Watch this short film clip 3.3 and see how to measure an apical pulse correctly. After watching the clip, try the technique yourself. You can watch the clip and practice as many times as you like.
Alternatively, if viewing textbook as a pdf, use this link: https://www.youtube.com/embed/JJ9VEymVl8Q?rel=0
Film clip 3.3: Correct measurement of apical pulse