Final answer:
A concern during the ball crunch exercise is proper spinal alignment. High impact on joints, breathing technique, and stretching the hamstrings are not primary concerns during this exercise.
Step-by-step explanation:
A concern during the ball crunch exercise is proper spinal alignment. It is important to maintain a neutral spine throughout the exercise to prevent any strain or injury on the back. This can be achieved by keeping the head, neck, and spine in a straight line.
High impact on joints is not a concern during the ball crunch exercise as it is a low impact exercise that primarily targets the abdominal muscles. Breathing technique is also important during the exercise to provide oxygen to the muscles and help maintain proper form.
Stretching the hamstrings is not directly related to the ball crunch exercise as it primarily targets the abdominal muscles. If you're looking to stretch the hamstrings, other exercises or stretches may be more appropriate.