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de Sena Fraga CD, de Araújo RC, de Sá L, Santos Bertoldo AJ, Rodarti Pitangui AC. Use of a peanut ball, positioning and pelvic mobility in parturient women shortens labour and improves maternal satisfaction with childbirth: a randomised trial. J Physiother 2024; 70:134-141. [PMID: 38494404 DOI: 10.1016/j.jphys.2024.02.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 02/12/2024] [Accepted: 02/26/2024] [Indexed: 03/19/2024] Open
Abstract
QUESTION What is the effect of a protocol targeted at the various stages of labour - with a peanut ball, positioning and pelvic mobility - on the duration of labour, pain severity, fatigue, maternal outcomes, neonatal outcomes and satisfaction in parturients without analgesia? DESIGN A randomised trial with concealed allocation, blinding of assessors and intention-to-treat analysis. PARTICIPANTS One hundred women in active labour. INTERVENTION The experimental group received the protocol targeted at the various stages of labour, with a peanut ball, positioning and pelvic mobility, whilst the control group received usual care. OUTCOME MEASURES The primary outcomes were the duration of labour and pain severity. The secondary outcomes were maternal fatigue, mode of delivery, risk of perineal laceration, severity of perineal laceration, use of synthetic oxytocin, satisfaction with delivery, Apgar scores, admission of the neonate to an intensive care unit and resuscitation of the neonate in the delivery room. In the active phase of labour, the numerical rating scale and maternal perception of childbirth fatigue questionnaire were applied; they were taken again when the parturient had 8 to 10 cm of dilation. The numerical rating scale was also applied postpartum to evaluate satisfaction with childbirth. RESULTS The use of the protocol with a peanut ball reduced the duration of active and expulsive phases and the total duration of labour, with mean differences of 82 minutes (95% CI 41 to 125), 8 minutes (95% CI 0 to 18) and 89 minutes (95% CI 45 to 132), respectively. Maternal satisfaction was better in the experimental group: mean between-group difference on the 10-point scale was 1.1 (95% CI 0.4 to 1.8). The effects on the other outcomes were either similar between groups or unclear. CONCLUSION A protocol with a peanut ball, positioning and pelvic mobility reduced the duration of labour and improved maternal satisfaction with childbirth. REGISTRATION RBR-74wcnjc.
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Affiliation(s)
| | - Rodrigo Cappato de Araújo
- Postgraduate Program of Rehabilitation and Functional Performance, University of Pernambuco, Petrolina, Brazil
| | - Layane de Sá
- Postgraduate Program of Rehabilitation and Functional Performance, University of Pernambuco, Petrolina, Brazil
| | - Ana Julia Santos Bertoldo
- Postgraduate Program of Rehabilitation and Functional Performance, University of Pernambuco, Petrolina, Brazil
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Mitteroecker P, Fischer B. Evolution of the human birth canal. Am J Obstet Gynecol 2024; 230:S841-S855. [PMID: 38462258 DOI: 10.1016/j.ajog.2022.09.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 09/07/2022] [Accepted: 09/07/2022] [Indexed: 03/12/2024]
Abstract
It seems puzzling why humans have evolved such a small and rigid birth canal that entails a relatively complex process of labor compared with the birth canal of our closest relatives, the great apes. This study reviewed insights into the evolution of the human birth canal from recent theoretical and empirical studies and discussed connections to obstetrics, gynecology, and orthopedics. Originating from the evolution of bipedality and the large human brain million years ago, the evolution of the human birth canal has been characterized by complex trade-off dynamics among multiple biological, environmental, and sociocultural factors. The long-held notion that a wider pelvis has not evolved because it would be disadvantageous for bipedal locomotion has not yet been empirically verified. However, recent clinical and biomechanical studies suggest that a larger birth canal would compromise pelvic floor stability and increase the risk of incontinence and pelvic organ prolapse. Several mammals have neonates that are equally large or even larger than human neonates compared to the size of the maternal birth canal. In these species, the pubic symphysis opens widely to allow successful delivery. Biomechanical and developmental constraints imposed by bipedality have hindered this evolutionary solution in humans and led to the comparatively rigid pelvic girdle in pregnant women. Mathematical models have shown why the evolutionary compromise to these antagonistic selective factors inevitably involves a certain rate of fetopelvic disproportion. In addition, these models predict that cesarean deliveries have disrupted the evolutionary equilibrium and led to new and ongoing evolutionary changes. Different forms of assisted birth have existed since the stone age and have become an integral part of human reproduction. Paradoxically, by buffering selection, they may also have hindered the evolution of a larger birth canal. Many of the biological, environmental, and sociocultural factors that have influenced the evolution of the human birth canal vary globally and are subject to ongoing transitions. These differences may have contributed to the global variation in the form of the birth canal and the difficulty of labor, and they likely continue to change human reproductive anatomy.
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Affiliation(s)
- Philipp Mitteroecker
- Unit for Theoretical Biology, Department of Evolutionary Biology, University of Vienna, Vienna, Austria.
| | - Barbara Fischer
- Unit for Theoretical Biology, Department of Evolutionary Biology, University of Vienna, Vienna, Austria
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Wiseman AL, Charles JP, Hutchinson JR. Static versus dynamic muscle modelling in extinct species: a biomechanical case study of the Australopithecus afarensis pelvis and lower extremity. PeerJ 2024; 12:e16821. [PMID: 38313026 PMCID: PMC10838096 DOI: 10.7717/peerj.16821] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 01/02/2024] [Indexed: 02/06/2024] Open
Abstract
The force a muscle generates is dependent on muscle structure, in which fibre length, pennation angle and tendon slack length all influence force production. Muscles are not preserved in the fossil record and these parameters must be estimated when constructing a musculoskeletal model. Here, we test the capability of digitally reconstructed muscles of the Australopithecus afarensis model (specimen AL 288-1) to maintain an upright, single-support limb posture. Our aim was to ascertain the influence that different architectural estimation methods have on muscle specialisation and on the subsequent inferences that can be extrapolated about limb function. Parameters were estimated for 36 muscles in the pelvis and lower limb and seven different musculoskeletal models of AL 288-1 were produced. These parameters represented either a 'static' Hill-type muscle model (n = 4 variants) which only incorporated force, or instead a 'dynamic' Hill-type muscle model with an elastic tendon and fibres that could vary force-length-velocity properties (n = 3 variants). Each muscle's fibre length, pennation angle, tendon slack length and maximal isometric force were calculated based upon different input variables. Static (inverse) simulations were computed in which the vertical and mediolateral ground reaction forces (GRF) were incrementally increased until limb collapse (simulation failure). All AL 288-1 variants produced somewhat similar simulated muscle activation patterns, but the maximum vertical GRF that could be exerted on a single limb was not consistent between models. Three of the four static-muscle models were unable to support >1.8 times body weight and produced models that under-performed. The dynamic-muscle models were stronger. Comparative results with a human model imply that similar muscle group activations between species are needed to sustain single-limb support at maximally applied GRFs in terms of the simplified static simulations (e.g., same walking pose) used here. This approach demonstrated the range of outputs that can be generated for a model of an extinct individual. Despite mostly comparable outputs, the models diverged mostly in terms of strength.
