My guess would be running, if you do not have Global Entry and have checked bags.

Depending on what time your MAN-PHL flight arrives, you may likely find yourself in a long and slow line for immigration. PHL baggage delivery is snail-like, after which you will find yourself in a line to get out of the hall and past the customs inspectors who collect the blue customs forms as passengers shuffle by. Then you have a line to re-check your bag with your onward carrier, then you have to go through security again, and only then do you get to run to the inter-terminal bus to F (where you will have to wait for the bus, which then takes about 10-15 minutes to load, drive, and unload).

In other words, move smartly and don't hit the bathrooms until you get to terminal F!