A resting heart rate of 26.25 beats per minute (bpm) seems unusually low, as typical resting heart rates for teenagers usually range from 60 to 100 bpm. It might be worth checking with a healthcare professional to ensure that this measurement is accurate and to rule out any potential health concerns.
Regarding your heart rate after one minute of jumping jacks, it's difficult to predict an exact number as it can vary widely based on fitness level, overall health, and intensity of the exercise.
However, during aerobic exercise like jumping jacks, it's common for a person's heart rate to elevate significantly, often reaching 60-85% of their maximum heart rate. For a 13-year-old, the maximum heart rate can be roughly estimated as 220 minus your age, which would be around 207 bpm.
During intense activity such as jumping jacks, your heart rate could increase to about 115-175 bpm, depending on how hard you're working out.
If you’re physically fit and used to exercising, you might experience a lower rise in heart rate compared to someone who is less accustomed to physical activity. It's best to monitor your heart rate during exercise to get a more accurate understanding of how your body responds.