Topic

Aerobic exercise

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Contents
  1. Aerobic exercise benefits the brain, not just the heart.
    1. Estimating maximal heart rate
  2. Aerobic exercise exerts myriad effects on human health.
    1. A single bout of aerobic exercise alters more than 9,000 molecules in the blood.
    2. Aerobic exercise increases mitochondrial fat metabolism.
    3. Aerobic exercise benefits people with depression, especially those with more severe symptoms.
    4. Aerobic exercise induces changes in blood flow in brain regions involved in memory.
    5. Higher cardiorespiratory fitness may support brain structure and memory for nearly a decade.
    6. Sauna and hot-water immersion complement aerobic exercise but do not replace it.
    7. Antihistamine use blunts functional adaptations in exercise capacity.
    8. Related Topics and Episodes

Aerobic exercise can be defined as physical activity that increases aerobic metabolism, meaning energy-generating processes that require oxygen. Common examples of aerobic exercises are walking, running, swimming, dancing, and other activities that increase heart rate and breathing. Exercise elicits a wide range of physiological changes in the body that improve cardiovascular, neurological, and metabolic health.

Current physical activity guidelines from the United States Department of Health and Human Services recommend the following.

  • Adults should do at least 150 minutes of moderate-intensity exercise or 75 minutes per week of vigorous-intensity aerobic physical activity.
  • Physical activity of moderate intensity beyond 300 minutes per week provides additional health benefits.
  • Adults should also do muscle-strengthening activities of moderate or greater intensity that involve all major muscle groups on two or more days a week.

In 2008, just 18 percent of adults in the United States met the combined aerobic and muscle-strengthening physical activity guidelines. In 2017, this rate increased to over 24 percent.[1] While this improvement is encouraging, increasing exercise participation is still a top priority for reducing the disease burden for the individual and the population.

A wealth of research is available to support a strong relationship between physical activity and disease prevention. A large-scale prospective study found that among adults 50 years of age and older, achieving 150 minutes of moderate-intensity exercise per week reduced the risk of death from all causes by 27 percent. Older adults who achieved 60 minutes of vigorous exercise per week had a 32 percent reduction in risk of death.[2] Among adults 40 years and older, more calories burned with daily physical activity reduced the risk of death from all causes.[3]

Aerobic exercise benefits the brain, not just the heart.

While aerobic exercise is often viewed preferentially through the lens of cardiovascular health, the diverse cascade of biological effects from exercise as a whole — and aerobic exercise, in particular — culminate to make it one of the most formidable and immediately practical real-world interventions for human aging and the brain.

In the context of the brain, exercise is a potent stimulant of brain-derived neurotrophic factor (BDNF), a cell signaling protein that plays a key role in numerous signaling pathways associated with a variety of disorders ranging from depression and dementia to obesity and diabetes. The primary role of BDNF is to stimulate the formation, growth, survival, and development of neurons. It is responsible for mediating the beneficial cognitive effects associated with exercise. The decline of BDNF function during aging may contribute to deficits in learning and memory and the progression of dementia and Alzheimer's disease.[4] Some have estimated that one-third of dementia cases are attributable to modifiable risk factors, including aerobic exercise.[5]

Exercise that requires output at 80 percent of a person's maximum heart rate for at least 40 minutes creates the greatest probability of significant BDNF elevation.[6] See below for common methods for calculating an age-based estimated maximal heart rate.

Estimating maximal heart rate

Thinking about exercise from the standpoint of the physiological demand it creates as a function of percent maximal heart rate allows clinical studies to compare training that may have similar perceptual effort even among participants with varying degrees of fitness.

There are a variety of formulas that estimate maximal heart rate (HRmax), each with varying degrees of underestimation or overestimation,[7] depending on the aerobic fitness, gender, and age of the population. These formulas overestimate maximum heart rate in trained populations and underestimate them in older and untrained populations.[8] Nevertheless, estimates are a valuable starting point for heart rate-based zone training:

Aerobic exercise exerts myriad effects on human health.

A single bout of aerobic exercise alters more than 9,000 molecules in the blood.

"One acute bout of aerobic exercise elicited extensive changes in...molecules involved in energy metabolism, oxidative stress, inflammation, tissue repair, and growth factor response." Click To Tweet

Aerobic exercise is associated with improvements in whole-body health; however, the cellular mechanisms that support this relationship require further research. Findings from one study suggest that an acute bout of aerobic exercise alters more than 9,000 distinct molecules in the human body to influence health positively.

