Recently I started biking to work, which surprisingly has been working out well for me. It's a 10 mile commute each way, and I've been biking 4 days a week now. It's basically my only source of exercise currently, as I've never really been able to stick to a gym regime.
I've been slowly getting faster and faster on the commute, but, being able to speed through to work may not be the best idea since there's a lot of foot traffic on my bike path and I don't want to be constantly zooming around people at high speeds. Since my bike has panniers on the back that I use to carry my work stuff, I was wondering if it would be a decent idea to load the bike a bit heavier to make for a tougher commute?
Or any other suggestions that would help my commute-style training?