Energy commitment and cardiovascular effort of workers

Metabolic load or energy expenditure is a measure of the physical effort that is carried out during the execution of a job, making it one of the main components that make up working conditions, whose intensity is influenced by the level of physical work required in certain

environmental conditions.

This has been demonstrated in various investigations carried out with the aim of evaluating thermal overload in different environments (1-3).

There are various methods to calculate energy expenditure, the most accurate being that based on ergo spirometry, but its application lends itself to laboratories due to the necessary technology, so it is better limited to laboratory work. These reasons lead to the use of other methodologies, for example: tables that consider posture, sex, the type of movements, among others.

In field studies in a large number of subjects, indirect estimation methods have been established based on the great correlation between energy expenditure and some physiological variables, mainly heart rate and minute respiratory volume (4-9).

In investigations carried out by the author, the energy commitment has been estimated from the respiratory minute volume in nine construction activities and in workers who work in spinning workshops.

At present, the energy commitment is estimated based on ISO 8996 and the criteria of experts Frimat, Chamoux and Manero. The respiratory minute volume has not been applied since the necessary instruments are not available.

The methodology carried out by Manero is a Cuban experience and also an achievement of the Institute of Workers' Health, the graduates of the Master's Degree in Occupational Health have the knowledge for its application, but this is a small group that cannot cover the entire labor universe by which makes it necessary for all personnel involved in the health of workers to know these criteria and, in the case of graduates from other countries, to apply and select the one they deem most appropriate.

They also serve as a great help in the training of industrial engineers since this subject is studied in Ergonomics in the third year of the degree.

These methodologies based on heart rate are very important since cardiovascular effort can be assessed together, which allows us to know if there is a physiological mismatch or if, on the contrary, a position that requires great effort does not reflect it due to the low use of the working day.

Goals:

Provide staff working in the field of occupational health with a simple and useful tool to assess the energy commitment and cardiovascular effort of workers.

Materials and methods:

The jobs of vehicle inspector, bricklayer and spinners and maintenance personnel were analyzed. The sample size was 11, 12, 13 and 10 workers respectively, for a total of 46 workers.

The metabolic load in spinners and bricklayers was assessed using the minute respiratory volume, ISO 8996 standard and the expert criteria of Frimat Chamoux and Manero.

Vehicle inspectors and maintenance personnel applied the ISO 8996 standard and expert criteria.

Analysis of the results:

Table 1 shows the centers and number of workers studied in each center.

Table 2 shows the criteria for the physical workload considering the methods used. As can be seen, there are no differences in terms of the classification of physical activity in the methods used in the studied jobs.

The vehicle inspection post according to the ISO standard can be classified as low metabolic rate from the Frimat criterion as minimum physical load and from the absolute cardiac cost and the relative cardiac cost, its classification is very light and light.

As it can be seen, these results are in correspondence, the same is observed in the other jobs, so the classification of one method does not differ significantly from another.

The importance of applying these methods lies in the information they also provide on the cardiovascular effort involved in carrying out the activities.

Which is quickly known

Of course, each method has its advantages and disadvantages, but there is no doubt that the assessment of the physical workload by monitoring the heart rate is easier and provides important physiological data that corresponds precisely to knowing the achieved values of the heart rate during the workday or a period of this, in case we do not have a heart rate monitor or frequency meter, it will only be enough with the measurement through the radial pulse.

If alarming values of cardiovascular or energy compromise are found that could affect health or the good performance of tasks, other methods will be available to determine the positions or operations responsible for the problem and take corrective measures.

Conclusions:

For all the above, we can infer that the assessment of the physical workload of workers based on heart rate monitoring is an easy, economic and useful method that must be known and used by staff working in workplaces. in the field of occupational health.

It also allows an assessment of the most suitable thermal overload based on knowledge of the physical work load.

Benefits:

These methods allow to know the energetic and cardiovascular effort of the workers in the accomplishment of the corresponding tasks in a fast, efficient and economic way.

Bibliographic references.

1. Padilla MC et al.: Thermal overload and its effects on workers in three construction activities. Rev. Ing Ind., 1994 Oct; 15 (3): 63-66

2. Padilla MC et al: Work and thermal overload in Cuban working women. An experience in a spinning workshop. Rev. Ing Ind., January 1997; 12 (3): 33-38

3. Padilla MC et al.: Thermal overload and its effects on nine construction activities. Rev Ing Ind, 1999. March 10 (3): 57-61.

4. Malhotra, M et al.: Press count as a measure of energy expenditure appl physiol 1964 18: 994-996.

5. Verma s and col.: Indirect assessments of energy expenditure at different work rates. 1979 ergonomics 22: 1039-1044.

6. Arana, VI Echeberria.: Heart rate monitoring in the study of physical workload, 1999 Rev. MAPFRE safety n ° 73 first quarter.

7. Álvarez F.: Assessment of heart rate in the study of physical workload 1999 Rev. MAPFRE safety n ° 73 first quarter.

8. During and Edwards r.: Pulmonary ventilation as an index of energy expenditure. 1955 quart j.exp.physiol 40: 370-377.

9. Manero AR et al.: Practical methods to estimate physical work capacity 1986 100: 170-182.

Table 1. List of work centers and number of workers.

Workplace	No. of workers
Vehicle inspection workshop	eleven
Construction contingent	12
Spinning workshop	13
Maintenance department	10
Total	46

Table 2.Classification of physical activity based on the applied criteria.

Exercise	VMR w / m ²	ISO 8996 w / m ²	Frimat	Chamoux CCA	ICCV Manero
Vehicle inspector	L (100)	RMB (106)	CFM (2-4)	ML (8.2)	L (6.7)
Builder	L (120.1)	RMB (116.5)	L (6.0)	L (17)	L (15.5)
Spinner	L (89.5)	RMB (100)	L (6.5)	L (15.4)	L (13.5)
Mantenance staff	L (130.4)	RMB (132)	L (6.4)	L (15)	L (15.8)