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Affiliation(s)
- Ashleigh L.A. Wiseman
- McDonald Institute for Archaeological Research, University of Cambridge, Cambridge, United Kingdom
| | - James P. Charles
- Evolutionary Morphology and Biomechanics Lab, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, United Kingdom
| | - John R. Hutchinson
- Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, Royal Veterinary College, Hatfield, United Kingdom
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Delgado A, Amorim MM, Oliveira ADAP, Souza Amorim KC, Selva MW, Silva YE, Lemos A, Katz L. Active pelvic movements on a Swiss ball reduced labour duration, pain, fatigue and anxiety in parturient women: a randomised trial. J Physiother 2024; 70:25-32. [PMID: 38036399 DOI: 10.1016/j.jphys.2023.11.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 08/30/2023] [Accepted: 11/01/2023] [Indexed: 12/02/2023] Open
Abstract
QUESTION How much do active pelvic movements on a Swiss ball during labour affect maternal and neonatal outcomes? METHOD A randomised trial with concealed allocation, blinded assessors and intention-to-treat analysis. PARTICIPANTS Two-hundred parturient women. INTERVENTION The experimental group performed pelvic anteversion and retroversion, lateral pelvic tilts and circular hip movements according to individual obstetric evaluation (foetal station and position, cervical dilatation and the presence of early pushing urge) on a Swiss ball. The control group received usual care. Both groups were permitted to walk and shower. OUTCOME MEASURES The primary outcome was the duration of the first stage of labour. The secondary outcomes were the duration of the second stage of labour, pain intensity, delivery mode, medication use, local swelling, fatigue, anxiety, satisfaction and neonatal outcomes. RESULTS The experimental intervention reduced the duration of labour by 179 minutes (95% CI 146 to 213) in stage one and 19 minutes (95% CI 13 to 25) in stage two. It decreased pain by approximately 2 points (95% CI 2 to 2) on a 0-to-10 scale at 30, 60 and 90 minutes. It reduced the risk of a caesarean section (ARR 0.14, 95% CI 0.03 to 0.25; NNT 7, 95% CI 4 to 32) and vulvar swelling (ARR 0.11, 95% CI 0.03 to 0.19; NNT 9, 95% CI 5 to 31). It reduced fatigue by 18 points (95% CI 16 to 21) on a 15-to-75-point scale and anxiety by 9 points (95% CI 8 to 11) on an 18-to-72-point scale. Other effects were negligible or unclear. CONCLUSION Active pelvic movements on a Swiss ball during labour reduced the duration of labour, pain intensity, and maternal fatigue and anxiety; they also lowered the risk of caesarean section and vulvar swelling. Several effects exceeded the smallest worthwhile effect. REGISTRATION NCT04124835.
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Affiliation(s)
- Alexandre Delgado
- Instituto de Medicina Integral Prof. Fernando Figueira, Recife, Brazil.
| | - Melania M Amorim
- Instituto de Medicina Integral Prof. Fernando Figueira, Recife, Brazil; Medical Academic Unit, Federal University of Campina Grande, Campina Grande, Brazil
| | | | | | | | | | - Andrea Lemos
- Physical Therapy Department, Universidade Federal de Pernambuco, Recife, Brazil
| | - Leila Katz
- Instituto de Medicina Integral Prof. Fernando Figueira, Recife, Brazil
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Warrener A. The multifactor pelvis: An alternative to the adaptationist approach of the obstetrical dilemma. Evol Anthropol 2023; 32:260-274. [PMID: 37527355 DOI: 10.1002/evan.21997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 02/23/2023] [Accepted: 07/08/2023] [Indexed: 08/03/2023]
Abstract
The obstetrical dilemma describes the competing demands that a bipedally adapted pelvis and a large-brained neonate place on human childbirth and is the predominant model within which hypotheses about the evolution of the pelvis are framed. I argue the obstetrical dilemma follows the adaptationist program outlined by Gould and Lewontin in 1979 and should be replaced with a new model, the multifactor pelvis. This change will allow thorough consideration of nonadaptive explanations for the evolution of the human pelvis and avoid negative social impacts from considering human childbirth inherently dangerous. First, the atomization of the pelvis into discrete traits is discussed, after which current evidence for both adaptive and nonadaptive hypotheses is evaluated, including childbirth, locomotion, shared genetics with other traits under selection, evolutionary history, genetic drift, and environmental and epigenetic influences on the pelvis.
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Affiliation(s)
- Anna Warrener
- Department of Anthropology, University of Colorado Denver, Denver, Colorado, USA
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Crompton RH, Sellers W, Davids K, McClymont J. Biomechanics and the origins of human bipedal walking: The last 50 years. J Biomech 2023; 157:111701. [PMID: 37451208 DOI: 10.1016/j.jbiomech.2023.111701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 06/22/2023] [Accepted: 06/23/2023] [Indexed: 07/18/2023]
Abstract
Motion analysis, as applied to evolutionary biomechanics, has experienced its own evolution over the last 50 years. Here we review how an ever-increasing fossil record, together with continuing advancements in biomechanics techniques, have shaped our understanding of the origin of upright bipedal walking. The original, and long-established hypothesis held by Lamarck (1809), Darwin (1859) and Keith (1934), amongst others, maintained that bipedality originated in an arboreal context. However, the first field studies of gorilla and chimpanzees from the 1960's, highlighted their so-called 'knucklewalking' quadrupedalism, leading scientists to assume, semi-automatically, that knucklewalking must have been the precursor to bipedality. It would not be until the discovery of skeletons of early human relatives Australopithecus afarensis and Australopithecus prometheus, and the inclusion of methods of analysis from computer science, biomechanics, sports science and medicine, that the knucklewalking hypothesis would be most robustly challenged. Their short, but human-like lower limbs and human-like hand indicated that knucklewalking was not part of our ancestral locomotor repertoire. Rather, most current research in evolutionary biomechanics agrees it was a combination of climbing and bipedalism, both in an arboreal context, which facilitated upright, terrestrial, bipedal walking over short distances.
