The solution for this is simple. Avoid decelerating and run at the maximum speed for as long as possible.
Unfortunately, it is easier said than done. But there are simple ways for you to train, improve, and plan your 400m race so that you can run the distance in a faster time.
Below are some tips for running a faster 400m race.
Maintain your form throughout the race.
You want to keep your form so that you maintain the same stride length and power throughout the race. As your body fatigues, your form will break down which means you will have a shorter stride length and you will need to put in more effort to finish the distance.
To improve, you need to do cadence training. This means running repetitions of 400-600m in 80-95% of your maximum speed, but focusing on maintaining your form for the duration of the run.
Run to a rhythm.
Your cadence should be to a rhythm during the event. This should allow you to pace your energy and execute the speed and endurance bursts needed for the event.
Improve your explosiveness.
You need to improve your explosiveness so that you generate more horizontal power when you are running. Doing exercises such as bounding, skipping, hip thrusts, and reverse lunges will help you improve your strength and power.
Improve your core and hip flexor strength.
These can easily fatigue. So you want to improve the strength so that you can get your knees higher and increase your stride length when you are running.