Which of the following is a common mistake made during planks?

Arching the back during a plank is indeed a common mistake and can lead to improper form, which diminishes the effectiveness of the exercise and increases the risk of injury. Proper plank form requires a straight line from the head to the heels, meaning that the spine should remain neutral. When the back arches, it often indicates that the core is not adequately engaged, which is essential for stability and support. This misalignment not only reduces the effectiveness of the core workout but can also place undue stress on the lower back, potentially leading to pain or injury over time.

In contrast, maintaining a straight body line, even breathing, and engaging the glutes are all critical components of an effective plank. These practices help ensure that the core, glutes, and shoulders are activated and working together, promoting overall strength and stability during the exercise.