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Affiliation(s)
- Robin Huw Crompton
- Musculoskeletal and Ageing Science, The University of Liverpool, William Henry Duncan Building, West Derby Street, Liverpool L7 8TX, UK.
| | - William Sellers
- Earth and Environmental Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Keith Davids
- Sport and Physical Activity Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK
| | - Juliet McClymont
- Musculoskeletal and Ageing Science, The University of Liverpool, William Henry Duncan Building, West Derby Street, Liverpool L7 8TX, UK
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Grunstra NDS, Betti L, Fischer B, Haeusler M, Pavlicev M, Stansfield E, Trevathan W, Webb NM, Wells JCK, Rosenberg KR, Mitteroecker P. There is an obstetrical dilemma: Misconceptions about the evolution of human childbirth and pelvic form. AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY 2023; 181:535-544. [PMID: 37353889 PMCID: PMC10952510 DOI: 10.1002/ajpa.24802] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2023] [Revised: 05/27/2023] [Accepted: 06/11/2023] [Indexed: 06/25/2023]
Abstract
Compared to other primates, modern humans face high rates of maternal and neonatal morbidity and mortality during childbirth. Since the early 20th century, this "difficulty" of human parturition has prompted numerous evolutionary explanations, typically assuming antagonistic selective forces acting on maternal and fetal traits, which has been termed the "obstetrical dilemma." Recently, there has been a growing tendency among some anthropologists to question the difficulty of human childbirth and its evolutionary origin in an antagonistic selective regime. Partly, this stems from the motivation to combat increasing pathologization and overmedicalization of childbirth in industrialized countries. Some authors have argued that there is no obstetrical dilemma at all, and that the difficulty of childbirth mainly results from modern lifestyles and inappropriate and patriarchal obstetric practices. The failure of some studies to identify biomechanical and metabolic constraints on pelvic dimensions is sometimes interpreted as empirical support for discarding an obstetrical dilemma. Here we explain why these points are important but do not invalidate evolutionary explanations of human childbirth. We present robust empirical evidence and solid evolutionary theory supporting an obstetrical dilemma, yet one that is much more complex than originally conceived in the 20th century. We argue that evolutionary research does not hinder appropriate midwifery and obstetric care, nor does it promote negative views of female bodies. Understanding the evolutionary entanglement of biological and sociocultural factors underlying human childbirth can help us to understand individual variation in the risk factors of obstructed labor, and thus can contribute to more individualized maternal care.
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Affiliation(s)
- N. D. S. Grunstra
- Department of Evolutionary Biology, Unit for Theoretical BiologyUniversity of ViennaViennaAustria
- Mammal CollectionNatural History Museum ViennaViennaAustria
| | - L. Betti
- School of Life and Health SciencesUniversity of RoehamptonLondonUK
| | - B. Fischer
- Department of Evolutionary Biology, Unit for Theoretical BiologyUniversity of ViennaViennaAustria
| | - M. Haeusler
- Institute of Evolutionary MedicineUniversity of ZurichZurichSwitzerland
| | - M. Pavlicev
- Department of Evolutionary Biology, Unit for Theoretical BiologyUniversity of ViennaViennaAustria
| | - E. Stansfield
- Department of Evolutionary Biology, Unit for Theoretical BiologyUniversity of ViennaViennaAustria
| | - W. Trevathan
- School for Advanced ResearchSanta FeNew MexicoUSA
| | - N. M. Webb
- Institute of Evolutionary MedicineUniversity of ZurichZurichSwitzerland
- Institute of Archaeological Sciences, Senckenberg Centre for Human Evolution and PalaeoenvironmentEberhard‐Karls University of TübingenTübingenGermany
| | - J. C. K. Wells
- UCL Great Ormond Street Institute of Child Health, Population, Policy and Practice Research and Teaching ProgrammeChildhood Nutrition Research CentreLondonUK
| | - K. R. Rosenberg
- Department of AnthropologyUniversity of DelawareNewarkDelawareUSA
| | - P. Mitteroecker
- Department of Evolutionary Biology, Unit for Theoretical BiologyUniversity of ViennaViennaAustria
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Wiseman ALA. Three-dimensional volumetric muscle reconstruction of the Australopithecus afarensis pelvis and limb, with estimations of limb leverage. ROYAL SOCIETY OPEN SCIENCE 2023; 10:230356. [PMID: 37325588 PMCID: PMC10265029 DOI: 10.1098/rsos.230356] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 05/24/2023] [Indexed: 06/17/2023]
Abstract
To understand how an extinct species may have moved, we first need to reconstruct the missing soft tissues of the skeleton, which rarely preserve, with an understanding of segmental volume and muscular composition within the body. The Australopithecus afarensis specimen AL 288-1 is one of the most complete hominin skeletons. Despite 40+ years of research, the frequency and efficiency of bipedal movement in this specimen is still debated. Here, 36 muscles of the pelvis and lower limb were reconstructed using three-dimensional polygonal modelling, guided by imaging scan data and muscle scarring. Reconstructed muscle masses and configurations guided musculoskeletal modelling of the lower limb in comparison with a modern human. Results show that the moment arms of both species were comparable, hinting towards similar limb functionality. Moving forward, the polygonal muscle modelling approach has demonstrated promise for reconstructing the soft tissues of hominins and providing information on muscle configuration and space filling. This method demonstrates that volumetric reconstructions are required to know where space must be occupied by muscles and thus where lines of action might not be feasible due to interference with another muscle. This approach is effective for reconstructing muscle volumes in extinct hominins for which musculature is unknown.
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Kramer PA, Sylvester AD. Hip width and metabolic energy expenditure of abductor muscles. PLoS One 2023; 18:e0284450. [PMID: 37071649 PMCID: PMC10112780 DOI: 10.1371/journal.pone.0284450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 04/01/2023] [Indexed: 04/19/2023] Open
Abstract
Despite a paucity of physiological evidence, simplistic biomechanical analyses have led researchers to assume that humans who have wider hips use more energy to walk. Pitting biomechanical first principles against physiological data has led to little deepening of our understanding of bipedalism and its evolution. Both approaches, however, use proxies for the energy used by muscles. We decided to approach the question directly. Using a musculoskeletal model of the human body that estimates the metabolic energy expenditure of muscle activation for 48 people (23 women), 752 trials were evaluated. Metabolic energy consumption for the abductor muscles was summed over a stride to create total abductor energy expenditure. We calculated the maximum hip joint moment acting in the coronal plane and the functional distance between the hip joint centers. We hypothesize that wider hips would be correlated with both maximum coronal plane hip moment and increased total abductor energy expenditure when mass and velocity were controlled. Linear regressions with multiple independent variables, clustered by participant to control for the non-independence of the data points, were performed in Stata. We found that hip width does not predict total abductor energy expenditure, although mass and velocity combine to predict 61% of the variation (both p<0.001). Maximum hip joint coronal plane moment is predicted by pelvic width (p<0.001) and, in combination with mass and velocity (both p<0.001), explains 79% of the variation. Our results indicate that people use their morphology in ways that limit differences in energy expenditure. Consistent with recent discussion, intraspecific variation might not be useful to understand differences among species.
