It’s not “endurance” in a cardiovascular or conditioning sense. Playing an instrument like a guitar is the act of getting very small muscles in your arms and hands to produce and repeat a series of submaximal contractions for an extended period of time. What you’re really talking about is building strength in these muscles. The greater your total strength, the less each muscle has to work as a percentage of it’s total capacity. Thus, total fatigue is reduced allowing you to play for a longer time.
