Instead of changing the strumming for each bar it is quite common to play the same pattern of strums throughout the chord progression. This is called a rhythm pattern. It is placed above the staff and represents which strumming pattern is played in each bar of music.
Rhythm Pattern
The chord shapes given in this lesson and throughout the remainder of this book are called open chords because they contain open strings (i.e., no finger is placed on the fret). Another type of chord to learn is called a bar chord. These are commonly used in Country music. To learn about bar chords see Progressive Country Guitar Technique.