What is a common cause of nail weakness in clients, particularly in relation to filing techniques?

Using back and forth filing motions is a common cause of nail weakness because this technique can create micro-tears in the nail plate, leading to increased susceptibility to splits and breaks. When filing, it's essential to use a gentle, one-directional motion to ensure that you are smoothing the nail without causing structural damage. The back and forth action can lead to significant friction and stress on the keratin structure of the nails, weakening them over time.

In this context, other options may relate to nail health, but they do not specifically focus on the technique of filing. For example, improper tool maintenance, while important, primarily impacts the effectiveness of tools rather than directly causing nail weakness. Similarly, excessive moisture exposure and overuse of nail polish could contribute to nail issues, but they are not directly tied to the act of filing itself and its immediate repercussions on the nails' integrity. Hence, the filing technique outlined is directly linked to nail weakness, making it a primary concern for technicians to address with clients.