ABSTRACT

Understanding ATP production and energy utilization of superheroes can help guide scientific efforts in optimizing human energy utilization and performance. Herein, we perform a theoretical examination of the biological changes that might have endowed the Marvel Universe fictional character, Peter Parker™(alias: Spiderman™), with superhuman ability. We calculate the energy expenditure of Spiderman™ during an episode of heroic activity and attempt to localize the biological process that has allowed Peter Parker™ to augment ATP production and physical performance without modifying his macro biology. Our analysis leads us to the hypothesis that only a modification in cellular oxidative phosphorylation would permit the exponential increase in energy production observed in superhuman feats performed by Spiderman™.  

COMPLETE MANUSCRIPT

Understanding ATP production and energy utilization of superheroes can help guide scientific efforts in optimizing human energy utilization and performance. Spiderman™ is a useful superhero for study as he is the alias of Peter Benjamin Parker (aka Peter Parker™) who was born without superhuman powers. An encounter with an experimentally modified arachnid resulted in a biological change and acquisition of superhuman powers by Peter Parker™[1-4]. In this study, we estimate the energy consumption of Spiderman™ during an episode of heroic activity and attempt to localize the biological process that has allowed Peter Parker™ to augment performance without modifying his macro biology.

Spiderman™ has been observed to demonstrate superhuman strength, speed, stamina, and agility [1-4]. These physical attributes are complemented by boosted immunity, rapid healing, and enhanced neurological function, marked by remarkable equilibrium, reflexes, and his trademark spidey-sense™[1-5]. Spiderman’s™ abilities are not attributed to extra-celestial and/or divine origins as it has been for his superhuman counterparts including, Superman™, Captain Marvel™, Thor™, The Green Lantern™, Star Lord™, etc. [6-10]. Moreover, Spiderman’s™ powers also cannot be attributed to inordinate financial wealth and technology as in the case of Bruce Wayne™/The Batman™ or Tony Stark™/ Iron Man™ [11, 12].  Lastly, it is worth noting that upon acquisition of superhuman abilities, Peter Parker™ did not substantially increase his muscle bulk, weight, and/or head circumference (as observed in the case of The Hulk™) that might explain his enhanced performance [13].

Energy is necessary for the execution of biological processes [14]. Biological function requires energy in the form of Adenosine Triphosphate (ATP) consumption. In humans, oxygen consumption and nutrient intake (sugar, fats, protein) is required for ATP production [14]. Human performance is rate-limited by ATP availability; in the absence of available energy units, the muscle fatigues causing strength and endurance to diminish [14]. Without divine and/or extra-celestial powers, it is likely that Spiderman’s™ enhanced biological performance reflects an augmentation of human energy utilization. Localizing the molecular, cellular, and/or physiologic changes associated with energy utilization requires an awareness of the magnitude of energy generated and consumed to execute superhuman feats. To quantify the maximal energy utilization of Spiderman™, we examine the energy utilization associated with his heroic activity of halting a runaway train [3]. This heroic activity required Spiderman’s maximal ability as he collapsed (presumably due to fatigue) and had to be carried away from the scene after stopping the train, thereby confirming maximal energy expenditure.

A calculation has previously been done to estimate the force experienced by the web during this activity [15]. We have used this as the starting point of our analysis; however, we have changed some of the parameters that we believe were incorrect. In the scene, Spiderman™ stops a New York City subway train consisting of six cars that appear to be moving at full speed. The Bryan et al. paper assumed four fully loaded R160 subway trains moving at the maximum speed of 24.6 m/s (55 mph). From the movie, it does not appear that the train is the R160 model, which was introduced in 2006, two years after the release of Spiderman 2™ [3, 16]. It instead appears to be six R42 train cars, which were still in service until at least 2007 [3, 17]. Similar to the study authored by Bryan et al., we assume each of the six cars is fully loaded (44 seats) with individuals of an average mass of 70 kg. The maximum speed of both trains is identical, but the R42 has a mass of 33,742 kg instead of 38,600 for the R160. The total mass of the train and passengers is then calculated as 220,932 kg. To simplify the calculation, we will ignore other resistances experienced by the train (friction, air resistance, etc.) as the work done by these forces are likely small in magnitude compared to the kinetic energy permitting forward movement. The total energy to stop the train is therefore equal to the kinetic energy of the train as follows:

