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26 sierpnia 2016 Redakcja Bieganie.pl Sport

Rhythm


Make the impossible possible, the possible easy, the easy elegant.
M. Feldenkrais
Everything you’ve always wanted to know about running rhythm but couldn’t find in books

Rhythm

Rhythm, synonymous with cadence or frequency, can be represented as a certain value. Such a value reflects the amount of revolutions per minute (leaps/steps executed per minute), less commonly per second. These days, the control of rhythm during running is fairly easy. One can systematically track its value, as well as make use of a metronome which is built into a watch. The sonic signal of the metronome allows the runner to maintain a given cadence. Difficulties begin only after one has already obtained the values and attempts to draw some conclusions.
In what rhythm should we run?

180
180 constitutes a magic number in running world, which entices many authors of the publications devoted to running form. This number relates to the execution of 180 steps per minute, and its usually cited as an indicator of a good technique. The popularity of this magic number stems from the observations of professional endurance athletes. The rhythm of the majority of pro athletes is characterized by the exact number of 180 steps per minute. Should we, then, follow this pattern?

The answer to this question is determined by our understanding of the word rhythm. If we perceive it as a word synonymous with cadence, it’s impossible to propose an absolute formula answering this query. Consequently, the problem stems from the semantic characteristics of the word rhythm, as well as the narrow spectrum of words referring to the typology of movements described in this article. Therefore, I would like to differentiate between the Rhythm of running (from now on marked by an uppercase letter) and the rhythm standing for cadence (beginning with a lowercase letter).
Movement
Movement can be described in two ways. The first one refers to a detailed analysis of angles, velocities and accelerations of the particular biomechanic elements/parts. Unfortunately, what looks promising on paper or a computer screen, may turn out to be completely impractical while we begin to change our movement. Therefore, I would like to stress the importance of reaching to the scientific domains which meticulously (and by means of extensive and practical terminology) analyze human movement.
The second way in which movement may be described involves mental images, predominantly the visual ones. In this case, the experience of dance instructors comes in handy. Their illustrative advice focuses on posture, sensing one’s body movement and how it is initiated. Such practical instructions may prove more useful than any mathematical tools and algorithms.

The biomechanical approach leads us to believe that the movement in running is extremely complex and difficult to describe in a concise way. However, this type of movement may be referred to by means of a single adjective, namely, proximal. Exemplary running, which is the main subject of this article, falls into the category of proximal movements. These movements are initiated from the center of our body, close to the pelvic area (to which the strongest muscles are attached). The initiation and transfer of proximal movement to other parts of the body may be compared to the mental image of the domino effect. Proximal movements are involved in the movement of the entire body, and may be more efficient than their direct opposites, namely, distal movements. Distal initiation of movement refers to the execution of some precise moves in the parts of the body which are distant from its center.

The visualization of the Rhythm on the graph 
The silhouette depicted on the graph below is a two-dimensional mathematical model simulating running in the sagittal plane. It combines the movements of three long-distance runners – Haile Gebrselassie, Keneniks Bekele and Wilson Kipsang. Such a choice of the runners is not random. Their movements are exemplary, and the animated graph allows for the precise presentation of the addressed issues without the excessive reliance on the reader’s imagination.

The description of the silhouette 
The head, neck and torso (hidden in order to achieve greater transparency) represent the part zero of the biomechanical chain. The shoulders and hips constitute the primary part, the arms and thighs are the second part, and the forearms along with the hands and lower legs – the third part. The feet are represented in a simplified way by means of three lines highlighting the heel (the fourth part), the mid foot (the fifth part) and the toes (the sixth part). The right part of the body is represented in the color red, whereas the left side in black.