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Affiliation(s)
- Patricia Ann Kramer
- Department of Anthropology, University of Washington, Seattle, Washington, United States of America
| | - Adam D. Sylvester
- Center for Functional Anatomy and Evolution, The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
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10
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McPhee AM, Cheung TCK, Schmuckler MA. Dual-task interference as a function of varying motor and cognitive demands. Front Psychol 2022; 13:952245. [PMID: 36248521 PMCID: PMC9558828 DOI: 10.3389/fpsyg.2022.952245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 08/25/2022] [Indexed: 11/13/2022] Open
Abstract
Multitasking is a critical feature of our daily lives. Using a dual-task paradigm, this experiment explored adults’ abilities to simultaneously engage in everyday motor and cognitive activities, counting while walking, under conditions varying the difficulty of each of these tasks. Motor difficulty was manipulated by having participants walk forward versus backward, and cognitive difficulty was manipulated by having participants count forward versus backward, employing either a serial 2 s or serial 3 s task. All of these manipulations were performed in single-task conditions (walk only, count only) and dual-task conditions (walk and count simultaneously). Both motor performance variables (cycle time, stride length, walking velocity) and cognitive variables (counting fluency, counting accuracy) were assessed in these conditions. Analyses of single-task conditions revealed that both motor and cognitive manipulations predictably influenced performance. Analyses of dual-task performance revealed influences of motor and cognitive factors on both motor and cognitive performance. Most centrally, dual-task costs (normalized difference between single- and dual-task conditions) for motor variables revealed that such costs occurred primarily for temporal or spatiotemporal gait parameters (cycle time, walking velocity) and were driven by cognitive manipulations. Dual-task cost analyses for cognitive measures revealed negative dual-task costs, or dual-task benefits, for cognitive performance. Finally, the effects of dual-task manipulations were correlated for motor and cognitive measures, indicating dual-task performance as a significant individual difference variable. These findings are discussed with reference to theories of attentional allocation, as well as the possible role of auditory–motor entrainment in dual-task conditions.
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11
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Wiseman ALA, Demuth OE, Pomeroy E, De Groote I. Reconstructing Articular Cartilage in the Australopithecus afarensis Hip Joint and the Need for Modeling Six Degrees of Freedom. Integr Org Biol 2022; 4:obac031. [PMID: 36060864 PMCID: PMC9428927 DOI: 10.1093/iob/obac031] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 07/08/2022] [Accepted: 07/26/2022] [Indexed: 11/13/2022] Open
Abstract
The postcranial skeleton of Australopithecus afarensis (AL 288-1) exhibits clear adaptations for bipedality, although there is some debate as to the efficiency and frequency of such upright movement. Some researchers argue that AL 288-1 walked with an erect limb like modern humans do, whilst others advocate for a "bent-hip bent-knee" (BHBK) gait, although in recent years the general consensus favors erect bipedalism. To date, no quantitative method has addressed the articulation of the AL 288-1 hip joint, nor its range of motion (ROM) with consideration for joint spacing, used as a proxy for the thickness of the articular cartilage present within the joint spacing which can affect how a joint moves. Here, we employed ROM mapping methods to estimate the joint spacing of AL 288-1's hip joint in comparison to a modern human and chimpanzee. Nine simulations assessed different joint spacing and tested the range of joint congruency (i.e., ranging from a closely packed socket to loosely packed). We further evaluated the sphericity of the femoral head and whether three rotational degrees of freedom (DOFs) sufficiently captures the full ROM or if translational DOFs must be included. With both setups, we found that the AL 288-1 hip was unlikely to be highly congruent (as it is in modern humans) because this would severely restrict hip rotational movement and would severely limit the capability for both bipedality and even arboreal locomotion. Rather, the hip was more cartilaginous than it is in the modern humans, permitting the hip to rotate into positions necessitated by both terrestrial and arboreal movements. Rotational-only simulations found that AL 288-1 was unable to extend the hip like modern humans, forcing the specimen to employ a BHBK style of walking, thus contradicting 40+ years of previous research into the locomotory capabilities of AL 288-1. Therefore, we advocate that differences in the sphericity of the AL 288-1 femoral head with that of a modern human necessitates all six DOFs to be included in which AL 288-1 could osteologically extend the hip to facilitate a human-like gait.
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Affiliation(s)
- Ashleigh L A Wiseman
- McDonald Institute for Archaeological Research, University of Cambridge, Cambridge CB2 1TN
- Research Centre in Evolutionary Anthropology and Paleoecology, Liverpool John Moores University, Liverpool, Merseyside L3 5UX
| | - Oliver E Demuth
- Department of Earth Sciences, University of Cambridge, Cambridge CB2 1TN
- Structure and Motion Laboratory, Royal Veterinary College, London NW1 0TU
| | - Emma Pomeroy
- Department of Archaeology, University of Cambridge, Cambridge CB2 1TN
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Delgado A, Katz L, Melo RS, Amorim M, Lemos A. Effectiveness of the peanut ball use for women with epidural analgesia in labour: a systematic review and meta-analysis. J OBSTET GYNAECOL 2022; 42:726-733. [PMID: 34996318 DOI: 10.1080/01443615.2021.1997959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
This meta-analysis aimed to evaluate, using the best level of evidence, the possible benefits and advantages of using peanut ball (PB) in women with an epidural during labour on the maternal and neonatal outcomes. This research was conducted using MEDLINE/PubMed, Embase, LILACS, CINAHL, CENTRAL, PEDro, Web of Science and SCOPUS databases, with no period or language restrictions. The terms 'labor' and 'peanut ball' were used. Clinical trials (randomised and non-randomised) were included when comparing a group of parturients using PB with a control group under usual care. Randomised clinical trials (RCTs) or quasi-randomised were eligible for this systematic review. Two reviewers independently screened studies, extracted data and assessed the quality of evidence which was evaluated by the GRADE system. Quantitative analysis through meta-analysis was also applied whenever possible. In this updated review, we included four studies with a total of 818 women in labour after the use of pharmacological analgesia. Our GRADE ratings of evidence ranged from high to low quality. Overall, the included studies varied in their risk of bias, in which most were considered with some concerns. There is high evidence that the use of PB after epidural analgesia reduces the duration of the first period of labour by 87 minutes and moderate evidence that it increases the chance of vaginal delivery 11%. However, there is no evidence about other maternal and neonatal outcomes.Impact StatementWhat is already known on this subject? The peanut ball (PB) is used after the use of pharmacological analgesia, as it favours the opening of the pelvic canal and helps women to adopt more comfortable postures, but its real effects are not clear.What do the results of this study add? Our results suggest that using the PB reduces the duration of the first period of labour after an epidural and increases the chance of a vaginal birth.What are the implications of these findings for clinical practice and/or further research? These findings recommend the use of a PB after an epidural and further research with women without the use of pharmacological analgesia.
