The effect of a month's high-intensity fitness varies from person to person, depending on the individual's physical condition, fitness goals and training plan. The following are some possible impacts:

1. Increase muscle mass: HIIT is an effective way to increase muscle mass and strength.

2. Improve cardiopulmonary function: High-intensity aerobic exercise can improve cardiopulmonary function and enhance cardiopulmonary health.

3. Reduce body fat: High-intensity training can burn more calories, help reduce body fat and improve body composition.

4. Improve metabolic rate: High-intensity training can improve the body's metabolic rate and make the body burn calories more effectively at rest.

5. Improve mental health: High-intensity training can release chemicals such as endorphins, which helps to relieve stress and anxiety and improve mental health.

It should be noted that high-intensity fitness also has certain risks, such as overtraining and injury. Therefore, before high-intensity training, you should consult a professional coach or doctor and make a reasonable training plan that suits you.