The description of the graph 
The graph has been created in the framework of 512 still model, depicting the layered courses of the silhouette’s motion paths in the regular time intervals. The movement of both sides of the body is registered simultaneously for two steps. The left side of the body is delayed in relation to the right side for about a half of the animation’s phase/course. The stills marked on the bottom part of the graph correspond with the time line (with a calibration of 20 ms intervals). Consequently, the two-step cycle takes 0,64 s. In the case of the real/actual/real-life movement, the cycle results in a running rhythm amounting to 187,5 steps per minute. The vertical axis of the graph represents the dimensionless lift of the silhouette’s parts.
The image of the Rhythm

The Rhythm can be observed when the phenomena of motion occur. These phenomena are characterized by the simultaneous intensification, namely, synchronized, local shifts of the velocities of the biomechanical parts. Curves 1,2 and 3 (respectively – the motion paths of the elbow, the center of gravity, the knee) represent the previously mentioned synchronization (its common peak is visible in the still 352).

The motion track of the centre of gravity

Curve 2 represents the motion track of the part zero, and reflects the vertical oscillations resulting from the cyclic characteristics of running. If one assumes the loss-free transfer of potential energy into kinetic energy (and the other way round as well), curve 2 will represent the motion track of the center of gravity. Such an assumption simplifies the entire situation by turning the running analysis into the analysis of the situation in which any suppression effects between the parts of the biomechanic chain do not occur. Suppression effects will be discussed by the end of the article.

From the point of view of curve 2 analysis, the range between 240 and 352 still is the most important. The lift of the center of gravity can be tracked along the curve similar to a fragment of a parable and a curve resembling a part of a sinusoid.

The parabolic lift is more steep in the early phase and changes faster throughout time. During the final phase, right before reaching the maximal value, the parabolic lift is milder than the sinusoidal one. Such seemingly subtle differences have very far-reaching consequences.

First of all, the characteristics of the course of the lift influence the entire biomechanical chain, as well as geometrical and phasal relations between its parts. One of the most crucial traits occurring at that time is the location of the feet in the back pendulum in relation to the supporting leg. The fastest and more dynamic is the lift, the more delayed is the feet in passing the supporting leg. Such a relation improves the dynamics of movement from the back to the front pendulum.

Secondly, a dynamic or stifled impression of running is determined by the course of the lift (shaping and presentation of various aspects of the lift is unfortunately very time-consuming and exceed the scope of this article).

Lastly, in order to focusing on the achievement of the desired, parabolic characteristics one shifts towards such issues as prioperception, coordination, flexibility and muscle tonus, as well as elasticity known also as „elastic recoil”. As a result, such parameters as maximal oxygen intake or maximal heart rate (which are fundamental aspects of modern physiology-based training schools) are neglected. Another popular term, namely, the level of running strength seems irrelevant in the generation of parabolic lift.

The motion track of the elbow and the knee

Curves 1 and 3 show trace the motion track of the second part of the biomechanical chain, namely, the arm and the thigh. The motion track of the elbow shows a complex movement, which combines the movement of part zero (a lift), the movement of the primary part (the shoulders), and a change in the angle of the arm throughout time. The motion track of the knee constitutes a similarly complex movement, which includes the movement of the part zero and the primary part (the hips), as well as the change in the angle of the thigh throughout time. Consequently, the trajectories of these motion tracks can be altered in order to achieve less or more dynamic picture of running.

At this stage it is necessary to mention that the previously mentioned relations are simplified and presented in one-dimensional space. Therefore, any attempts at measuring the angles, the location of the parts, and modeling oneself after them is rather pointless. However, the actual importance can be attributed to the relation between maximal values which are correlated in time, and constitute the most crucial aspect of the Rhythm.

Perfect proprioception (deep sense of own position and movement) is a term which entails such issues as coordination, elasticity, muscle tonus. Additionally, creates a basis for the propagation/spreading of proximal movement.

Elastic recoil is a phenomena which can replace a strong spring, by using the ability of muscles to quickly gather and give out the energy of elasticity. An accurate arrangement of the proximal movement propagation and the effect of elastic recoil allows for achieving the Rhythm, which is the full motion potential of our bodies.

Running form

Firstly, to start any action aiming at changing the way of movement, one needs to consider a “philosophical” problem of the so-called ideal form and the individual form. It seems contradictory, if we assume that such an ideal does not exist. There is no sense in changing movement if there is nothing to which we can relate our individual form.

