If your cadence is only 60 rpm which I've heard is average. Dropping a gear and spinning faster is one of the quickest fixes. 90-100 rpm is a good goal. That transfers more of the work to the cardio system which i think responds to training quicker than adding muscle mass. In my limited experience (second season) trying to add muscle mass while trying to lose weight is difficult in the extreme. Over the winter I cut way back on cardio work and concentrated on building strength. My hope this season is just to maintain that new strength. Any average speed increases will have to come from being able to maintain that effort for longer periods and getting more aero in my riding position( greater time in the drops, arms bent more, elbows back). But like I said I'm pretty new at this.