Which technology keeps track of heart rate during a workout?

When a patient is incapacitated, providers are required to follow any instructions outlined ina. an advanced care directiveb.patient educational materialsc. a willd. a consent form

Ihave a really high metabolism and only weigh 70 pounds (13 almost 14). people always ask me two questions: do you ever eat and how do you eat so much and stay so skinny.i am worried that a high metabolism wont me forever. what are some safe steps i can take to maintain being fit. (also, i already work out i am a dancer so i get cardio a lot)

Which of these activities would better would maintain and improve muscle endurance