in general, seated is always best. you are best in control of the bike and using the least amount of energy. that standing sprint with all the big guys rocking the bike back and fourth at the end of the race is always the most exciting but the rest of the race was in the saddle conserving juice.......buttttttt, obviously this isn't the case in the real world especially riding one gear bikes. really we are trying to protect the knees. and knees dont like to be overload or twisted. some kind of retention system also helps keep the foot in place and leg track straight among other things. im not too on board with fixed gear myself, just single speed but i can see its allure. im40 and creaky from other dumb $h!t as a kid so i like to coast too!