Benefits of physical activity at all ages

Jean-Fran­cois Gros­set is a lec­tur­er-cum-research sci­en­tist at UTC, spe­cial­iz­ing in phys­i­ol­o­gy at the UTC-BMBI (bio­me­chan­ics and bio-engi­neer­ing) Lab­o­ra­to­ry. He teach­es human phys­i­ol­o­gy at both engi­neer­ing and Master’s degree levels.

«The phys­i­ol­o­gy of both healthy and patho­log­i­cal per­sons,» he explains. His areas of research? «I’m par­tic­u­lar­ly inter­est­ed in the periph­er­al ner­vous sys­tem — in oth­er words, all the “cables” run­ning from the spinal cord to mus­cle effec­tors or from sen­so­ry sen­sors — as well as the func­tion­ing of mus­cles and ten­dons link­ing mus­cles to bone. I’m par­tic­u­lar­ly inter­est­ed in the adap­ta­tions of neu­ro­mus­cu­lo- tendi­nous struc­tures», he explains. 

It was defend­ing his the­sis on the effects of mat­u­ra­tion in chil­dren that his inter­est in these lines of research became appar­ent. «I first car­ried out tests with pre­pu­ber­ty chil­dren to obtain ref­er­ence curves for the var­i­ous neu­ro-mus­cu­lar para­me­ters in healthy chil­dren and then assessed the effect of pro­longed immo­bi­liza­tion on hos­pi­tal­ized chil­dren with pri­ma­ry hip osteo­chon­dri­tis. We need to know how this works in healthy sub­jects so that we chil­dren,» empha­sizes Jean-François Grosset.

The effects of applying electro-stimulation

Research he pur­sued dur­ing a Post-Doc peri­od at Man­ches­ter and Dublin. «I was inter­est­ed in the evo­lu­tion of mechan­i­cal, mus­cu­lar and ten­don prop­er­ties in sub­jects under­go­ing strength train­ing, and in the analy­sis of post-exer­tion mus­cle and ten­don char­ac­ter­is­tics. Hyper­tro­phy or atro­phy for the for­mer, more elas­tic or stiffer for the lat­ter», he explains.

His research con­tin­ued when he arrived at UTC, where he worked with a master’s stu­dent to devel­op a train­ing pro­to­col based on Elec­tro-Myo- Stim­u­la­tion. What was the aim of this pro­to­col? «We were inter­est­ed in eval­u­at­ing the effect of train­ing based on high-fre­quen­cy elec­tros­tim­u­la­tion at the max­i­mum inten­si­ty tol­er­at­ed by the sub­jects for 4 weeks, with 3 train­ing ses­sions per week in the lab, and assess­ing whether the invol­un­tary mus­cle con­trac­tion induced by elec­tro-stim­u­la­tion was of suf­fi­cient inten­si­ty to induce an adap­ta­tion process in the ten­don struc­tures con­nect­ed to the mus­cles. We there­fore set up this pro­to­col for mon­i­tor­ing mus­cu­lar char­ac­ter­is­tics, based on ultra­sound imag­ing and ergo­met­ric tools, to see the archi­tec­ture and mechan­i­cal prop­er­ties of mus­cles and ten­dons, and the effects of train­ing on them», he explains.

A project that mere­ly con­firmed the results of pre­vi­ous stud­ies on the role of elec­tros­tim­u­la­tion in improv­ing mus­cle strength and vol­ume, but showed, for the first time, the impact on ten­dons. «Four weeks of high-fre­quen­cy elec­tros­tim­u­la­tion increas­es mus­cle strength by 25%. But for the first time, high-fre­quen­cy elec­tro-stim­u­la­tion has also been shown to induce ten­don adap­ta­tion. Indeed, max­i­mum stim­u­la­tion at high fre­quen­cy induced a con­trac­tion equiv­a­lent to 55% of max­i­mum force. We have shown that, despite an inten­si­ty that can be con­sid­ered aver­age, the ten­don adapts, show­ing a slight hyper­tro­phy but above all a mod­i­fi­ca­tion of its mechan­i­cal prop­er­ties. These are very inter­est­ing results, par­tic­u­lar­ly for the treat­ment of tendinopathies», explains Jean-François Grosset.

Prolonging autonomy for the elderly

These results led them, as part of Adrien Létocart’s the­sis in part­ner­ship with the Insti­tute of Sports Med­i­cine in Copen­hagen, to ask whether this aver­age inten­si­ty was ulti­mate­ly suf­fi­cient to induce mus­cu­lar and ten­don adap­ta­tion in the elder­ly, and thus pro­long their auton­o­my. «We knew that train­ing the elder­ly at 80% of their max­i­mum strength induced mus­cu­lar and ten­don adap­ta­tions. But what inter­est­ed us was whether it was worth impos­ing such high inten­si­ties on the elder­ly, who are nonethe­less more frag­ile and there­fore more like­ly to suf­fer injury than younger peo­ple. We test­ed the hypoth­e­sis that an aver­age inten­si­ty of 55% would not allow the same mus­cu­lar and ten­don adap­ta­tion as 80%,» he says.

