What a Welder Feels is Made Visible – Sports Scientists Investigate Exertion
Spraying sparks, the bright shimmering arc gives a clue of the extremely high temperatures, which can be endured only with special protective clothing. Despite everything, the man works with great concentration, using his welding torch to ensure that the metal is joined.
Physically, the eight-hour day of a welder is extremely tiring. How tiring it is was investigated in a study by the department of sports medicine at Justus-Liebig University (JLU). “What the welder feels is made visible,” explains its director, Prof Frank C. Mooren. The aim was to investigate where the main exertions lie
in the muscular domain. Based on scientific findings, compensatory exercise programs can be developed and posture recommendations given, which protect workers in the sense of preventing the consequences of one-sided exertion and permanent bodily injury.
The project team (from left to right): Dr. Karsten Krüger, Jan Hasselbaum, Carmen Petermann, Prof. Frank C. Mooren
The data compiled is also used in the development of new ergonomic welding torches, as the research project is backed by ABICOR BINZEL. Over a period of two years the innovative company financed the research, which was set out as a doctoral thesis. The scientists from the Kugelberg in Gießen broke new ground with the co-operation. Mooren knows that “sports and occupational medicine are not that far apart.” Whether top athletes or welders, both deliver a performance and both become fatigued by doing so. With physical fatigue performance declines and concentration declines with it. In the course of an entirely normal eight-hour day, the welder is subject to severe physical exertion. Holding a specific posture over a long period, high temperatures, the weight of the welding torch and the required protective clothing including the gloves and welding mask as well as high precision work with the materials – whether robust steel or sensitive aluminium – stretch the worker to the limit.
Thesis as a challenge
To get an idea of the exertion, “I held a welding torch myself,” Carmen Petermann recounts. The petite sports scientist and sports therapist from Heidelberg applied for the doctoral thesis advertised by the department of sports medicine in Gießen and ABICOR BINZEL and was awarded the contract. Together with the scientific assistant in the sports institute, Dr. Karsten Krüger, who is supervising the doctoral thesis, she initially had to developan understanding of how to weld. “The existing statistics reveal that welders increasingly have back and shoulder problems,” Krüger describes the approach. It was therefore decided to focus the research work on the muscle groups involved.
The research methods used in sports medicine were adapted to the unusual task of making it possible to measure and thereby reveal the physical exertion of a welder. “We used a combination of different, complementary methods,” the scientific assistant explains.
In the 60-minute preparation time for each guinea pig, the electrodes for the EMG measurement were fixed to the eight muscles being investigated and the blood pressure meter secured. Blood lactate was then taken for the first time and blood pressure and heart rate were determined. After around 10 minutes of dynamic warm-up exercises for the respective muscles being measured, where each exercise comprised 3 lots of 15 repetitions, maximum strength tests were conducted on the muscular system to be investigated. These included maximum static tensing of the muscle for 5 seconds in a physical posture geared to the muscle concerned. The actual welding process was then carried out using the MAG process with mix gas M21. The positions PF (uphand position) seated and PD (horizontal/overhead position) standing were observed. In each position welding was carried out for 5 lots of 5 minutes with pauses of 30 seconds between stages.
After each of the two positions, blood lactate, blood pressure and heart rate were measured and the subjective perceived exertion was queried during the welding activity. To assess the subjective perceived exertion the Borg* scale was used. On this scale from 6 to 20, the evaluation of the exertion increases linearly with performance and can then be related to the physiological measurement parameters. After the first welding activity of almost 1 hour a maximum strength test and hand force measurement were again taken on the muscles.
