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.

Inclusion Criteria:

• Able to understand and communicate in English
• 19-35 years of age
• 65 years of age or older
• All "No" answers on the CSEP Get Active questionnaire or doctors' approval to participate

Exclusion Criteria:

• BMI lower than 18 or greater than 32
• Current use of cigarettes or other nicotine devices
• Any major uncontrolled cardiovascular, muscular, metabolic, and/or neurological disorders
• Any medical condition impacting the ability to participate in maximal exercise
• Type one or type two diabetes
• Diagnosis of cancer or undergoing cancer treatment in the past 12 months
• Taking blood-thinning medication or the presence of a bleeding disorder
• Drug therapy with any drugs that alter skeletal muscle metabolism (i.e., Metformin, Benzodiazepines)
• Lowest calculated exercise testing load is less than the lightest weight able to be provided by the lab gymnasium equipment
• In the past six months, completing more than 300 minutes of moderate physical activity or 150 minutes of vigorous physical activity per week
• In the past six months, completing less than 150 minutes of moderate physical activity or 75 minutes of vigorous physical activity