Age-related loss of muscle mass, strength, and function is called sarcopenia. This condition starts around the age of 30 where the body would start to lose some muscle mass and decrease in its function. Symptoms of this conditions are loss of stamina and weakness which would affect your daily activities.
Hello,
The answer would be about "8-9 hours of sleep per day".
Reason:
At that age the body is growing therefore the body would need more energy to grow so thats why the amount of sleep would increase because adults, and teenagers would be into more physical activities and work that would drain his or her energy therefore they should get to 8-9 hours of sleep in order to last the person the whole day.
If you need anymore help feel free to ask me!
Hope this helps!
~Nonportrit