HoldsUp

DavidPerlmutterMD · 2025-03-10 · David Perlmutter (host), Sharon Horesh Bergquist

The Stress Paradox: How to Harness Pressure for a Stronger, Healthier Life | Sharon Berguist

27 research-tied claims examined: 2 contradicted 2 overstated 6 context 14 supported 3 unverified

2

Contradicted by research

0:50:52Sharon Horesh Bergquistcontradictedhigh

The transient spike in cortisol during a high-intensity interval workout is necessary for subsequent muscle building and adaptation.

"if you do a high-intensity interval workout, you are going to get a spike in your cortisol, but you need that spike to build the muscle that follows. Without the cortisol, you do not get the adaptation, you don't get the muscle building." (said at 0:50:52)

The speaker claims that the acute transient spike in cortisol during high-intensity interval or resistance exercise is necessary for subsequent muscle building and adaptation, stating that without this cortisol spike, muscle building and adaptation do not occur. This claim is contradicted by exercise physiology research. Transient post-exercise systemic hormonal spikes (including cortisol, growth hormone, and testosterone) are not required for exercise-induced muscle hypertrophy or adaptation. Mechanistic and clinical studies demonstrate that load-induced muscle hypertrophy is driven primarily by intrinsic cellular mechanical tension and local signaling pathways (such as mTORC1 activation), rather than systemic hormonal surges. In fact, studies manipulating systemic hormonal responses show that muscle protein synthesis, muscle cross-sectional area gains, and strength adaptations occur to an equivalent degree regardless of whether post-exercise systemic hormone levels are elevated or kept at basal levels. Furthermore, cortisol is primarily a glucocorticoid with catabolic effects on skeletal muscle, and comprehensive analyses of acute post-exercise hormonal responses demonstrate that systemic hormone elevations do not drive or dictate muscle hypertrophy.

0:51:23Sharon Horesh Bergquistcontradictedmoderate

After exercise, cortisol levels for the remainder of the day drop below baseline, heart rate variability improves, and blood pressure decreases.

"And interestingly enough, after exercise, cortisol levels the rest of the day are lower than baseline, heart rate variability improves, your blood pressure lowers." (said at 0:51:23)

The statement bundles three acute post-exercise physiological claims, two of which are inaccurate: 1. **Cortisol levels**: Acute exercise triggers a transient increase or maintenance of circulating cortisol; it does not depress daytime cortisol levels below normal baseline for the rest of the day. Diurnal tracking shows the typical circadian decline remains largely unaltered aside from transient post-exercise increases. 2. **Heart rate variability (HRV)**: In the immediate hours following an acute bout of exercise, heart rate variability (specifically vagally mediated parasympathetic indices such as RMSSD) is temporarily depressed due to sympathetic predominance and delayed parasympathetic reactivation, rather than acutely improved above baseline. 3. **Blood pressure**: The assertion that blood pressure decreases is partially accurate; post-exercise hypotension (PEH) is a well-documented acute phenomenon, particularly in hypertensive or prehypertensive individuals.

2

Overstated

0:30:22David Perlmutter (host)overstatedlow

Microglial cells can transfer mitochondria to other dysfunctional microglial cells via microtubules, and a deficiency in this mitochondrial sharing mechanism is linked to familial Parkinson's disease.

"these microglial cells can come to the aid of another microglial cell in whom the mitochondria is not working effectively and share mitochondria via these microtubules, and a deficiency in their ability to share mitochondria is related to familial Parkinson's disease." (said at 0:30:22)

The speaker conflates two distinct mechanisms observed in preclinical research. Published studies show that microglia donate healthy mitochondria to damaged neurons (not to other microglia) to rescue them, whereas microglia transfer toxic α-synuclein aggregate cargo to neighboring microglia to distribute the burden of degradation. These transfers occur via tunneling nanotubes (F-actin-dependent cellular projections, rather than simple microtubules). Deficits in this tunneling nanotube network are observed in microglial cells carrying the LRRK2 G2019S mutation, a genetic variation causing familial Parkinson's disease, but the evidence comes from in vitro and animal models.

