I decided to do premed late in college. My numbers are above average, but my extracurriculars are pretty lacking. I'm about to start applying to gap year clinical research positions (probably for two years). I didn't really start any real ECs until my senior year, because I was still maturing, but now I want to devote my life to medicine and make up for lost time. If my undergrad ECs are lacking, can I make up for that doing research, volunteering, and clinical work for a couple years after college and still have a shot at a top 20 school, or is it too late to make a good impression at this point? I could probably gain hundreds of hours of volunteering and clinical experience during this time, and probably become author on a few papers, possibly even first author based on what the research groups I've been talking to have been telling me about past RAs. I just don't know how much my first 3 years of college can hurt me.