The study involved 36 adults between the ages of 40 and 75 years with insulin resistance and overweight or obesity (BMI greater than 25). Half of the participants engaged in an acute bout of aerobic exercise on a treadmill for 8 to 12 minutes at their maximum capacity, while the other group of participants did not perform any exercise. The authors collected blood before and after the participants exercised and when they were fasted.

One acute bout of aerobic exercise elicited extensive changes in 9,815 molecules involved in energy metabolism, oxidative stress, inflammation, tissue repair, and growth factor response. Acute exercise was powerful enough to reduce insulin resistance, amplifying the molecular response to exercise. This finding suggests insulin participates in many molecular pathways modulated by exercise. The study's authors suggested that their findings could lay the groundwork for developing a simple blood test that measures fitness in the future. Learn more about exercise's molecular metabolic and immune benefits with Dr. Michael Synder in this clip.

Aerobic exercise increases mitochondrial fat metabolism.

"Just one session of moderate-intensity aerobic exercise in sedentary adults increases the metabolism of both fat and non-fat energy sources." Click To Tweet

During aerobic exercise, the body increases the delivery of fats to the muscle mitochondria and increases mitochondrial capacity to metabolize fats, a process called beta-oxidation. The inner membrane of mitochondria possesses a series of enzymes called the electron transport chain. These enzymes transfer electrons from carbohydrates and fats to the final enzyme in the chain that produces ATP. Electron transfer flavoprotein is an enzyme in this chain that transfers electrons from fats, specifically.

The investigators recruited fifteen healthy sedentary adults (average age, 28 years) with a normal body mass index. Participants completed one hour of cycling at 65 percent of their maximum aerobic capacity on one day and rested the next day. The researchers collected biopsies from the participants' thigh muscles after they had rested and 15 minutes after they exercised. They analyzed the muscle mitochondria for the abundance of electron transfer flavoprotein activity and the metabolism of fats and nonfat fuel sources.

Following exercise training, mitochondrial metabolism of fats and nonfat sources increased, although this relationship was not statistically significant. Also noted was a six percent increase in hydrogen peroxide, a byproduct of fat metabolism that damages cells. Although fat metabolism increased, the authors reported no increase in the abundance of electron transfer flavoprotein activity.

The authors concluded that just one session of moderate-intensity aerobic exercise in sedentary adults increases the metabolism of both fat and nonfat fuel sources.

Aerobic exercise benefits people with depression, especially those with more severe symptoms.

"Incorporating aerobic exercise programs into treatment protocols for people with depression might be beneficial in reducing depressive symptoms, especially in cases of more severe symptoms." Click To Tweet

Major depressive disorder is characterized by altered sleep and appetite, fatigue, sadness, and feelings of guilt or low self-worth. Although pharmaceutical treatments for depression are available, many people with depression do not respond to the medications. The findings of one study demonstrate that aerobic exercise benefits people with depression, especially those with more severe symptoms.

The intervention study involved 66 young adults (average age, 20 years) who had major depressive disorder. About half of the participants completed an eight-week moderate-intensity aerobic exercise program, while the remainder completed an eight-week light stretching program. The study's authors tracked the participants' depressive symptoms throughout the study and assessed their reward processing and cognitive control before and after the intervention.

They found that aerobic exercise reduced the participants' depressive symptoms better than light stretching. Neither form of activity affected reward processing or cognitive control. However, participants whose depressive symptoms were more severe and scored high in reward processing were more likely to respond to the aerobic program than the stretching program.

These findings demonstrate that incorporating aerobic exercise programs into treatment protocols for people with depression might be beneficial in reducing depressive symptoms. Learn more about exercise as a treatment for depression in this video featuring Dr. Rhonda Patrick.

Aerobic exercise induces changes in blood flow in brain regions involved in memory.

"Aerobic exercise increased blood flow to the anterior cingulate cortex region of the brain, an area associated with empathy, impulse control, decision-making, and memory." Click To Tweet

Mild cognitive impairment and memory loss often precede the development of Alzheimer's disease, a neurodegenerative disorder characterized by progressive memory loss, spatial disorientation, cognitive dysfunction, and behavioral changes. Aerobic exercise may improve memory function in older adults. Findings from one study suggest that exercise improves cerebral blood flow in brain regions involved in memory.

The prospective clinical trial involved 30 adults (average age, 66 years) with mild cognitive impairment. Half of the participants engaged in a supervised aerobic exercise program of 25 to 30 minutes per session three times per week, gradually increasing to 30 to 40 minutes per session three or four times per week. The other half of the participants engaged in stretching only. At the end of the 12-month intervention, the study's authors assessed the participants' memory function, cardiorespiratory fitness, and cerebral blood flow.

