Restricted wiper travel

My wipers don't seem to have the same range of travel that the may have had previously, any ideas as to what might be the problem?

Thanks in advance!
 
could be the nuts that arnt tight enough mate and they are slipping or a worn motor.
 
Turns out the linkage was really siezed, but has now been freed off and will hopefully be ok. If your wipers seem slower than they should be, or don't appear to have enough travel, this may be worth investigating before it gets too bad.