0:47:46Sharon Horesh Bergquistoverstatedmoderate

Hormetic stressors induce cross-adaptation, meaning that exposure to one physical stressor confers biological resilience against other distinct stressors through shared and overlapping cellular pathways.

"hormetic stressors work through cross-adaptation, meaning that you can use any one of these stressors to build resilience against the others because they work through synergistic and overlapping pathways." (said at 0:47:46)

Cross-adaptation and cellular cross-tolerance are well-documented physiological concepts, where sub-lethal exposure to one physical stressor (e.g., heat acclimation) activates shared molecular defense mechanisms—such as heat shock protein upregulation, antioxidant defenses, and autonomic adaptations—that can reduce physiological strain during subsequent exposure to a distinct stressor like hypoxia. Systematic reviews and meta-analyses confirm moderate physiological benefits for specific stressor pairs, such as heat acclimation reducing physiological strain in hypoxic environments. However, claiming that 'any one' hormetic stressor universally confers resilience against 'the others' is overstated: cross-adaptation is not universal across all combinations of environmental, physical, or psychological stressors, and literature reviews note non-transferability or mixed outcomes between certain stressor pairs.

6

Needs context

0:12:22Sharon Horesh Bergquistneeds contextlow

Vitagenes comprise approximately 500 genes that encode antioxidant and inflammatory defense responses.

"Vitagenes are about 500 genes, and when nature conserves something, as you know, it's telling us this is super important. They encode our ability to ramp up our antioxidant defenses, our inflammatory defenses." (said at 0:12:22)

The speaker conflates the specific concept of 'vitagenes' with the broader cytoprotective regulon (such as genes regulated by the Nrf2 transcription factor). In biomedical literature, 'vitagenes' refer specifically to a conserved network of cellular stress-response genes that encode heat shock proteins (such as Hsp32/heme oxygenase-1 and Hsp70), the thioredoxin system, and sirtuins. While vitagenes work within antioxidant and anti-inflammatory pathways, the specific figure of approximately 500 cytoprotective genes typically refers to the broader network of downstream target genes activated by master regulators like Nrf2.

0:14:44Sharon Horesh Bergquistneeds contextvery low

Allicin in allium vegetables opens calcium-permeable channels that stimulate growth factors such as brain-derived neurotrophic factor (BDNF).

"We have allicin, which is another phytochemical in garlic and onions and leeks, and it opens pores um that allow calcium in that stimulates growth factors like brain-derived neurotrophic factor." (said at 0:14:44)

The biological mechanisms described by the speaker are supported in preclinical and in vitro models, but evidence linking dietary allicin directly to calcium influx-mediated brain-derived neurotrophic factor (BDNF) elevation in humans is limited. Allicin, an organosulfur compound from allium vegetables (such as garlic), is well established as an agonist of transient receptor potential (TRP) channels (notably TRPA1 and TRPV1), which are calcium-permeable cation channels that facilitate cellular Ca2+ influx. In rodent and neuronal cell culture models, allicin exposure has been shown to upregulate BDNF expression and activate downstream neuroprotective signaling pathways (such as PKA/CREB). However, whether typical dietary intake achieves sufficient bioavailability and central nervous system exposure to drive this cascade in humans has not been established in clinical trials.

0:19:01Sharon Horesh Bergquistneeds contextmoderate

Human DNA incurs roughly 10,000 injuries per day, or about seven per minute.

"So on any given day, you're going to have 10,000 injuries to your DNA, right? Seven a minute, which is profound. And our body, in the background basal level, has a DNA repair response, and it's constantly trying to repair." (said at 0:19:01)

The estimate of approximately 10,000 to 100,000 DNA lesions per day (equating to roughly 7 or more events per minute: 10,000 / 1,440 minutes ≈ 6.94) is a widely established biochemical estimate in genomic research, but it applies to the genome of each individual human cell, not the human body as a whole. Across the entire body (composed of trillions of cells), the total number of DNA lesions occurring daily is far larger.

