Rando Race Boots & Stride Dynamics

Recently there has been a lot of heated discussion on the dynamics of boots and their relationship between sole flex and better stride.  So let’s get down into the two separate theories behind both ideas behind a bellowed boot, the Scarpa F1, and the Pierre Gignoux XP444, a solid non-flexible sole. 

Bellowed Boots

A boot that has bellows on it, like the Scarpa F1, is designed to flex at the metatarsals of the foot giving the Rando Racer the most natural stride as possible.  When you are skinning, after the foot lands and is drawn behind the body (this motion is known as “Dorsiflexion,” the toes are brought closer to the shin, and the foot is angled with the shin approximately 20º-30º) and then goes into it’s “Plantarflexion,” stage.  During the last portion of Dorsiflexion, the toes bend at the Metatarsals and the foot Plantar Flexes, which is where the foot gets its maximal stride power. 

So how is this techno jargon related to Rando Stride?  Well, allowing the foot to flex as naturally as possible, its thought that the boot will not restrict the natural movement of the foot.  This way the tendons and muscles of the foot can perform unheeded.  With this idea, while the foot pushes off the ground, it allows for an added “kick” to the stride. 

The downside to this boot design is that it is intended for a rolling low angle course design.  As long as the boot is on this style of terrain it can be an excellent choice.  On a course that is steeper, the flex of the bellows actually is an disadvantage, as it does create some energy loss in the boot which causes more muscular strain on the foot.  This muscular strain may tip the lactic acid scales over into the red zone if the racer does not pay attention to what they are doing.

Fitting this boot, should you choose, the foot and boot must allow at least 0.5º or greater, of pronation to get the most natural effect of the boot. 

Stiff Soled Boots 

A stiff soled boots, such as the Pierre Gignoux XP444, Spanish Ara Components boot, or La Sportiva, is its designed to support the foot in a more neutral position.  Much like the description of foot in the past section, it follows the same combinations of movement, but without the toes flexing at the Metatarsals.  It is thought that there is no energy loss, due to the stiff sole, and lack of Metatarsals flexing. 

This boot takes advantage of this of the lack of energy loss, and is why it caters to steeper courses, rather than low angle and rolling courses.  The disadvantage with the boot is that it does not allow for that extra “kick,” on the low angle rolling courses. 

Fitting this boot, the foot and boot are should allow the foot to be at approximately 0.5º of pronation without going over, to take advantage of the foot’s power during the Plantarflexion phase of the Rando Stride. 

Two Schools Of Thought… Or Three?

We can never know for sure which boot is truly the fastest, with the most amount of energy transfer or loss, but certain ideas are close.  The Dynafit Dy.N.A boot allows for 5mm of flex, where the bellows would be on an F1, without the bellows.  The boot is cut away so that the boot can flex, but a carbon limiter is installed to keep that within the 5mm limit, combining the large flex of the F1 and the zero flex of the Pierre Gignoux.

Conclusions?

So a real conclusion, other than inconclusive?  The largest asset that a boot can have is a non-limiting lower shell.  Meaning that when the foot is striding forward (Plantarflexion), elongating, and gaining as much forward distance as possible, it must not be limited by the lower shell.  The higher the internal cuff, the more chance that calf will "bottom out," and limit the stride length.  Boots with stiff backed liners may also have the same problems as boots with high internal lower shells.  By getting the boot with the least limitation to the foot, the racer will see the largest gains, the slightest energy transfer gains or losses are barely an issue.  Find the boot that works best with your foot, and have it fit correctly, to get the best results.