Weightlifting Shoes: What Does Research Tell Us About WL-Shoes' Effect on Performance, Form & Muscle Activity?

With the majority of the research involving squats, it makes sense to focus, at least for this basic research overview, on studies in which the squat performance, biomechanics and muscle activation with running shoes and/or minimalist/no shoes were compared to weightlifting shoes.

Table 1: Overview of studies comparing squatting in weightlifting shoes to other shoes/barefoot.

All in all, I was able to dig up 14 studies with 7-32 subjects (both male, female and mixed), each. Almost all subjects had previous squatting/weightlifting/strength training experience, were normal-weight and healthy. The various weightlifting shoes (as you would have expected, brands and models differed significantly) were mostly compared to running shoes and/or squatting barefoot. Alternatively, some studies used Vibrams or similar minimalist shoes as a comparison. A medium intensity (~60% 1RM) was chosen in most studies to prevent that high weights would compromise the form.

The study outcomes included 2D/3D kinematic analyses of the actual squat, measurements of the EMG activity of the subjects' leg (and in some cases trunk) muscles, the force (re-)distribution during the squat (measured with force plates = scales that can determine the gravitational force different parts of your feet exert on the ground), and direct measurements of the joint angles (vs. 2D/3D video analysis) by the means of electrogoniometers... all that with very heterogeneous results, I've briefly summarized for each of the N=14 studies in Table 1.

What the tabular overview in Table 1 doesn't really give you, though, is a visual representation of the differences that were observed in some studies. That's a problem because not every statistically significant difference is also practically relevant. Let's take a look at Fortenbaugh et al.  (2010; Figure 1), for example.

Figure 1: Comparison of squat kinematics between running and weightlifting shoes (Fortenbaugh 2010).

In their study, the scientists observed significant effects on horizontal trunk displacement and ankle peak flexion. With a quantitative difference of only 10% and 3%, respectively, and in the absence of measured shear forces, it is yet difficult to tell how practically relevant the "more vertical shank position and erect posture during squatting" (Fortenbaugh 2010) actually is. The fact that the optimal biomechanics will also depend on your individual physique (e.g. the ratio of leg to torso length, etc.) and variables like bar-positioning were often not even standardized within the individual studies (let alone between studies), doesn't make it easier to interpret the results.
The same goes for the results of a more recent study by Legg et al. (2017) whose 3D motion capturing study was more state of the art, but observe likewise only small magnitudes of changes in knee and ankle joint moments - and that without the often-advertised reduced chance of having your knees pass past your toes when squatting w/ the right gear: when depth and knee movement were unrestricted, the knees would very well be moving anteriorly beyond the toes during the squat movement, albeit with high inter-individual differences.

Heterogenous study design, heterogeneous outcomes

Even if we focus only on the more recent 3D (vs. older 2D) analyses of the movement patterns while squatting, studies by Wilkins et al. (2016), Sinclair et al. (2014) or Lee et al. (2017) report conflicting or null results with respect to the effect of using weightlifting shoes on the stability of the subjects' center of pressure. The same can be said for the results of EMG measurements, which reveal (in most cases) no relevant effect on trunk/leg muscle activation.

That some studies found (at least statistically) significant differences, while others didn't can be explained by dozens of confounding variables - with the three most important ones probably being:

• differences in the weightlifting and control shoes that were used
• the effect of training load which differed between studies (25-80% 1RM)
• subject variables such as habituation to footwear, squat technique etc.

Finally, it's also worth mentioning that the increase in knee flexion and thus quad involvement may come handy for athletes competing in sports where that's the muscle which makes the difference between victory and defeat.

On the other hand, we should not forget that anterior-/posterior-chain muscle imbalances (which usually favor the anterior chain) are pretty common. People who are already "quad dominant" will not necessarily want to increase their problem even more by squatting with weightlifting shoes.

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