0:23:39Sharon Horesh Bergquistneeds contextmoderate

There are approximately 9,000 published studies evaluating cardiorespiratory fitness.

"There are about 9,000 studies on cardiorespiratory fitness. We know it's important. It simply hasn't made it to guidelines" (said at 0:23:39)

Cardiorespiratory fitness (CRF) is the subject of an extensive body of scientific literature comprising thousands of publications. In a scientific statement from the American Heart Association (AHA), experts noted that mounting epidemiological and clinical evidence demonstrates CRF is a robust independent predictor of cardiovascular disease, cancer mortality, and all-cause mortality—frequently matching or exceeding traditional risk factors. The statement advocates for integrating CRF assessment into routine clinical practice and guidelines as a vital sign.

  • context: Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness… (Circulation 2016) · cited 2471x in the literature
    "Mounting evidence has firmly established that low levels of cardiorespiratory fitness (CRF) are associated with a high risk of cardiovascular disease, all-cause mortality, and mortality rates attributable to various cancers. A growing body of epidemiological and clinical evidence demonstrates not only that CRF is a potentially stronger predictor of mortality than established risk factors such as smoking, hypertension, high cholesterol, and type 2 diabetes mellitus, but that the addition of CRF to traditional risk factors significantly improves the reclassification of risk for adverse outcomes." (abstract, passage verified)
    pubmedfull study (doi)
0:33:27Sharon Horesh Bergquistneeds contextmoderate

Human core body temperature is maintained around 98.7 degrees Fahrenheit, which is the optimal temperature for human enzymes to function.

"Our body wants to be at 98.7 degrees Fahrenheit. That is the temperature where our enzymes work optimally, and that's so critical that our body's going to defend that." (said at 0:33:27)

Human thermoregulation defends core temperature within a dynamic homeostatic range rather than a single static set point of 98.7°F (37.06°C). While Carl Wunderlich historically established 98.6°F (37.0°C) as the canonical human baseline, modern physiological measurements demonstrate that mean normal oral temperature in healthy adults is approximately 98.2°F (36.8°C), exhibiting diurnal variation typically ranging between ~97.2°F (early morning nadir) and ~99.0°F–99.9°F (late afternoon zenith). Human enzymes have evolved to operate efficiently within this regulated physiological temperature window.

0:30:54David Perlmutter (host)needs contextmoderate

Evidence indicates that mitochondria can travel throughout the entire body to assist other cells and mitochondria in distress.

"there's evidence that mitochondria travel throughout the entire body and go around to assist themselves when when their brethren are in trouble." (said at 0:30:54)

Intercellular mitochondrial transfer is an established biological phenomenon in which donor cells (such as mesenchymal stem cells, astrocytes, or immune cells) transfer functional mitochondria or mitochondrial components to metabolically stressed or damaged recipient cells to restore bioenergetics and aid tissue repair. However, this process occurs predominantly within local tissue microenvironments via specialized structures such as tunneling nanotubes (TNTs), gap junctions, and extracellular vesicles (EVs), rather than free mitochondria autonomously roaming throughout the entire body.

  • context: Intercellular Mitochondrial Transfer and Mitochondrial Transplantation in Cardiovascular D… (The Canadian journal of cardiology 2026) · cited 1x in the literature
    "Mitochondria have traditionally been regarded as intracellular powerhouses; however, they are now recognized as dynamic intercellular signaling organelles capable of moving between cells to coordinate tissue adaptation and repair. This Review examines the emergence of mitochondria transfer as a fundamental mechanism of cardiovascular communication, integrating current evidence for the exchange of intact mitochondria, mitochondrial DNA, and mitochondrial components among cardiomyocytes, endothelial cells, vascular smooth muscle cells, fibroblasts, and immune cells." (abstract, passage verified)
    pubmedfull study (doi)
  • context: Context-Dependent Functional Outcomes of Mitochondrial Transfer: A Donor-Recipient Perspec… (Advanced biology 2026)
    "Intercellular mitochondrial transfer has emerged as a fundamental mechanism regulating tissue homeostasis and disease progression, yet its complex regulatory network remains incompletely understood. This review synthesizes the principal transfer mechanisms, focusing on tunneling nanotube (TNT)-mediated direct contact and extracellular vesicle (EV)-mediated indirect transport. Based on the functional disparity between donor and recipient cells, we categorize four prototypical pairing modes and delineate the functional diversity of mitochondrial transfer in metabolic support, tissue repair, and stress responses." (abstract, passage verified)
    pubmedfull study (doi)
14

