Z. M. Zolina and M. G. Tikhaya

Some Principles for Establishing a Work Rhythm in Industrial Settings

From the Institute of Occupational Hygiene and Occupational Diseases, Academy of Medical Sciences of the USSR

To increase labor productivity, the development of rational, physiologically grounded methods of work organization is of great importance, alongside improvements in production equipment and processes.

In socialist industry, a substantial proportion of work involves operating complex machinery without great physical exertion and requires fine, precise coordination of movements. This places considerable demands on the central nervous system, particularly its highest division, the cerebral cortex.

I. P. Pavlov’s physiological theory of the principles governing higher nervous activity in humans and of the leading role of the cerebral cortex in maintaining equilibrium between the organism and its external environment opens new avenues for addressing the problem of increasing human work capacity.

In various industrial settings, countless stimuli from both the external environment and the internal organs continuously act on the cerebral hemispheres. The cerebral cortex analyzes and at the same time synthesizes all the stimuli it receives. If these stimuli are presented in an unchanging, uniform order, both in their sequence and in the intervals between individual stimuli, the cerebral cortex functions as a dynamically integrated system.

A dynamic stereotype is established—that is, a coordinated, balanced system of internal processes.

The establishment of a dynamic stereotype involves a certain degree of difficulty. Maintaining an established stereotype, however, requires minimal expenditure by the cerebral cortex; the stereotype is therefore the easiest mode of cortical activity.

One method of developing a dynamic stereotype in industrial settings is to establish a rhythm of work.

The beneficial effect of working rhythmically is not in itself a new discovery. It is one of the practical truths of human experience, established through practice but still inadequately explained in physiological terms. A steady rhythm is characteristic of the work of many Stakhanovites.

The task is to use specific examples to clarify and generalize the advantages of rhythmic work, provide a physiological explanation for it, and develop recommendations for organizing work rhythmically in industrial settings.

The studies were conducted at a factory, in a product assembly shop.

The work of the female assemblers consists of assembling products from a large number of very small parts, some of which have shiny surfaces.

This work places particularly high demands on the eyes’ ability to distinguish fine details.

Before beginning the main work of improving the rhythmic organization of the work process, we proposed several measures to improve general working conditions in the shop. These proposals were implemented by the factory management.

The product assembly area was assigned a separate room. The assemblers’ worktables were redesigned: the working surface was enlarged by reducing the size of the fluorescent lamp and changing how it was mounted on the table, and special containers were provided for small parts.

After a thorough study of the product assembly process and detailed time measurements of all operations performed under an hourly schedule, several methods were developed to make the work more rhythmic.

Work under the hourly schedule was organized with hourly monitoring of the productivity of the assembly team as a whole and was linked to a light signal. When the entire team met its average hourly production quota, a red lamp lit up on a panel mounted on the wall. This signal served as a check primarily for the team leader and only to some extent for the assemblers. This arrangement enabled the team leader to correct problems that interfered with the relatively rhythmic work of the team in a timely manner, thereby increasing productivity and improving the quality of the products.

However, time-and-motion observations of the assemblers under these conditions showed that work proceeded unevenly over the course of the hour (Fig. 1). This was because the lamp, when lit, did not serve as a signal to the assemblers: it was located at a distance from their workstations and was lit only at long intervals—once an hour.

Fig. 1. Variation over an hour in the time required to assemble one product under the hourly schedule and to complete a group of elements under the “flow-to-self” system.
1—“flow-to-self”; 2—hourly schedule.
Vertical axis: percent; horizontal axis: time in minutes.

We attempted to test the effect of light signals by bringing them directly to the assemblers’ workstations and giving them at shorter intervals—every 15 minutes. It was assumed that more frequent signals would more quickly establish a sense of time in the assemblers, thereby helping to make the work process still more rhythmic.

Time-and-motion observations of the assemblers under these conditions showed a further increase in productivity for most of them, but did not reveal the expected consistency in the time taken to assemble one product over the course of the hour. This was because the workers did not all respond in the same way to the light stimuli. Some reacted unfavorably to the signals. According to the workers, the signals irritated them, in some cases even reducing their productivity.

The need for a different approach to improving the rhythm of work was suggested by the following circumstances. Under the hourly schedule, an assembler who assembled a product from start to finish had to fit up to 15 parts in a strict sequence. This required sustained attention; moreover, the large number of parts occupied the entire working surface of the table. The worker had to reach for them and make unnecessary movements, thereby taking more time and disrupting the rhythm of work.

A different organization of labor was needed, one that would reduce the number of work movements and have them repeated sequentially and cyclically—that is, establish a simpler dynamic stereotype.

On this basis, we proposed a different method of work for the assembly workers.

Instead of having a worker perform all 15 elements of the assembly operation in succession, the operation was divided into 3 cycles: the first 5 elements were to be performed on 50 products, followed by the next 5 elements and, finally, the last 5 elements of the assembly operation. Thus, a complex stereotype was replaced by a simpler one.

There were 9 to 12 such recurring cycles per work shift. Each work cycle lasted approximately 40–50 minutes, during which

Fig. 2. Time taken by assembly workers to assemble one product.
1—hourly schedule; 2—“flow toward oneself.”

Fig. 3. Changes in discrimination thresholds among assembly workers.
1—hourly schedule; 2—“flow toward oneself”; 3—flow.
Vertical axis: relative values.

the assembly worker performed a particular group of elements of the operation. For this period, she brought all the necessary parts closer to herself, placing the other group of parts, already used, in more distant areas of her workstation. We called this method the “flow toward oneself” method.