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Affiliation(s)
- Alexandre Delgado
- Post-Graduate Program on Integral Medicine, Instituto de Medicina Integral Prof. Fernando Figueira (IMIP), Recife, Brazil
| | - Leila Katz
- Post-Graduate Program on Integral Medicine, Instituto de Medicina Integral Prof. Fernando Figueira (IMIP), Recife, Brazil
| | - Renato S Melo
- Department of Physical Therapy, Universidade Federal de Pernambuco (UFPE), Recife, Brazil
| | - Melania Amorim
- Post-Graduate Program on Integral Medicine, Instituto de Medicina Integral Prof. Fernando Figueira (IMIP), Recife, Brazil
| | - Andrea Lemos
- Department of Physical Therapy, Universidade Federal de Pernambuco (UFPE), Recife, Brazil.,Post-Gratuate Program of Physical Therapy, Universidade Federal de Pernambuco (UFPE), Recife, Brazil
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Childbirth and Infant Care in Early Human Ancestors: What the Bones Tell Us. EVOLUTIONARY PSYCHOLOGY 2022. [DOI: 10.1007/978-3-030-76000-7_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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14
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Stansfield E, Fischer B, Grunstra NDS, Pouca MV, Mitteroecker P. The evolution of pelvic canal shape and rotational birth in humans. BMC Biol 2021; 19:224. [PMID: 34635119 PMCID: PMC8507337 DOI: 10.1186/s12915-021-01150-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 09/09/2021] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND The human foetus typically needs to rotate when passing through the tight birth canal because of the complex shape of the pelvis. In most women, the upper part, or inlet, of the birth canal has a round or mediolaterally oval shape, which is considered ideal for parturition, but it is unknown why the lower part of the birth canal has a pronounced anteroposteriorly oval shape. RESULTS Here, we show that the shape of the lower birth canal affects the ability of the pelvic floor to resist the pressure exerted by the abdominal organs and the foetus. Based on a series of finite element analyses, we found that the highest deformation, stress, and strain occur in pelvic floors with a circular or mediolaterally oval shape, whereas an anteroposterior elongation increases pelvic floor stability. CONCLUSIONS This suggests that the anteroposterior oval outlet shape is an evolutionary adaptation for pelvic floor support. For the pelvic inlet, by contrast, it has long been assumed that the mediolateral dimension is constrained by the efficiency of upright locomotion. But we argue that the mediolateral elongation has evolved because of the limits on the anteroposterior diameter imposed by upright posture. We show that an anteroposteriorly deeper inlet would require greater pelvic tilt and lumbar lordosis, which compromises spine health and the stability of upright posture. These different requirements of the pelvic inlet and outlet likely have led to the complex shape of the pelvic canal and to the evolution of rotational birth characteristic of humans.
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Affiliation(s)
- Ekaterina Stansfield
- Department of Evolutionary Biology, Unit for Theoretical Biology, University of Vienna, Djerassiplatz 1, 1030, Vienna, Austria.
| | - Barbara Fischer
- Department of Evolutionary Biology, Unit for Theoretical Biology, University of Vienna, Djerassiplatz 1, 1030, Vienna, Austria
| | - Nicole D S Grunstra
- Department of Evolutionary Biology, Unit for Theoretical Biology, University of Vienna, Djerassiplatz 1, 1030, Vienna, Austria
- Konrad Lorenz Institute for Evolution and Cognition Research, Martinstrasse 12, 3400, Klosterneuburg, Austria
- Mammal Collection, Natural History Museum Vienna, Burgring 7, 1010, Vienna, Austria
| | - Maria Villa Pouca
- Faculty of Engineering of University of Porto (FEUP), Rua Dr. Roberto Frias, s/n, 4200-465, Porto, Portugal
- Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI/LAETA), Rua Dr. Roberto Frias, 400, 4200-465, Porto, Portugal
| | - Philipp Mitteroecker
- Department of Evolutionary Biology, Unit for Theoretical Biology, University of Vienna, Djerassiplatz 1, 1030, Vienna, Austria.
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Haeusler M, Grunstra ND, Martin RD, Krenn VA, Fornai C, Webb NM. The obstetrical dilemma hypothesis: there's life in the old dog yet. Biol Rev Camb Philos Soc 2021; 96:2031-2057. [PMID: 34013651 PMCID: PMC8518115 DOI: 10.1111/brv.12744] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 05/06/2021] [Accepted: 05/10/2021] [Indexed: 12/17/2022]
Abstract
The term 'obstetrical dilemma' was coined by Washburn in 1960 to describe the trade-off between selection for a larger birth canal, permitting successful passage of a big-brained human neonate, and the smaller pelvic dimensions required for bipedal locomotion. His suggested solution to these antagonistic pressures was to give birth prematurely, explaining the unusual degree of neurological and physical immaturity, or secondary altriciality, observed in human infants. This proposed trade-off has traditionally been offered as the predominant evolutionary explanation for why human childbirth is so challenging, and inherently risky, compared to that of other primates. This perceived difficulty is likely due to the tight fit of fetal to maternal pelvic dimensions along with the convoluted shape of the birth canal and a comparatively low degree of ligamentous flexibility. Although the ideas combined under the obstetrical dilemma hypothesis originated almost a century ago, they have received renewed attention and empirical scrutiny in the last decade, with some researchers advocating complete rejection of the hypothesis and its assumptions. However, the hypothesis is complex because it presently captures several, mutually non-exclusive ideas: (i) there is an evolutionary trade-off resulting from opposing selection pressures on the pelvis; (ii) selection favouring a narrow pelvis specifically derives from bipedalism; (iii) human neonates are secondarily altricial because they are born relatively immature to ensure that they fit through the maternal bony pelvis; (iv) as a corollary to the asymmetric selection pressure for a spacious birth canal in females, humans evolved pronounced sexual dimorphism of pelvic shape. Recently, the hypothesis has been challenged on both empirical and theoretical grounds. Here, we appraise the original ideas captured under the 'obstetrical dilemma' and their subsequent evolution. We also evaluate complementary and alternative explanations for a tight fetopelvic fit and obstructed labour, including ecological factors related to nutrition and thermoregulation, constraints imposed by the stability of the pelvic floor or by maternal and fetal metabolism, the energetics of bipedalism, and variability in pelvic shape. This reveals that human childbirth is affected by a complex combination of evolutionary, ecological, and biocultural factors, which variably constrain maternal pelvic form and fetal growth. Our review demonstrates that it is unwarranted to reject the obstetrical dilemma hypothesis entirely because several of its fundamental assumptions have not been successfully discounted despite claims to the contrary. As such, the obstetrical dilemma remains a tenable hypothesis that can be used productively to guide evolutionary research.