Supported by research

0:04:36Sharon Horesh Bergquistsupportedmoderate

The human body contains over 30 trillion cells.

"Our cells are the basic building blocks in our body; we have over 30 trillion." (said at 0:04:36)

Comprehensive biophysical and anatomical modeling studies estimate that a standard adult human body contains approximately 30 to 37 trillion human cells. Bianconi et al. (2013) systematically estimated a total of 3.72 × 10¹³ (37.2 trillion) human cells across various organ systems. A revised quantitative analysis by Sender et al. (2016) estimated approximately 3.0 × 10¹³ (30 trillion) human cells in a standard 70 kg reference adult, with red blood cells accounting for the majority of the total count.

0:13:52Sharon Horesh Bergquistsupportedmoderate

Resveratrol activates the sirtuin response and helps build mitochondria.

"So resveratrol, as you mentioned, activates our sirtuin response. It helps us build mitochondria. It also helps DNA and a lot of other functions." (said at 0:13:52)

The claim that resveratrol activates the sirtuin response and promotes mitochondrial biogenesis is well supported by extensive preclinical, cellular, and animal research. Resveratrol functions as a natural activator of SIRT1 (a class III histone deacetylase). Activation of SIRT1 leads to the deacetylation and activation of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), a key master regulator that induces the gene expression required for mitochondrial biogenesis and function, as well as maintaining genomic integrity and metabolic homeostasis. While the biological pathway is well established in cell and animal models, translation and clinical efficacy in humans remain an active area of investigation due to bioavailability considerations.

0:14:24Sharon Horesh Bergquistsupportedhigh

Sulforaphane in broccoli and cruciferous vegetables activates the Nrf2 pathway, increasing antioxidant and detoxification systems.

"Sulforaphane is another plant chemical in broccoli and cruciferous vegetables. It activates a master regulator called Nrf2, which increases our antioxidant and detoxification systems." (said at 0:14:24)

Sulforaphane is a well-characterized isothiocyanate derived from glucosinolates found in cruciferous vegetables such as broccoli. Extensive biochemical, preclinical, and clinical research confirms that sulforaphane activates the Nrf2 (nuclear factor erythroid 2-related factor 2) signaling pathway by modifying Keap1 sensor cysteines, leading to nuclear translocation of Nrf2 and subsequent transcriptional activation of antioxidant response element (ARE)-driven Phase II detoxification and cytoprotective antioxidant enzymes.

0:22:07Sharon Horesh Bergquistsupportedmoderate

Cardiorespiratory fitness is the single biggest predictor of longevity and disease risk.

"cardiorespiratory fitness, or our aerobic fitness, is the single biggest predictor of our longevity and our risk of developing disease." (said at 0:22:07)

Large prospective and retrospective cohort studies consistently show that cardiorespiratory fitness (exercise capacity measured in METs or VO2 max) is the single strongest modifiable predictor of all-cause mortality and longevity, outperforming traditional cardiovascular and clinical risk factors such as smoking, diabetes, hypertension, and coronary artery disease. In landmark cohorts (e.g., Myers et al., 2002; Mandsager et al., 2018), low cardiorespiratory fitness conferred a higher risk of death than any of the other tested clinical risk factors. Certainty is moderate due to reliance on observational cohort designs.

0:24:35Sharon Horesh Bergquistsupportedhigh

A Japanese study in older adults found that interval walking (3 minutes fast, 3 minutes slow) produced greater improvements in cardiorespiratory fitness and cardiometabolic risk factors than continuous walking.

