As I start to ride longer distances, I wanted to see if there is a better more efficient way to peddle. I am good for about 30km but then get my legs get tired. It could just be that I need to get in better shape since I've only been cycling for 2 weeks.

I have read up on spinning vs mashing and realise that I am a masher. I have strong legs so using the lower gears is not an issue for me but that also means I find myself getting tired. I tried spinning but quickly realised I didn't have the cardio to keep it up and that I can go further mashing.

What do you do and any advice for me?