A personal trainer uses a heart rate monitor during a client's training session to provide...

NASM defines external feedback as information provided by an outside source — such as a trainer, mirror, video, or device — to help a client understand their performance. A heart rate monitor delivers real-time data from an external device, which the trainer can use to guide intensity adjustments. This differs from internal feedback, which comes from a client’s own sensory awareness (e.g., perceived exertion). External feedback tools are essential in monitoring physiological responses and ensuring clients work within safe and effective training zones .