Product launch · Sport & Officiating

RSA Test: two iPhones instead of a set of timing gates.

Our second hockey fitness-test app is on the App Store. It times the 6 × 40 m Repeated Sprint Ability test with two phones you already own, keeps a picture of every crossing, and prints the sheet the witness signs.

TL;DR

The Repeated Sprint Ability test needs electronic timing gates, and a pair costs between about A$1,000 and A$3,000. Most umpires and clubs never see a set, so they time it with a stopwatch. RSA Test stands one iPhone or iPad at each line, links them over a Personal Hotspot, and times each sprint to a couple of milliseconds. Free on the App Store.

The test, and the problem with timing it

The Repeated Sprint Ability test is six 40 m sprints with up to 60 seconds of walking recovery between them, each timed from a start gate to a finish gate. Hockey umpires know it as one half of the fitness assessment the International Hockey Federation sets for its international panels, with pass targets of 6.2 to 6.8 seconds depending on gender and panel. Clubs, schools and conditioning coaches use the same test as a plain fitness benchmark.

The protocol is written around electronic gates because the margins are small: a sprint of 6.3 seconds against a 6.2 target is a fail. Yet a pair of gates costs A$1,069 for the cheapest wireless kit we could find in Australia and around A$3,000 for the systems national bodies use, before tripods, batteries and repairs. The fallback the guidelines allow is a handheld stopwatch, which adds a reaction-time error of a tenth or two of a second at each end. That error is bigger than the margin the result is decided by.

What we built

RSA Test uses the cameras and clocks of two ordinary Apple devices as the gates. The finish device turns on Personal Hotspot; the start device joins it; the app finds its partner and shows Linked on both. From then on the two devices compare clocks twenty times a second, trusting only the fastest exchanges, and agree to about 0.2 milliseconds for the whole session. Each device watches its line at up to 240 frames per second and fires on the first part of the body to cross it, the way a single-beam photocell does. The finish device subtracts one crossing from the other, judges the sprint against the target, counts down the recovery, and handles the seventh sprint rule and the two-fails verdict exactly as the guidelines describe.

Because the test has to be witnessed and evidenced, each gate keeps the frame it fired on with the sprint, gate and time burned in, and the app produces a one-page results sheet with signature lines and a shareable folder of everything. Nothing leaves the device unless the tester shares it: no account, no server, no analytics.

How we made sure it works

We did not start with the app. We started with three small experiments on real devices on a hockey pitch, each answering one question the design depended on:

  • Do two phones agree on the time at 40 m? Over a direct phone-to-phone link, yes, but the link dropped at about 50 m. Over a Personal Hotspot it held across the whole field at 0.2 ms agreement, so that is what the app uses.
  • Can a camera time a crossing? A pendulum taught us about ghosts in the background, shadows and processing speed, and every lesson went into the code with an automated test that reproduces it.
  • Do two gates agree with each other? Both devices on one line, timing the same crossings, differed by 1.7 ms per gate. The published validation of camera timing apps against photocells lands in the same range, and a stopwatch is fifty times worse.

The full story, with the numbers, is in the RSA Test white paper.

Part of a family

RSA Test sits alongside the YoYo App, which runs the Yo-Yo Intermittent Recovery Test, the other half of the umpire fitness assessment, on iPhone, Apple Watch, Android and the web. Between them a tester can run a complete fitness day with the devices in their pocket. They join WhistleIQ, our platform for umpire and official development, UMPY, and the Hockey Shoot-out App. The approach is the same in each: take the rule or the protocol exactly as written, build the tool around the way officials and coaches work on the day, and take out the cost that stops people doing it properly.

RSA Test is an independent Stacksy product. It follows the FIH's published targets and rules and is not affiliated with or endorsed by the FIH.

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