Usain Bolt stayed on track for an Olympic sprint double as he and Jamaican rival Yohan Blake cruised into Thursday\'s final of the 200m with commanding runs in their semi-finals on Wednesday. Blake strolled to victory in his heat in 20.01sec but eased up before the line, while 100m champion Bolt was imperious as he held off the field to win his race in 20.18sec, looking around all the way down the home straight.