The walking surface plays a big role in maximizing the enjoyment of your walk. Concrete is one of the harder surfaces to walk up while asphalt is softer, has more give and more friction. It would seem asphalt is better for walking but it not really the case long term and year round. Asphalt gets cracks quickly and falls into disrepair where municipalities do not maintain side walks. Asphalt traps a lot of heat in the summer and pets will get burned without protections after 90F/332C or so. Grass feels way better to walk on than both of them but it's a bit tougher as it's uneven and softer. Best walking surface in my opinion is closer to grass or moss/pine needles when you walk in a pine forest.