In contrast, the world’s strongest man demonstrated his strength by lifting a giant log of 460 lbs (208.7 kg) [18]. During this lift, Žydrūnas Savickas lifted the log approximately 1.88 m off the ground (Figure 1), expending approximately 3.86 kJ of energy. Fiji (an open source image processing package) was used to calculate the height of the lift as follows [19]. Mr. Savickas’s height is listed as 1.91 m [20]. In Figure 1, lengths 1 and 2 were measured to be 707.376 pixels total. This length scale of 1.91 m/707.376 pixels was used to calculate the height of the lift by half of the log diameter from the length of the line 4. This results in a lift height of 1.88 m. The total energy expenditure is calculated as the potential energy of the log at this height as follows:

These calculations quantitatively demonstrate that Spiderman’s™ superhuman abilities require exponentially more energy [approximately 17,300 times] than that of one of the strongest feats performed by a human.

Human biology adapts to permit augmentation of energy utilization during activity. In case of physical exertion, the neurologic and endocrine systems will generate neurohormonal signals to augment cardiac output by increasing heart rate and stroke volume to enhance delivery of oxygen to target tissues for ATP synthesis (Equation 1) [21]. We considered the possibility that Spiderman’s™ cardiovascular system is responsible for increased energy utilization. However, this was determined to be unlikely for several reasons. Peter Parker™ does not experience a significant change in body habitus following acquisition of powers, therefore his heart is unlikely to have undergone structural change to permit increased cardiac output. In Spiderman™ Homecoming we observed his resting heart rate was 84bpm which is typical for a human being without superhuman strength [4]. In fact, it is slightly faster than what one might expect for a well-conditioned athlete [22]. Secondly, the healthy human heart in an individual at rest will typically eject 60% of blood with a heart rate of 60-90bpm. With exertion, the ejection fraction can approach 90%, and heart rate can approach a value that is proportional to age (Equation 2). It is unlikely that Spiderman™ generates a maximal heart rate faster than 300bpm as this would impair ventricular filling time and lead to cardiovascular collapse [21]. Nevertheless, even if we assume that his heart rate may approach 300bpm during strenuous activity, and he simultaneously were to have adequate ventricular filling while ejecting 100% of the ventricular volume during systole, he will still only deliver 30-40% more oxygen to target tissues compared to a well-conditioned human being. This does not meet the marked energy utilization previously calculated for his feat of superhuman strength. 

Equation 1: Cardiac Output = Heart Rate x Stroke Volume

Equation 2: Maximal Heart Rate = 220 - Age

Next, we considered the possibility that Spiderman’s ™ hematopoietic system may have been modified to augment oxygen carrying capacity and thus, oxygen delivery, to target tissues. We speculated that this may manifest in the form of increased red-blood cell count, increased hemoglobin production, and/or increased number of heme-units carried per molecule of hemoglobin. We determined that each of these scenarios were unlikely as these changes would manifest with plethora (redness of the skin) and polycythemia (itchy skin). These phenomena are neither apparent in his visage nor his behavior. Moreover, if these modifications to the hematopoietic system were responsible for Spiderman’s™ superhuman ability, they would generate pronounced abnormalities in the complete blood-count and iron-study panels that are not infrequently examined by family physicians. Finally, it is worth noting that small changes in red-blood cell count, hemoglobin, and/or heme-units carried per molecule of hemoglobin would not be sufficient create the exponential changes in energy delivery needed for superhuman activity.

