or valid. In doing so, we sometimes overlook the empirical evidence that exists around us, including certain health traditions or behaviors that have been practiced for thousands of years. It’s extremely important to give serious consideration to the practices and health habits that appear to have served so many so well throughout the ages, even if our current default mode is to rely most heavily on randomized controlled trials and clinical studies to determine the merits of a particular idea or approach.
Flip flops have been used (and continue to be used) by hundreds of millions of people on continents such as Asia, Africa, and South America. I’ve personally had the great privilege of spending a total of 7 months in South and Southeast Asia over the span of three trips, including time in Nepal, India, Sri Lanka, and Indonesia. This time, especially my experience in Nepal, was revelatory to me in terms of the footwear I observed and its apparent effects on foot anatomy and foot health. Among the many wearers of flip flops and other similar footwear I met throughout the developing world (including mountain porters in the High Himalayas), I observed in this large group both incredible foot structure and foot health. In fact, on the trekking routes of Nepal, the only people complaining about aching, pained feet were Westerners, in their stiff, heavy hiking boots.
Many people who argue that flip flops are detrimental to foot health have not visited the developing world and witnessed, firsthand, just how commonly (and successfully) this footwear option is used, without the widespread foot health issues we experience in our society. The American Podiatric Medical Association notes that 77 percent of US adults over the age of 18 have experienced foot pain or problems, whereas this study conducted in China and India back in 1949 noted that only 9 percent of the thousands of people studied—some who had never worn shoes, some who had worn only “a light, flat and very pliable sandal”—experienced foot problems (and most of those problems were dermatological issues, not musculoskeletal issues). The following logic is intended to demonstrate why flip flops are not the harmful footwear they are often made out to be:
Flip flops are used en masse in the developing world. The foot health issues that plague shod Westerners are significantly lower in these societies. If flip flops do indeed contribute to a breakdown in feet and foot health, we would expect to see large swathes of people in the developing world crippled by them. This is clearly not the case.
So, real-world observations into footwear and foot health are valid too. When it comes to health issues, including foot issues, it's extremely important to do your own investigating and challenge long-held beliefs and assumptions. Sometimes it turns out that we had it right all along; other times it turns out that a paradigm shift is required.
Where Problems Might Arise
Our perspective on flip flops is that they can be foot-health-positive, provided certain criteria or conditions are met. First, and perhaps most importantly, the strapping system on the flip flop must be sufficiently snug to prevent slippage of the sandal under the foot. One of the biggest complaints about this kind of footwear from healthcare professionals is that too-loose flip flops can result in an excessive amount of toe flexion or gripping to keep the sandals on. And, indeed, this is a legitimate concern and a potential problem. In this scenario, with a loose strapping system around the forefoot, the foot is not capable of acting as nature intended, and repetitive toe gripping can lead to unanticipated (and undesirable) foot and toe problems. It’s best to find a pair of flip flops that fit snugly around the forefoot to prevent repetitive toe gripping. Or better yet, select a men’s or women’s sandal that possesses a heel strap to keep your foot firmly rooted in place on the sandal's footbed.
Another possible problem associated with flip flops is that not all flip flops are created equal when it comes to their design. Many flip flops have heel elevation, rigid soles, and toe spring, among other problematic design features. The same criteria that apply to regular shoes (in terms of foot-healthy design features) also apply to flip flops. It’s always a good idea to come back to the foundational concepts of what constitutes a truly foot-healthy shoe when shopping for footwear, including flip flops.
Also, most of us wear closed-toe shoes or boots during the cooler months before adopting more airy options in the warmer months. This transition can sometimes be abrupt, especially for those individuals who go from a conventional shoe with heel elevation to a pair of flip flops that possess little or no heel elevation. Achilles tendon issues are one possible outcome of this rapid transition. The main point here is that the transition to wearing flat-soled flip flops should be a gradual one, so that your body can adapt slowly and minimize the risk of an injury. Our article entitled How to Transition to Minimalist Shoes offers some insightful tips for those who are transitioning from cold weather footwear to flip flops.
One final consideration with flip flops is the importance of respecting the structural limitations of this minimalist footwear. In most cases, flip flops were not created to be used in adventurous or high-intensity situations. This footwear option generally works best in low-intensity situations, such as at the beach, around the house, or for casual trips around town. Once the footbed wears down, it’s important to introduce a new pair as soon as possible so that you can avoid the problems associated with aging footwear.
So, where do flip flops rank on the scale of foot-healthiness? I think the answer largely depends on the specific design features included in the sandal and whether or not the strapping system is sufficiently snug. I think it also depends on the state of readiness of the user to wear this flat and flexible sandal. If the criteria for foot-health-positive design features are all satisfied, and if the transition to this type of minimalist footwear is gradual and measured, then flip flops can indeed be a viable warm-weather footwear option that allows the foot to function as nature intended. And that's a good thing! When the foot functions as nature intended, it means that the toes are well splayed, the intrinsic foot muscles are strong and balanced, and the main foot arch, the medial longitudinal arch, is strong and stable on its own, all of which help prevent pain and problems.
I hope this article has provided you with an alternative perspective to most of the content out there about flip flops and their possible effects on the feet and foot health. Ultimately, the decision of what you choose to put on your feet is yours, and I wish you success with whatever you deem to be in the best interests of your own foot’s form and function.