title: The cross-sectional area of the gluteus maximus muscle varies according to habitual exercise loading: Implications for activity-related and evolutionary studies.
abstract: Greater size of the gluteus maximus muscle in humans compared to non-human primates has been considered an indication of its function in bipedal posture and gait, especially running capabilities. Our aim was to find out how the size of the gluteus maximus muscle varies according to sports while controlling for variation in muscle strength and body weight. Data on gluteus maximus muscle cross-sectional area (MCA) were acquired from magnetic resonance images of the hip region of female athletes (N=91), and physically active controls (N=20). Dynamic muscle force was measured as counter movement jump and isometric knee extension force as leg press. Five exercise loading groups were created: high impact (triple-jumpers and high-jumpers), odd impact (soccer and squash players), high magnitude (power-lifters), repetitive impact (endurance runners) and repetitive non-impact (swimmers) loadings. Individuals in high impact, odd impact or high-magnitude loading groups had greater MCA compared to those of controls, requiring powerful hip extension, trunk stabilization in rapid directional change and high explosive muscle force. Larger body size and greater muscle strength were associated with larger MCA. An increase in dynamic force was associated with larger MCA, but the strength of this relationship varied with body weight. Thus, gluteal adaptation in humans promotes powerful lower limb movements required in sprinting and rapid changes in direction, as well as maintenance and stabilization of an erect trunk which also provides a platform for powerful motions of the upper limbs. These movements have likely evolved to facilitate food acquisition, including hunting.
authors.affiliation: Department of Archaeology, University of Oulu, PO Box 1000, 90014 Oulu, Finland; Department of Ecology, University of Oulu, PO Box 3000, 90014 Oulu, Finland. Electronic address: sirpa.niinimaki@oulu.fi.
authors.forename: Sirpa
authors.initials: S
authors.lastname: Niinimäki
authors.affiliation: Department of Ecology, University of Oulu, PO Box 3000, 90014 Oulu, Finland; Department of Biology, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland.
authors.forename: Laura
authors.initials: L
authors.lastname: Härkönen
authors.affiliation: Department of Health Sciences, University of Jyväskylä, PO BOX 35, 40014 Jyväskylä, Finland; GeroCenter Foundation for Aging Research and Development, Rautpohjankatu 8, 40700 Jyväskylä, Finland; Jyväskylä Central Hospital, Keskussairaalantie 19, 40620 Jyväskylä, Finland.
authors.forename: Riku
authors.initials: R
authors.lastname: Nikander
authors.affiliation: Department of Mechanical Engineering and Industrial Systems, Tampere University of Technology, PO Box 589, 33101 Tampere, Finland.
authors.forename: Shinya
authors.initials: S
authors.lastname: Abe
authors.affiliation: De la Préhistoire à l'Actuel-Culture, Environnement, et Anthropologie (PACEA), UMR5199 PACEA, Bâtiment B8, Allée Geoffroy Saint Hilaire, CS 50023, Pessac Cedex 33615, France.
authors.forename: Christopher
authors.initials: C
authors.lastname: Knüsel
authors.affiliation: The UKK Institute for Health Promotion Research, Kaupinpuistonkatu 1, PO Box 30, 33501 Tampere, Finland.
authors.forename: Harri
authors.initials: H
authors.lastname: Sievänen
mesh_terms: D000293:Adolescent; D000328:Adult; D005075:Biological Evolution; D001696:Biomechanical Phenomena; D001835:Body Weight; D015444:Exercise / Q000502:physiology*; D005260:Female; D005684:Gait / Q000502:physiology; D006615:Hip; D006801:Humans; D008279:Magnetic Resonance Imaging; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D009929:Organ Size; D013177:Sports; D016474:Weight-Bearing / Q000502:physiology; D055815:Young Adult
keywords: Bipedalism; Endurance running; Hominin; Human evolution; Hunting; Medical imaging; Sprinting