Background/Introduction
Evolutionary biomechanics provides unique insight into physiological adaptation, for which there is no better teacher than experience. Humans have developed a throwing motion that allows projectiles to be propelled with high speed and accuracy, which has been key in how our ancestors survived and hunted. Apart from allowing people to get food more safely from a distance, the ability to throw also had an offensive function. In this paper, I examine what changes and anatomical structures permit humans to possess such a celebrated ability and how elastic storage energy develops along with high-speed throwing in the shoulder. Understanding the physiological changes underlying this function can also provide clues about where we come from and how our anatomy differs from other primates.
Methods
Human evolution and the resulting anatomical changes caused by it illuminate many fields of research. The biomechanics of throwing are just one instance. Humans are fast, precise throwers, and it has been conjectured that throwing is part of our evolutionary survival advantage (Roach et al., 2013). To understand this skill at a deeper level, an imperfect biomechanical analysis was attempted, providing insight into how the absorption of elastic energy within the shoulder complex relates to throwing.
The test of throwing was set up as an experiment to see whether the physical structure of a shoulder had any contradictory effect. The 20 male subjects were all athletes who had developed throwing motions. Second, they had to put in trained personnel who knew how to maintain that throwing technique and make the variables for statistical analysis easier. (Roach et al., 2013) The subjects were male and female athletes aged 19-23, collectively sampled among those most likely to participate in high-level throwing sports. The key observation area is the shoulders, a highly complex structure with bone, muscle and tendons. In particular, they pared it down to the elastic energy stored and released by a thrower’s shoulders. Participants were asked to throw a ball overhand during standardized exercises while high-speed three-dimensional kinematic and kinetic data was recorded (Roach et al., 2013). Kinematic data was collected using an eight-camera Vicon T10s 3D motion capture camera, which recorded reflective markers placed on the participant’s throwing arm and torso. From statics, kinematic data were calculated to determine the forces within throwing motion rotation and then used with joint powers (torques) to identify moments.
The other key to the method was a shoulder brace that restricted movement in varying degrees. This suggests that this was an evolutionary standstill phase, and researchers can compare the biological functions of modern people with those who lived before them (Roach et al., 2013). This new brace was rarely applied, as it recreated conditions of a more primitive musculature in which the shoulder could not reach outward. The participants would then throw both with and without the brace to test their performance.
In addition to analyzing the mechanical work of throwing using dynamic mechanics, they employed radiographical methods that determined humeral torsion- the twist in bone from shoulder to elbow. That was interesting since it tested the maximum rotation (or torque) possible at the humerus, which is crucial to throwing speed and power. (Roach et al., 2013). The research coincided with a group of scholars in evolutionary biology, human ‘biomechanics and anthropologists. This diverse background assured him that design, fieldwork and data analysis would be conducted exhaustively.
Results
These results were beneficial, as they indicated the anatomical features that can help increase elastic energy storage and influence throwing performance. A study of human evolution determined that the morphological features of the shoulder evolved to store and release elastic energy, thus serving as a source for rapid rotation generated by throwing (Roach et al., 2013). Second, they noticed that at the cocking stage of throwing (raising one’s arm from down by their side to shoulder-level), subjects with injuries excessively externally rotate their humeri outside of normal active range due to passive stretch in response to overload on both joint capsule and muscles caused by prior injury (Roach et al., 2013). In other words, there was elastic storage of energy here too. Furthermore, adding a special shoulder brace further restricts the throwing motion and, consequently, both power and speed in emergency throws. These anatomical alterations make it abundantly clear what people mean by speaking of pitching ability.
Discussion
The findings have broader implications, proving that human anatomical structures are essential to storing elastic energy necessary for fast throwing. Methodologically, the number of samples was low when combined with selecting subjects who had been trained and using a shoulder brace as an active control method simultaneously (Roach et al., 2013). On the other hand, this restriction in subject selection can lead to unconscious bias, which may adversely impact the results ‘generalizability. Future research would need to address this shortcoming by focusing on a broader demographic (Roach et al., 2013). The results of this study prove crucial not only to our knowledge about human evolution but also to present-day sports science and the treatment of related injuries. This leads to more detailed investigations of the genetics and population diversity that account for such anatomical variation. Also, exploring the relationship between these characteristics and throwing injuries would help advance training and injury prevention.
In conclusion, the study of biomechanics in Homo sapiens concludes with a comprehensive review that discusses the evolutionary adaptations needed for human beings to have acquired specialized high-speed throwing skills. The experiment used twenty trained athletes to do various throwing tasks with and without the brace, collecting kinematic and kinetic data that explained how elastic energy is stored in their shoulder joints. The results also affirm the importance of specialized anatomical characteristics-especially, humeral torsion, and shoulder elastic energy storage capacity-that were developed with Homo erectus 2 million years ago. All these features, fundamental to the perfection of throwing movements, not only can serve as evidence for their evolutionary significance but may also explain current exercise methods and injury mechanisms. Therefore, the study connects our prehistoric ancestors with today’s man by showing that biomechanical efficiency is a key factor in evolution.
References
Roach, N. T., Venkadesan, M., Rainbow, M. J., & Lieberman, D. E. (2013). Elastic energy storage in the shoulder and the evolution of high-speed throwing in Homo. Nature, 498(7455), 483–486. https://doi.org/10.1038/nature12267
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