Participants enrolled in the one-year exercise program exhibited marked improvements in cardiorespiratory fitness and memory performance. Compared to stretching, aerobic exercise increased blood flow to the anterior cingulate cortex region of the brain, an area associated with empathy, impulse control, decision-making, and memory.

Exercise also reduced blood flow to the posterior cingulate cortex, a component of the default mode network associated with internally directed thought. The posterior cingulate cortex is highly sensitive to dementia and is resistant to the benefits of exercise. In cases of cognitive impairment, the brain shifts blood flow away from the posterior cingulate cortex toward healthier brain areas. These findings suggest that exercise can forestall the effects of age-related cognitive decline.

Higher cardiorespiratory fitness may support brain structure and memory for nearly a decade.

A nine-year follow-up of the Generation 100 trial tracked 106 adults who were 70 to 77 years old at baseline. For five years, participants were assigned to high-intensity interval training (HIIT), moderate-intensity continuous training (MICT), or an active control group asked to follow national physical activity guidelines.[11]

At year nine, higher baseline VO₂peak predicted larger cortical volume and better pattern-separation performance across all three groups. Greater hippocampal volume loss across participants was associated with poorer verbal memory, although verbal-memory and pattern-separation scores did not differ between groups.[11]

Surprisingly, the national-guidelines group had the least hippocampal volume loss, and HIIT did not preserve hippocampal volume better. This finding does not establish that HIIT harms the brain: the MRI substudy was small, only 73 participants had MRI data at year nine, exercise behavior was partly self-reported, and all three groups remained active. Instead, the findings suggest that entering older age with strong cardiorespiratory fitness and continuing to stay active may matter more for these long-term brain outcomes than any single intensity prescription.[11]

Sauna and hot-water immersion complement aerobic exercise but do not replace it.

"Heat can mimic some signals created by exercise, but it does not reproduce the full-body adaptation or replace aerobic training." Click To Tweet

Sauna and hot-water immersion raise core temperature, heart rate, cardiac output, skin blood flow, and sweating—acute responses that overlap with aerobic exercise. Exercise, however, also coordinates mechanical work and signaling across the lungs, skeletal muscle, bone, nervous system, and metabolism. Heat is therefore best understood as a partial exercise mimetic or adjunct rather than an equivalent intervention.

Observational data from a Finnish cohort suggest that high cardiorespiratory fitness and frequent sauna bathing may work synergistically. Each was independently associated with lower cardiovascular and all-cause mortality, and people with both high fitness and frequent sauna use had the lowest observed risk.[12] Because the study was observational, it cannot establish that sauna caused the lower mortality risk.

A 12-week randomized trial provides a more direct comparison of repeated heat and exercise.[13] Thirty-one inactive adults completed stationary cycling, 40°C (104°F) hot water immersion, or no intervention three times per week. Brachial flow-mediated dilation improved from baseline with hot water immersion, but only cycling clearly exceeded the inactive control. In the femoral artery, only cycling improved significantly from baseline and outperformed control. Neither intervention specifically improved resting blood pressure or central arterial stiffness.

The trial suggests that passive heat can create a vascular stimulus, but exercise produced the broader and more convincing adaptation. People who can exercise should continue to prioritize recommended aerobic and resistance training. Heat may still be useful as an optional complement or as a supervised accessibility bridge when conventional exercise is temporarily limited.

"People who engaged in recommended amounts of aerobic or muscle-strengthening activity had a lower risk of death from all causes, and these benefits were even greater if they engaged in both types of activities." Click To Tweet

Findings from one population-based cohort study demonstrate that combining aerobic exercise and strength training is best. The study, which involved nearly 480,000 adults, drew on data from the National Health Interview Survey, an ongoing, cross-sectional survey of people living in the United States. The study participants reported how much leisure time they engaged in aerobic and strength physical activity each week. Then, the study's authors categorized them as having insufficient activity, aerobic activity only, strength activity only, and both aerobic and strengthening activities, based on recommended guidelines.

The authors found that the participants who engaged in recommended amounts of aerobic or muscle-strengthening activity had a lower risk of death from all causes, and these benefits were even greater if they engaged in both types of activities. They noted similar reductions in the risk of death from cardiovascular disease, cancer, and chronic lower respiratory tract diseases.

These findings suggest that adherence to public health guidelines for exercise reduces the risk of disease and death and supports interventions to improve compliance.

