Physical performance
You want it high: aerobic capacity is among the strongest single predictors of healthy lifespan.
In depth
Aerobic performance — endurance and VO₂max, the whole-body measure of cardiovascular-metabolic fitness.
What drives it
Mitochondrial energy increases it.
Muscle-oxidative-capacity study 2024 — skeletal-muscle mitochondrial oxidative capacity is associated with whole-body aerobic performance (VO2max); higher mitochondrial respiratory function supports endurance and lowers fatigability. PMC10828458
Builds mitochondria increases it.
PGC-1α-b overexpression study 2011, PLoS One — skeletal-muscle PGC-1α overexpression raises VO2max and exercise capacity via mitochondrial biogenesis and an oxidative fiber switch. doi:10.1371/journal.pone.0028290. Gain-of-function with a hard endpoint: muscle-specific overexpression of PGC-1-alpha-a improved exercise performance and produced about 20 percent higher peak oxygen uptake than wild-type; a separate transgenic line overexpressing the exercise-responsive PGC-1-alpha-b isoform is titled for increasing exercise capacity and peak oxygen uptake. The authors note their own confound: the MCK-PGC-1-alpha-a mice also had elevated PGC-1-alpha-a mRNA in the heart, and it is speculated that cardiac expression alone may have been sufficient to produce the VO2-peak effect — so the muscle-specific claim is not clean. And more is not always better: a companion PNAS paper is titled 'paradoxical effects of increased expression of PGC-1-alpha on muscle mitochondrial function and insulin-stimulated muscle glucose metabolism' (2008;105:19926). doi 10.1371/journal.pone.0028290.
Cardiac output increases it.
Mitochondria and PGC-1-alpha are both peripheral factors, and the literature is explicit that they are not the ceiling for whole-body exercise: central circulatory factors mainly restrict VO2MAX when performing an all-round exercise, while peripheral factors might be dominant in regional exercise. A review is titled cardiac output limits maximal oxygen consumption. The practical reading: mitochondrial support addresses the factor that is not limiting for whole-body aerobic capacity in a trained person — it becomes limiting only for small-muscle-mass or regional work, where peak oxygen uptake is thought to be limited by oxygen extraction and mitochondrial oxidative capacity. Quantified in humans: in 26 women spanning VO2max 32-62 mL/kg/min, a 1 liter higher blood volume at VO2max was associated with a 16.2 mL higher maximal stroke volume (r=0.63, P<0.001) and 2.5 L/min higher maximal cardiac output (r=0.56, P<0.01); stroke volume correlated with left ventricular muscle mass and end-diastolic diameter at every intensity. Why heart rate cannot simply rise to compensate: heart rate is the main determinant of myocardial oxygen consumption, and ventricular filling and myocardial blood flow would be compromised by further increases, since myocardial flow is blunted by contraction and occurs principally during DIASTOLE. Ceiling: VO2max is approximately 50 percent genetically determined and 50 percent trainable. doi 10.1016/j.scispo.2021.02.001 · PMC12053887
Vessel formation increases it.
Increased capillary density is named as a major peripheral adaptation to endurance training, making it easier for blood and hemoglobin to travel close to working fibers and release oxygen — so oxygen extraction fraction rises as a typical training adaptation. Human, and it works in the old: in a training study including older and young adults, indices of capillarisation increased 30-40 percent in the older group and 20-30 percent in the young — the older group adapted more, and both showed capillary angiogenesis with improved mitochondrial respiratory capacity and a greater maximal a-vO2 difference. capillarity is a peripheral factor — see the Contractility → Aerobic Capacity link, where central delivery is stated to be the primary limit for whole-body exercise. (Study on file: PMC5735290 · doi 10.1016/j.cophys.2019.04.005 · doi 10.1111/sms.14442 (Hellsten 2024) · doi 10.3389/fphys.2025.1681184 ·. doi 10.1016/j.cophys.2019.04.005 · PMC5735290
Daily energy reduces it.
Cancer-related fatigue is described alongside decreased CARDIORESPIRATORY fitness as co-occurring adverse effects that can persist years after therapy ends. The two ARE partly the same measurement: reduced exercise capacity is both a cause and a symptom of fatigue, and no retrieved source separates them. Shown at reduced weight because the direction is not established - the Fatigue → Aerobic Capacity link and the Aerobic Capacity → Fatigue link are equally defensible from what was retrieved. PMC11264125
Muscle increases it.
And the dissociation is the point, not a caveat: the sarcopenia reviews state that nutritional interventions preserve lean mass but fail to consistently restore function independently. So mass drives performance without determining it - which is why EWGSOP diagnostic criteria require low muscle strength as the primary criterion and treat low mass as confirmatory. The map already carried the other half of this: the Mitochondrial Function → Aerobic Capacity link distinguishes central from peripheral limits. This is the peripheral-mass arm. doi 10.3390/ijms26146740 · PMC13074595
Heart & blood pressure increases it.
