Bremszüge

There are a few things which typically effect performance of brake cables through regular use.Brake cables are susceptible to water, dust and dirt getting between iner and outer cables. Lubrication between inner and outer cables can also become less effective and dry out. Bikes with trickier cable routing (through handlebars, frames etc), can suffer noticably worse braking peformance when cables are due for replacement. Damaged or split outer cable, ferrules and guides can also negatively effect performance. 

There are a couple of options with brake blocks (or pads). Most blocks slide into the block shoe / holder which attaches to the brake caliper, some do not - so you would need blocks with shoe / holders. Most blocks are designed for use with aluminium rims, if you ride carbon wheels, you will need carbon specific blocks which perform better on carbon surface.