However, if we assume that the ideal running form exists, it does not make this situation any easier. More and more theories concerning perfect running form are being proposed and they are often contradictory.

The criteria for the ideal
The way to break the deadlock is to find such criteria that would be independent from our individual physical characteristics, fitness, running pace, cadence, as well as preferences and trends.

The set of criteria includes physical laws, namely, gravity and elasticity.

The effective use of the physical laws is determined by the correct body posture, especially the position of the pelvis while running.

The second criterion is the proximal movement. The further the biomechanic element is from the pelvis, the greater is the inertia and diversity of its trajectory. The most spectacular example is the landing on the midfoot (the fifth element of the biomechanical chain) contrasted with the landing on the heel (the sixth element of the biomechanical chain). If we compare two elite runners who land in different manner but they keep the criteria of pelvis position and proximity, they will follow roughly the same motion pattern. However, when that analysis takes into account amateur runners (who learn how to run with midfoot strike but without the criteria of pelvis position and proximity) then despite a seemingly optimal landing manner, they will not comply to the examples above as their motion is initiated distally.

Running form theories

Among many theories, there are two popular ones which deserve attention, namely, Pose method by Nicholas Romanov and Chi Running by Danny Dreyer. Romanov’s major contribution to a new take on running form is his lecture on so-called ‘quadriceps paradox’. Romanov claims that the most important factor allowing us to move is the skillful use of physical laws. He rejects the proposal of the muscle rebound from the ground. Romanov replaces this kind of drive with more effective body position, thanks to which the runner is driven by gravity and elasticity generated in muscles and tendons. The function of the quadriceps is reduced from the driving force to a stabilizing support. Romanov reached these conclusions thanks to observations of the best runners in the world by a correct interpretation of what others perceived as an image of a strong rebound. It is an important step in understanding the way people move and it deserves consideration.
Dreyer, in many cases, agrees with Romanov. He focuses, however, on precise body positioning and mysticism. Such an approach stems from a Taoist assumption that the source of movement is the metaphysical Chi energy located near the pelvis and the flow of Chi (movement) depends on pelvis position. He places a great emphasis on looseness during running. Here we need to ask “what is Chi?”, because from the educational point of view the word ’Chi’ does not help in the learning process. If we then interpret Chi using dancing terminology, it turns out that it stands for the positioning of the pelvis allowing for proximal motion generation (by means of the work of the lower abdominal muscles).

Both methods promote the midfoot strike justifying it with greater effectiveness, and claiming they are less injury-prone than the heel strike.
Unfortunately, Pose and Chi theories feature such controversial issues as the necessity of taking up the foot under the buttock using muscle action while the back leg draws the back pendulum. It seems that even Romanov himself succumbs to a certain illusion and interprets the inertial effect as purposeful muscle action. Dreyer, on the other hand, contradicts his Chi energy as the source of the motion stemming from the pelvis. On the other hand, he claims that 'high knee’ which is a notion of proximal motion in the front pendulum, is an error. He interprets that as forceful running which is opposing the Chi ideas.

The next thing that raises objections is the proposal to shorten the running stride. Both Pose and Chi styles are characterized by the flattened incline trajectory of the second curve in the range between 240 and 480 still. The decrease of the vertical oscillation causes shortening of air time. Consequently, there is no possibility to fully use the rear leg motion range. The shortening of the stride is then necessary to land under the center of gravity.

A run with 'stylized’ heel lift which reduces the range of the back pendulum, shortens the stride, and reduces the range of the front pendulum, is an example of distal motion and does not resemble the spacious proximal pendulums of Gebrselassie or Bekele.
Romanov’s and Dreyer’s use of mental images visualizing the circle trajectories of foot movement is also controversial. As much as the circle idea is tempting with its elegance, it is far from the actual foot trajectory which is marked in the graph as a blue loop.

Natural running
It is difficult to find a more ambiguous term.

