Emmanuel Mutai will bid for back-to-back London Marathon titles Sunday as Kenyan runners look to dominate in the men\'s and women\'s races of the gruelling event. Mutai, 27, heads a strong field which includes fellow Kenyans, Patrick Makau, the world record holder and Abel Kirui, the reigning world champion. All three are determined to impress in London as they aim to secure one of the three spots available to marathon runners in Kenya\'s Olympic team. Mutai\'s preparations for the race have been disrupted by a bout of typhoid last month but the talented distance runner says he is back to full fitness and determined to impress Kenya\'s Olympic selectors. \"For me this will definitely be a tougher competition than last year because the field is so strong,\" said Mutai. \"Everyone has run a good time so I will have to perform at my best. \"I had a fever a few weeks ago and was under medication. But I am feeling better now and my recovery has been good. I will have to try my best.\" \"The selection is challenging, but I think if I can finish in the top three here I will qualify,\" he said. \"The extra pressure is there because of the Olympic selection, but I\'ve been concentrating on running well in London. What comes after London, I will think about then.\" In the women\'s race, defending champion Mary Keitany will aim to emulate her compatriot Mutai by romping to victory last year. Keitany is planning to use the race as a dry run for an assault on the London games in four months\' time. Keitany\'s winning time last year of two hours, 19 minutes and 19 seconds made her the second fastest woman over the London course. \"I\'m in the same shape as last year and I hope to defend my title and win despite the field being so competitive,\" Keitany said. \"It will be very hard because of the strong athletes. Almost every runner has a good time, and many have run around 2hrs 20mins, but I am determined to defend my title.\" However Keitany acknowledged she is still learning the tactical ropes following last year\'s New York Marathon, where she finished third after losing a two-minute lead. \"Sometimes your body can cheat you and tell you that you are OK when you fail to understand your body is having problems,\" she said. \"But I don\'t fear the marathon. I think of myself as a marathon runner now and I also think I have to better understand tactics, to know the tactics of running and handling a race.\"