Working by this method reduced the time required to assemble one product by 10% (Fig. 2). Labor productivity increased by 10–15%, and defects decreased by 1–2%.

Physiological studies of the eye’s powers of discrimination showed that they did not decline over the course of the working day. There was a tendency for them to improve compared with work under the previous conditions; in every case without exception, the visual discrimination threshold at the end of the working day was 6–7% lower than the values obtained under the previous conditions (Fig. 3).

Organizing work by the “flow toward oneself” method further subdivides the stereotype and improves the establishment of rhythm compared with organizing work on an hourly schedule, in which an electric light is switched on every hour (Fig. 1), as well as every 15 minutes. Indeed, reducing the number of elements of the operation performed by one assembly worker over an extended period (40–50 minutes) creates conditions for the formation of a new, more

…a short dynamic stereotype underlying the establishment of rhythm. Combined with the elimination of unnecessary movements, the establishment of rhythm in such work makes it possible to develop a system of precise movements in which each element of an operation takes approximately the same or the same amount of time to perform.

When these elements of an operation are performed in the same sequence within a single cycle, each serves as a conditioned signal for the subsequent operation and thereby prepares the body to perform it.

Limiting the number of operation elements performed in this way promotes automatization—that is, a change and simplification in the form of control exercised by the higher divisions of the nervous system. This undoubtedly makes the work easier to perform, as our findings confirm.

Studies by I. P. Pavlov and his pupils on animals give reason to believe that repetition of the same movements can also have a negative effect owing to the use of the same elements of the nervous system, potentially resulting in a certain degree of inhibition and fatigue. Under the proposed method, monotony is avoided by periodically switching—every 40–50 minutes—to the assembly of the next group of elements.

However, repeated switching, with cycles changed as many as 12 times per shift, cannot provide the best solution in this case, since the worker’s actions still demand considerable concentration and probably cause considerable fatigue. Moreover, the tabletop remains excessively crowded, restricting the worker’s freedom of movement when she moves parts from the back to the front as she switches from one work cycle to another. Thus, despite the division into cycles and the consequent shortening of the stereotype, and despite the positive results in productivity, quality of work, and physiological measures, we believe that this method can be recommended only for work areas with a small number of operations.

The next stage in the further improvement of rhythmic work confirmed this conclusion.

An attempt to improve the rhythm of work further in this area took the form of organizing a production line, as yet without a moving belt. This involved subdividing the process further and thus shortening the stereotype. To this end, the assembler’s entire task, consisting of 15 operation elements, was divided into 4 cycles and distributed accordingly among four workers, each of whom performed one group of operation elements throughout the working day. This approach began with the organization of the workstations and containers and the establishment of a rational arrangement of parts at each workstation on the line, taking into account the parts assembled there. The assemblers’ workstations became less crowded, and the former congestion on the worktable surfaces was eliminated. The variety of parts handled by each assembler was reduced fourfold. Consequently, by performing a limited group of assembly elements throughout the working day, the assembler was able to work more rhythmically.

To avoid monotony, we recommended that all assemblers change places on the line daily. This organization of work makes it possible, on the one hand, to demonstrate a practical way of overcoming the inherent contradiction in stereotyped work: automatization makes the work easier to perform, while the resulting monotony can lead to an intensification of the pro—

…processes of inhibition) and avoid a possible decline in work capacity. On the other hand, such rotation of positions on the production line allows the assembly workers to maintain their skills.

The time-study data and physiological investigations obtained under these conditions showed the following.

Under these new conditions, we achieved a further improvement in the regularity of the work rhythm. The percentage of cases involving shorter time intervals increased considerably more with the production-line method (Fig. 4).

Fig. 4. Change in the time required to weld one part.
1—production line; 2—individual assembly.
Graph labels: Number of cases, %; time in seconds; from 6–9 seconds: 67%.

Labor productivity (Fig. 5) increased noticeably after approximately one month of work by this method and continued to rise over four months, subsequently stabilizing at that level. The vast majority of assembly workers, who had previously shown low productivity compared with a small group of Stakhanovites, came to achieve the same high productivity as the Stakhanovites. The quality of work also improved by 2–3% among all the assembly workers.

Other time-study data confirm this advantage. Thus, in Fig. 6 we see a reduction in the time required to perform the component elements of the operation under the production-line method compared with data obtained under the previous conditions. There is also some reduction in this time over the course of the working day.

Fig. 5. Productivity as a percentage of productivity under individual assembly.
1—production line; 2—individual assembly.

Fig. 6. Change in the time required to perform a group of elements over the course of the working day.
1—individual assembly; 2—production line.
Graph labels: Time in seconds; 8 o’clock; 12 o’clock; 4 o’clock; lunch break.

Under individual assembly conditions (Fig. 6), by contrast, this time increases somewhat by the lunch break and still more by the end of the working day.

The eye’s discriminatory sensitivity shows small changes during work by the production-line method (Fig. 3). As the data presented show, we obtained a further improvement in this function.

The substantial increase in working speeds and the resulting rise in productivity of up to 20% or more did not, by the assemblers’ subjective assessment, make the work feel more strenuous. Their comments amounted to the following: “easier to work,” “calmer,” and “we get less tired.”

At present, all the assemblers in this shop work by the flow method.

However, introducing the flow method does not provide a definitive solution to the problem of establishing a proper rhythm in the work process at all production stations. Nor does it resolve questions concerning the pace of work. We believe this can be achieved by organizing work on a moving-belt conveyor.

Research under such conditions, with work and rest properly organized, will make it possible to establish a physiological basis for optimal working speeds and their levels throughout the working day.