>>33511496>Consider this: We had to make massive changes to our hips, knees, ankles, toes, feet, skull and spinal cord JUST to walk efficiently as a biped.
Nah, the human walking gait is CRAZY efficient. Go look at passive-dyanmic gravity-walkers (e.g. https://www.youtube.com/watch?v=_2pAMe_5VeY
). You get a swing-hip ock-knee gait than can walk down an incline unpowered and un-actuated. Humans are endurance hunters, so this is understandable.
But running? Not that apart from when wearing thick-soled running shoes, people tend to run on the balls of their feet. This is you you can get not only the muscles around the knees and hip in play for power delivery, but the muscles around the ankle too. But this sort of gait isn't energy efficient; you burn a whole lot of energy for that increase in available motive power.
Even just standing on the balls of your feet is easy, but you can feel yopur muscles straining to keep you there. But standing on the flat of your feet with your knees locked and feet spread, leaning slightly forwards to engage the tendons running around the back of your ankle. you can do that all day with minimal energy expenditure.
A digitigrade biped would not have this ability. They're either going to sit down a lot when not in motion, or have semi-locking joints (e.g. slip-lock tendons) in order to stand and walk with minimal energy expenditure.