A cell stack comprising an electrochemical cell, or a plurality of axially arranged electrochemical cells, with an end plate at each end of the stack, each cell comprising an active area surrounded by a peripheral area, wherein the active area comprises the membrane electrode assembly, and the peripheral area includes one or more channels for reactants, and wherein the stack comprises means for applying pressure axially to the active area to contact the membrane and electrodes, and separate means for applying pressure axially to the peripheral area. Further, a method of performing an electrochemical reaction in a cell comprising an active area surrounded by a peripheral area, comprises applying pressure to the active area, and varying the pressure during operation of the cell, wherein the active area includes the membrane electrode assembly and is the area where the cell reaction occurs.