World men's 800m champion Alfred Kirwa is hoping that change in his running style will yield a successful title defence.

Speaking after winning his heat from gun to tape during first day action at the Kenya Athletics Championships held in Nairobi on Thursday, Kirwa told journalists his previous tactic of hanging with a group of runners at the bell had cost him several races.

"I changed my running style this season from waiting at the back to attacking from the front after realizing I lose many races in the last 200m when I'm boxed in with others," Kirwa said.

Kirwa won Heat 1 in 1:48.75 ahead of Eliud Rutto (1:49.17) and Rajab Hussein (1:49.96). In the second two-lap heat, Africa champion and 2006 world junior gold medalist David Rudisha took the honors in 1:48.7.

"I chose to race here since the championships will give me a feel of Berlin since you run in heats, semis and the final. So far, I have had no reaction to my injury and if my body holds, I will perform well at World Championships," said Rudisha who missed the Beijing Olympics with a calf injury.

The two 800m aces were among a collection of international distance stars who performed before a disappointing home crowd on the first of three days action as Kenya seeks her national athletics champions.

 Vivian Cheruiyot, the world 5,000m silver medalist won the first women's 1,500m heat in 4:17.4. "I have big hopes for Berlin. For long Ethiopians have been beating usin the last lap but since I beat Meseret Defar (Africa champion) last year, I feel I'm getting very close to them," Cheruiyot said.

In the second heat, Olympics and world fourth placer at 5,000m Sylvia Kibet booked her place in the final with a 4:19.3.

 "I will compete at the Oslo Golden League meeting in 5,000m and then return to train for the trials. It is my prayer that I will make the national team to Berlin and win a medal," Kibet said.

Both Cheruiyot and Kibet were using the shorter race to sharpen on speed. Former world junior 3,000m champion, Veronica Nyaruai, who has had a difficult transition to senior ranks, was third in the heat won by Kibet with 4:22.

"I will be back in my former form probably next season. I'm working to get back my shape after military training but I will attempt to qualify for Berlin in the 5,000m team," Nyaruai stated.

Former world Junior 10,000m silver medalist, Joseph Ebuya (13:49.6) beat 2007 World Cross junior race silver winner, Vincent Kiprop (13:49.9) and North Rift's Philemon Limo (13:50.0) to the podium in the men's 5,000m first semifinal.

In the other, Police runner, Joseph Kitur (13:40.7) topped teammate Alex Macharia (13:42.0) and Beijing seventh finisher, Thomas Kemei Longosiwa (Prisons, 13:42.0).

In the sprints, US based second year college student, Anderson Mureta and Armed Forces sensation, Kipkemoi Soi showed glimpses of why they are rated as likely qualifiers for Berlin World Championships.

Mureta (Kenya Police) won his 200m (21.50) and 400m (46.84) heats by blowing away the competition while Soi (Armed Forces) raced clear of rivals in 100m (10.59) and 200m (21.16).

Another men's 400m hopeful, Thomas Musembi (Prisons, 47.79) also won his heat. The event continues Friday with the women's 10,000m final.