Final answer:
When working at the same work rate at high altitude, the heart rate is higher compared to sea level due to the decreased atmospheric pressure.
Step-by-step explanation:
When working at the same work rate at 3,000 meters altitude compared to sea level, the heart rate is higher. At high altitude, there is a decrease in atmospheric pressure, which makes it more difficult for the body to achieve the same level of oxygen saturation. As a result, the heart has to work harder to pump enough oxygen to the body.