What are negative?
With this strategy you will train with a greater weight than the one you can lift.
You're going to need a training partner.
Put between 10 and 30% more weight than you do for a given exercise and ask your training partner for help to give evident help in the eccentric phase of exercise but the least help (or none) in the negative phase, or, concentric.
You put 300 pounds on the flat supine.
Your training partner helps you bring the bar up but you can hold the bar down with little or no help.