Hunter has provided lots of good info for the discussion. most folks when they picked up something they are thinking of pulling it up, especially something light. internal folks train to get underneath and push it up, even with a feather. and we already talked about efficiency on the other thread.
here is an exercise that Sigman got us to do. stand normally with feet parallel about shoulder width. take a small weight, less than 1 kg. hold it in between your palms and raise it with arms straight, straight up the top of your head. hold it there. now relax your body and let the weight pushes down to your feet so that you will only feel the weight pressure on your palms and the bottom of your feet. you should feel like you are now holding the weight by pushing from underneath (pushing isn't the right word to use here, but for simplicity, i am using it). hold it there for awhile and try to let go off your shoulder muscles.
now, drop your arms (still straight out) 45 degree from vertical. the weight should be infront of you and above your shoulders. don't move the rest of your body, but use your intent to adjust your body so that you still pushing it from underneath and there would still be pressure between the palms and the bottom of your feet, i.e. your body doesn't exist, only palms and feet. then drop your arms to 90 degree from vertical. do the same thing as before. allow your body to adjust. then drop to 135 degree from vertical. then 180 from vertical which at this point the weight should be around your crotch. and you are still pushing from underneath. it should feel like you are pushing the thing up with your feet. this is bringing the ground to the object or a simple model of ground path. experts will tell you that there are more it than that and they are right. because your focus is pushing from underneath, your body will microscopically adjust internally to use the blue line (don't think of line but tubes) that Hunter mentioned.
it's a simple exercise from Sigman, but it has some profound implication. so now, the question is why? why would we want to do that? ask a judo person, what would he/she/it give for the ability to get underneath the other person, without physically squatting down beneath the other person, with just a mind focus intent and the other person won't feel it or realize that you are underneath them? i am thinking first born, second born, possibly spouse, but not the dog since you can't just give up your best friend. this little exercise related to the SJT "sink the qi" or my terms "get underneath". btw, you need to use very light weight for a long period of time, months (took me over a year and still finding more interesting stuffs to it), to allow your body to reorganize itself for optimal ground path.
There is an opposite exercise which i called "getting on top", i.e. the ability to put your weight on top another person without physically changing your posture. after that then another exercise where you do "get underneath" then switch to "getting on top" which just a switch in your intention without moving your physical posture.
i can provide a video but you would only see my good looking self stand there not doing much. i might eat a donut or two with coffee.