{"title":"Evidence of invariant lower-limb kinematics in anticipation of ground contact during drop-landing and drop-jumping","authors":"Romain Bechet , Romain Tisserand , Laetitia Fradet , Floren Colloud","doi":"10.1016/j.humov.2024.103297","DOIUrl":null,"url":null,"abstract":"<div><div>Gravity is a ubiquitous external force that must be considered when producing coordinated movements. Drop-landing is a popular task to study how humans cope with gravity, because anticipatory muscle activations can be released before the estimated ground contact. But the consequences of these anticipatory muscle activations have only been interpreted in terms of stiffening the lower-limbs in preparation for ground contact, without considering potential anticipatory kinematic consequences. The objective of this study is to quantify the kinematic consequences of anticipatory muscle activations in two different landing tasks, to clarify whether anticipatory muscle activations are adapted to cope with gravity, to the dynamic constraints of the movement to perform, or both.</div><div>Twenty young athletes performed drop-landing and drop-jumping from a 35 cm elevated platform. Sagittal angles and angular velocities of the hip, knee, and ankle joints, and acceleration of the foot were computed, as well as the onset of joint flexions and onset of foot vertical acceleration change.</div><div>We found the same pattern of anticipatory hip and knee flexion, both starting <em>before</em> ground contact in all participants and in both tasks. We found no anticipatory kinematics for the ankle joint. Consecutive to the hip and knee flexion, the foot accelerated upwards before ground contact.</div><div>Our results show that anticipatory muscle activations used by humans have systematic and invariant kinematic consequences during the air-time phase to cope with gravity: they initiate the hip and knee joints flexion <em>before</em> ground contact. This strategy likely limits the amount of ground reaction forces developed to oppose the gravity external force, and completes the stiffening role already described in the literature. These two complementary consequences —rotation and stiffening— seem to serve the same purpose of protecting the skeletal system. Since gravity is ubiquitous, these automated movements must be considered in other movements involving landing phases, such as heel strikes during gait.</div></div>","PeriodicalId":55046,"journal":{"name":"Human Movement Science","volume":null,"pages":null},"PeriodicalIF":1.6000,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Human Movement Science","FirstCategoryId":"102","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0167945724001222","RegionNum":3,"RegionCategory":"心理学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"NEUROSCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
Gravity is a ubiquitous external force that must be considered when producing coordinated movements. Drop-landing is a popular task to study how humans cope with gravity, because anticipatory muscle activations can be released before the estimated ground contact. But the consequences of these anticipatory muscle activations have only been interpreted in terms of stiffening the lower-limbs in preparation for ground contact, without considering potential anticipatory kinematic consequences. The objective of this study is to quantify the kinematic consequences of anticipatory muscle activations in two different landing tasks, to clarify whether anticipatory muscle activations are adapted to cope with gravity, to the dynamic constraints of the movement to perform, or both.
Twenty young athletes performed drop-landing and drop-jumping from a 35 cm elevated platform. Sagittal angles and angular velocities of the hip, knee, and ankle joints, and acceleration of the foot were computed, as well as the onset of joint flexions and onset of foot vertical acceleration change.
We found the same pattern of anticipatory hip and knee flexion, both starting before ground contact in all participants and in both tasks. We found no anticipatory kinematics for the ankle joint. Consecutive to the hip and knee flexion, the foot accelerated upwards before ground contact.
Our results show that anticipatory muscle activations used by humans have systematic and invariant kinematic consequences during the air-time phase to cope with gravity: they initiate the hip and knee joints flexion before ground contact. This strategy likely limits the amount of ground reaction forces developed to oppose the gravity external force, and completes the stiffening role already described in the literature. These two complementary consequences —rotation and stiffening— seem to serve the same purpose of protecting the skeletal system. Since gravity is ubiquitous, these automated movements must be considered in other movements involving landing phases, such as heel strikes during gait.
期刊介绍:
Human Movement Science provides a medium for publishing disciplinary and multidisciplinary studies on human movement. It brings together psychological, biomechanical and neurophysiological research on the control, organization and learning of human movement, including the perceptual support of movement. The overarching goal of the journal is to publish articles that help advance theoretical understanding of the control and organization of human movement, as well as changes therein as a function of development, learning and rehabilitation. The nature of the research reported may vary from fundamental theoretical or empirical studies to more applied studies in the fields of, for example, sport, dance and rehabilitation with the proviso that all studies have a distinct theoretical bearing. Also, reviews and meta-studies advancing the understanding of human movement are welcome.
These aims and scope imply that purely descriptive studies are not acceptable, while methodological articles are only acceptable if the methodology in question opens up new vistas in understanding the control and organization of human movement. The same holds for articles on exercise physiology, which in general are not supported, unless they speak to the control and organization of human movement. In general, it is required that the theoretical message of articles published in Human Movement Science is, to a certain extent, innovative and not dismissible as just "more of the same."