Alternatively, we considered the possibility that Spiderman™ may possess increased efficiency of oxygen extraction from circulating hemoglobin such that 4 units of oxygen as opposed to 1-2 units are removed from a single hemoglobin molecule circulating through the body. If we permit this theoretical modification in biology, Spiderman’s™ oxygen delivery capacity would only be expected to increase 2-4 fold. This is notably short of what we’ve calculated to be needed to demonstrate superhuman activity.

Energy units (NADH, NADPH, FADH2) are generated from catabolic processes in the body, including glycolysis (using glucose as a substrate), fatty acid metabolism, and the Tricarboxylic Acid (TCA) cycle also known as the Krebs cycle [14]. These energy units are delivered to the mitochondria where they enter the oxidative phosphorylation pathway also known as the electron transport chain (ETC). The ETC is composed of several enzymes (Complexes I – IV) within the inner mitochondrial membrane which use energy from traveling electrons donated by NADH or FADH2 to facilitate transfer of H+ across the inner mitochondrial membrane from the mitochondrial matrix to the inter-membrane space [14]. A healthy ETC generates an electrochemical gradient which powers the synthesis of ATP from ADP and a phosphate group by means of an enzyme called ATP synthetase. This enzyme simultaneously facilitates the reduction of oxygen into water [14]. Of note, glycolysis and the TCA cycle also produce relatively small quantities of ATP independent of oxidative phosphorylation. In the normal human, a single unit of glucose will generate 2 units of ATP from Glycolysis and over 30 units of ATP from oxidative phosphorylation [14].

In the absence of significant biological changes that augment oxygen delivery to target tissue, it is likely that Spiderman™ possesses a single or multiple mutations within elements of the oxidative phosphorylation pathway that leads to exponential ATP production. It is worth noting that mutations enhancing the reaction rate of individual enzymes within glycolysis, or the TCA cycle are unlikely to be tolerated by the cell because such mutations would disrupt the equilibrium of metabolites that are necessary to drive the cellular energy metabolism. Rather, a single or multiple mutations increasing promiscuity of the components of the electron transport chain or ATP synthetase would be better suited to modify the ratio of ATP generated per unit of glucose and oxygen entering the cell (Figure 2).

Inherent in this model is the assumption that underlying energy consumption processes are also augmented exponentially. As such, the rate of ATP production is comparable in magnitude to the ATP consumption rate during superhuman feats. A detailed examination of the specific energy-consuming processes that are augmented is beyond the scope of this intellectual exercise. However, one might speculate that exponential ATP expenditure may occur as a function of enhanced neuromuscular function (ie: increased number of neuro-motor networks operating with faster signaling/shorter refractory period) and/or myofilament performance where ATP hydrolysis is required for contractile work produced by myosin-heads in the sarcomere [14]. Each of these processes may demand an exponential increase in ATP production to enhance physical agility and strength. Within this framework, ADP and phosphate but not ATP would be expected to be present in excess within the metabolically active cell. These are important considerations as excess ATP availability would lead to inhibition of ATP production steps in glycolysis and the TCA cycle.

Collectively, we hypothesize that one or more gain-of-function mutations in elements of the oxidative phosphorylation pathway (ETC or ATP-synthetase) would be required to facilitate exponential ATP production and metabolic rates high enough to support superhuman feats performed by Spiderman™.  

FIGURES

Figure 1: Photograph of Žydrūnas Savickas used to calculate the height of the log during an overhead press [23].

Figure 2: Illustration of glucose-metabolism with cellular respiration in normal cellular physiology (A) and in the case of superhuman performance (B). Superhuman cellular respiration generates exponential units of ATP relative to normal human cellular respiration. Created with BioRender.com [24].
A

B

REFERENCES

[1] Wikipedia contributors. Spider-Man. Wikipedia, The Free Encyclopedia. Last Revision: August 16, 2023 18:40 UTC. Date Retrieved: August 18, 2023 20:16 UTC. Page Version ID: 1170709418. Permanent link: https://en.wikipedia.org/w/index.php?title=Spider-Man&oldid=1170709418.

