Step ups are a great way to build up the strength in your legs.
You do not necessarily have to have a step up block.
Instead, you can improvise by using the stairs in your house or a bench.
STEP ONE
The key to doing step ups correctly is to get into a good rhythm.
Start the exercise by stepping on to the block or stair, leading with your left leg.
STEP TWO
Keeping the left foot on the block, step your right foot up onto the block.
Step back down, leading again with the left leg and bringing your right foot down to join it on the floor.
Keep this going for a minute and then try it again leading with your right leg.