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Affiliation(s)
- Martin Haeusler
- Institute of Evolutionary MedicineUniversity of ZurichWinterthurerstrasse 190Zürich8057Switzerland
| | - Nicole D.S. Grunstra
- Konrad Lorenz Institute (KLI) for Evolution and Cognition ResearchMartinstrasse 12Klosterneuburg3400Austria
- Department of Evolutionary BiologyUniversity of ViennaUniversity Biology Building (UBB), Carl Djerassi Platz 1Vienna1030Austria
- Mammal CollectionNatural History Museum ViennaBurgring 7Vienna1010Austria
| | - Robert D. Martin
- Institute of Evolutionary MedicineUniversity of ZurichWinterthurerstrasse 190Zürich8057Switzerland
- The Field Museum1400 S Lake Shore DrChicagoIL60605U.S.A.
| | - Viktoria A. Krenn
- Institute of Evolutionary MedicineUniversity of ZurichWinterthurerstrasse 190Zürich8057Switzerland
- Department of Evolutionary AnthropologyUniversity of ViennaUniversity Biology Building (UBB), Carl Djerassi Platz 1Vienna1030Austria
| | - Cinzia Fornai
- Institute of Evolutionary MedicineUniversity of ZurichWinterthurerstrasse 190Zürich8057Switzerland
- Department of Evolutionary AnthropologyUniversity of ViennaUniversity Biology Building (UBB), Carl Djerassi Platz 1Vienna1030Austria
| | - Nicole M. Webb
- Institute of Evolutionary MedicineUniversity of ZurichWinterthurerstrasse 190Zürich8057Switzerland
- Senckenberg Research Institute and Natural History Museum FrankfurtSenckenberganlage 25Frankfurt am Main60325Germany
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Vidal-Cordasco M, Rodríguez J, Prado-Nóvoa O, Zorrilla-Revilla G, Mateos A. Locomotor Economy and Foraging Ecology in Hominins. JOURNAL OF ANTHROPOLOGICAL RESEARCH 2021. [DOI: 10.1086/715402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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17
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Thompson NE, Rubinstein D, Parrella-O'Donnell W, Brett MA, Demes B, Larson SG, O'Neill MC. The loss of the 'pelvic step' in human evolution. J Exp Biol 2021; 224:271233. [PMID: 34412111 DOI: 10.1242/jeb.240440] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 07/06/2021] [Indexed: 12/12/2022]
Abstract
Human bipedalism entails relatively short strides compared with facultatively bipedal primates. Unique non-sagittal-plane motions associated with bipedalism may account for part of this discrepancy. Pelvic rotation anteriorly translates the hip, contributing to bipedal stride length (i.e. the 'pelvic step'). Facultative bipedalism in non-human primates entails much larger pelvic rotation than in humans, suggesting that a larger pelvic step may contribute to their relatively longer strides. We collected data on the pelvic step in bipedal chimpanzees and over a wide speed range of human walking. At matched dimensionless speeds, humans have 26.7% shorter dimensionless strides, and a pelvic step 5.4 times smaller than bipedal chimpanzees. Differences in pelvic rotation explain 31.8% of the difference in dimensionless stride length between the two species. We suggest that relative stride lengths and the pelvic step have been significantly reduced throughout the course of hominin evolution.
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Affiliation(s)
- Nathan E Thompson
- Department of Anatomy, NYIT College of Osteopathic Medicine, Old Westbury, NY 11568,USA
| | | | | | - Matthew A Brett
- NYIT College of Osteopathic Medicine, Old Westbury, NY 11568,USA
| | - Brigitte Demes
- Department of Anatomical Sciences, Stony Brook University, Stony Brook, NY 11794,USA
| | - Susan G Larson
- Department of Anatomical Sciences, Stony Brook University, Stony Brook, NY 11794,USA
| | - Matthew C O'Neill
- Department of Anatomy, Midwestern University, Glendale, AZ 85308,USA
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18
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Biomechanical trade-offs in the pelvic floor constrain the evolution of the human birth canal. Proc Natl Acad Sci U S A 2021; 118:2022159118. [PMID: 33853947 DOI: 10.1073/pnas.2022159118] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Compared with most other primates, humans are characterized by a tight fit between the maternal birth canal and the fetal head, leading to a relatively high risk of neonatal and maternal mortality and morbidities. Obstetric selection is thought to favor a spacious birth canal, whereas the source for opposing selection is frequently assumed to relate to bipedal locomotion. Another, yet underinvestigated, hypothesis is that a more expansive birth canal suspends the soft tissue of the pelvic floor across a larger area, which is disadvantageous for continence and support of the weight of the inner organs and fetus. To test this "pelvic floor hypothesis," we generated a finite element model of the human female pelvic floor and varied its radial size and thickness while keeping all else constant. This allowed us to study the effect of pelvic geometry on pelvic floor deflection (i.e., the amount of bending from the original position) and tissue stresses and stretches. Deflection grew disproportionately fast with increasing radial size, and stresses and stretches also increased. By contrast, an increase in thickness increased pelvic floor stiffness (i.e., the resistance to deformation), which reduced deflection but was unable to fully compensate for the effect of increasing radial size. Moreover, larger thicknesses increase the intra-abdominal pressure necessary for childbirth. Our results support the pelvic floor hypothesis and evince functional trade-offs affecting not only the size of the birth canal but also the thickness and stiffness of the pelvic floor.
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Bruening DA, Baird AR, Weaver KJ, Rasmussen AT. Whole body kinematic sex differences persist across non-dimensional gait speeds. PLoS One 2020; 15:e0237449. [PMID: 32817696 PMCID: PMC7440644 DOI: 10.1371/journal.pone.0237449] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Accepted: 07/27/2020] [Indexed: 11/19/2022] Open
Abstract
Sex differences in human locomotion are of interest in a broad variety of interdisciplinary applications. Although kinematic sex differences have been studied for many years, the underlying reasons behind several noted differences, such as pelvis and torso range of motion, are still not well understood. Walking speed and body size in particular represent confounding influences that hinder our ability to determine causal factors. The purpose of this study was to investigate sex differences in whole body gait kinematics across a range of controlled, non-dimensional walking and running speeds. We hypothesized that as task demand (i.e. gait speed) increased, the influences of modifiable factors would decrease, leading to a kinematic motion pattern convergence between sexes. Motion capture data from forty-eight healthy young adults (24 M, 24 F) wearing controlled footwear was captured at three walking and three running Froude speeds. Spatiotemporal metrics, center of mass displacement, and joint/segment ranges of motion were compared between sexes using 2x6 mixed-model ANOVAs. Three dimensional time-series waveforms were also used to describe the time-varying behavior of select joint angles. When controlling for size, sex differences in spatiotemporal metrics and center of mass displacement disappeared. However, contrary to our hypothesis, sagittal plane ankle, frontal plane pelvis, and transverse plane pelvis and torso range of motion all displayed sex differences that persisted or increased with gait speed. Overall, most spatiotemporal sex differences appear to be related to size and self-selection of gait speeds, while in contrast, sex differences in joint motion may be more inherent and ubiquitous than previously thought. Discussion on potential causal factors is presented.
