Olympic archers performed worse when they had higher heart rates

High stress levels hinder performance on all kinds of tasks. But do elite athletes suffer in the same way? In the past, this has been difficult to measure. But during the 2020 Tokyo Olympics, remote cameras measured the heart rates of competitors in two of the archery competitions. And now an analysis of this data in Psychological Science shows that higher heat rates — an indicator of greater stress — were indeed associated with lower scores. "Our results provide the first direct evidence in support of the detrimental effect of psychological stress measured by a real-time biomarker in a high-stakes competitive setting," write Yungfeng Lu of Nanjing University and Songfa Zhong of the National University of Singapore.

Of the 128 archers who took part in the women's and men's individual archery competitions, 122 agreed to have their heart rate measured using the camera system, and to have it broadcast on television. The cameras, which were placed 12 metres from the shooting line, captured the subtle changes in the reflectance of the athletes' skin that are caused by changes in blood flow. This was used to infer their heart rate; earlier tests of the technique showing that it is 96% as accurate as an electrocardiogram.

Heart rate data was broadcast on TV for each round, including the final. Two archers competed in each match, which usually consisted of five sets. In each set, archers took turns to fire three arrows at a target; the maximum they could score with a single arrow (i.e. by hitting the bullseye) was 10.

Overall, the heart rate data showed a wide range — from 61 to 190 beats per minute, with a mean of 134. But when the researchers looked for links between the archers' heart rates before they took their shots and the scores for the corresponding arrows, they found a clear link: higher rates were associated with lower scores. (This was the case whether the team considered the mean heart rate in the period prior to shooting — they had twenty seconds to take each shot - or the heart rate immediately prior to shooting.)

Neither age nor gender had any impact on the strength of the relationship between greater stress and poorer performance. But the stage of the competition did. In later rounds this relationship was stronger, perhaps because the athletes were feeling more pressure at this point, the pair suggests.

Earlier studies have suggested that while too much stress is detrimental to performance on a task, stress is beneficial up to a point. The pair explored whether this was the case with these elite archers. They did indeed find evidence for such a pattern among lower-ranking archers – but "intriguingly, not among the high-ranking athletes," they report.

Previously, a link between greater stress and poorer performance in elite sports has been only anecdotal. And anecdotal reports from the archers' themselves also support the team's finding that the link is real. For instance, in one match, the top seed, Kim Je-deok, had a heart rate of 120bpm in the first set and 170bpm in the fifth set. He lost the match, and later said, "I felt a bit of pressure, and was nervous," and accepted that this had affected his performance, the researchers report.

Elite athletes usually receive training to manage psychological stress, the team notes. But their results suggest that they are still impacted by it, potentially costing them a win, or even a medal.