However, they are absorbed, usually as methyl mercury, by algae at the start of the food chain. This algae is then eaten by fish and other organisms higher in the food chain. Fish efficiently absorb methyl mercury, but excrete it very slowly. Methyl mercury is not soluble and therefore not excreted.
For example, a 10- to 15-minute brisk walk typically elevates the heart rate to 110 to 120 beats per minute. Also, the sinus node increases the heart rate when the body is stressed because of illness. In all of these circumstances, the heart rate increase is a normal response. Likewise, the sinus node signals the heart to slow down during rest or relaxation.
Different physical activities cause the heart to beat at different rates. Moderate physical activity corresponds to a heart rate of 50 to 60 percent of maximum, or 93 to 157 beats per minute for a 35-year-old. Increasing your heart rate to 60 to 70 percent of maximum improves cardiovascular endurance and burns fat.oderate physical activity corresponds to a heart rate of 50 to 60 percent of maximum, or 93 to 157 beats per minute for a 35-year-old. Increasing your heart rate to 60 to 70 percent of maximum improves cardiovascular endurance and burns fat.