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Affiliation(s)
- Dustin A. Bruening
- Exercise Sciences Department, Brigham Young University, Provo, Utah, United States of America
| | - Andrew R. Baird
- Mechanical Engineering Department, Brigham Young University, Provo, Utah, United States of America
| | - Kelsey J. Weaver
- Exercise Sciences Department, Brigham Young University, Provo, Utah, United States of America
| | - Austin T. Rasmussen
- Exercise Sciences Department, Brigham Young University, Provo, Utah, United States of America
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20
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Ricklan SJ, Decrausaz SL, Wells JCK, Stock JT. Obstetric dimensions of the female pelvis are less integrated than locomotor dimensions and show protective scaling patterns: Implications for the obstetrical dilemma. Am J Hum Biol 2020; 33:e23451. [PMID: 32567787 DOI: 10.1002/ajhb.23451] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 05/14/2020] [Accepted: 05/15/2020] [Indexed: 12/31/2022] Open
Abstract
OBJECTIVES The "obstetrical dilemma" hypothesis assumes that the modern human female pelvis serves two discrete functions: obstetrics and locomotion. We investigate whether these differing functions create observable patterns of morphological covariation and whether those patterns differ by height, weight, and age. This allows evaluation of evidence for canalization and phenotypic plasticity relevant to obstetric and locomotor function among a living female population. METHODS Landmarks (N = 86) were collected and inter-landmark distances were calculated (N = 36) on the pelvis and proximal femur of CT scans of living women aged 20 to 90 years (M = 93) receiving a routine CT scan. Partial least squares and relative SD of eigenvalues analyses were used to evaluate integration overall and within locomotor and obstetric modules, respectively. Ordinary Least Squared regression was used to evaluate scaling relationships between inter-landmark distances and height, weight, and age. RESULTS The obstetric pelvis was significantly less internally integrated than the locomotor pelvis. Many obstetric measurements were constrained in absolute terms relative to height; shorter women had relatively larger birth canal dimensions, and several key obstetric dimensions showed relative freedom from height. Lower weight women had some relatively larger obstetric and locomotor dimensions. Regarding age, younger women showed a few relatively larger outlet dimensions. CONCLUSIONS This study suggests that the obstetric pelvis and the locomotor pelvis function are morphologically distinct, with the obstetric pelvis showing relatively greater flexibility. These relationships between relative constraints support the hypothesis that the modern female pelvis shows evidence of both canalization and phenotypic plasticity in obstetric and locomotor structures.
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Affiliation(s)
- Sarah J Ricklan
- Department of Archaeology, University of Cambridge, Cambridge, UK.,New York University Grossman School of Medicine, New York, New York, USA
| | - Sarah-Louise Decrausaz
- Department of Archaeology, University of Cambridge, Cambridge, UK.,Department of Anthropology, University of Victoria, Victoria, British Columbia, Canada
| | - Jonathan C K Wells
- Childhood Nutrition Research Centre, Population, Policy, and Practice Research and Teaching Department, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Jay T Stock
- Department of Archaeology, University of Cambridge, Cambridge, UK.,Department of Anthropology, Western University, London, Ontario, Canada.,Department of Archaeology, Max Planck Centre for the Science of Human History, Jena, Germany
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21
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Pavličev M, Romero R, Mitteroecker P. Evolution of the human pelvis and obstructed labor: new explanations of an old obstetrical dilemma. Am J Obstet Gynecol 2020; 222:3-16. [PMID: 31251927 PMCID: PMC9069416 DOI: 10.1016/j.ajog.2019.06.043] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 06/17/2019] [Accepted: 06/19/2019] [Indexed: 12/18/2022]
Abstract
Without cesarean delivery, obstructed labor can result in maternal and fetal injuries or even death given a disproportion in size between the fetus and the maternal birth canal. The precise frequency of obstructed labor is difficult to estimate because of the widespread use of cesarean delivery for indications other than proven cephalopelvic disproportion, but it has been estimated that at least 1 million mothers per year are affected by this disorder worldwide. Why is the fit between the fetus and the maternal pelvis so tight? Why did evolution not lead to a greater safety margin, as in other primates? Here we review current research and suggest new hypotheses on the evolution of human childbirth and pelvic morphology. In 1960, Washburn suggested that this obstetrical dilemma arose because the human pelvis is an evolutionary compromise between two functions, bipedal gait and childbirth. However, recent biomechanical and kinematic studies indicate that pelvic width does not considerably affect the efficiency of bipedal gait and thus is unlikely to have constrained the evolution of a wider birth canal. Instead, bipedalism may have primarily constrained the flexibility of the pubic symphysis during pregnancy, which opens much wider in most mammals with large fetuses than in humans. We argue that the birth canal is mainly constrained by the trade-off between 2 pregnancy-related functions: while a narrow pelvis is disadvantageous for childbirth, it offers better support for the weight exerted by the viscera and the large human fetus during the long gestation period. We discuss the implications of this hypothesis for understanding pelvic floor dysfunction. Furthermore, we propose that selection for a narrow pelvis has also acted in males because of the role of pelvic floor musculature in erectile function. Finally, we review the cliff-edge model of obstetric selection to explain why evolution cannot completely eliminate cephalopelvic disproportion. This model also predicts that the regular application of life-saving cesarean delivery has evolutionarily increased rates of cephalopelvic disproportion already. We address how evolutionary models contribute to understanding and decision making in obstetrics and gynecology as well as in devising health care policies.
