Here are the answers to the questions based on the information provided:
Question 1:
When is the best time for her to begin gathering data to do this calculation?
Answer: When she is resting.
Question 2:
If they decrease their heart rates by 20bpm, who will be in her THR zone?
Answer: Both Sandra and Marissa.
(Sandra's heart rate after decreasing by 20bpm would be 124bpm, and Marissa's would be 124bpm, so neither would be in their target heart rate zones)
Question 3:
Which of the following would be the best option for anaerobic exercises?
Answer: Lifting weights.
Question 4:
How should you use a heart rate monitor?
Answer: Measure your heart rate before, during, and after workouts.
Question 5:
What should he do the next time he uses this machine to get the most effective workout?
Answer: Use the settings of the machine to decrease the intensity.
(If George's heart rate exceeded his maximum target heart rate, he should lower the intensity to stay within a safe range)
Let me know if you need any more help!