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Why do runners wear arm sleeves and more track and field questions - answered!

Wondering why they wear arm sleeves but no socks? Here's the lowdown.

Olympic track and field events kicked off July 30 with some of the most anticipated events of the 2020 Tokyo Olympic Games.

Five-time Olympian Allyson Felix returns alongside first-time Olympian and the youngest American male track athlete to qualify for the Olympics in 57 years, Erriyon Knighton.

The U.S. Olympic track and field team is no stranger to the Olympic podium, but those of us watching may be strangers to track and field traditions. We checked with the folks at USA Track & Field to get answers to some of your most-googled questions about the 2021 Olympic track and field competition.

TODAY Illustration / Getty Images

Who are the Team USA athletes to watch in 2021?

Pay special note to Allyson Felix, the most decorated U.S. woman in Olympic track and field history with nine career medals, six of them gold. She’s competing in two events: The 400 meter, and the 400 meter relay.

Plus, you’ll want to watch both current and former world record holders in the women's 400 meter hurdles, Sydney McLaughlin and Dalilah Muhammad. And there’s Ryan Crouser, the shot-put gold medalist who’ll be looking to defend his hardware in Tokyo.

Hurdlers Grant Holloway and Rai Benjamin are gold medal favorites as well. Benjamin is competing in the 400 meter hurdles, while Holloway is handling the 110 meter hurdles. And in the 1,500 meters, Matthew Centrowitz became the first American man since 1908 to win the gold at Rio, and he’s defending his title.

Why do sprinters use starting blocks?

In events from 100 to 400 meters, including the hurdles, athletes are required to use starting blocks. This is because of the false start sensors attached to the blocks which indicate when an athlete has applied pressure above a certain level less than .1 of a second after the starting gun has fired. If the reaction time is faster than .1, the athlete can be disqualified.

Usain Bolt takes the start of the Men's 200m at the 2016 Rio Olympics.MARTIN BERNETTI / AFP via Getty Images

In the shorter dashes, blocks are also very helpful in providing a solid platform for the athlete to push off of in order to get a more powerful and rapid start. The first stride that a sprinter takes is the longest and the starting blocks allow the sprinter to increase their acceleration and position themselves upright to move as fast as possible.

Why do runners jump before a race?

This explosive movement before getting in the blocks helps activate neurons and muscle fibers to prepare for the demands of the sprint to follow. It is called Post-activation Potentiation (PAP) by sports scientists.

According to research from the Journal of Sports Sciences, jumping before a race prevents the risk of injury and can decrease your overall race time.

Why do sprinters wear arm sleeves?

Arm sleeves don't just look cool; they serve multiple purposes. Arm sleeves reduce swelling of the arms while making such intense movements in a short period of time, reduce energy loss while running, and increase blood circulation in the muscles, aiding in a quick recovery.

Why don’t runners wear socks?

Socks or no socks is a personal choice for each athlete. Many athletes like the feel of their competition spikes as tight to their feet as possible to avoid any chance of slippage when applying maximal forces. Runners in longer races are a bit more likely to choose to wear socks because of the threat of blisters.

Andrea Rooth of Norway competes in the women's 400m hurdles in Tallinn, Estonia.Joosep Martinson / Getty Images for European Athletics

Why do sprinters run with their hands open?

Having loose muscles is essential to sprinters. No amount of energy can be wasted on tightened muscles because sprinters need their energy to go into their long strides to the finish line.

The clenching of fists can lead to the clenching of other body parts including biceps and shoulders. The range of motion with the arms allows the sprinters to move quickly and efficiently.

Why do long jumpers lean back?

To maximize distance, an athlete must do all they can to avoid forward rotation during the flight phase of the jump. There are three techniques jumpers can use in the flight phase — the sail, the hang or the hitch-kick. In the first two, the torso remains virtually perpendicular to the ground.

The hitch-kick (the one that looks like the athlete is running in the air) tends to create a backward lean of the upper body, which prepares the athlete better for an efficient landing.

None of this has a major effect on distance, because the athlete's "flight path" is largely determined by projection velocity and angle of takeoff — once you're in the air, you can't apply any more force!

Sara Simeoni from Italy during the women's high jump at the 1984 Olympic Games. She won the silver medal.Gilbert Iundt / Corbis / VCG via Getty Images

Why do high jumpers jump backward?

Dick Fosbury popularized the "flop" that bears his name at the 1968 Olympic Games. The flop allows a jumper to clear the bar while their center of mass travels under the bar, and is much easier to learn for the majority of jumpers than the straddle, which is the technique used by the top Russian jumpers before Fosbury came along.

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