## 4 Discussion  
The use of surface electromyography in order to determine the dynamic load for farmer workers is an innovative approach in the field of ergonomic research, as well as workplace safety among Polish farmers. The indisputable advantage of the method is its high accuracy of measurement in comparison to the tabular or quantitative-qualitative methods that have so far been used. So far, [PERSON] analyzed a load influenced biological material, but in this study, they described a load generated by farmer's muscles during silage feeding [39]. This was the case with milking activities in a herring bone milking shed and when milking with a bubble milking machine. One of the research assumptions in this work was the determination of the maximum unit mass of the load that was being transferred in the process of silage loading. This goal guided the research of scientists in the past, where, for example, a maximum mass of 3 kg was determined for the milking machine in the milking shed [34]. The forearm load values that were obtained, expressed in % MVC, are similar to the results of the loads for a milker while washing, massaging and attaching the milking apparatus, being in the range of 15-25% MVC [34]. [PERSON] emphasized in their scientific papers that a %MVC score above 15% may be a contributory factor in the development of musculoskeletal complaints among employees [14, 40, 41]. The physical-load results obtained by milkers, in most cases, was in excess of the acceptable level, reaching values above 30% MVC. The authors also emphasized that roughly 50% of all farm workers have complained of pain and discomfort when performing physical activities on a farm. In the case of manually transporting silage, the forearm load exceeded 30% MVC, hence it can lead to discomfort while working and, consequently, could lead to injury or other complaints. Similar studies were carried out among employees who were handling manual loads of 10-30 kg in production halls. The EMG results showed the load to be in the range of 30%-40% MVC, i.e., similar to the result obtained in the work of farmers who were transporting silage. The results that were obtained expand the scope of the current state of knowledge in regarding women's physical loads, determining the level of the maximum unit load for repetitive tasks. In addition, in the studies conducted by [PERSON], 5% of surveyed farmers noted that negative symptoms in the musculoskeletal occurred regularly after physical load [42]. For instance, a work in the construction industry can be classified as one of the most dangerous professions, because of many disorders occurring in the worker's musculoskeletal [43]. Ensuring safety on construction site is one of the most important elements of the entire safety management [44]. Musculoskeletal disorders are one of the most common health problems at work and affect millions of employees every year [45]. So far, the OCRA (Occupational Repetitive Actions) or Strain Index (SI) methods have been used to assess the load associated with the physical work of upper limbs. These methods are based on specific patterns. They allow one to evaluate an occupational risk [46, 47]. From the point of view of muscle load, a time  
Figure 8: Mean muscle load in the during manual unloading of the maize silage. of load, body position, but also work breaks are important. [PERSON] developed the concept of the optimal position during work in order to reduce muscle fatigue [48]. [PERSON] evaluated some of postures among workers. He defined the most acceptable position at work. From his studies it follows that, right work condition without overloading body parts result in lower risk of musculoskeletal disorders [49]. Generally, they observed workers at work, in comparison to these studies, when the EMG system allows to record real biological signal adequate to examined farmer. Nowadays, the worker's muscles are exposed to different disorders. It depends mainly on the structure of the muscle, load of the muscle or hormonal balance.