Yeah it did, search for microgravity exercises for astronauts, I found one article where they simulated lower body micro gravity and tested it against standing. It showed that the one under micro gravity had much greater efficiency. In that they were able to have a greater output per work as repetitions increased, this may be how less lactate is produced when horizontal. To achieve the same level of output less work is required, hence less energy and less lactate. However didn't really look into it too much as couldn't find too many articles on that specifically.