Run­ning on Power

Stryd Sum­mit

Canadian Running - - DEPARTMENTS - By Justin Van­der­leest

While new to run­ning, power me­ters are al­ready main­stream in cy­cling. Power is more re­li­able than time, speed, ca­dence or heart rate alone for eval­u­at­ing per­for­mance. As such, many cy­clists are con­stantly aware of their power out­put when rac­ing and use power zones as guides for more ef­fec­tive train­ing.

There are many types of cy­cling power me­ters, but each one uses a strain gauge to mea­sure the force your body ex­erts on a com­po­nent of the bike. That force is then mul­ti­plied by the an­gu­lar ve­loc­ity of the com­po­nent to cal­cu­late power out­put.

In run­ning, it’s a bit more com­pli­cated. There’s an axis of mo­tion to ap­pre­ci­ate at ev­ery joint, as well as ef­fort dur­ing both stance and swing phases of gait to con­sider. Stryd is try­ing to ap­pre­ci­ate this com­plex­ity of move­ment and its meta­bolic re­quire­ments us­ing a sin­gle-sided foot pod.

Care­ful to pro­tect their pro­pri­etary se­crets, Stryd isn’t shar­ing their equa­tions, nor their spe­cific un­der­stand­ing of run­ning me­chan­ics. There’s no gold stan­dard against which to com­pare their prod­uct, so it’s dif­fi­cult to val­i­date their tech­nol­ogy. But, they do wel­come in­quiries through their web­site’s live chat fea­ture.

A year af­ter its de­but and al­ready in its sec­ond it­er­a­tion, the Sum­mit is a sleek foot pod that clips onto your laces. It comes with a wire­less charger, is com­pat­i­ble with some of the most pop­u­lar Garmin and Su­unto gps watches and has An­droid and iOS com­pat­i­ble apps that are pol­ished and easy to use. In ad­di­tion to power, the Sum­mit mea­sures pace, el­e­va­tion, dis­tance, ca­dence, ground time, ver­ti­cal os­cil­la­tion, form power and leg spring stiff­ness. Stryd has priced the Sum­mit at us$ 199, which is rea­son­ably af­ford­able com­pared to cy­cling power me­ters, which start at about four times that price.

On my first run with the power meter, there were no sur­prises. The power dis­play re­sponded ac­cord­ingly when I ran faster, and it spiked when I ran up stairs. The dis­tance and el­e­va­tion changes recorded on the app were ac­cu­rate, as well.

Out­doors, changes in speed are mea­sured by the gps in your phone or watch, and the el­e­va­tion of the ter­rain is mea­sured by the foot pod’s barom­e­ter.

In­doors, the tread­mill mode is es­sen­tial and re­quires that you in­put your speed and the tread­mill in­cline, and up­date them through­out the run. This is a bit of a has­sle, but Stryd says they know how they’ll mea­sure in­cline au­to­mat­i­cally in the fu­ture.

The user’s stated weight is an­other ma­jor fac­tor in Stryd’s equa­tion, ref lect­ing the big­gest dif­fer­ence be­tween run­ning and cy­cling power me­ters, the lat­ter be­ing blind to the rider’s size.

It might seem strange to cal­cu­late power us­ing a for­mula that hasn’t been vet­ted and re­quires users to in­put tread­mill in­clines and speeds as well as daily weight f luc­tu­a­tions to get an ac­cu­rate read­ing. But, power aside, the ac­celerom­e­ters and gy­ro­scopes in the pod are mea­sur­ing other met­rics that may be use­ful as well.

Stryd claims that you can im­prove your run­ning ef­fi­ciency if you find the tech­nique that uses the least power at a given speed. To test this as­ser­tion, I ex­per­i­mented with dif­fer­ent tech­niques while main­tain­ing a con­stant tread­mill speed.

I found no dif­fer­ence in power out­put be­tween “gazelle” and “shuff ling” tech­nique. How­ever, “form power,” which rep­re­sents the ef­fort re­quired to lift your cen­tre of mass in prepa­ra­tion to move for­ward, did in­crease slightly with gazelle tech­nique and de­creased slightly with shuff ling. Leg spring stiff­ness is a mea­sure of ef­fi­ciency that also in­creased with the gazelle tech­nique.

When I mim­icked a bounc­ing tech­nique, my ver­ti­cal os­cil­la­tion and form power in­creased, as ex­pected, in­di­cat­ing de­creased ef­fi­ciency.

Ac­cord­ing to the Stryd team, the great­est ef­fi­ciency is achieved by strik­ing a bal­ance be­tween form power and leg spring stiff­ness. I struck a bal­ance be­tween the two by us­ing the gazelle tech­nique while in­creas­ing my ca­dence from 165 to 180 steps per minute. Leg spring stiff­ness re­mained high, while form power de­creased by a whop­ping 9%.

In Novem­ber, triath­lete Lionel San­ders was wear­ing the Stryd Sum­mit for the first time when he set the Iron­man world record in Ari­zona. Two weeks later, at the Per­sonal Best triathlon clinic at McMaster Univer­sity, San­ders re­ported that he would be us­ing the power meter on­go­ing as a train­ing tool. He noted his leg spring stiff­ness de­clined grad­u­ally over the course of his run, in­di­cat­ing the ef­fect of fa­tigue, and won­dered if he could im­prove it by fo­cus­ing on main­tain­ing his form.

As ath­letes and coaches grap­ple with ques­tions like these, try­ing to de­ter­mine what the data means and how to use it, one thing is clear: they’re ex­cited about the tech­nol­ogy. While the de­vice can’t fully as­sess your tech­nique, it can help, and the met­rics do give con­text to an ef­fort. I sus­pect run­ning power me­ters are here to stay. Time will tell whether it’s a fad or an im­por­tant train­ing tool. Justin Van­der­leest is an FCAMPT phys­i­cal ther­a­pist based in Toronto. Visit justin­van­der­ and fol­low him on Twitter @JD­van­derLeest

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