Final answer:
The HR and cardiac output response to exercise in cold environments are similar to those in hot environments, where the body needs to regulate its temperature either by generating extra heat or dissipating excess heat through sweating.
Step-by-step explanation:
The HR (heart rate) and cardiac output response to exercise in a cold environment are similar to those of a hot environment. In both scenarios, the body must work to regulate its internal temperature. During exercise in a hot environment, the body produces excess heat due to the inefficiency of muscle contractions. This excess heat needs to be dissipated, which typically happens through sweating and increased blood flow to the skin. However, in a humid environment, the sweat response is less effective, as the sweat does not evaporate as well, potentially leading to dangerously high internal body temperatures. Exercising in the cold brings different challenges since hypothermia can slow heart rate and strength of heart contractions, yet the body still needs to generate additional heat to maintain core temperature, increasing demand on the heart. Increased exercise elevates body temperature and the requirement for heat dissipation, but a decreased body temperature from external environmental conditions or otherwise can impede oxygen transfer to tissues due to reduced enzyme effectiveness.