What Do Triathletes Wear on Their Ankles And Why ?!

You’ve probably noticed that triathletes wear what looks like an ankle bracelet, usually on their left leg. No, it’s nothing to do with wetsuit gear or attached to the bike; it plays a much more important role.

So, what do triathletes wear on their ankles? Triathletes wear a timing chip on their ankle that calculates the time and distance during the event, and it remains on throughout the entire race. It can provide instant race updates, eliminate cheating, and deal with congested start and finish areas.

Before chip technology, events were manually timed. Things got complicated at the start lines with overcrowding.

The gun would fire, but some people didn’t get to ‘start’ for up to a few minutes later, significantly affecting their ability to place at the top.

There was also an issue with people cheating, taking shortcuts, and not actually completing the whole event.

Timing chips ended both of these problems.

How Does the Whole “Timing Chip” Thing Work?

The timing chip works differently from the technology in a sports watch; instead of relying on GPS, it takes data from strategically placed mats. There’s a mat at the start and the finish which records those times sourced from the chip and determines the runners’ place in the event. (source)

The Tech Part

The chip contains an energizing coil that doesn’t activate until it comes into contact with the mat’s electromagnetic field.

The chip then sends an electronic signal to a computer, all in a fraction of a second. Numerous people can cross through the mat at one time, and as each chip has a unique number, they can all be correctly identified.

Live Updates

For long events, like triathlons, ultra-marathons, and ironman, mats are placed along the course at key places. As the runner passes each of these, the chip sends the signal, which can update everyone on their progress.

This concept is helpful for friends or family watching the event online and for officials to keep track of each competitor.

Eliminate Cheating

In an event where there are u-turns, it’s sometimes easy for a competitor to take a shortcut and not complete the entire distance. In the past, in some elite events, officials would stand along the course to ensure this didn’t happen. 

Race volunteers would wait at the u-turn checkpoints and provide the competitor with a band to wear around their wrist. This would indicate to those at the finish point that the person had competed for the whole distance. 

I’ve been in events with multiple checkpoints and ended up with 3–4 elastic bands around my wrist — it’s very uncomfortable, let me assure you.

With chips, a mat is now placed at the entrance and exit to the checkpoints. The athlete must pass both for the chip to record a successful turn. If there is no record of the person registering at those mats, their final time isn’t accepted.

Gun Time vs. Chip Time

The gun time begins when the start gun is fired until you cross the finish line. Chip time is calculated from when you cross the start line until you cross the finish line. These times will be similar if you’re at the front when the race starts. If not, they could fluctuate up to a couple of minutes. (Source)

Event placement times are based on the gun time; the chip time is primarily used for your own personal record keeping.

If you’re serious about scoring a place in the event, ensure you’re at the front when the event begins. You should always base your race results on the chip time, though.

Where to Strap It

Ankle chips are best located on the outside of the left ankle. For some events, like the Ironman,  it’s compulsory to be on the left side. For other events, it’s a personal preference. There are added advantages to keeping it left. (Source)

The left side of the body is the least likely to interfere with any bicycle part, especially the chain. The other reason they’re worn near the feet is to avoid interference with the readings — more on that in a sec.

Most timing chips are worn on a strap. Feed the strap through the holes on each side of the chip, and place it around your left ankle, with the chip facing out. This video demonstrates it exceptionally well.

How To Put On a Timing Chip and Strap (ChampionChip)

For events that are just for running quite often the chip is a disposable plastic strip attached to the back of the bib. The bib should be worn on the front of the body for the best reading by the mat signal.

Race Timing Chip Cost

In a professional event, the chip is provided by the event organizer. It comes with a way to attach it, often a velcro strap. Some athletes complain that this type of strap irritates the skin, so bring their own neoprene version.

You can hire timing chips for around $1–$1.50 each. If you’d like to train with one, they’re available. I would recommend investing in a neoprene band for your ankle. 

How Accurate Is Chip Timing?

Chip timing is highly accurate, from 99.3–99.7%. However, advances in technology have created this less than 100% success rate. Previously LF RFID was 100% accurate. These days most chips are UHF RFID; it’s cheaper but not as accurate. (Source)


Low-frequency (LF) RFID is suitable for long-distance communication and operates in the frequency range of 30–300 kHz. It doesn’t get interrupted by other external interferences. The results were almost always 100% accurate. The chips were heavy and expensive.


Ultra-high frequency (UHF) RFID operates at ~850-925MHz, which is excellent for short-distance readings. However, UHF has two enemies, water and metal. They can interfere with the readings if the chip is too close to water, like the human body, hence wearing them on the ankles.

The reading inaccuracies usually happen at the start of the event. With everybody bunched in together, a significant body of water is present. It’s not a huge issue, though.

99.3% suggests that maybe six runners in every 1,000 might not get a start reading. These will be from the middle of the pack and not the front-runners, who are the ones most likely in the awards category.

Advances in Technology

The good news is that the problem of accuracy is being researched. The larger plastic chips that road and trail runners now wear on the bibs, displayed on the front of the body, have more accurate readings. (Source)

Do Magnets Interfere With Timing Chips?

Some runners use magnetic clips to fasten their bibs to their shirts and wonder if they can interfere with the chips. Some manufacturers recommend leaving 1 inch between any magnet and the chip.

There isn’t any direct evidence that racing timing chips can be affected by magnets. The concern is that the magnets can wipe data from chips. But as these don’t store data, they only transmit it when hitting the electromagnetic field for less than a second; it’s unlikely that’s an issue.

Timing chips have revolutionized event tracking. They can provide instant results on a race while still in progress, eliminate cheating, and accurately report on thousands of race starters and finishers.

Stephen Christopher

began running at the age of 50 and 2 years later ran his first marathon in just over 5 hours. He continues to join events all over Thailand and South East Asia with Berlin and London on the list for the future.

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