When the spine is vertical our posture tends to direct energy, which should naturally pool in the dantien, up into the chest and head. This is because:
1. the legs are hard and forceful (straightening) rather than soft and energetic (bending);
2. the lumbar spine is lordotic allowing the tail to project backwards rather than downwards;
3. the belly area is flabby, slack and weak, offering little support to the lower back.