Partly because of the weather, I have not got the sort of quantity and quality of training under my belt that I would have hoped for just 3 weeks prior to a marathon. I have therefore been thinking - what is it possible to do so close to a race that will help performance on the day? It is certainly too late to be thinking about working on endurance - indeed in the last 1-2 weeks prior to a race you need to be thinking about tapering to ensure you are really fresh for the race. You also need to be cautious working on speed endurance as well. However, there are a couple of things you can do that will potentially help you on the day. These include 1) one or two good tough effort sessions, but NOT in the last week before the race; 2) stretching. Working on flexibility will help your performance and you can do some useful work even in just 3 weeks; 3) keeping your weight down. In the marathon, each pound will cost you a minute plus of time. However, don't go on a crash diet for three weeks since this will leave you weak for the runs that you are doing. But watch carefully what you eat; 4) get plenty of rest. Early nights are the order of the day to make sure you are rested for the big day.
UKA Level 2