What zone do females need to remain in for cardiac?

For women, build cardiovascular training around polarized intensity: avoid lingering at moderate intensity, and favor low-intensity recovery alongside genuinely high-intensity work—not a prescribed 75% of maximum heart rate. 1

• HIIT intervals: Aim for efforts of 1–4 minutes at 80% or more, or all-out sprints of 30 seconds or less. 2
• Frequency: Do HIIT a couple of times per week, rather than daily, so you can recover enough to reach those intensities. 3

For easier cardiovascular work, the guidance describes low-intensity activity such as long, slow walking on a separate day. 4