If you're landing heel-first, that same energy needs to be dissipated by your skeletal structure.
Finally I tried barefoot shoes and cautiously increased my distance, I can finally get to that point of leaning forward and hitting mid-foot and feeling the springiness, feels way easier but now my heartrate is the bottleneck.
I started running with classmates without learning proper form and had joint pain in knees and hips within the first 5 km. It never felt good and I never got faster.
I started practicing barefoot a couple times a week to work on form. After the first few (painful) lessons I managed to improve my form and I could run faster and for longer distances.
Eventually I realized I enjoyed the barefoot training sessions more than running in shoes and I (slowly) switched all my runs to barefoot shoes and sandals, though that may not be the right approach for everyone. I've done a few marathons since then and now my bottleneck seems to be free time -- I'd love to try a 50k but those longer runs eat up so much more time.
