The Sci­en­tist

Bicycling (South Africa) - - CONTENTS - By Jeroen Swart

Don’t let your butt suf­fer any more. Here’s how to find your per­fect sad­dle.

Q HOW DO I KNOW WHICH SAD­DLE TO BUY? THERE SEEM TO BE SO MANY DIF­FER­ENT THE­O­RIES, AND SO MANY OP­TIONS AVAILABLE. SNAKES, BULLS, SLITS, HOLES, GELS. CAN YOU GIVE US THE LOW­DOWN ON THE LOW DOWN, SO TO SPEAK?

– James, New­lands

A SAD­DLE SIZES, SHAPES, CUT- OUTS AND OTHER FEA­TURES HAVE PRO­LIF­ER­ATED GREATLY IN THE LAST DECADE, and the num­ber of choices available is mak­ing it in­creas­ingly con­fus­ing for both con­sumers and shop own­ers.

In ad­di­tion, a num­ber of dif­fer­ent man­u­fac­tur­ers have dif­fer­ent tech­niques and sys­tems to ‘ fit’ the end users to their sad­dles.

Be­fore we look at the dif­fer­ent sys­tems and op­tions, let’s start by un­der­stand­ing what a sad­dle needs to do. A sad­dle is de­signed to sup­port your pelvis in a sta­ble po­si­tion, while still al­low­ing you to move your legs in a great enough range to ex­ert force on the ped­als. As luck would have it, we have two con­ve­niently po­si­tioned bony points under our pelvis that we can use as sup­ports. These are pop­u­larly called our sit-bones, and are the pri­mary points of con­tact for the sad­dle.

When we sit, most of the pres­sure is ap­plied on these bones, with a lit­tle bit also be­ing ex­erted at the front of the pelvis – which acts to tri­an­gu­late the forces ap­plied, so that the pelvis is pre­vented from ro­tat­ing for­wards and back­wards dur­ing each pedal stroke. Think of a tri­pod, with two of the legs be­ing the sit- bones and the third be­ing the pelvis.

This is why the gen­eral shape of sad­dles has re­mained un­changed for al­most 100 years, as it con­forms to the re­quire­ments of this tri­an­gu­lar sup­port, while leav­ing room for the thighs to move up and down the sides of the sad­dle.

For most men, the width of the sit-bones is very sim­i­lar, which is why most brands and sad­dle mod­els re­mained con­stant for decades. With the in­creased pop­u­lar­ity of cy­cling, it be­came vi­able to cater for in­di­vid­u­als who fell out­side the av­er­age. As a re­sult, dif­fer­ent sad­dle widths be­came available.

In ad­di­tion to this, man­u­fac­tur­ers added in­creas­ing num­bers of fea­tures to lure cus­tomers to their prod­ucts: dif­fer­ent sad­dle pro­files (round to flat), firmer or softer shells and pad­ding, gel in­serts, cut-outs, etc. Although some of these fea­tures may add value, they won’t fun­da­men­tally change whether a sad­dle works for you or not.

SO HOW DO I CHOOSE THE RIGHT SAD­DLE FOR MY BUTT?

Ini­tially, sad­dle siz­ing and fit­ting fo­cused on mea­sur­ing the width of the in­di­vid­ual’s sit-bones. This re­quires sit­ting on mem­ory foam or gel, and mea­sur­ing the width of the in­dents made by the sit-bones. A chart is then used to iden­tify an ap­pro­pri­ate sad­dle width.

How­ever, this is only half of the equa­tion. The above sys­tem would work fine if sit-bones were round; un­for­tu­nately, they are elon­gated (like the hulls on a cata­ma­ran), and also not par­al­lel. They con­verge to­wards the front. As a re­sult, the for­ward and rear­ward rolling

of your pelvis will nar­row or widen (re­spec­tively) the space be­tween the sit-bones’ con­tact points.

To ad­dress this, a few man­u­fac­tur­ers have come up with tech­niques to de­ter­mine which pelvic po­si­tion an in­di­vid­ual will adopt when on the bike, and then use this to sug­gest the cor­rect sad­dle size.

But these tech­niques make the as­sump­tion that a more flex­i­ble in­di­vid­ual will adopt a more ag­gres­sive rid­ing po­si­tion by tilt­ing the pelvis for­ward, there­fore re­quir­ing a nar­rower sad­dle. This is in­cor­rect.

Although a more flex­i­ble spine will al­low the in­di­vid­ual to reach fur­ther for­ward more eas­ily, it does not de­ter­mine the po­si­tion of the pelvis. Given the same bike fit, a more flex­i­ble in­di­vid­ual will adopt a more upright pelvis, sim­ply be­cause they can reach the bar more eas­ily and won’t re­quire the pelvis to ro­tate for­ward.

SO HOW DO I GET THE RIGHT FIT?

Com­plet­ing the bike fit­ting be­fore choos­ing the sad­dle is the key. Once the bike has been fit­ted, the po­si­tion of the pelvis can be mea­sured us­ing a dig­i­tal in­cli­nome­ter. The in­di­vid­ual can then be seated on a sad­dle-sizer in the same pelvic po­si­tion (at the same pelvic an­gle) that they adopt on their bike. Only then should the cor­rect sad­dle width be cal­cu­lated. Once sad­dle width has been es­tab­lished, ad­di­tional fac­tors such as pad­ding thick­ness, pro­file, cov­er­ing and other fea­tures can be de­cided on, based on ex­pe­ri­ence.

Dr Jeroen Swart is a sports

physi­cian and ex­er­cise phys­i­ol­o­gist at the Sports Sci­ence In­sti­tute of

South Africa.

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