Ziv wrote in 2017, edited in 2020, republish in 2023
While studying at National Dong Hwa University, I used to spend my free time reading reference books on sports science. After graduating, I pursued my postgraduate studies at National Taiwan Normal University, specializing in the field of sports biomechanics. I analyze sports techniques from the perspective of human biomechanics, which necessitates a solid understanding of mathematics, particularly in the application of various physical formulas and calculus. Fortunately, I gained valuable experience in calculus during my time at the business school.
Upon conducting rigorous experiments and research, I have found that the Pose Method of Running simplifies the categorization of gait phases, possibly for the sake of practicality in its promotion. However, from an academic standpoint, there are indeed aspects that could benefit from refinement, especially the limited discussion of muscle electromyography signals. I make this observation based on my doctoral studies, which involved publishing research papers in academic journals and books, conducting hands-on experimental analyses, and presenting posters and giving oral presentations at academic conferences. Throughout these activities, I received feedback from professors.
Oral Presentation at an Academic Conference:
Internal Presentation on October 5, 2017, at the Department of Physical Education, National Taiwan Normal University, as part of the regular academic seminar series. The presentation topic was “Analysis of Lower Limb Electromyographic Signals in Various Running Styles.”
The seminar had a total attendance of 185 graduate students, and this information was obtained from the department’s sign-in and attendance tracking system.
I will be giving an external oral presentation on November 19, 2017, at the Annual Academic Conference on Sports Biomechanics in Taiwan. The event will be held at the International Performance Hall of National Pingtung University.
Title of the presentation: “Analysis of Lower Limb Electromyographic Signals in Various Running Styles.”
The content of the presentation was initially prepared for an internal presentation within the university and was later submitted, with additional sports science parameters, to the 2017 Annual Sports Biomechanics Conference in Taiwan. The conference was organized by the Department of Physical Education at National Pingtung University, and the submitted papers went through a review process by a committee of professors in the relevant field. It was accepted for presentation at the symposium and subsequently published in the proceedings of the 2017 Annual Sports Biomechanics Conference. The presenter acknowledges that there is room for further improvement in the content and plans to submit it for journal publication. The submission deadline for this symposium was October 18th, and despite the tight schedule, the presenter received confirmation of successful publication.
Regarding the Extensor’s Paradox, which is frequently discussed in the context of Pose Running, it has been observed that the quadriceps muscles (specifically the rectus femoris) are not activated during the 20 milliseconds following the conclusion of the mid-stance phase of running. In the experimental division of this motion, these 20 milliseconds are considered as part of the push-off phase. Consequently, this research finding suggests that during the push-off phase, the primary extensor muscles of the lower limb, such as the quadriceps, are not being activated. However, it is essential to note that the absence of quadriceps activation during this period does not necessarily imply that the center of pressure of the foot has shifted to the forefoot. This indicates that the classic pattern of the terminal stance phase has not yet occurred. In other words, the runner has not entered the true propulsion phase.
I can confirm that Pose Running is an instructional method with certification exams that cover fundamental concepts of sports biomechanics and physics. However, in the finer details, there may be inaccuracies, and I also maintain some skepticism regarding this method.
After reading the Extensor’s Paradox from 1990, I had several questions of my own.
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- The experimental results were published in 1990, and at that time, the technology for EMG (electromyography) was not as advanced as it is today. The sampling frequency in the experiment was only 500 Hz (500 data points per second). According to the Nyquist Theorem, the effective frequency is half of the sampling frequency. In other words, to obtain 500 effective data points per second, the sampling frequency should be set to 1000 samples per second. Additionally, the use of a 75Hz high-pass filter in the experimental design appears to be unusual. In typical gait analysis, the high-pass filtering is usually not set at 75Hz. Could this design choice have obscured any truly important signals?
- The experimental results did not provide a specific definition of the different phases of the gait cycle. Instead, they were explained within the context of a single-foot landing gait chart and knee extension/flexion. The absence of a detailed breakdown of the gait phases raises questions about the accuracy of interpreting the EMG signals.
