A hi rep set is perfect for the over 60 crowd and the under 60 crowd too. As we get older and stop making enough taurine, our mitochondria stop being able to use fat efficiently. They shrink and atrophy. Our bodies start relying more on glucose for energy.
Before we get deep into the discussion, let put things into context. Mitochondria/ATP is
a source of energy used during exercice. Before thinking and discussing what it does to fat, I would like to agree on what it actually mean, establish it's role when we exercise. The process of exercising is not just about shedding fat storage.


To me and many it is not just about getting rid of fat storage.
What is the main function of mitochondria?
Known as the “powerhouses of the cell,” mitochondria
produce the energy necessary for the cell's survival and functioning. Through a series of chemical reactions, mitochondria break down glucose into an energy molecule known as adenosine triphosphate (ATP), which is used to fuel various other cellular processes.
Regardless of age our body uses 2 types of fuel/energy, ATP and glycogen. Our body can not use fat (mainly stored) all the time while exercising, it needs to switch to glycogen,
consumed --- Carbohydrate after a brief time exercising. Not that long. Now, depending on the type of intensity produced while exercising, we can use up glycogen.
Now taurine is an amino acid --- Food consumption. I do not see any link between taurine and ATP ability to use fat efficiently. That being said, muscle mass through body composition help in improving metabolism.
It is a fact. This happen regardless of the age. All it require is
to build muscle and maintain. should it be through high or low rep and heavy, moderate and light load in
YOUR opinion and
ability.
Now your study talk about a decline of aerobic capacity aka VO2 max in healthy older adults. I can not see any statement regarding "An elderly body not being efficient on using or burning fat during exercising. Nor have I read the same for rest period. It is stating a decline of VO2 max every decade, without being 100% accurate

Please correct me if I have missed something. This study does not mention the intensity. It would have been helpful if it mentioned low versus high intensity.
This study does not contain any indication about intensity to establish the type of energy used throughout the exercise. That is where your beloved mitochondria should come to light and eventually confirm your highlighted statement.

BTW, mitochondria can get small but sadly we can't see it with out own humain eye but muscle can get really big --- joking!!


ATP/mitochondria is mainly energy used in the begining of short moment during low-moderate intensity. High intensity uses another energy source glycogen. That is what any human need for better body composition. I have not come across an over 40 woman who does not want a better body compositiion. One's vo2 max can slightly decline but if she/or he is strong holding a very good body composition through muscle mass, she or he can still burn fat. Mitochondria is not the sole requirement to burn fat or to maintain a solid metabolism. That is my understanding. In fact, gaining a better body composition through muscle mass is the best ever investment one's would make as far as HEALTH is concerned.
Here below is a recap of 2 different intensity, not impact!
Low-intensity cardio (LISS) uses a steady, easy pace for 45 to 60 minutes to burn fat and recover fast. High-intensity cardio (HIIT) uses short, hard bursts for 15 to 20 minutes to save time and boost fitness fast. Most people do best by mixing both. [
1,
2,
3,
4]
Low-Intensity Cardio (LISS)
- Pace: Easy movement where you can talk easily (50% to 65% max heart rate).
- Examples: Fast walking, light cycling, or easy swimming.
- Pros: Safe for joints, easy to recover from, and great for daily stress relief.
- Cons: Takes a long time to complete each session. [1, 2, 3, 4, 5]
High-Intensity Cardio (HIIT)
- Pace: Very hard effort followed by rest (80% to 95% max heart rate).
- Examples: Sprinting, hard bike intervals, or jump rope circuits.
- Pros:Saves time and builds high VO2 max (oxygen capacity
- Cons: High risk of burnout or joint injury if done too often
#We shall not FEAR the intensity