A newer prospective analysis adds dose context. It followed 147,374 U.S. health professionals across three cohorts for up to 30 years and repeatedly assessed both resistance training and aerobic activity. Compared with no resistance training, 90–119 minutes per week was associated with a 13% lower all-cause mortality rate after accounting for aerobic activity and other health and lifestyle factors. People reporting 30 to under 45 MET-hours of weekly aerobic activity plus 60–119 minutes of resistance training had a 45% lower all-cause mortality rate than those reporting inadequate aerobic activity and no resistance training.[14]

The newer study did not find statistical evidence of synergy, so the data support complementary rather than multiplicative benefits. Because the study was observational and relied on self-reported exercise, it cannot prove causation. Read the full FoundMyFitness research summary.

A 2026 systematic review adds a postmenopausal cardiovascular perspective. Across 60 controlled studies involving 1,931 women ages 52 to 78, resistance training produced small standardized improvements in resting heart rate and diastolic blood pressure and moderate improvements in systolic and mean blood pressure. Most programs involved two or three sessions per week for eight to 24 weeks at roughly 50% to 80% of one-repetition maximum.[15]

These findings do not make resistance training a replacement for aerobic exercise. The review measured intermediate physiological outcomes rather than heart attacks, strokes, or cardiovascular mortality, and every randomized trial was rated at high risk of bias. Instead, the findings strengthen the case for a complete program: aerobic training directly develops cardiorespiratory fitness, while resistance training supports muscle, bone, physical function, and potentially blood-pressure and autonomic regulation after menopause. Read the full FoundMyFitness research summary.

Antihistamine use blunts functional adaptations in exercise capacity.

"Exercise stimulates histamine release and promotes increased blood circulation, which may be important for facilitating muscle adaptation." Click To Tweet

Some of these benefits of aerobic exercise are due to adaptations in skeletal muscle that arise from the repair of cellular damage produced by the demand of exercise. Histamine is an organic molecule that acts as a neurotransmitter in the brain and spinal cord while regulating gut and immune function. Much of the research surrounding histamine relates to its effects on allergies and inflammation; however, recent research has demonstrated the role of histamine as a mediator of exercise-induced physiological responses. Exercise stimulates histamine release and promotes increased blood circulation, which may be important for facilitating muscle adaptation.

The investigators conducted two phases of research, including a randomized cross-over study of antihistamines and their effect in acute exercise and a double-blind, placebo-controlled, randomized study of chronic exercise training and antihistamine use. Participants in the acute exercise trial completed two exercise sessions on separate days. One day, they took an antihistamine one hour before aerobic exercise; on the alternate day, they took a placebo treatment. The researchers measured heart rate during exercise and blood pressure, heart rate, and arterial blood flow in the thigh before and after exercise.

In the placebo group, blood flow in the thigh was increased by approximately threefold 15 minutes following exercise and remained 50 percent higher two hours following exercise. However, post-exercise blood flow reduced markedly in participants who took an antihistamine (about 35 percent). Histamine treatment did not alter blood pressure or heart rate before or after exercise compared to the placebo group.

For the study on chronic exercise, participants completed six weeks of high-intensity interval training consisting of three weekly cycling sessions. Half of the participants took an antihistamine one hour before exercise, and the other half took a placebo. The researchers measured maximum exercise capacity by having participants exercise to exhaustion and measuring their oxygen output. They measured metabolic health by having participants complete an oral glucose tolerance test in which they consumed 75 grams of sugar (the amount of sugar in about two cans of non-diet soda) and measured their blood glucose over two hours. They assessed vascular function by using ultrasound to measure the rate of blood flow in the thigh. Finally, the researchers took muscle biopsies from participants' thighs to measure muscle adaptation.

Over the six weeks of training, resting heart rate tended to decrease in the placebo group but not in the antihistamine group, indicating a blunting of exercise-induced adaptation. Peak power output during exercise also increased in both groups; however, this increase was significantly greater in the placebo group (12 percent increase) compared to the antihistamine group (7 percent increase). The time to exhaustion also improved significantly with training in the placebo group (81 percent increase) compared to the antihistamine group (31 percent increase). Training improved glucose tolerance significantly in the placebo group (26 percent increase), but this effect was blocked in the antihistamine group (1 percent increase). Finally, participants in the placebo group experienced a 37 percent improvement in vascular function, while those in the antihistamine group experienced a 14 percent decrease in vascular function. Maximal blood flow during exercise increased due to training in the placebo group only.

In conclusion, antihistamine use blunted the functional adaptations in exercise capacity, whole-body glycemic control, and vascular function produced by exercise.

