Sprinting insoles — the spike fit, trimming and 3/32-inch questions

That is the normal case. Many sprint spikes have a thin pad sewn or glued into the shoe, though construction varies — check your own pair. If the pad does not lift out cleanly, leave it in place and lay the Springsole on top of it, printed side up, heel seated all the way back and pressed flat from heel to toe. Nothing gets removed, and nothing goes under the pad.

Springsoles are 3/32 of an inch (about 2.4 mm) of 1,4-polybutadiene, full length. A sprint spike has almost no internal volume, so a thicker insert can shift heel position and lacing pressure. The 3/32-inch layer is designed to minimize changes to heel position, plate feel, pin or stud angle, lace tension and brace compatibility — confirm actual fit in your own footwear.

Try it untrimmed first. The 3/32-inch layer is designed to minimize changes to fit. Confirm flat placement, lockdown, lace tension, spike fit and any brace compatibility in your own footwear before training or competition, then lace as normal and jog, do build-ups and one full-speed rep before you race in them.

Try the Springsole without trimming first. Trim only if needed for a flat fit, starting at the toe/forefoot and removing a very small amount at a time. Do not trim the heel and do not unnecessarily narrow the sides. Recheck the fit after every small trim. In a spike that means the toe only, in small passes, tracing the outline of the factory pad until it lies flat in a narrow sprint last. Most pairs fit untrimmed.

No. Cutting or peeling a stitched-in footbed damages the upper and the plate bond, and it is not needed — the Springsole is designed to sit on top of it. Never force out a firmly bonded or stitched liner.

Those usually have a loose, removable insole: lift it out, lay the Springsole flat on the footbed, then put the insole back on top — the opposite order from a spike with a sewn-in pad.

It is designed to stay put when the heel is seated all the way back and the surface is pressed flat from heel to toe. Lace as normal, then jog, do build-ups and one full-speed rep to confirm it stays in place in your own spike.

Yes — hurdlers, jumpers, throwers and distance runners use the same 3/32-inch layer. Hurdle touchdowns, jump plants, throwing-ring plants and distance volume are intended applications of the thin resilient layer. Event-specific outcomes have not been directly measured, and individual results vary.

Force plate testing at the Weber State University Human Performance Laboratory found that more than twice the force was required to displace a person standing on Springsoles compared with standing without them. That is a standing resistance-to-displacement measurement. It did not directly measure sprint speed, block starts, ground-contact time, hurdle or jump performance, landing forces, energy returned to the athlete, injury or fatigue. Block starts, sprint drive phases, jump plants and hurdle touchdowns are intended applications, not measured outcomes.

They are an insole inside your shoe, not an assisting device attached to it. We are not aware of any federation rule against them, but confirm with your meet officials.

Springsoles are not a medical device and are not designed to treat or prevent shin splints or any condition. They are a thin resilient layer designed for repeated track-and-field use. If you have pain, see a qualified clinician.

Order by your US shoe size: US men's 6/7, 8/9, 10/11; US women's 7/8, 9/10, 11/12; EU 38/40, 41/42, 43/45; UK 5/6, 7/8, 9/10. If you are between sizes, take the larger range and try it untrimmed first. Pick a size range below and it drops straight into your springbak.net cart, ready to check out. Springbak® Springsoles are made in the USA.