Reclaiming autonomy : the repaired human

Around twen­ty indi­vi­duals are trai­ning today in a rather unu­sual gym, on bicycles and sta­tio­na­ry rowing machines. These people are spe­cial in that they are all living with a disa­bi­li­ty. Their legs and arms shouldn’t be able to move, but thanks to elec­tro­sti­mu­la­tion, their muscles can now respond again.

Vance Ber­ge­ron, direc­tor of research at the Phy­sics Labo­ra­to­ry of the ENS in Lyon, him­self tetra­ple­gic fol­lo­wing a cycling acci­dent, is at the ori­gin of the S.P.O.R.T (Sti­mu­la­ting People and Orga­ni­zing Recrea­tio­nal The­ra­pies) room, crea­ted in 2018 by the asso­cia­tion ANTS (Advan­ced Neu­ro-reha­bi­li­ta­tion The­ra­pies & Sports).

“The idea of elec­tri­cal­ly sti­mu­la­ting muscles is not new,” explains Vance Ber­ge­ron. “In fact, it was a French­man, Dr Duchenne de Bou­logne, who stu­died the phy­sio­lo­gy of move­ment using elec­tri­cal expe­ri­ments in a book publi­shed in 1867 that has remai­ned a refe­rence ever since ! The deve­lop­ment of exos­ke­le­tons came later, star­ting in the 1950s, but research in the field stag­na­ted until the semi­con­duc­tor and elec­tro­nics boom of the 1990s.”

Japan is lea­ding the way in this area, with exos­ke­le­tons seen as a good way to sup­port an ageing popu­la­tion. The Uni­ted States, on the other hand, is focu­sing on mili­ta­ry appli­ca­tions. What remains is to com­bine the two tech­no­lo­gies ; exos­ke­le­ton and elec­tri­cal sti­mu­la­tion. This is what the com­pa­ny Cli­na­tec, foun­ded in 2006 by Pro­fes­sor Alim-Louis Bena­bid, a neu­ro­sur­geon in Gre­noble, is doing. By desi­gning an implan­table device that col­lects the brain signals emit­ted when a per­son intends to make a move­ment, the Cli­na­tec resear­chers hope to give tetra­ple­gics the pos­si­bi­li­ty of men­tal­ly control­ling an exos­ke­le­ton robot to walk and mani­pu­late objects.

Gré­goire Cour­tine, a neu­ros­cien­tist at the Ecole Poly­tech­nique Fédé­rale de Lau­sanne (EPFL), is also wor­king towards this goal and has just tes­ted the pos­si­bi­li­ty of allo­wing tetra­ple­gics to walk again using an abdo­men-implan­ted car­diac neu­ro­sti­mu­la­tor and spi­nal-cord-implan­ted elec­trodes (see box). These devices are very inva­sive, howe­ver, and results still uncer­tain. Main­tai­ning phy­si­cal acti­vi­ty in the disa­bled brings imme­diate bene­fits though and is safe. “Sti­mu­la­ting inju­red limbs effec­ti­ve­ly com­bats the risk of secon­da­ry com­pli­ca­tions that can arise fol­lo­wing an inju­ry to the spi­nal cord,” explains Vance Ber­ge­ron, “whe­ther it is cau­sed by an acci­dent or a stroke.”

Fol­lo­wing his acci­dent, Vance Ber­ge­ron reo­rien­ted his laboratory’s acti­vi­ty to deve­lop an elec­tro­sti­mu­la­tion bicycle. It works as fol­lows : the pedal­ling move­ment is recrea­ted via non-inva­sive sur­face elec­trodes, sim­ply pla­ced on the legs of the para­ly­sed per­son. An elec­tric cur­rent sti­mu­lates the motor nerves to trig­ger muscle contrac­tions in a sequence that allows them to pedal again. “We thus prevent various phy­si­cal risks, such as bed­sores, bone demi­ne­ra­li­sa­tion and blood cir­cu­la­tion disor­ders,” conti­nues Vance Ber­ge­ron. “Elec­tro­sti­mu­la­tion also has a psy­cho­lo­gi­cal impact : main­tai­ning muscle volume gives the per­son a bet­ter body image and makes dai­ly move­ments easier, espe­cial­ly trans­fers from the wheel­chair, which require consi­de­rable phy­si­cal effort.”

Final­ly, being in a place such as a gym makes social rein­te­gra­tion easier, reduces iso­la­tion and the­re­fore the risk of depres­sion. Two bicycles and a rowing machine are now avai­lable in the S.P.O.R.T room, which is still the only one of its kind in France. There is pro­blem with these elec­tro­sti­mu­la­tion devices, howe­ver, in that they cause signi­fi­cant muscle fatigue. “When a mara­thon run­ner trains, he uses dif­ferent muscles from those used by a sprin­ter,” explains Vance Ber­ge­ron. “In the labo­ra­to­ry we are trying to see how we can tar­get cer­tain muscles, and not sti­mu­late them all at the same time.”

The labo­ra­to­ry is also wor­king on impro­ving the equip­ment, with a Blue­tooth sys­tem that would make it pos­sible to get rid of the wires by inte­gra­ting the elec­trodes into clo­thing. Final­ly, the aim is to offer finan­cial­ly com­pe­ti­tive equip­ment. “The first bike desi­gned for elec­tro­sti­mu­la­tion that I impor­ted from the US and adap­ted it so that it could be used in France cost €30,000 ! Now I’m wor­king with a Ger­man com­pa­ny¹ on a model that is acces­sible to the public, at around €2,000.”

What equip­ment will be used by disa­bled people in the future ? Exos­ke­le­tons cer­tain­ly allow people to stand up, but even in their non-inva­sive ver­sion, they are very hea­vy, and their ope­ra­ting-time is limi­ted by bat­te­ry life. In com­pa­ri­son, elec­tro­sti­mu­la­tion is very simple : a few watts are enough to make the device work…