This hypoth­e­sis led Jean-François Gros­set and the PhD stu­dent to set up a test­ing pro­to­col for the elder­ly. «We took two groups of elder­ly peo­ple on a 3‑month train­ing pro­gram, 3 times a week, super­vised by the PhD stu­dent. One group trained at a high inten­si­ty, viz., 80%, the sec­ond at a medi­um inten­si­ty, 55%. At the end of the pro­to­col, both groups of elder­ly peo­ple had equiv­a­lent mus­cle and ten­don adap­ta­tion for all para­me­ters. An increase in inten­si­ty does not result in a pro­por­tion­al increase in gains for the elder­ly, but rather presents an increased risk of mus­cu­lar, ten­don or spinal injury. We were the first to demon­strate this,» con­cludes Jean- François Gros­set. These results have already been pub­lished in BMC Geri­atrics, while two oth­ers are cur­rent­ly being sub­mit­ted to the Euro­pean Jour­nal of Applied Physiology.

40 years of biomedical research

Cécile Legal­lais is Direc­tor of the Bio­me­chan­ics and Bio­engi­neer­ing Lab­o­ra­to­ry (BMBI), a joint UTC/CNRS research unit. She looks back over the laboratory’s 40 years.


When the UTC was found­ed in 1973, Guy Denielou, the University’s first Direc­tor, had the idea of found­ing a depart­ment of bio­med­ical engi­neer­ing or engi­neer­ing for health. This was quite vision­ary for the time. To this end, he sought out research sci­en­tists in the USA and else­where to form a core group, to be in charge of explor­ing pure­ly bio­me­chan­i­cal phe­nom­e­na that had been lit­tle stud­ied in France at the time. Dominique Barthes-Biesel, Michel Jaf­frin and Fran­cis Goubel were among the pio­neers to join UTC. The first named was a spe­cial­ist in the flow of cap­sules in blood ves­sels, the sec­ond a spe­cial­ist in arti­fi­cial organs and the third in the bio­me­chan­ics of mus­cu­lar activ­i­ties, to com­ple­ment the phys­i­o­log­i­cal approach which was dom­i­nant in France then.


ACCREDITATION In the ear­ly ‘80s, these pio­neers suc­cess­ful­ly sub­mit­ted a project to the CNRS. ≪1982 is to be remem­bered as the year the lab­o­ra­to­ry was cre­at­ed, because that was the year we received accred­i­ta­tion for a joint research unit (UMR) with the CNRS. From then on, the teams, which ini­tial­ly com­prised around twen­ty research sci­en­tists, began to grow,≫ asserts Cecile Legallais.


Over the years, the Lab’s orig­i­nal themes have been enriched by new research approach­es. ≪First there was the inte­gra­tion of a team of cell biol­o­gists at the end of the 1980s, which led 20 years lat­er to the cre­ation of a ≪cells, bio­ma­te­ri­als and biore­ac­tors≫ team. Thanks to this rein­force­ment, it then seemed log­i­cal to bring togeth­er arti­fi­cial organs and cell biol­o­gy in a broad­er group known as tis­sue engi­neer­ing. Sim­i­lar­ly, the arrival of Marie- Chris­tine Ho Ba Tho enabled us to broad­en our ini­tial focus on mus­cu­lar bio­me­chan­ics by adding bone bio­me­chan­ics. Today, we speak of bio­me­chan­ics of the mus­cu­loskele­tal sys­tem, this also com­bin­ing elec­tro­phys­i­o­log­i­cal sig­nals and move­ment analy­sis. As for flu­id bio­me­chan­ics, it cur­rent­ly cov­ers all the scales of the human body, from micro­cir­cu­la­tion to major blood ves­sels. Final­ly, more recent­ly, we cre­at­ed the Dan Istrate Chair in Con­nect­ed Med­ical Tools. This brings an e‑health com­po­nent to med­ical devices that can be applied to our research themes≫, she adds.

From its ini­tial staff of around twen­ty, the BMBI will have grown to almost one hun­dred by 2023 – researcher-sci­en­tists, PhD stu­dents, tech­ni­cal and admin­is­tra­tive staff and trainees — and 40 years on it still has its CNRS accred­i­ta­tion. A sign of pos­i­tive vitality!

Le magazine

Novembre 2023 - N°61

Activité physique, nutrition & santé

linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram