Hell, even watching sports can teach you something about how muscles respond to stress, strain, and compensate to achieve a result. One of the more interesting trends I have been following is that when an athlete suffers an injury - and then continues to perform without letting the injury heal properly - the athlete will often suffer another injury. And, presumably, this stems from the body trying to compensate for the compromised portion of the body by putting strain on another part of the body in an often inefficient, and hence injury prone way. Now this highlights several things; heroics aside, you can do more harm to your injured body by not letting it heal; the body can recruit other muscle groups to help in movements during an injury; in most motions many muscle groups work together to achieve a movement.
Now going further with the concept of multiple muscles or even muscle groups collaborating to achieve a movement look at the impressive list of muscles used to achieve the deadlift.
According to the wiki page a proper deadlift engages 27 muscles from the legs, abdomen, back, and forearms. Even thought it is called a "lift" it is more of a pull and arm muscles only grip while the legs and core do the majority of the work. Now with these thoughts in mind regarding the diversity of muscles utilized in a bipedal hominid deadlift let us look at a recent paper looking at this question from the perspective of a gigantic bipedal theropods: the critical analysis of Robert Nicholls' "double death" scenario Balance and Strength - Estimating the Maximum Prey Lifting Potential of the Large Predatory Dinosaur Carcharodontosaurus saharicus. May 6 2015 The Anatomical Record.
ABSTRACT
Motivated by the work of palaeo-art “Double Death (2011),” a biomechanical analysis using three-dimensional digital models was conducted to assess the potential of a pair of the large, Late Cretaceous theropod dinosaur Carcharodontosaurus saharicus to successfully lift a medium-sized sauropod and not lose balance. Limaysaurus tessonei from the Late Cretaceous of South America was chosen as the sauropod as it is more completely known, but closely related to the rebbachisaurid sauropods found in the same deposits with C. saharicus. The body models incorporate the details of the low-density regions associated with lungs, systems of air sacs, and pneumatized axial skeletal regions. These details, along with the surface meshes of the models, were used to estimate the body masses and centers of mass of the two animals. It was found that a 6 t C. saharicus could successfully lift a mass of 2.5 t and not lose balance as the combined center of mass of the body and the load in the jaws would still be over the feet. However, the neck muscles were found to only be capable of producing enough force to hold up the head with an added mass of 424 kg held at the midpoint of the maxillary tooth row. The jaw adductor muscles were more powerful, and could have held a load of 512 kg. The more limiting neck constraint leads to the conclusion that two, adult C. saharicus could successfully lift a L. tessonei with a maximum body mass of 850 kg and a body length of 8.3 m. Anat Rec, 2015. © 2015 Wiley Periodicals, Inc.
According to this study although one individual C. saharicus could balance with an added weight at the front of 2.5 tons these animals were limited to lifting a weight of 425 kg singly or 850 kg doubly by a limited neck musculature. And just on the face of it this should raise some suspicions because the world record dead lift by a modern Homo sapien is more than what C. saharicus could do according to this study.
1155 lbs = 524 kg basically lifting 100 kg more than C. saharicus!?!
Wait a second this can't be write can it? Let us revisit the multitude of muscle groups that humans use in the deadlift - again arms are not that important - but the legs, abs, and arse sure are!! If you go back and read the abstract you will find no mention of the legs, abs, and arse compensating to help lift exceptional loads in C. saharicus. And when we are talking about the legs of theropods we are talking about the largest muscle group in them and any analysis of lifting would be remiss to discount them. Just like in humans where the arms/hands simply act as grips while the lower body does the lifting I would not be surprised if it was not much the same in theropods. To lift up something the whole body is lowered and the teeth, head, and neck simply get a good grip while it is the legs that do the heavy lifting. Lift with your legs they always say right!!
So yeah I think this paper attacks an interesting topic but I think it falls down a bit for me because it does not take into account the largest muscular group in theropods and does not account for multiple muscular groups working in concert.
How much could a large theropod like Caracharodontosaurus lift? I dunno but I think limitations based on balance such as those mentioned in the paper (2.5 tons individually for a 6 ton carch) are useful guidelines. I mean with increasing size muscle is going to be relatively less strong than at smaller sizes so I would not expect large theropods to hoist stuff up as big or larger than themselves like modern leopards do.
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| credit Cindy Corcoran |
If not lift completely off the ground I think it probable that large theropods could drag along fairly large carcasses on the ground like any good, self-respecting large predator today. Certainly activities like the one pictured below that inspired the paper in discussion by Robert Nicholls were par for the course and bodies of several thousand kilograms frequently tossed about like rag dolls by the largest theropods.
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| credit Robert Nicholls |
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The thing about the deadlift is that, as you say, the arms and hands 'merely' grip, while the rest does the lifting. They're just hanging - or rather being pulled - straight down.
ReplyDeleteI have no doubt the leg and trunk muscles of a carcharodontosaur would be mighty indeed, but would they have much effect on extending and raising the head and neck (the 'hand' and 'arm' in this particular weightlifting example) to around horizontal or higher, while gripping 420kg+? How did you envision it?
(BTW, followed a DML post here to see your series about plesiosaurs. A very good, thought-provoking read, thanks!)
Muscles do not work as discrete units but cooperate and recruit in unison to achieve goals. Maybe a better analogy on a more horizontal plane in humans is core and leg muscles engaged in the popular "planking" exercise. As to how leg muscles would help go google images of a bird moving from a sitting to a standing position. Theropods would move much the same. Head, neck, torso, leg, and even tail muscles would be taut in such a lifting scenario all aiding in the lift.
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