So if you're sure that it's going to go into a recession, you invest in medium-to-long-term bonds, because recessions cause interest rates to fall, and bond prices go up as interest rates fall. Then, approximately when the recession hits bottom, sell the bonds and buy stocks.

Note that this requires that you approximately time the market twice, which can be difficult. Also hazardous.

Note well: I am not a financial advisor. Follow this advice at your own risk.