The Lunk Alarm is a feature in Planet Fitness gyms that is designed to discourage intimidating behavior or overly aggressive grunting in the gym. It is an audible siren that is triggered when someone grunts too loudly, drops weights too hard on the floor, or breathes too loudly. The alarm alerts gym managers to the person who made the noise, and the manager will intervene if necessary. The Lunk Alarm is part of Planet Fitnesss fitness philosophy and culture, which aims to create a welcoming environment for everyone. The gyms "No Judgment Zone" mantra is not used to excuse gym-goers behaving poorly, but rather to hold members accountable for their behavior.

The term "lunk" is used to describe a person who draws attention upon themselves, whether intentionally or not. A lunk is someone who yells and drops weights when they are lifting, or who does not respect the space of others trying to exercise. The Lunk Alarm is a way for Planet Fitness to discourage this type of behavior and create a more inclusive gym environment.

While the Lunk Alarm has been controversial, many people, from beginners to weightlifters and bodybuilders, support using it to preserve the welcoming, judgment-free culture that Planet Fitness is known for. Overall, the Lunk Alarm has become a key part of Planet Fitnesss identity and culture and serves as an important tool for creating an inclusive gym environment where all members feel supported and welcome.