Intensive preparation: Ante up of the electrodes for the EMG – rating, warm-up exercises and maximum force measurement
Evaluation via Borg scale
The muscle activity was measured using 8-channel EM and the software for computer-aided recording and analysis of the data. In addition, at the same time, the welding activities were recorded with a video camera. Eight muscles were measured on the dominant hand: Mm. flexor (forearm flexor muscles), Mm. extensor (forearm extensor), M. biceps brachii (upper arm flexor), M. triceps lateralis (upper arm extensor), M. deltoideus pars mediale (large shoulder muscle), M. trapezius pars ascendens (neck muscle), M. infraspinatus (shoulder muscle) and M. erector spinae pars lumbalis (lower back extensor). The electrodes were applied parallel to the muscles and fixed with flexible tape in order to prevent the electrodes from slipping due to the high level of sweating.
The results for the perceived exertion (fig. 1) show that the welders feel significantly less exertion when working with the reduced-weight torch. Evidence of this is also provided by the slightly lower blood pressure values.
The most important result is that the muscular exertion on 5 out of 8 muscles is significantly lower in both welding positions when the reduced-weight ABIMIG® GRIP A LW torch is used. Fig. 2 shows the results for position PD and fig. 3 shows those for position PF. The shoulder and arm muscles in particular are subject to significantly less strain. In practical continuous operation, this results in fewer complaints and consequently lower downtimes caused by absence due to injury.
Results of the subjective feeling of extension via the Borg scale
Results muscle activity of the 8 different muscles while welding in position PF (standing)
Results muscle activity of the 8 different muscles while welding in position PD (sitting)
* The Borg scale is an evaluation method invented by Prof. Dr. Gunnar Borg (Stockholm) for the evaluation of subjective perceived exertion.
Practical experience confirms research results
An additional measuring campaign by an automotive supplier where the ABIMIG® GRIP A LW torch has been in use for several months confirms the above research. The welders commented very positively and did not want to let go of the ABIMIG® GRIP A LW torch. “My shoulder complaints have practically vanished,” one of the welders confirms in a succinct statement!
“We are constantly developing new welding torches so a welder is able to work to the precision level required.” Jan Hasselbaum, who works in the Sales
and Marketing division at ABICOR BINZEL knows what he is talking about. “Our developments focus on the person, the welder.” Prof. Mooren adds: “We are
finding that companies are increasingly identifying employees as capital, which they need to protect.” As occupational health management this is increasingly finding its way into companies. Extending the working lifetime of employees and qualified staff, keeping them fit and healthy, must be the aim of any employer.
Sports scientist and medic Mooren describes the cooperation with the “global player” from Buseck as a lucky break that came about through personal contacts. “ABICOR BINZEL Managing Director Dr. Emil Schubert was in the sports institute for performance diagnostics,” he recounts. However, at some point the conversation ceased to be about the physical performance of the subject, Schubert. “We discussed that performance relates not only to sport but also to work, that performance is associated with level of fatigue and that it can be illustrated.”
The idea of a co-operation took shape. “Our developers consider how the welding torches can be designed to be user friendly. The practical experience of the workers is incorporated into this,” Hasselbaum explains that another reason for the company financing the doctoral thesis, in which the co-operation with the sports scientists from Gießen is described as “intensive and exciting.”
Conclusion: To summarize, it may be stated that it is primarily the shoulder and arm muscles that are strained during welding work in the PF and PD positions and that a lighter welding torch proved to be advantageous and less of a strain.
Weather standing or sitting – a light welding torch means less stress for the shoulder and arm muscles
The reduced-weight welding torches in the ABIMIG® GRIP A LW range have been in use on an industrial scale for over a year and have received a very positive reception among professional welders. The excellent balance and slightly curved handle sits comfortably in the hand and the weight reduction means that welders feel less strain in their daily work. The weight reduction has been possible largely due to the use of light metal components for the live cables in the hose package where the otherwise conventional copper has been substituted by light metal components. Despite the reduced weight, the welding torches are completely suited to industrial use and compliant with the current standards and regulations, particularly DIN/EN 60974-7.
M. deltoideus medialis
M. erector spinae
M. biceps brachii caput breve
M. triceps brachii caput lateralis
M. erector spinae
M. erector spinae