You have a certain amount that is available for use each day, which is based on your income. The actual amounts you use during each day are your expenditures. You also have a savings account or reserve of muscles. If your lifestyle continuously exceeds your daily income, then you begin depleting your savings account until there is no reserve. Lifestyle modification is the way to protect your muscles so they will last.
Functional devices can help take the strain off weak muscles and joints if appropriate.
Remember, a muscle has only so many contractions within its lifetime, and once used up, there is no turning back. Make a note of how the various activities affect how you feel. This monitoring system might help you make adjustments to your lifestyle.