The Short Version
The best available evidence — including large pre-registered studies and meta-analyses — shows power posing produces a real but small effect on subjective feelings of power. It does not reliably change hormones, and behavioral or cognitive outcomes that would constitute "success" are weak or absent. The claim's use of "significantly" overstates the effect size, and pairing "confidence" with "success" implies downstream real-world benefits that the evidence does not support. The original 2010 findings have been substantially undermined by replication failures.