Muscle Fatigue Caused by Repetitive Muscle Exercise

The purpose of this study is to learn how aging affects muscle endurance during resistance exercise, and how oxygen delivery to the muscles plays a role in these changes. To answer this question, we are comparing how many repetitions of a leg exercise (knee extensions) younger and older adults can do at different exercise intensities. We will also look at how the muscles use oxygen during these exercises. Participants will take part in 12 different exercise sessions. In each session, they will perform as many knee extensions as possible using different amounts of weight-consisting of 20%, 30%, 40%, 50%, 60% and 70% of the maximum weight they can lift one time. Each weight will be tested both with and without a cuff on the leg that temporarily reduces blood flow to the muscle.