Standing is one of my favorite skills to help people embrace. Yes sitting is efficient because we don’t support our body weight BUT it is not efficient on all terrains (ie. bumpy downhill or short climb or you find yourself in wrong gear or end of race sprint) AND it is not efficient if you get saddle sores or a sore back and don’t ride or finish your ride. For many athletes of all abilities they are missing the hinge at the hips (like all athletic positions), elbows out and the side to side motion of the bike under their body. The best way to practice is to do it more !