Until today, optical observation stands as the most prevalent method for motion analysis. This can be applied in real-time or retrospectively using video footage. For relatively straightforward or slower (athletic) movements, this approach can prove highly effective. However, as the complexity of a motion increases, the efficacy of this subjective perception diminishes rapidly. For instance, walking is an instinctive and reflexive controlled action where both legs and various body components within them move in and out of phase within approximately one second. In essence, a substantial amount transpires within a brief timeframe.
Despite the human eye’s acute ability to detect deviations from the typical gait pattern, it does not necessarily excel in recognizing fundamental issues or compensatory strategies.[1] In actuality, the genuine attributes of walking are minimally visually discernible to us.[2] In other words, we may perceive that something is different, yet understanding what it is, and its underlying causes often remains an enigma.
While a trained eye might perceive more than an untrained one, a critical limitation is that the human eye does not detect movements occurring in less than 0.25 seconds.[3] Consider the loading response phase, where the leg must bear and stabilize the body weight immediately after landing; it is barely longer than that. When we look at the stride duration in running, it is already very short (<0.6 s). As for ground contact time, it is often not longer than 0.25 seconds in good runners. Sprinters are even briefer on the ground, and it’s essential to realize that the first half of the support phase (where stabilization and propulsion must happen almost instantly) can be less than 0.17 seconds.
Another challenge that should not be underestimated is that motion occurs in three different anatomical planes, while we can only study one plane at a time. The same applies to the ‘level’ of motion – we can either examine the overall pattern or zoom in on a specific joint. Analyzing both simultaneously is nearly impossible, just as we are incapable of visually estimating the degree of variability in someone’s movement.[4]
In summary, we do observe movement, but we see very little. Finally, there can be a debate about the reliability and objectivity of the findings due to observer bias.[3] The solution is the use of technology and application of data. Discover the options by checking our blog:
Movement analysis- how to capture and analyze biomechanics of human (loco)motion
[1] Baker, R, Esquineza, A, Benedetti, MG, Desloovere, K. 2016. Gait analysis: clinical facts. European Journal of Physical and Rehabilitation Medicine 52 (4): 560-574.
[2] Lagerberg, A., Riezebos, C. 1994. Bewegingen van romp en wervels. Versus – Tijdschrift voor Fysiotherapie 1: 17-42. (in Dutch only)
[3] Bartlett, R. 2007. Introduction to sports biomechanics. New York (USA): Routledge.
[4] Stergiou, N. 2020. Biomechanics and Gait Analysis. London: Academic Press.