Improving my chances to qualify for the Comrades Marathon

The next question on Ask Coach Parry today comes in from Marie. Marie says that she entered the Comrades Marathon 2014, but could not compete due to the fact that she did not qualify.

She wants to know how she improve her time to be able to qualify for the Comrades Marathon 2015 which she has entered. She is currently running a marathon in about 5h20. She keeps a good pace up until 30m, and then she struggles to keep a good pace to the finish.

What can Marie do to help her situation?