Running 5 kilometers every morning may have some negative effects on your body during fitness and muscle training, because this kind of high-intensity aerobic exercise may consume too many calories, thus affecting muscle growth.

If you want to do aerobic exercise during muscle gain, it is recommended to choose some low-intensity and long-term exercises, such as jogging, brisk walking and cycling. These exercises can promote heart and lung function and metabolism, while not consuming too many calories, which helps to maintain muscle quality.

In addition, you mentioned that running for about 28 minutes every morning may not be an ideal time period. The body's metabolic rate and body temperature are relatively low in the morning, which may affect the exercise effect and physical recovery. Therefore, it is recommended to exercise in the afternoon or evening, which is more suitable for muscle building training and aerobic exercise.

In short, if you want to do aerobic exercise during muscle gain, it is recommended to choose appropriate intensity and time to avoid excessive calorie intake. At the same time, pay attention to the reasonable arrangement of training plan to ensure adequate rest and recovery, so as to better promote muscle growth and development.