Which action is NOT allowed on the platform during a lifter's attempt?

Changing weights without notifying the referee is not allowed on the platform during a lifter's attempt because it is crucial for maintaining order and safety during the competition. The referees must be aware of any weight changes to ensure that the correct weight is loaded on the barbell and that all procedures are followed properly. This helps prevent any possible misunderstandings or mistakes regarding the weight being lifted, which could affect the lifter's performance and the integrity of the competition.

In contrast, using chalk in designated areas is permitted as it helps lifters maintain a proper grip on the bar, adjusting grip on the bar is allowed to ensure the lifter's comfort and stability, and following the command of the head referee is essential for a fair and orderly process during the lifts.