Japan Para Badminton Federation (JPBF) chairman Kazumi Hirano has conceded that some of the country's players were not in good condition when they returned to training following coronavirus restrictions.
Badminton is due to make its Paralympic debut at the postponed Tokyo 2020 Games next year, with Japan hoping for a strong showing on home soil.
Squad members returned to training at the Hulic Nishikasai Gymnasium in Tokyo last month, after gaining approval from the Japanese Paralympic Committee.
"The players showed symptoms such as weight gain, loss of motivation and psychological stress," said Hirano.
"Some players were able to return smoothly to training, while others are starting from scratch.
"Some players are wary of COVID-19 because they need to travel.
"Each player has different feelings but by explaining the phases and the JPBF's strengthening plan, I feel that the players are becoming more optimistic."
The Tokyo 2020 Paralympics are now due to take place between August 24 and September 5 next year after coronavirus forced a delay to the Games.
"The psychological damage caused by the postponement of the Paralympic Games is big, and the reason being the pandemic has resulted in some players having a negative attitude," Hirano added.
"But the world is currently disrupted by COVID-19.
"We need to act and think positively, to look forward to the day when humanity will overcome this situation and we can meet our Para-badminton family around the world again.
"When the players were in isolation, the coaches and I monitored their training and fitness.
"We then started to work to restore the athletes to perfect condition.
"When they returned, the coaches studied each player's condition and offered a suitable course for each one of them.
"This is an ongoing process involving the JPBF coaches and medical team, the sports science department of the National Science and Sports Centre, and myself.
"For now, I think it's going well.
"We understand the condition of each athlete and are responding to their needs.
"We have strict rules in the gymnasium and players have been told to avoid using public transportation, to reduce the risk of exposure to COVID-19 as much as possible.
"If adjustments are needed depending on the coronavirus situation in Tokyo, we are prepared to respond flexibly."