"So there was a study done in Japan in older adults—where the one group just walked continuously, another group was told, "Walk 3 minutes really fast, and then just back off, catch your breath, walk slow for 3 minutes, and then do it again in intervals." Same duration of physical activity. And as they followed them—I believe the study was for a month, or maybe it was 3 months—but the group that did the interval walking developed a higher cardiorespiratory fitness and greater reduction in their cardiometabolic risk factors." (said at 0:24:35)

A randomized controlled trial conducted in Japan by Nemoto et al. (2007) evaluated 246 middle-aged and older adults (mean age 63 years) over a 5-month intervention. Participants were assigned to no walking, moderate-intensity continuous walking, or high-intensity interval walking (repeating sets of 3 minutes of slow walking at 40% peak aerobic capacity and 3 minutes of fast walking at >=70% peak aerobic capacity). The interval walking group achieved significantly greater gains in peak aerobic capacity (walking and cycling) and knee muscle strength, as well as significantly larger reductions in resting systolic blood pressure, compared with the continuous walking group.

0:25:33Sharon Horesh Bergquistsupportedmoderate

Rapidly depleting energy reserves triggers mitochondrial biogenesis and stimulates mitophagy.

"If we rapidly deplete our energy reserves, we are sending a strong signal to our body to increase mitochondrial biogenesis, so create new mitochondria, and we're also stimulating mitophagy, which is a selective form of autophagy that takes our damaged mitochondria and helps through a process of fission and fusion to make them healthier." (said at 0:25:33)

Rapid depletion of cellular energy reserves (such as from exercise or energetic stress) increases the cellular AMP/ATP ratio and activates AMP-activated protein kinase (AMPK). AMPK activation coordinates mitochondrial quality control by promoting mitochondrial biogenesis (primarily via the PGC-1α signaling pathway) and inducing mitophagy and general autophagy (via ULK1 activation and mTORC1 suppression) alongside mitochondrial fission and fusion dynamics to clear damaged mitochondria and renew the pool.

0:29:13David Perlmutter (host)supportedhigh

Mature human erythrocytes (red blood cells) do not contain mitochondria.

"Except for the erythrocyte, of course." (said at 0:29:13)

Mature human erythrocytes (red blood cells) lack mitochondria as well as nuclei and other organelles. During terminal erythroid differentiation, immature reticulocytes systematically eliminate their entire cohort of mitochondria via programmed mitophagy. Abnormal retention of mitochondria in mature erythrocytes is only seen in pathological states such as sickle cell disease.

0:34:58Sharon Horesh Bergquistsupportedmoderate

Both cold and heat exposure raise metabolic rate in the body.

"They both are going to raise metabolism. One in the cold, we're doing it to generate heat. With exposure to heat, we're raising our metabolism essentially to get rid of heat, to dissipate the heat." (said at 0:34:58)

The claim is supported by thermoregulatory physiological evidence. Human resting metabolic rate is minimal within the thermoneutral zone (TNZ). When exposed to temperatures below the lower critical limit of the TNZ, metabolic rate rises via shivering and non-shivering thermogenesis to generate heat and preserve core temperature. Conversely, when exposed to heat stress above the upper critical temperature of the TNZ, metabolic rate increases due to the metabolic cost of heat dissipation mechanisms (such as increased cardiac output, cutaneous vasodilation, and sweat gland activity) as well as the temperature-dependent acceleration of cellular metabolic processes (the Q10 effect).

0:36:02Sharon Horesh Bergquistsupportedhigh

Shear stress on arterial endothelium increases nitric oxide production, which dilates blood vessels, prevents platelet clumping, and reduces cholesterol plaque formation.

