Simplify the following text for a Grade 9 native English-speaking person.
Original: å æ , nÃ ijiÄ quÃ n ) , while others concentrate on improving muscle and cardiovascular fitness and are labeled external ( å -- å æ , wÃ ijiÄ quÃ n ) .
Simplified: å æ , nÃ ijiÄ quÃ n ) , while others concentrate on improving muscle and heart fitness , and are called external ( å -- å æ , wÃ ijiÄ quÃ n ) .