Natural running, due to its amazing fertility as a field, provides also great opportunities. It has been especially favored by some ambitious running shoes producers who, besides production, took on creating their own biomechanical theories. Analysis of such theories does not contribute to the ideal form. Working on foot biomechanics, regardless of the rest of the body, does not lead to any conclusions that would be relevant beyond the issue of the foot itself. It is a vivid example of distal understanding of running.

Landing
The manner of landing has become the most important factor in the running form evaluation. This aspect has dominated other features of running movement to such an extent that a person interested in changing the motion does not ask ‘how to do it?’ but ‘what kind of shoes do I need to buy?’ .
Curve 4 in the graph shows the motion path of the movement of the midfoot and forefoot in time. The midfoot and forefoot together with toes (the fifth and the sixth component of the chain), play the role of the endings which are subjected to the greatest inertia in the pendulums. When it comes to the Rythm, the range between the 352nd and the 448th still is the most relevant for the midfoot’s/forefoot’s movement. Watching trajectory of the silhouette’s feet in this range (the blue loop), one notice the moment of braking and the moment of foot’s and lower leg’s backward movement in relation to the center of gravity. Such a peculiar trajectory allows to lengthen the floating phase, and to use the full range of the front leg, delaying landing. The maximum lengthening of the running stride with a backward movement of the foot are results of the inertia generated by a proximal motion. It is an alternative to the distal shortening of the stride suggested by Pose and Chi methods. Moreover, it allows to land on the midfoot under the center of gravity. The backward movement of the foot is exceptional and cannot be executed by a muscle action. Everything relies on loosening and inertia. The key to this kind of operation in the front pendulum is the Rhythm, namely, the amplified vertical oscillations of the whole body, which are often considered a flaw of the running form. However, it is exactly the amplifications of the vertical oscillations that allow for initiation of the movement. In dancing one would say: it allows to “release” the movement.

The moment when the movement is “released” is very clearly visible on the animation below. The “waving” muscles and the movement of the foot indicate loosening and inertia of the front pendulum just before landing. Analysis of the midfooot landing is very hard to conduct. However, midfoot landing is performed starting from the sixth rather than from the fourth element. It buys some time before the full landing below the center of gravity. The contact with the ground is very short. Moreover, the shifting of the body mass is performed from the fifth to the first head of midfoot bone with full strain on the foot arch, without putting stress on the heel.

Now I would like to put forward the issue of suppression during running. Suppression is defined literally as any loss that accompanies our every step. Retracted pelvis and landing in front of the center of the runner’s gravity are the main suppressors. The way to minimize the suppression is to increase running strength, which is very effective. However, only the effort put in correct pelvis placement allows to use the full potential residing in the loins and to improve the relation between the center of the runner’s gravity and the point of support during landing. One of the mental images I tend to use in order to visualize correct pelvis arrangement is the motion of putting the full throttle on a motorbike or a fine pelvic thrust. Both images can be visualized at the same time with one objection, namely, “do not flex the glutes”.
The analysis of the position of the pelvis during running is the most effective while performed in the frontal plane. The analysis of the pelvic retraction in the sagittal plane (from the side) is to a large extent disturbed by runner’s clothes. Observation from the front, as in the animation above, allows for noticing any potential leaning to the sides, so-called “sitting” on the supporting leg, which also evokes a tilt of the shoulders. The animation features a constant pelvis position, without leaning to the supporting leg, which proves its perfect placement.

Summary 
There are many runners with a fast rhythm, but only a few of them can run maintaining the Rhythm.

Imitating the Rhythm itself is rather useless. High cadence around 180 steps per minute favors the elastic recoil effect because leg’s contact with the ground is shorter (too long support phase fights decreases elasticity), but it constitutes only one among many elements of the Rhythm. However, the pursuit to imitate the Rhythm is a way to change one’s manner of motion.

The analysis of our own running form is not too difficult. The problem is to find such methods that will allow to improve our movement. Searching these methods is related to building specific training know-how and its detailed description constitute a topic for another article.

Translation: Iga Krzysik, Michał Wierzbicki, Kuba Krause