"when that shear stress goes across the lining of our arteries, it increases our production of nitric oxide. And nitric oxide dilates our blood vessels, it prevents our platelets from clumping, it reduces the risk of cholesterol plaques building." (said at 0:36:02)

The speaker's statement accurately reflects well-established cardiovascular physiology. Fluid shear stress acting on the endothelial lining of arteries stimulates endothelial nitric oxide synthase (eNOS) activity and expression, increasing nitric oxide (NO) synthesis. In turn, endothelium-derived NO acts on vascular smooth muscle to cause vasodilation, inhibits platelet adhesion and aggregation (clumping), and provides atheroprotective effects that attenuate the initiation and progression of atherosclerotic plaque formation.

0:40:40David Perlmutter (host)supportedmoderate

The relative drop in oxygenation following hyperbaric oxygen therapy triggers hypoxia-inducible factor 1-alpha (HIF-1a), which stimulates angiogenesis and nitric oxide synthesis.

"it was the drop in oxygenation from the 100% back down to room air or even lower. It's the change that initiates the activation of something in this case called hypoxia-inducible factor 1-alpha, which stimulates the body to make more blood vessels, increase nitric oxide production" (said at 0:40:40)

The speaker accurately describes the physiological mechanism known as the 'hyperoxic-hypoxic paradox' (or 'normobaric oxygen paradox'). Research demonstrates that cellular sensing responds to relative fluctuations in oxygen partial pressure: returning to normal atmospheric oxygen (or baseline) following a hyperoxic exposure is interpreted by cells as a relative hypoxia. This relative drop stabilizes and activates hypoxia-inducible factor 1-alpha (HIF-1α), triggering downstream transcriptional pathways that promote angiogenesis, erythropoiesis, and nitric oxide synthesis.

  • supports: Pulsed high oxygen induces a hypoxic-like response in human umbilical endothelial cells an… (Journal of applied physiology (Bethesda, Md. : 1985) 2012) · cited 63x in the literature
    "According to this hypothesis describing the "normobaric oxygen paradox", normoxia following a hyperoxic event is sensed by tissues as an oxygen shortage, upregulating HIF-1 activity. With the aim of confirming, at cellular and at functional level, that normoxia following a hyperoxic event is "interpreted" as a hypoxic event, we report a combination of experiments addressing the effects of an intermittent increase of oxygen concentration on HIF-1 levels and the activity level of specific oxygen-modulated proteins in cultured human umbilical vein endothelial cells... Our experiments confirm that, during recovery after hyperoxia, an increase of HIF expression occurs in human umbilical vein endothelial cells" (abstract, results, passage verified)
    pubmedfull study (doi)
  • supports: The Hyperoxic-Hypoxic Paradox. (Biomolecules 2020) · cited 211x in the literature
    "Interestingly, fluctuations in the free oxygen concentration rather than the absolute level of oxygen can be interpreted at the cellular level as a lack of oxygen. Thus, repeated intermittent hyperoxia can induce many of the mediators and cellular mechanisms that are usually induced during hypoxia. This is called the hyperoxic-hypoxic paradox (HHP)." (abstract, background, passage verified)
    pubmedfull study (doi)
0:46:16Sharon Horesh Bergquistsupportedmoderate

Only one out of ten Americans currently consumes the recommended amounts of fruits and vegetables.

"only one out of 10 Americans right now is getting the recommended fruits and vegetables, so just add one more piece of fruit or vegetable." (said at 0:46:16)

National dietary surveillance data published by the Centers for Disease Control and Prevention (CDC) from the Behavioral Risk Factor Surveillance System (BRFSS) support this claim. In the 2019 assessment, only 10.0% of US adults met the recommended intake for vegetables (2-3 cup-equivalents daily) and 12.3% (approximately one in eight) met the recommendation for fruits (1.5-2 cup-equivalents daily). Earlier assessments yielded similar findings, with 9.3% meeting vegetable recommendations in 2015 and 8.9% in 2013.

0:52:25David Perlmutter (host)supportedmoderate

Blunting post-exercise inflammation and cytokine release (particularly interleukin-6) reduces some of the cardiovascular adaptations to exercise.

