Cyclography

CYCLOGRAPHY (from the Greek kyclos—circle and grapho—I write), the most precise of the methods developed to date for the photographic registration of movements. Cyclography originated in the 1890s as a modification of chronophotography (see). The first cyclographic images were obtained in the laboratory of Marey; at the same time, cyclographic filming using spark discharges as a light source, and later Geissler tubes, was applied by Braune and Fischer to the study of the kinematics of joints and human movements during walking. After a long hiatus, it was applied again in very primitive forms by Gilbreth, Thun, and Townsend. In 1921, this method was applied in our country by N. Tikhonov and N. Kekcheev, who introduced a number of improvements to it. By the present time, the technique of cyclography has reached a high level of development as a result of the work of a number of Moscow laboratories. Cyclography in its basic form is the photographing onto a stationary light-sensitive

Figure 1. From left to right—a small cartridge and light bulb for cyclography of the Bernstein-Wolff system and an ordinary light bulb from a pocket flashlight for comparison. All three objects are placed on a millimeter grid for scale.

surface of the trace of the movement of some point light source. By placing one or several small light bulbs on moving points of the human body and photographing them, the researcher obtains a cyclogram of the movement of these points in the form of curves depicting a planar projection of the movement trajectories. If the light bulbs are powered by an intermittent current or the lens is opened and closed periodically, then instead of continuous lines on the image, dashed lines will be obtained, with the distances between successive points of the dashed line depending on the frequency of the current interruption in the light bulbs or on the speed of the lens shutter. Such a cyclogram with time marks on its trajectories is called a chronocyclogram.

In modern cyclography, the light sources are special miniature incandescent bulbs with a point spiral filament (bulb diameter... The speed of rotation of the shutter is the most critical moment of the work, requiring high precision. The best methods of measurement are stroboscopic, consisting of illuminating with intermittent light of a strictly stable frequency (by means of a neon lamp) one or another rosette with a special pattern, which appears stationary if

Figure 4. Strobometric rosette (accuracy up to 1.25%).

the frequency of the intermittent light is equal to the number of revolutions of the motor multiplied by the number of petals of the rosette. Bernstein's rosettes (Figs. 3 and 4) allow for measuring any rotation speeds with an accuracy of up to 1%: they consist of a series of concentric circles with figures alternating on them. When such a rosette, connected to the axis of the shutter motor and illuminated by intermittent light of a stable frequency, rotates, all its circles appear uniformly gray, while one appears stationary (Fig. 5) and indicates the desired rotation speed on the scale adjacent to the rosette. It is significantly more accurate not to measure the speed of the shutter, but to automatically stabilize it at the expense of the same strictly stable frequency source (e.g., an electromagnetic tuning fork made of Elinvar) by means of a low-frequency electronic amplifier and a Lacour wheel or tonrad (Fig. 2). Any high frequencies can be used in cyclography; in practice, frequencies from 60 to 250 per second are most commonly used. If the points being filmed do not return periodically to the same place in their movement, but are carried further in one direction (e.g., during walking or running), then the cyclogram is legible and clear (Fig. 6). In the case of cyclic movement, however, illegible tangles of trajectories will inevitably appear on the image. For filming such cyclic movements, a variety of cyclography is used—kymocyclography, which consists of cyclographic filming onto a uniformly moving film (Fig. 7). With this method, any movements, even the most complex and minute, are obtained in a legible form. The camera of P. Pavlenko's design (VIEM) used for kymocyclographic filming is shown in Fig. 8. To study non-planar movements occurring in three dimensions, one point of view is insufficient. Here, three methods can be applied: 1) stereoscopic filming with two lenses with parallel optical

Figure 5. Strobometric rosette during rotation and illumination with intermittent light.

Figure 6. Cyclogram of running (world champion Dumeg).

axes, covered by one large shutter. The accuracy of this method is generally low. 2) Converging filming with two or several cameras, the optical axes of the lenses of which meet at a certain point. In this method, separate shutters are used near each camera, connected by one or another precise synchronization device. This method is very accurate but requires well-calibrated lenses and impeccable synchronization. 3) Mirror filming with one camera, in which the object is visible simultaneously from two points of view: in a direct image and in a reflection from a large mirror. The method is very accurate and at the same time simple, as it does not need lens calibration or shutter synchronization. Control of the cyclographic filming is carried out centrally from a distribution panel, in which all elements of filming control are concentrated. A finished cyclographic image is the most precise document of movement; if it is made according to all the rules of modern technology, it ensures spatial accuracy of up to 0.5 mm of the natural size and temporal accuracy of up to ±0.005%. The analysis of cyclographic and kymocyclographic planar and mirror images of movement has already grown into a whole science in itself—cyclogrammetry. A correctly performed analysis allows one to determine from a cyclographic image: a) the positions successively occupied by the object in space (coordinates), b) the angles between identification lines on the object at all successive moments of movement, c) the velocities of the points of the object, d) the accelerations of these points, e) angular velocities and angular accelerations. Given data on the masses of the moving parts, cyclogrammetric analysis further allows for establishing a quantitative picture of the flow of forces in the centers of gravity of the elements of the moving system and in the general center of gravity of the entire system, and for measuring the force moments of muscle groups. The data obtained in this way possess a high degree of accuracy, unattainable by any other modern method of registration. Cyclography and its varieties are used in the study of labor movements for the purpose of their rationalization; in labor pedagogy—for the purpose of analyzing correct and incorrect methods of training (training in production skills, playing musical instruments, etc.). Furthermore, cyclography finds application in the field of study and rationalization of labor and labor aids for the disabled (the blind, amputees, etc.). Finally, an extremely broad field for the application of cyclography is the clinic, where this method allows for the very precise study of the most diverse path. disturbances in the motor sphere.

Figure 7. Mirror kymocyclogram of a piano passage (on the right are 4 trajectories of the direct image, on the left are 4 reflections of the same trajectories in an inclined mirror, in the middle is a control dashed line of a stationary light bulb on the mirror).

Figure 8. Kymocyclographic camera in open form, Department of Physiology of Movements, VIEM.

Here, one should mention organic lesions of the central and peripheral nervous system, functional disorders in the area of tendon reflexes, tonic and labyrinthine reflexes, etc., and further, motor and psychomotor phenomena in mental illnesses, etc.