FIGURE 1.

From evolution to modern-day athleticism. Evolutionary selection of 5 main traits has facilitated the prolonged upright, bounding, bipedal locomotion in humans. Energetic barriers are lowered by long, spring-like tendons (in particular the Achilles tendon), the longitudinal plantar foot arch, ankle ligaments, long legs, in particular femur length, and short toes (to increase stride length and reduce vertical trajectories for better locomotor economy), thinner heart ventricles and larger cavity, increased hind limb muscle mass, and other adaptations. Skeletal strength is conferred, e.g., by larger joint areas in lower but not upper limbs to dissipate impact forces. Stabilization for bipedal movement is mediated by large erector spinae and gluteus muscles opposed to reduced forearm mass and an elongated, narrow waist and broad shoulders to facilitate counterrotation of thorax and arms, while decreased facial length helps head stabilization or an integrated system of bio-tensegrity for embedded perturbation repelling. Eccrine sweat glands, with a particular high density in the head for brain cooling, reduced body hair, dense skin vascularization, mouth breathing, and a large nasal epithelial area all contribute to thermoregulation. Finally, coevolution of locomotion and the brain resulted in expanded cerebello-cerebralcortical circuitry (for anticipation, pre-preparation, sensory integration, pre-planned multilevel compensation to deal with perturbations and destabilizations), cognitive capabilities (to recognize landmarks, long-range orientation, recognizing prey and predators, tracking and speculative tracking/anticipation), perception, fine motor control, and balance. See Refs. 1–8 for more information. Modern-day athletic peak performances most likely exceed these general evolutionary traits because of efficient training strategies and paradigms, nutrition and supplements, technological innovations, i.e., pertaining to equipment and facilities, and genetic and epigenetic predispositions. Figure created with BioRender.com, with permission.