By AJ Fisher, M.S., C.S.C.S.
2021 Sports and Health Sciences Master’s Degree Graduate
and Daniel G. Graetzer, Ph.D.
Faculty Member, School of Health Sciences
During progressive-intensity exercise, the demand for the lungs to absorb more oxygen into and expel more carbon dioxide from the bloodstream increases greatly. According to Medical News Today, the breathing rate in adults normally increases from about 12-20 breaths per minute (4-15 liters bulk flow of air depending on an exerciser’s body size) during rest to a higher level.
During maximal exercise, healthy adults can increase their breathing rate to 40–50 breaths per minute (150-200 liters), says Personal Training Director and the American Physiological Society. However, the increase in breathing rate depends on an exerciser’s body size, lung capacity and fitness level.
By contrast, a normal resting breath rate for infants is about 40-60 breaths per minute, according to Stanford Medicine. That rate slows to 30-40 breaths per minute when an infant is sleeping.
How Does Normal Breathing Work?
Human lungs are made from an expandable spongy material and are protected by the ribcage, and inhalation at rest is normally powered by the diaphragm muscle exclusively. As the dome-shaped diaphragm contracts, it flattens out to enlarge chest volume and literally sucks more air into the lungs.
Exhalation at rest is a passive process requiring no muscle input, according to Teach to Inspire. When the diaphragm relaxes and recoils, air is automatically expelled from the lungs.
During exercise, the diaphragm is assisted by additional inspiratory and expiratory muscles to increase breath frequency and overall air movement. Breathing becomes more forceful with the external intercostal muscles assisting the diaphragm during air inhalation.
According to BioNinja, exhalation goes from passive at rest to active during increased exercise via the contraction of internal intercostal and abdominal muscles to more rapidly force more air out of the body.
Abnormalities in Breathing Rates
Some individuals have abnormal breathing rates due to medical problems. WebMD notes that these breathing problems include:
- Bradypnea – an abnormally slow breathing rate
- Tachypnea – an abnormally fast breathing rate, with breaths generally being more shallow
- Dyspnea – a shortness of breath which can occur with high, normal, or low breathing rates
- Hyperpnea – a deep and labored breathing, which can happen with or without rapid breathing
- Apnea (literally meaning “no breath”) – a temporary cessation of breathing
- Kussmaul breathing – fast and deep breathing in diabetics with diabetic ketoacidosis
Using Progressive-Intensity Exercise to Assess Fitness and Exercise Metabolism
Many recreational and competitive athletes now get tested regularly in an exercise physiology laboratory. A treadmill or stationary cycle ergometer is used to assess physical changes that occur during training, such as changes in exercise metabolism.
According to the Gatorade Sports Science Institute, the athlete performs an incremental exercise test up to the point of fatigue. At the same time, the athlete breathes through a face mask that is hooked to a metabolic/calorimetry assessment apparatus.
Normal room air contains a constant composition of 20.95% oxygen, 0.04% carbon dioxide, 78.09% nitrogen and 0.93% argon, according to Vendantu. The athlete inhales this room air through the sides of the face mask. Any exhaled air goes through a tube for an analysis of the athlete’s metabolic and pulmonary responses during progressive-intensity exercise.
As the exercise intensity gets more and more difficult for the athlete, the athlete’s ventilation rate (the bulk flow of air in and out of the lungs) increases as muscles consume more oxygen and produce more carbon dioxide. As more oxygen is consumed by working muscles, less oxygen within the exhaled air is recorded by the calorimetry system.
The oxygen consumption (VO2) of the athlete is then analyzed via a computer using metabolic and ventilatory meters. This technology can precisely assess both the composition and total amount of air exhaled through the face mask into the tube, while the composition of inhaled air remains exactly the same.
Carbon dioxide is a metabolic byproduct of energy metabolism. During progressive-intensity exercise, an athlete’s level of carbon dioxide increases in the muscle cells, bloodstream and exhaled air.
This increase in carbon dioxide production is detected by chemoreceptors throughout the body. In combination with an elevation in lactic acid production, the increased carbon dioxide level sends signals to the brain to increase an athlete’s breathing rate.
A necessary increase in breathing rate (hyperpnea) occurs during low-intensity, incremental exercise. However, an overcompensatory increase in ventilation (hyperventilation) occurs during a high-intensity workout, which indicates the onset of fatigue.
People with healthy lungs generally have a large breathing reserve. So even though they may feel out of breath during and after exercise, they are never really dangerously low on air.
Patrick McKeown, a renowned respiratory physiologist and author of “The Oxygen Advantage,” states that many athletes “over-breathe” or hyperventilate during exercise. This tendency to hyperventilate contributes to physiological maladaptations.
Nasal breathing during moderate-intensity exercise is quickly becoming a worldwide method to reduce the flow of air during exercise, positively affecting both the nervous and cardiovascular systems. People can have reduced lung function due to various medical causes, including:
- Chronic obstructive pulmonary disease (COPD)
- Adverse drug reactions
- Heart/blood pressure issues
Athletes with asthma must use a larger portion of their breathing reserve, which can be documented during an exercise stress test. Often, the breathing reserve can be improved with proper breathing techniques.
New Breathing Techniques Can Increase Core Muscle Strength and Reduce Injury, Especially During Progressive-Intensity Exercise
New breathing techniques, such as the Pilates method or the Breathography method, can be used to purposely increase the body’s recruitment of the deep abdominal muscles for breathing during exercise. The tactic of using resisted inhalation and exhalation can increase the strength of core muscles and reduce the risk of injury, especially during progressive-intensity exercise.
About the Authors
Adrienne “AJ” Fisher, M.S., C.S.C.S., earned her bachelor of science and master of science in sports and health sciences from American Public University. She maintained a 4.0 GPA, which earned her an academic scholar award. Her capstone project, “Intermittent Hypoxia with Exercise, Voluntary Breathing, and Rest: Potential Benefits for Physical and Mental Performance, Injury Prevention, and Heart Rate Variability” is available online and was written under the guidance of Dr. Daniel Graetzer.
AJ serves on the University’s Sports and Health Sciences advisory board and is a personal trainer for high-profile celebrities in NYC, L.A., and London. She has also worked with clients such as Adidas, Reebok, and Marvel in movies such as “Black Panther, Wakanda Forever.”
AJ combines her former career as a Broadway entertainer with her research in breath-work and hypoxic training in HYPOXiX fitness programming, which integrates breathing patterns that restore core strength and optimize the nervous system, body composition, and brain function.
Daniel G. Graetzer, Ph.D., received his B.S. from Colorado State University/Fort Collins, a M.A. from the University of North Carolina/Chapel Hill and a Ph.D. from the University of Utah/Salt Lake City. He has been a faculty member in the School of Health Sciences, Department of Sports and Health Sciences, since 2015. As a regular columnist in social media blogs, encyclopedias, and popular magazines, Dr. Graetzer greatly enjoys helping bridge communication gaps between recent breakthroughs in practical application of developing scientific theories and societal well-being.