- The experimental results described the 20 milliseconds following the mid-stance phase as the “propulsion phase” and explained that the quadriceps muscles, specifically the rectus femoris, were not active during this period. However, I believe that this 20 milliseconds might correspond to the early terminal stance phase, where the heel is just lifting off the ground (heel-off). Whether there was propulsion during this time is uncertain, especially considering that the experiment did not simultaneously record the EMG signals from the calf muscles. The study’s conclusion that the quadriceps did not activate during this period might also be influenced by issues related to the sampling frequency of the EMG signal.
At 80 milliseconds, we are in the mid-stance phase, while the experiment claims that the propulsion phase occurs at 100 milliseconds. The typical propulsion phase usually occurs from around 120 milliseconds, marked by heel-off, to approximately 200 milliseconds when toe-off is about to happen. Typically, the push-off action occurs between 160 and 200 milliseconds. This suggests that it is unlikely for the 100-millisecond point to be in the propulsion phase. Since the experiment did not explicitly define the phases of gait and instead used knee joint angles as a reference, it raises concerns about the scientific rigor of the study.
The maximum knee joint angle occurs at 80 milliseconds, which is during the mid-stance phase. However, at 100 milliseconds, the quadriceps muscles do not show significant activation. This doesn’t mean they are completely inactive. Conducting experiments with Pose Running practitioners, it is evident that the quadriceps muscles still exhibit some activation during the propulsion phase, although it might be less compared to typical runners. This suggests that quadriceps activation is necessary for maintaining proper knee flexion.
4. The Pose Running method emphasizes the concept of “pulling” the foot off the ground while maintaining a straight alignment of the hip, knee, and ankle joints in the sagittal plane. However, it does not provide detailed information regarding the exact angle at the knee joint because it is not possible to achieve a completely straight knee joint angle during running. In biomechanics, the angle ∠ABC is commonly used to assess joint angles and motion in the sagittal plane. This angle is calculated using reference points such as the greater trochanter, lateral femoral condyle (knee), and lateral malleolus (ankle). In the Pose Running method, the focus is on maintaining proper alignment and minimizing excessive knee extension to reduce impact forces and energy waste.
5. I asked a Pose Running practitioner to run at a speed of 15 kilometers per hour (kph) and found that it took approximately 30 milliseconds from mid-stance to the moment just before toe-off, as shown in the figure above. Therefore, in the experiment designed with a speed of 4 m/s (approximately 14.4 kph), it is unlikely to achieve a push-off within just 20 milliseconds.
My thoughts are as follows:
According to the principles of action and reaction, when two objects come into contact, they generate forces of equal magnitude but in opposite directions. On Earth, the reason we can walk and run freely is due to the presence of sufficient friction between our feet and the ground, which enables us to maintain contact. Just before lifting off the ground, we exert a backward and downward force, enabling us to move forward and upward. Additionally, due to our forward lean and the force of gravity, we have a natural forward momentum and angular momentum resulting from the forward lean angle. This enables us to take stable and confident steps. Support is essential for movement. In space, two astronauts can push off each other in opposite directions, creating equal and opposite forces to move away from each other. This is likely the underlying principle.
In my understanding of Pose Running, it encourages runners to minimize vertical oscillations of the body’s center of mass. It promotes not actively pushing off, but this does not mean there is no application of force to the ground to propel forward.
In any case, these opinions are not solely my own. As a master’s student, I developed these concepts into a research conference paper, which was subsequently published in academic journals. During Pose Running training, it was evident that many of the attending coaches lacked a thorough understanding of biomechanics and dynamics. Even Teacher Xu struggled with directly interpreting terms like “Kinetics” and “Kinematics” from English to Chinese during impromptu interpretation. I found this to be quite disappointed.
I consider myself fortunate to have the opportunity to thoroughly validate new trends or theories in the real world using robust experimental designs and high-quality sports science instruments. This allows me to clarify misconceptions among students who may lack the necessary background knowledge. I am always patiently waiting for opportunities, not out of passivity, but with the intention of thoroughly preparing myself before embarking. This ensures a steady and long-term journey.
In conclusion, I want to reiterate that what I can confirm is that Pose Running is a teaching framework that incorporates fundamental principles of biomechanics and physics in its certification exams. However, it may not be entirely accurate in its details, and I do not fully endorse this method.
Postscript:
In 2020, I revised my master’s thesis into a conference paper and submitted it to the Taiwan Sports Biomechanics Annual Conference, which is the largest conference in our field in Taiwan. I presented it as a poster and received the Best Paper Award.