[2] Raimi, S (Director). 2002. Spider-Man [FILM].

[3] Raimi, S (Director). 2004. Spider-Man 2 [FILM].

[4] Watts, J (Director). 2017. Spider-Man: Homecoming [FILM].

[5] Kakalios, James. The Physics of Superheroes. Gotham Books. 2005.

[6] Snyder, Z (Director). 2013. Man of Steel [FILM].

[7] Boden, A and Fleck, R (Directors). 2019. Captain Marvel [FILM].

[8] Gunn, J (Director). 2014. Guardians of the Galaxy, Vol 1 [FILM]. 

[9] Branagh, K (Director). 2011. Thor [FILM].

[10] Campbell, M (Director). 2011. Green Lantern [FILM].

[11] Synder, Z (Director). 2017. Justic League [FILM].

[12] Favreau, J (Director). 2008. Iron Man [FILM].

[13] Leterrier, L (Director). 2008. The Incredible Hulk [FILM].

[14] Reece, Taylor, and Simon. Campbell Biology. ‎Pearson; 12th edition. January 17, 2020.

[15] Forster J, Bryan M, Stone A. A2_4 Doing Whatever a Spider Can. Physics Special Topics. 2012 Nov 20;11(1).

[16] Wikipedia contributors. R160 (New York City Subway car). Wikipedia, The Free Encyclopedia. Last Revision: August 11, 2023 17:42 UTC. Date Retrieved: August 18, 2023 20:51 UTC. Page Version ID: 1169850716. Permanent link: https://en.wikipedia.org/w/index.php?title=R160_(New_York_City_Subway_car)&oldid=1169850716

[17] Wikipedia contributors. R42 (New York City Subway car). Wikipedia, The Free Encyclopedia. Last Revision: August 8, 2023 13:47 UTC. Date Retrieved: August 18, 2023 20:55 UTC. Page Version ID: 1169338858. Permanent link: https://en.wikipedia.org/w/index.php?title=R42_(New_York_City_Subway_car)&oldid=1169338858

[18] Wikipedia contributors. World’s Strongest Man. Wikipedia, The Free Encyclopedia. Last Revision: August 11, 2023 02:17 UTC. Date Retrieved August 18, 2023 20:59 UTC. Page Version ID: 1169753849. Permanent link: https://en.wikipedia.org/w/index.php?title=World%27s_Strongest_Man&oldid=1169753849

[19] Schindelin, J., Arganda-Carreras, I., Frise, E., Kaynig, V., Longair, M., Pietzsch, T., … Cardona, A. (2012). Fiji: an open-source platform for biological-image analysis. Nature Methods, 2019.

[20] Wikipedia contributors. Žydrūnas Savickas. Wikipedia, The Free Encyclopedia. Last Revision: July 27, 2023 07:09 UTC. Date Retrieved: August 18, 2023 22:51 UTC. Page Version ID: 1167355151. Permanent link: https://en.wikipedia.org/w/index.php?title=%C5%BDydr%C5%ABnas_Savickas&oldid=1167355151

[21] Bonow, Libby, Mann, Tomaselli, Bhatt, Solomon, and Braunwald. Braunwald’s Heart Disease, 2 Vol Set, 12th Edition. 2021.

[22] Jensen-Urstad K, Ericson M, Stock N, Jensen-Urstad M. Pronounced resting bradycardia in male elite runners is associated with high heart rate variability.  Scandinavian Journal of Medicine & Science in Sports. 1997.

[23] Photograph of Zydrunas Savickas from the log-lift competition, circa 2015. Photograph.   https://www.facebook.com/photo.php?fbid=463851665100351&set=a.248205073331679&type=3&theater

[24] Images were created with BioRender.com