The hallmarks literature describes what drives aging and what aging drives, in the same reviews. Named across five inflammaging and hallmarks-of-aging reviews. The systemic inflammation stemming from dysbiosis adversely affects multiple organ systems, and the reviews trace increased frailty, diminished physical capacity, cognitive impairment, and elevated mortality risk as the shared downstream set. doi 10.1016/j.molmet.2023.101755 · PMC11233824
Bone health increases it.
NBK448171 — Bone mass and fracture risk determine what a body can safely do. Drawn on physiological consensus; no dedicated effect size retrieved.
Nerve protection reduces it.
10.1007/s13300-017-0295-y — This is what the symptom costs rather than what it causes physiologically. It is shown at reduced weight because no separate effect size has been reported for this arm. The asymmetry is deliberate and stated. Sensory and motor loss limits function. doi 10.1007/s13300-017-0295-y
Joint wear reduces it.
10.1038/s41572-025-00594-6 — This is what the symptom costs rather than what it causes physiologically. It is shown at reduced weight because no separate effect size has been reported for this arm. The asymmetry is deliberate and stated. Joint pain limits capacity. doi 10.1038/s41572-025-00594-6
Strengthens veins increases it.
10.1590/1677-5449.20140039 — This is what the symptom costs rather than what it causes physiologically. It is shown at reduced weight because no separate effect size has been reported for this arm. The asymmetry is deliberate and stated. Symptomatic venous disease limits standing and walking tolerance. doi 10.1590/1677-5449.20140039
Vessel growth signal increases it.
A negative that corrects the obvious assumption: at least the structural aspects of the capillary bed do not appear to be reduced in a manner that would compromise the capacity for muscle oxygen diffusion even in senescence. Capillary rarefaction is the intuitive explanation and this review says it is not the limiting one. doi 10.1139/H07-174 · PMC10102650
Blood flow (nitric oxide) increases it.
Named across the retrieved reviews as a determinant of this outcome. doi 10.1139/H07-174 · PMC10102650
Cellular aging reduces it.
Named across the retrieved reviews as a determinant of this outcome. doi 10.1139/H07-174 · PMC10102650
What it drives
It reduces Daily energy.
Reduced aerobic capacity presents as fatigue.
It increases Heart & blood pressure.
10.3389/fpubh.2023.1076065 — Cardiorespiratory fitness is among the strongest predictors of cardiovascular mortality - recorded on the cardiac reviews. doi 10.3389/fpubh.2023.1076065
It increases Mood.
10.1038/s41598-026-41932-2 — Exercise capacity and mood co-travel; the exercise node already reaches mood. This link rests on the reviews of this outcome as a whole, and no effect size specific to it has been reported. doi 10.1038/s41598-026-41932-2
It reduces Cellular aging.
10.1093/gerona/glaf068 — VO2max decline is a canonical aging marker. Direction contestable - it may be a readout of aging rather than a driver. Low. doi 10.1093/gerona/glaf068
It increases Muscle.
Reverse arm of the Skeletal Muscle Mass → Aerobic Capacity link. Use drives mass. Low.
It increases Iron & oxygen carriage.
The mechanism that makes iron supplementation fail: anemia of inflammation is characterized by the insufficient production of erythropoietin and decreased response of erythroid progenitors to EPO. In addition, it inhibits the release of iron from the body stores and alters the iron status after being stimulated by hepcidin. Inflammation locks iron away - so oral iron given into an inflammatory state does not reach the marrow. Anemia affects 1.62 billion people. And the periodontal link is measured: a meta-analysis of sixteen studies on hemoglobin and iron metabolism in periodontitis - though the authors call the association still controversial and ask for larger cohorts (PMC7005133; PMID 835510). REFUTED ON A SECOND READING. This link was shown by linked steps until a source was opened that does not support it: “Endurance training and sex did not affect Hb FSR.” — Hemoglobin synthesis rates in young trained and untrained males and females are not different. Physiological Reports, 2025, 13(8). doi 10.14814/phy2.70311 · PMID 835510 · PMC7005133
It increases Supports airflow & lung function.
10.1164/rccm.201610-2089OC — Drawn from reviews of neighboring outcomes rather than from studies of this outcome itself, which is weaker evidence, and the map marks it so. Verbatim: “Our results suggest bi-directional causation and support a true protective effect of physical activity on lung function in smokers, after accounting for reverse causation and time-dependent confounding”. doi 10.1164/rccm.201610-2089OC · PMC7446897
It increases Balance & falls.
10.1038/s41598-025-02128-2 — Drawn from reviews of neighboring outcomes rather than from studies of this outcome itself, which is weaker evidence, and the map marks it so. doi 10.1038/s41598-025-02128-2
Blends that modulate it
Each blend page names this pathway and carries the study behind its claim.
See it on the map
Open the causal map to follow this pathway upstream and downstream, arrow by arrow, each with its study.