Basal metabolic rate be elevated in stress, illness, and diabetes. Menopause may also affect metabolism. Heart rate is determined by the medulla oblongata and part of the pons, two organs located inferior to the hypothalamus on the brain stem. Heart rate is important for basal metabolic rate and resting metabolic rate because it drives the blood supply, stimulating the Krebs cycle. During exercise that achieves the anaerobic threshold, it is possible to deliver substrates that are desired for optimal energy utilization. The anaerobic threshold is defined as the energy utilization level of heart rate exertion that occurs without oxygen during a standardized test
Heart rate reference period is associated with a higher level of cardiac fitness. Heart rates that do not drop by more than 12 bpm one minute after stopping exercise are associated with an increased risk of death. Investigators of the Lipid Research Clinics Prevalence Study, which included 5,000 subjects, found that patients with an abnormal HR (defined as a decrease of 42 beats per minutes or less at two minutes post-exercise) had a mortality rate 2.5 times greater than patients with a normal recovery. Another study by Nishime et al. and featuring 9,454 patients followed for a median period of 5.2 years