TAIPEI (Taiwan News) — Taiwanese tennis veteran Lu Yen-hsun (盧彥勳) had heart palpitations and was short of breath at the Tokyo Olympics, his fifth and also last time to participate in the Games.

The 37-year-old lost his first-round battle against German opponent Alexander Zverev, who later took the gold medal in the men's singles. Lu said that many players sent their best wishes on his retirement from the game, per CNA.

"There are no regrets, and also much less pressure," Lu said about his retirement. He said he had not been himself at the Games due to a tight schedule — and his case highlights the difficulties some athletes face due to unreported health problems.

Lu took part in the French Open in June, then Wimbledon, with the Tokyo Olympics soon after. CNA cited Lu as saying that three months of constant tennis had worn him down.

After three consecutive months of playing, Lu was suffering from gastroesophageal reflux disease (GERD), was short of breath, coughing, and experiencing heart palpitations while playing the Zverev in Tokyo.

Lu has been one of Taiwan's top professional tennis players since 2001, winning more ATP titles than any other Taiwanese player. The pressure to perform, though, led to insomnia in 2012.

Athletes' health problems have come under the spotlight partly due to the experiences of American gymnastics star Simone Biles, who quit the team final at the Olympics. Research conducted by Strava and Stanford University shows that out of 131 professional athletes, one in five reported problems related to mental health, motivation, and COVID-19.

According to Athletes for Hope, 35% of elite players deal with health issues that may manifest as stress, eating disorders, burnout, or depression and anxiety. The organization has called for more attention to athletes' mental health problems.