"and it was found that some of the benefits from a cardiovascular perspective of exercise were blunted when those inflammatory cytokines—well, particularly interleukin-6—were blunted." (said at 0:52:25)

Human randomized controlled trial evidence indicates that interleukin-6 (IL-6) signaling is required for several exercise-induced cardiovascular and cardiometabolic adaptations. In double-blind RCTs administering an IL-6 receptor antibody (tocilizumab) during exercise training, pharmacologically blocking IL-6 blunted exercise-induced reductions in visceral and epicardial adipose tissue, altered cardiac muscle mass adaptations, and impaired exercise-induced improvements in left ventricular global longitudinal strain.

0:52:56David Perlmutter (host)supportedmoderate

Interleukin-6 activates AMP-activated protein kinase (AMPK) during or following exercise.

"And now we're seeing that, yes, matter of fact, interleukin-6 is what activates AMP kinase, which is one of our goals of exercise." (said at 0:52:56)

Interleukin-6 (IL-6) functions as an exercise-induced myokine that is released in large quantities by contracting skeletal muscle. Both in vitro, animal in vivo models, and human infusion studies demonstrate that IL-6 directly stimulates the phosphorylation and activation of 5' AMP-activated protein kinase (AMPK) in skeletal muscle and adipose tissue, enhancing glucose uptake and fatty acid oxidation. While muscle contraction also activates AMPK through cellular energy depletion (increased AMP/ATP ratios) and upstream kinases like LKB1 and CaMKKbeta independently of IL-6, IL-6 contributes significantly to AMPK activation during and after exercise.

0:57:02Sharon Horesh Bergquistsupportedlow

Mild to moderate cortisol levels enhance synaptic plasticity and brain cell communication, whereas very high sustained cortisol levels cause synaptic pruning and neurotoxicity in the hippocampus.

"from Dr. Sapolsky's work, we know the same hormone, cortisol, can in a low, mild-to-moderate range, it can enhance synaptic plasticity, it can help the communication in our brain cells. And when it's at a very high level, it prunes them, right?" (said at 0:57:02)

Robert Sapolsky's neuroendocrinological research and extensive review literature establish an inverted-U dose-response curve for glucocorticoids in the hippocampus. Preclinical electrophysiological and cellular studies show that mild-to-moderate or acute glucocorticoid elevations facilitate hippocampal synaptic plasticity (such as long-term potentiation) and cognitive performance. In contrast, sustained, severe, or excessive glucocorticoid exposure suppresses synaptic plasticity, causes dendritic atrophy and synaptic loss, and exacerbates excitotoxic neurotoxicity and cell death in the hippocampus.

3

No source found (not proven false)

0:22:47Sharon Horesh Bergquistunverifiedvery low

About 40% of people who exercise solely at moderate intensity fail to increase their cardiorespiratory fitness (non-responders).

"but the people who do it through moderate intensity, a brisk walk, which is probably the most common form of exercise, about 40% of people are non-responders to increasing their cardiorespiratory fitness." (said at 0:22:47)

No published record matching the specific claim that approximately 40% of individuals exercising solely at moderate intensity fail to increase cardiorespiratory fitness (non-responders) was located; this does not prove the claim false.

0:29:09Sharon Horesh Bergquistunverifiedvery low

A single human cell can contain thousands of mitochondria.

"And what we know—Except for the erythrocyte, of course. Yeah, and we know now that you can have thousands in one cell" (said at 0:29:09)

No published record matching the specific claim that a single human cell can contain thousands of mitochondria (while erythrocytes contain none) was located; this does not prove the claim false.

0:35:31Sharon Horesh Bergquistunverifiedvery low

Heat exposure increases heart rate and cardiac output to the same degree as moderate to vigorous exercise.

"We mimic exercise, moderate to vigorous exercise, because our heart rate and our cardiac output goes up to the same degree as exercise. That's going to create shear stress in our arteries." (said at 0:35:31)

No published record matching the claim that heat exposure increases heart rate and cardiac output to the same degree as moderate to vigorous exercise was located; this does not prove the claim false.

Unverified means no publication matching the claim was located; it does not prove the claim false. Spotted an error? See the corrections policy - disputes from the people quoted are prioritized.