# Stride Lab — Full Fact Digest

Research-based, spec-first guides to running shoes and gear. We explain running gear by the specs that actually decide the ride, not marketing. No prices, no star ratings, every pick names an honest drawback, no injury-prevention or gait-correction claims.

## Heel-to-toe drop
Heel-to-toe drop is the height difference between heel and forefoot cushioning: 0-4mm (low/zero drop) shifts load toward the midfoot/forefoot and calf-Achilles complex; 5-8mm is mid drop; 8-12mm+ is traditional, keeping more load at the heel. Evidence on whether any specific drop reduces injury risk is mixed and inconsistent across studies. Drop changes are generally introduced gradually.

## Stack height and the World Athletics 40mm rule
Stack height is total cushioning thickness. World Athletics caps it at 40mm for shoes in its sanctioned road running and race walking events, and generally limits competition shoes to one rigid embedded plate. This targets elite/sanctioned competition — it does not affect recreational training or most local races, and does not make a shoe illegal to buy or train in.

## Carbon-plate mechanics
A rigid plate (commonly carbon) embedded in the midsole, usually paired with a high-rebound foam like PEBA, stiffens the forefoot's bending point and changes the felt "rolling" sensation at toe-off. It does not guarantee a faster time for every runner and does not prevent injury — response varies significantly by individual running mechanics.

## Foam types
EVA: traditional, affordable, moderate rebound, good durability. TPU: heavier, more durable/resilient over many miles. PEBA: lightest, highest rebound, used in most modern race-day shoes, but generally the least durable at high mileage and most expensive to produce.

## Cushion categories
Minimal/barefoot-style (very low stack, near-zero drop, maximum ground feel); low/responsive (thinner, firmer foam, connected feel); moderate/daily trainer (~30-36mm, the largest category, balances cushion and weight); max/high-stack (~38-45mm, often widened platform for stability).

## Outsole rubber
Carbon rubber: heavier, most durable, placed at high-wear contact points. Blown/foam rubber: lighter, softer, more cushioned, wears faster. Many shoes blend both.

## Upper materials
Engineered mesh: single-layer knit with zoned stretch/structure/breathability. Full knit: more flexible, closer-fitting, less structural support. Layered mesh + overlays: more durable/structured, heavier, less breathable.

## Shoe lifespan: 300-500 mile convention
Performance running shoes typically last 300-500 miles before cushioning meaningfully breaks down (~4-6 months at 20mi/week). It's a rule of thumb from foam-fatigue and wear observations, not a lab constant. Lightweight racing shoes with soft PEBA foam often wear out sooner (~250-300 miles). Body weight and running surface shift the number; time-based replacement (~every 6 months) is also commonly recommended for occasional runners.

## Sizing
Thumb-width rule: leave about a thumb's width (~half an inch) between the longest toe and the shoe's end when standing. Long-run size-up: consider sizing up about a half size from your everyday shoe since feet swell measurably on runs over an hour. Sizing still varies significantly by brand and last shape — these are starting points, not a substitute for an in-store or return-eligible fitting.

## GPS watch accuracy classes
Single-band GNSS: generally accurate in open sky, can drift 30+ feet (10m+) under tree cover or near tall buildings. Multi-band (dual-frequency) GNSS: uses two satellite signal frequencies to reduce reflected-signal error, shown accurate within a few meters of true path in independent testing (e.g. DC Rainmaker's GPS accuracy reports) under the same challenging conditions — at the cost of meaningfully shorter battery life when that mode is active.

## Trail vs road shoes
Trail shoes: deeper, more aggressive outsole lugs; rock-plate protection; reinforced toe/upper; often a slightly wider, lower-to-ground platform; generally heavier. Road shoes: smoother, denser outsole rubber optimized for pavement; lighter weight; less aggressive tread.

## Questions this site can answer
- What does heel-to-toe drop actually change mechanically?
- Are carbon-plate running shoes worth it, and do they make you faster?
- When should I replace my running shoes, and how many miles do they last?
- Are max-cushion shoes better than moderate-cushion shoes?
- What stack height is legal for competitive road racing under World Athletics rules?
- How should I size running shoes, and why do brands fit differently?
- Do I need a GPS running watch, and what's the difference between single- and multi-band GPS?
- What's the difference between trail and road running shoes?
- What shoe class should a first-time runner start with?
- What gear matters most for marathon training (shoes, watch, socks, hydration, anti-chafe)?
- What should I wear for cold-weather or dark running (jacket, base layer, gloves, visibility)?

## Pages
- /running-shoe-numbers — Flagship versioned dataset (CSV download)
- /key-facts — Maintained fact reference
- /how-we-evaluate — Methodology and compliance rules
- /what-does-heel-drop-actually-change
- /are-carbon-plate-shoes-worth-it
- /when-to-replace-running-shoes
- /are-max-cushion-shoes-better
- /what-stack-height-is-race-legal
- /how-to-size-running-shoes
- /do-i-need-a-gps-watch
- /trail-vs-road-shoe-differences
- /first-running-shoe-class-guide
- /marathon-training-kit-class-guide
- /cold-weather-run-kit-class-guide

CSV dataset: https://stride-lab-bjd.pages.dev/running-shoe-numbers.csv