Topic articles

  • Exercise Snacks explains how brief, deliberately planned bouts of vigorous activity can improve fitness and glucose regulation.
  • Exercise and Cognitive Function covers the effects of structured exercise and brief movement breaks on memory, creativity, and executive function.
  • Brain-Derived Neurotrophic Factor (BDNF) is a growth factor that increases neuroplasticity. Exercise robustly increases BDNF.
  • Depression is a neuropsychiatric disease causing pain and disability to millions of people. Exercise reduces symptoms of depression and improves brain health.
  • Sauna and whole-body hyperthermia mimic aerobic exercise in their ability to improve cardiovascular health through many of the same mechanisms.

Episodes

  1. ^ Whitfield, Geoffrey P.; Carlson, Susan A.; Ussery, Emily N.; Fulton, Janet E.; Galuska, Deborah A.; Petersen, Ruth (2019). Trends In Meeting Physical Activity Guidelines Among Urban And Rural Dwelling Adults — United States, 2008–2017 MMWR. Morbidity And Mortality Weekly Report 68, 23.
  2. ^ Leitzmann, Michael F. (2007). Physical Activity Recommendations And Decreased Risk Of Mortality Archives Of Internal Medicine 167, 22.
  3. ^ Brage, Soren; Mok, Alexander; Khaw, Kay-Tee; Luben, Robert; Wareham, Nick (2019). Physical Activity Trajectories And Mortality: Population Based Cohort Study Bmj , .
  4. ^ Laske, C.; Stransky, E.; Leyhe, T.; Eschweiler, G. W.; Wittorf, A.; Richartz, E., et al. (2005). Stage-dependent BDNF Serum Concentrations In Alzheimer’s Disease Journal Of Neural Transmission 113, 9.
  5. ^ Farrow, Maree; Alty, Jane; Lawler, Katherine (2020). Exercise And Dementia Prevention Practical Neurology 20, 3.
  6. ^ Schmolesky MT; Webb DL; Hansen RA (2013). The effects of aerobic exercise intensity and duration on levels of brain-derived neurotrophic factor in healthy men. J Sports Sci Med 12, 3.
  7. ^ Shookster D; Lindsey B; Cortes N; Martin JR (2020). Accuracy of Commonly Used Age-Predicted Maximal Heart Rate Equations. Int J Exerc Sci 13, 7.
  8. ^ Moholdt, Trine; Berglund, Ida J.; Sørås, Sara E.; Relling, Bård E.; Lundgren, Kari M.; Kiel, Ida A. (2019). The Relationship Between Maximum Heart Rate In A Cardiorespiratory Fitness Test And In A Maximum Heart Rate Test Journal Of Science And Medicine In Sport 22, 5.
  9. ^ Fox SM 3rd; Naughton JP; Haskell WL (1971). Physical activity and the prevention of coronary heart disease. Ann Clin Res 3, 6.
  10. ^ Wisløff, Ulrik; Nes, Bjarne; Karlsen, Trine; Janszky, I.; Støylen, A. (2012). Age-predicted Maximal Heart Rate In Healthy Subjects: The HUNT Fitness Study Scandinavian Journal Of Medicine & Science In Sports 23, 6.
  11. ^ a b c Reitlo LS; Pani J; Stensvold D; Wisløff U; Håberg AK (2026). Long-Term Effects of a 5-Year Randomized Controlled Exercise Trial on Brain Volumes and Cognitive Function in Older Adults: A 4-Year Post-Intervention Follow-Up Study. Sports Medicine 56, 8.
  12. ^ Kunutsor SK; Khan H; Laukkanen T; Laukkanen JA (2018). Joint associations of sauna bathing and cardiorespiratory fitness on cardiovascular and all-cause mortality risk: a long-term prospective cohort study. Ann Med 50, 2.
  13. ^ Costa JG; Locatelli JC; Wigati KW; Naylor LH; Jones H; Haynes A, et al. (2026). Comparison of exercise training and repeated hot water immersion on vascular function in overweight older adults. Experimental Physiology , .
  14. ^ Zhang Y; Lee DH; Rezende LFM; Ma Y; Giovannucci E (2026). Long-term resistance training with all-cause and cause-specific mortality: assessing dose-response and joint associations with aerobic physical activity. British Journal of Sports Medicine 60, 12.
  15. ^ Rivera-Mejía SL; Rúa-Alonso M; Rial-Vázquez J; Nine I; Camacho-Villa MA; Enríquez-González MG, et al. (2026). Resistance training improves cardiovascular health in postmenopausal women: systematic review and meta-analysis. Journal of Applied Physiology 141, 2.