What is going on with shoes nowadays? It seems like the footwear we’ve worn for years is somehow no longer adequate. Fitflops, MTB’s, Reetone, Shape-Ups — there is an influx of new shoes on the market, all of which make some pretty lofty claims about the benefits of wearing them. In this article, we’ll explore these claims, as well as the scientific facts and fallacies behind them.
First off, we need to start by gaining a little understanding of the biomechanics of gait and ground striking. So that we’re all on the same page, gait is simply defined as the series of mechanical actions that result in limb movement to produce (typically linear) motion. Ground striking is a component of gait — and arguably the most important component — as it is the physical act of ground contact that transfers muscular forces to earth, so the earth can push back on you (remember Newton’s third law of motion; action-reaction) to produce movement).
To spare you a bunch of complicated physics and a discussion of the mechanics of gait, let me summarize some generally accepted facts from the biomechanics research:
- The human body typically self-selects the least injurious and most efficient gait and ground striking pattern.
- Abnormalities in gait or ground striking are typically due to bone alignment, not musculoskeletal factors; therefore, poor running (or walking) mechanics cannot be corrected by exercise.
- Gait modification (making mechanical modifications to gait, ground striking, stride length, and stride frequency), although occasionally appropriate, does not come without risks (going back to the first statement above about gait self-selection). As gait is modified, mechanical forces shift from areas that are acclimated to handling that mechanical stress to areas that aren’t. Sometimes this is good, as stress is taken off an area that injured. However, sometimes that stress is shifted to an area that is not capable of tolerating it, and an injury results. As a result of this potential outcome, gait modification is looked at as a last resort for runners and walkers alike. Furthermore, due to its complexity, gait modification should be directed and supervised by a trained professional (such as a biomechanist or physical therapist).
OK, done with the science lesson — on to the shoes! So, what are the claims? Well, they run the spectrum from mechanical to aesthetic. The mechanical claims relate to more favorable mechanical position of the leg to reduce joint pain, increases in muscle activation, and reduced pressure on the bottom of the foot. The aesthetic claims (which certainly seem to be the overwhelming focus of the advertising) are that you will have nice, firm, tone, and shapely calves, thighs, and butt.
Let’s address the biomechanical claims first. If you look at the websites for these different brands of shoes/sandals, they will all quote some sort of “research” that has been performed on the mechanical advantage of wearing their footwear. When you actually dive into the research (or try to), however, you find that very few of the studies actually appear to be published in any scientific journal. In fact, a Medline search (Medline is the National Institute of Health’s electronic database of scientific journals, pretty much THE source for reputable research) returns no studies performed on these specific kinds of footwear. Publication in these journals suggests the research was of academic and scholarly value. Put in simple terms, the science was solid and the researchers came to a reasonably valid conclusion that should be shared with the population at large. Now, there are a handful of studies that actually appear to have been published in scientific journals. Below is a summary of some of the claims of the published and non-published research, as well as the truth behind those claims:
- Reduced Joint Pain: although some of the studies suggest a reduction in joint pain (ankle, knee, hip, and lower back), there is one big confounding factor: pain is perceptual and therefore very hard to quantify scientifically. Since pain is so elusive, making claims about its reduction is dicey. For some, there may be actual reductions in pain; others may experience more of a placebo effect; and still others will find that wearing this footwear leads to more (not less) pain.
Improved Posture: there are an infinite number of mechanical interactions that result in body posture. The suggestion that changing ground striking mechanics alters posture into a more mechanically advantageous position is simply an exaggerated claim. Any reputable biomechanist will tell you that there is no “perfect” posture, and deviations from a correct posture (if one does exist) are complex. It is, therefore, unlikely that a pair of shoes can have that big of an effect on postural mechanics.
- Increased Muscle Activation: this is one of those “relative to what” statements. In other words, sure, you might see minor increases in muscle activation, but does that lead to anything significant? In terms of strength and endurance, the answer is certainly no, as the level of muscle activation is still ‘hundreds of times below the threshold needed to actually stimulate significant change in the muscle fiber on a muscular fitness level.
- Increased Metabolism: some studies report a 2.5% increase in oxygen consumption when wearing this footwear (basically, this claim suggests that more calories get burned when the footwear is worn). Sounds like a difference, right? Well, yeah, but even if it’s statistically significant (an important term in research), it’s not practically significant, as that 2.5% increase during standard walking would result in a 0.3 calorie-per-minute increase in energy expenditure. Over the course of one hour of walking, that’s only 18 extra calories burned (roughly the amount of calories in two lifesavers), which hardly seems worth it, particularly if you consider the risk of injury associated from switching to this footwear.
Now, onto the aesthetic claims. No matter what any of these footwear manufacturers will tell you about the mechanical benefits of wearing their footwear, the overwhelming implication is that your legs will look better if you wear this footwear. Look at the ads and the websites, filled with models who have incredibly lean and well-developed leg musculature. No doubt their legs look great, but I can guarantee you they didn’t get legs like that by wearing this footwear. Why can I guarantee it? Well, mostly because it takes years to develop lean, muscular legs, and I’m sure that the first time most (if not all) of these models put on the shoes was FOR the ad. Beyond that, their legs look good not because of the muscularity, but because of the lack of fat tissue on top of the muscle, and this is the whole problem with this footwear – it does NOTHING to get rid of the fat.
How is fat lost? Yes, that’s right, a calorie deficit (expending a greater amount of calories than what you consume). So, you can wear these shoes all day long, and unless they walk you away from the refrigerator every time you want to eat, they’re not going to help. OK, maybe that point was little dramatic, but there’s truth behind it. The extra 50 or 60 calories (and that’s estimating high) you could burn by wearing this footwear daily won’t even begin to create a calorie deficit, and even if it did, it would result in somewhere around 1/70th of a pound of fat lost per day. Anyone interested in losing one pound every 70 days? Probably not what you were thinking, right?
The bottom line here is pretty straightforward. This footwear will not do anything to help any part of your body look better unless you restrict your calorie intake (once again, there’s no shortcut – nutrition has to be involved). Even if you do restrict your calorie intake, the degree to which this footwear will actually contribute to fat loss is so negligible that it hardly justifies the investment. Above and beyond all this, there is actually a chance that wearing this footwear can result in any number of orthopedic issues, from more benign tendonitis to much more severe stress fractures.
But, if you still insist on purchasing and using this footwear, let me give you a couple of words of caution.
First, integrate them in slowly. Wear them for an hour a day here and there; walk around the house in them before you exercise in them; essentially, break them in like you would a baseball glove – slowly and progressively. By doing so, you give your body a chance to acclimate to the shift in mechanical forces that will occur as a result of wearing this footwear, which should reduce your risk of injury from wearing them.
Second, do not wear this footwear for resistance training and/or any exercise that involves multi-directional movement (lateral motion, change in direction, etc.). These types of activities require SIGNIFICANT stability of the foot and ankle complex, and wearing this footwear can result in catastrophic injury (fractures, tendon tears, etc.). If this footwear is designed for anything, it is linear motion (walking or running forward), not anything else.
Lastly, and most importantly, don’t expect too much out of this footwear. As stated above, any benefit will be minimal at best, and it is a virtual certainty that you will not see any improvement to your body composition merely by wearing this footwear. So, buyer beware: before you go spending $100 (or more) on a shoe or sandal, consider some of the points discussed above. If you do, you’ll likely come to the conclusion that this footwear is not worth the money or the risk.