Experts say getting your ‘second wind’ is a real phenomenon

SECOND WIND TERMS• Glycogen — A carbohydrate that serves as the body’s primary energy source. During exercise, it initially is drawn from muscles and later from the liver.• Metabolism — The body’s process for breaking down stored fuel, such as glycogen and fatty acids, into useable energy.• Hitting the wall — The point of extreme fatigue caused by complete depletion of glycogen stores. Usually occurs during extreme long distance runs such as marathons.• Aerobic exercise — Activities during which oxygen intake meets the body’s needs. Occurs during low-intensity, long-term exercises such as distance running, swimming and cycling.• Anaerobic exercise — Activities during which oxygen intake doesn’t meet the body’s needs and must be supplemented by metabolism of glycogen. Occurs during high-intensity, short-term activities such as sprinting or weightlifting.• Lactic acid — A byproduct of anaerobic metabolism. Its buildup can impede muscle function and results in the uncomfortable burning sensation in muscles.• Homeostasis — The tendency of the body to achieve a state of equilibrium, as when metabolic rate and breathing level off after meeting the needs of vigorous exercise.• Steady-state exercise — Exercise performed at low enough intensity to be sustained for a prolonged period as opposed to alternating between high- and low-intensity, as in interval training.• Oxygen debt — The cause of heavy breathing resulting from vigorous exercise as the body seeks to take in enough oxygen to restore its systems and fuel metabolism.