What is a likely cause of a performance decline after a student has been using a training aid?

Improper use of the training aid is a likely cause of performance decline because the effectiveness of training aids heavily depends on how they are utilized during practice. If a student is not using the aid as intended, they might develop bad habits or reinforce incorrect techniques. Effective training involves understanding and applying the principles behind the aid, so misuse can lead to confusion and a decrease in performance.

In contrast, inconsistent practice can hinder progress, but it does not directly relate to the specific issues arising from the use of a training aid. Lack of physical fitness might affect overall performance but is not directly tied to the training aid's effectiveness. Insufficient guidance from the instructor could certainly contribute to improper use, but the primary issue stemming from directly using the aid incorrectly makes improper use the most immediate and relevant cause for a decline in performance.