A method is disclosed involving receiving GPS data from persona portable training devices of users when traversing an off-road segment of an electronic map together with associated data indicative of a heart rate of a user during the movements. The position and heart rate data for each user traversing the segment are processed using data indicative of a fitness profile for the user. The resulting data is used to determine a normalized cost to be associated with the segment, indicative of the difficulty in traversing the segment. The cost data is generated using a neural network. The resulting cost data for different segments in a network of segments is used to generate route suggestions for users based upon desired workout intensity, fitness levels, etc.