How to assist or augment workers

In 2012, INRS laun­ched an ini­tial pros­pec­tive stu­dy entit­led “Use of phy­si­cal assis­tance robots by 2030 in France”. At the time, there were two exos­ke­le­tons in France that were being tes­ted in com­pa­nies. Bare­ly ten years later, there are some for­ty of them avai­lable on the mar­ket ! They range from pos­ture har­nesses that help relieve the back to robo­tic exos­ke­le­tons that com­pen­sate for effort. For us, it is exci­ting that research and inter­ven­tions in the field are in phase with the emer­gence of these phy­si­cal assis­tance technologies.

Mus­cu­los­ke­le­tal disor­ders (MSDs) account for 87% of occu­pa­tio­nal ill­nesses and back pain accounts for 20% of work-rela­ted acci­dents – a sizeable num­ber ! As well as the damage cau­sed to employees, MSDs have a high eco­no­mic cost for com­pa­nies and social secu­ri­ty (days off work). This is why mecha­ni­cal devices that help com­pen­sate for the phy­si­cal efforts of ope­ra­tors or assist them in their move­ments are alrea­dy employed or being stu­died in all fields : from the auto­mo­tive to the nuclear indus­try, inclu­ding construc­tion, mass retai­ling, the health-medi­cal-social sec­tor, etc.

The labo­ra­to­ry stu­dies focus on hand­ling and hol­ding loads to observe the conse­quences on the acti­vi­ty of the muscles that are assis­ted as well as those that aren’t, on pos­ture and on motor coor­di­na­tion. For the shoul­der, for example, our team has stu­died the space bet­ween bone and bet­ween ten­don tis­sue using ultra­sound and com­pa­red the beha­viour of joints with and without exos­ke­le­tal assis­tance. We are also car­rying out assis­tance in conjunc­tion with pre­ven­tion net­works in com­pa­nies to ana­lyse how exos­ke­le­tons are inte­gra­ted and whe­ther or not they are being accep­ted by employees. It is impor­tant to unders­tand that the dif­fe­rence bet­ween this tech­no­lo­gy and “clas­sic” phy­si­cal assis­tance is that it is atta­ched to the per­son’s body. This assis­tance, while hel­ping to reduce effort, can, at the same time, be felt by the wea­rer as a phy­si­cal and psy­cho­lo­gi­cal restraint. 

Exos­ke­le­tons can bring signi­fi­cant bene­fits, but they offer very loca­li­sed assis­tance and do not address all the phy­si­cal constraints to which employees are expo­sed. Impor­tant­ly, they can them­selves create new bio­me­cha­ni­cal constraints : impact on the mus­cu­lar acti­vi­ty of muscles not assis­ted by the exos­ke­le­ton, impact on balance, on motor coor­di­na­tion, sui­ta­bi­li­ty for high rates of work and high degrees of move­ment repe­ti­ti­ve­ness, trans­fer of bio­me­cha­ni­cal demands to other parts of the body, etc. The nature and extent of the bene­fits or limi­ta­tions obser­ved depend on the acti­vi­ty per­for­med (the wor­king pos­ture adop­ted, load hand­led, work rhythm, etc.), the tech­ni­cal cha­rac­te­ris­tics of the exos­ke­le­ton (contact points, weight, stiff­ness, etc.), and the tasks identified.

They must think very care­ful­ly before choo­sing equip­ment and consi­der the impact it will have on the whole work orga­ni­sa­tion. We are publi­shing guides to help them ask the right ques­tions. First, thin­king about pos­si­bly making use of an exos­ke­le­ton must be accom­pa­nied by a broa­der reflec­tion aimed at redu­cing the constraints lin­ked to phy­si­cal acti­vi­ty through orga­ni­sa­tio­nal changes, trai­ning, etc. The pre­cise nature of the phy­si­cal assis­tance requi­red must then be defi­ned (the body areas to be assis­ted, pos­tures usual­ly adop­ted, load weights hand­led, etc.)

If the exos­ke­le­ton solu­tion is cho­sen, it is then cru­cial to ini­tiate a test pro­cess by addres­sing pre­cise eva­lua­tion cri­te­ria : to what extent has the ope­ra­tor taken on the equip­ment ? Is it easy to use ? Is it real­ly use­ful ? What are the effects of using the exos­ke­le­ton on the envi­ron­ment and the work group ? How many people in a team will be equip­ped with an exos­ke­le­ton ? How will others view those who wear it ? The exos­ke­le­ton must be inclu­ded in works­ta­tion ana­ly­sis risks, as it may, for example, lead to new col­li­sion risks for the per­son wea­ring the equipment.

Many com­pa­nies do not rea­lise the extent to which exos­ke­le­tons can dis­rupt an entire wor­king environment.

We must remem­ber that exos­ke­le­tons are there to “assist” ope­ra­tors and not to “enhance”. To put it plain­ly, in the future, ope­ra­tors will not be car­rying loads that they were not car­rying before, but rather car­rying loads that they were alrea­dy car­rying with less risk of impact on their health. In this res­pect, the stan­dards in force today concer­ning load and phy­si­cal stress limits for manual hand­ling tasks must conti­nue to be respected.