Muscle Fatigue Caused by Repetitive Muscle Exercise

This is an investigation into the differences in muscle activation and numerical difference in reps between the feeling of moderate discomfort and technical failure during a set of bodyweight resistance exercise. The investigators know that resistance training is an essential tool for older people to maintain muscle function, valuable independence and autonomy in daily tasks. The idea of completing a set of resistance training activity to the point of failing a repetition due to fatigue regularly has been shown to not be appealing and could be a reason why there are low participation rates among older people for in weight training regularly. Research has also shown that it is not necessary to train to failure (being unable to continue to complete repetitions of an exercise with the proper technique due to fatigue), but the investigators would like to know if training to a point of moderate discomfort can also allow for the muscles to gain the positive changes associated with weight training, potentially making it more accessible and enjoyable. Using bodyweight exercises (a squat pattern and a push up pattern) the investigators will see how many repetitions after the point of perceived moderate discomfort is stated at which the point of failure is. the investigators will also measure muscle activation in the quadriceps and triceps with EMG (a device that can detect the muscles' electrical activity/ how hard it is working) to see at which point the muscle is working the hardest.

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.