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Affiliation(s)
- Mihaela Pavličev
- Division of Human Genetics, Cincinnati Children`s Hospital Medical Center, Ann Arbor, MI; Department of Pediatrics, University of Cincinnati College of Medicine, Ann Arbor, MI; Department of Philosophy, University of Cincinnati, Ann Arbor, MI.
| | - Roberto Romero
- Perinatology Research Branch, Division of Obstetrics and Maternal-Fetal Medicine, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Ann Arbor, MI; Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI; Department of Epidemiology and Biostatistics, Michigan State University, East Lansing, MI; Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI; Detroit Medical Center, Detroit, MI; Department of Obstetrics and Gynecology, Florida International University, Miami, Florida
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22
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Grunstra NDS, Zachos FE, Herdina AN, Fischer B, Pavličev M, Mitteroecker P. Humans as inverted bats: A comparative approach to the obstetric conundrum. Am J Hum Biol 2019; 31:e23227. [PMID: 30810261 PMCID: PMC6492174 DOI: 10.1002/ajhb.23227] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2018] [Revised: 02/03/2019] [Accepted: 02/06/2019] [Indexed: 01/19/2023] Open
Abstract
OBJECTIVES The narrow human birth canal evolved in response to multiple opposing selective forces on the pelvis. These factors cannot be sufficiently disentangled in humans because of the limited range of relevant variation. Here, we outline a comparative strategy to study the evolution of human childbirth and to test existing hypotheses in primates and other mammals. METHODS We combined a literature review with comparative analyses of neonatal and female body and brain mass, using three existing datasets. We also present images of bony pelves of a diverse sample of taxa. RESULTS Bats, certain non-human primates, seals, and most ungulates, including whales, have much larger relative neonatal masses than humans, and they all differ in their anatomical adaptations for childbirth. Bats, as a group, are particularly interesting in this context as they give birth to the relatively largest neonates, and their pelvis is highly dimorphic: Whereas males have a fused symphysis, a ligament bridges a large pubic gap in females. The resulting strong demands on the widened and vulnerable pelvic floor likely are relaxed by roosting head-down. CONCLUSIONS Parturition has constituted a strong selective force in many non-human placentals. We illustrated how the demands on pelvic morphology resulting from locomotion, pelvic floor stability, childbirth, and perhaps also erectile function in males have been traded off differently in mammals, depending on their locomotion and environment. Exploiting the power of a comparative approach, we present new hypotheses and research directions for resolving the obstetric conundrum in humans.
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Affiliation(s)
- Nicole D. S. Grunstra
- Department of Theoretical BiologyUniversity of ViennaViennaAustria
- Mammal CollectionNatural History Museum ViennaViennaAustria
| | - Frank E. Zachos
- Mammal CollectionNatural History Museum ViennaViennaAustria
- Department of Integrative ZoologyUniversity of ViennaViennaAustria
| | | | - Barbara Fischer
- Konrad Lorenz Institute for Evolution and Cognition ResearchKlosterneuburgAustria
| | - Mihaela Pavličev
- Cincinnati Children's Hospital Medical CenterCincinnatiOhio
- Department of PediatricsUniversity of Cincinnati College of MedicineCincinnatiOhio
- Department of PhilosophyUniversity of CincinnatiCincinnatiOhio
| | - Philipp Mitteroecker
- Department of Theoretical BiologyUniversity of ViennaViennaAustria
- Konrad Lorenz Institute for Evolution and Cognition ResearchKlosterneuburgAustria
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DeSilva JM, Rosenberg KR. Anatomy, Development, and Function of the Human Pelvis. Anat Rec (Hoboken) 2017; 300:628-632. [PMID: 28297176 DOI: 10.1002/ar.23561] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 01/14/2017] [Indexed: 12/15/2022]
Abstract
The pelvis is an anatomically complex and functionally informative bone that contributes directly to both human locomotion and obstetrics. Because of the pelvis' important role in obstetrics, it is one of the most sexually dimorphic bony elements of the human body. The complex intersection of pelvic dimorphism, locomotion, and obstetrics has been reenergized by exciting new research, and many papers in this special issue of the pelvis help provide clarity on the relationship between pelvic form (especially female) and locomotor function. Compared to the pelvis of our ape relatives, the human pelvis is uniquely shaped; it is superoinferiorly short and stout, and mediolaterally wide-critical adaptations for bipedalism that are already present in some form very early in the history of the hominin lineage. In this issue, 13 original research papers address the anatomy, development, variation, and function of the modern human pelvis, with implications for understanding the selection pressures that shaped and continue to shape this bone. This rich collection of scholarship moves our understanding of the pelvis forward, while raising dozens of new questions that we hope will serve as inspiration for colleagues and students (both current and future) puzzled by this fascinatingly complex bone. Anat Rec, 300:628-632, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Jeremy M DeSilva
- Department of Anthropology, Dartmouth College, Hanover, New Hampshire, 03755
| | - Karen R Rosenberg
- Department of Anthropology, University of Delaware, Newark, Delaware, 19716
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24
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Vidal-Cordasco M, Mateos A, Zorrilla-Revilla G, Prado-Nóvoa O, Rodríguez J. Energetic cost of walking in fossil hominins. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2017; 164:609-622. [PMID: 28832938 DOI: 10.1002/ajpa.23301] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 01/15/2017] [Accepted: 08/05/2017] [Indexed: 01/24/2023]
Abstract
OBJECTIVE Many biomechanical studies consistently show that a broader pelvis increases the reaction forces and bending moments across the femoral shaft, increasing the energetic costs of unloaded locomotion. However, a biomechanical model does not provide the real amount of metabolic energy expended in walking. The aim of this study is to test the influence of pelvis breadth on locomotion cost and to evaluate the locomotion efficiency of extinct Pleistocene hominins. MATERIAL AND METHODS The current study measures in vivo the influence of pelvis width on the caloric cost of locomotion, integrating anthropometry, body composition and indirect calorimetry protocols in a sample of 46 subjects of both sexes. RESULTS We show that a broader false pelvis is substantially more efficient for locomotion than a narrower one and that the influence of false pelvis width on the energetic cost is similar to the influence of leg length. Two models integrating body mass, femur length and bi-iliac breadth are used to estimate the net and gross energetic costs of locomotion in a number of extinct hominins. The results presented here show that the locomotion of Homo was not energetically more efficient than that of Australopithecus and that the locomotion of extinct Homo species was not less efficient than that of modern Homo sapiens. DISCUSSION The changes in the anatomy of the pelvis and lower limb observed with the appearance of Homo ergaster probably did not fully offset the increased expenditure resulting from a larger body mass. Moreover, the narrow pelvis in modern humans does not contribute to greater efficiency of locomotion.
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Affiliation(s)
- M Vidal-Cordasco
- Paseo Sierra de Atapuerca, National Research Center on Human Evolution (CENIEH), 3, Burgos 09002, Spain
| | - A Mateos
- Paseo Sierra de Atapuerca, National Research Center on Human Evolution (CENIEH), 3, Burgos 09002, Spain
| | - G Zorrilla-Revilla
- Escuela Interuniversitaria de Posgrado en Evolucion Humana, Universidad de Burgos, Pza. Misael Bañuelos s/n, Burgos 09001, Spain
| | - O Prado-Nóvoa
- Paseo Sierra de Atapuerca, National Research Center on Human Evolution (CENIEH), 3, Burgos 09002, Spain
| | - J Rodríguez
- Paseo Sierra de Atapuerca, National Research Center on Human Evolution (CENIEH), 3, Burgos 09002, Spain
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