The 'Brat hot girl walk' routine, inspired by singer-songwriter Charli XCX's 'Brat summer' aesthetic, offers a cardio warmup suitable for various fitness levels. The routine involves specific treadmill settings, including adjustments to incline and speed, designed to provide a challenging yet accessible workout. It aims to motivate individuals whether they are already active or seeking a starting point for exercise, with options to repeat the circuit for increased intensity.