There are growing concerns that heat and humidityduring the Olympic Games in Tokyo next summer could be dangerous to the athletes.Summer temperatures in the Japanese capital often reach 35 degrees Celsius or higher.There also is strong sunshine and humidity can reach 80 percent.Earlier this month, a worker at the Olympic building area in the city died from heat stroke.This year, high temperatures beginning in late July were blamed for the deaths of at least 57 people.George Havenith is an expert on the effects of temperature and climateon athletes at Britain's Loughborough University.He said the heat and humidity could be dangerous.Humidity interferes with the body's natural cooling system, he said,and that could make it very difficult for the athletes.Heat stroke is a big danger, especially for endurance events, Havenith said."About 15 percent of athletes even in a cool environmenthave body temperatures above 40 degrees Celsius."But, when the temperature gets above 40 degrees Celsius, he said,more athletes could face heat stroke.Tokyo has held several endurance test events in recent weeks,including a triathlon and a swimming marathon.Japanese swimmer Yumi Kida hopes to compete in the Games next summer.She said conditions in Tokyo Bay were difficult."The sunlight was strong and the water temperature was high.When I joined the race, I worried I might suffer from heat stroke," she said.Event organizers have changed the start timesof several endurance events to begin early in the morning.They said they are taking other measures to ease concerns about the heat.Yasuo Mori is with the Tokyo 2020 Games Operations Bureau.He told reporters, "I also hear they are deploying medical staffevery 50 meters of the marathon course."He added that more water than usual will also be available.Havenith said additional measures may be needed."Having ice baths available for the athletes to cool them down quickly...it's very important to have that, because if you decide to (take) them to the hospitalbefore you do the cooling, you put them at risk."Tokyo last held the Olympics in 1964.At that time, the Games were moved to October to avoid the summer heat.That is no longer possible because of the demands of international broadcasters.Scientists say all athletes should arrive in Tokyo early so they can adapt to the climate.