Heart rate responds to training intensity according to factors such as fitness level and recovery as well as environmental factors. It is important to be aware of subjective feelings of fatigue and to adjust the training program accordingly, because if the athlete trains above the heart rate too much lactate will accumulate in the bloodstream and the athlete will not be able to continue training for long, because his lung capacity will be diminished, he will have very tired muscles and will have difficulty breathing.
Environment affects animal behavior by changing the availability of survival resources like food & shelter, as well as situational things like proximity to human activity. Sometimes the same species of animal will behave completely differently in a forest environment compared to an urban environment.
