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Impulse and momentum
Published in Paul Grimshaw, Michael Cole, Adrian Burden, Neil Fowler, Instant Notes in Sport and Exercise Biomechanics, 2019
In order to have achieved this action and jump into the air you will have applied a force to the ground for a period of time (contact with the ground). The ground reaction force (i.e. from the ground and acting on the person) would be the force that is used to determine the amount of impulse that is acting on the body (impulse = force × time). This impulse would provide a change in momentum (because the two are related by Ft = mv2 – mv1). Now, since your mass is constant throughout this activity, this change in momentum will result in a change in velocity. The greater the impulse (the more positive the net result) the greater will be the change in velocity. Since at the beginning of the jump you are not moving (zero velocity – stationary) the more net vertical impulse you can generate the greater will be the take-off velocity in a vertical direction (important since we are considering the vertical impulse generated). The more vertical take-off velocity you have, the higher you will jump, although, as we know, gravity, which is acting throughout this whole activity, will begin to slow you down at a constant rate as soon as you take off. However, if you have more vertical velocity to begin with, it will take longer for gravity to slow you down at this constant rate and hence you will jump higher.
The Effect of Backpack Load and Gait Speed on Plantar Forces During Treadmill Walking
Published in Youlian Hong, Routledge Handbook of Ergonomics in Sport and Exercise, 2013
Maintaining equilibrium during walking is a challenging task due to a number of factors including the small support area and the high centre of mass location. Several studies show that impact forces associated with walking were responsible for the load distributions of the musculoskeletal system (Fraysse et al., 2009; Wehner et al., 2009). Only currently has dynamic analysis of impact force at the foot-ground interface been possible during walking. Plantar pressure and force measurements provide information about loading to skeletal regions and lower extremities (Chesnin et al., 2000; Han et al., 1999). Evidence suggests that the vertical ground reaction force is dependent on the external factors such as gait speed, carrying weight, shoes and surface involved. Since force-generating activities have positive effects on adaptive skeletal responses, the relationships among gait speed and carrying load with the vertical ground reaction force are important for understanding osteogenic effects on walking (Kai et al., 2003).
Kinetics in Linear Motion
Published in Emeric Arus, Biomechanics of Human Motion, 2017
The ground reaction force is a resultant reaction force equal and opposite to the applied force on the supporting surface. The net force is a vector sum of all forces acting at a joint. The net force acting on a static body is zero. Normal (reaction) force is a component of a force that is acting perpendicular to the surface and the direction is always directed upwards. The opposing force is usually the weight of the body.
Individual muscle contributions to hip joint-contact forces during walking in unilateral transfemoral amputees with osseointegrated prostheses
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2020
Vahidreza Jafari Harandi, David Charles Ackland, Raneem Haddara, L. Eduardo Cofré Lizama, Mark Graf, Mary Pauline Galea, Peter Vee Sin Lee
All subjects performed three complete trials of over-ground walking in an 8-m walkway. They were given a 30-s rest between each trial. The three-dimensional positions of retro-reflective markers placed on each subject were recorded using an eight-camera motion capture system (Vicon, Oxford Metrics) sampling at 200 Hz while subjects walked at their preferred speed. Markers were placed using a modified marker set previously published (Dorn 2011). During testing, three AMTI force platforms embedded in the floor (Watertown MA, USA) were used to measure ground reaction force at a sample rate of 1000 Hz. Surface electromyography (EMG) was simultaneously recorded at a sample rate of 1000 Hz (Cometa, Milan, Italy) on intact limb muscles that included gluteus maximus (GMAX), gluteus medius (GMED), soleus (SOL), gastrocnemius (GAS) and vasti (VAS) and residual leg muscles GMAX and GMED following a previously published procedure (Hermens et al. 1999, 2000; Wentink et al. 2013) (see Supporting Information). Marker trajectories and ground reaction force data were low-pass filtered using a fourth-order Butterworth filter with a cut-off frequency of 4 Hz and 60 Hz, respectively. EMG offset signals were removed, rectified and low-pass filtered at 10 Hz using a second-order Butterworth filter to create linear envelopes (Schache et al. 2018; Harandi et al. 2020).
Validation of a wireless shoe insole for ground reaction force measurement
Published in Journal of Sports Sciences, 2019
Geoffrey T. Burns, Jessica Deneweth Zendler, Ronald F. Zernicke
The ground reaction force (GRF) during locomotion is a foundational component of biomechanical analyses and is critical to understanding an individual’s gait patterns both in health and injury (Inman and Eberhardt, 1953). The dynamic nature of these plantar forces can provide insights into the nature of gait pathologies (McCrory, White, & Lifeso, 2001; Muniz & Nadal, 2009; Zadpoor & Nikooyan, 2011) and sport performance alike (Cavanagh et al., 1980; Gottschall & Kram, 2005; Keller et al., 1996), yet the ability to measure them is limited (Kluitenberg, Bredeweg, Zijlstra, Zijlstra, & Buist, 2012). The gold standard for GRF measurement is a force-sensing platform, and though they are high in accuracy and precision, these platforms are limited to capturing single steps in stationary locations (Kluitenberg et al., 2012). Instrumented treadmills (Reed, Urry, & Wearing, 2013; Van Alsenoy, Thomson, & Burnett, 2016) and wired insoles (Fong et al., 2008; Hughes, Pratt, Linge, Clark, & Klenerman, 1991; Hurkmans, Bussmann, Benda, Verhaar & Stam, 2006a) have also been developed and have gained popularity among researchers to measure this force continuously over longer periods of activity. However, these methods limit the investigation to the laboratory, which may not fully capture the native mechanics of the activity being studied and could serve as a logistical deterrent for data collection on participants. Furthermore, these challenges inhibit wider clinical use of GRFs in assessing and monitoring patients with gait pathologies. Liberation of GRF recordings from the laboratory could provide more comprehensive and representative measurements to facilitate a better understanding of environment and activity-specific gait characteristics.
Perception of impact is affected by stimulus intensity
Published in Sports Biomechanics, 2021
Ana Paula Silva Azevedo, Katia Brandina, Juliana Pennone, Alberto Carlos Amadio, Júlio Cerca Serrão
Perception of physiological load (e.g., exertion and exhaustion) is well known and established in literature as a reliable tool to identify the effort during exercise and to modulate its intensity (Hackett, Johnson, Halaki, & Chow, 2012; Iellamo et al., 2014; Impellizzeri, Rampinini, & Marcora, 2005; Lagally, Robertson, Gallagher, Gearhart, & Goss, 2002; Lupo, Capranica, & Tessitore, 2014). On the other hand, the perception of external loads may be a central topic to understand the strategies adopted by human body to adapt to the mechanical demands during locomotion movements (Bastiaanse, Duysens, & Dietz, 2000; Chu, Hornby, & Schmit, 2015; Dietz & Duysens, 2000; Duysens, Clarac, & Cruse, 2000; Fiolkowski, Bishop, Brunt, & Williams, 2005; Gaudino et al., 2015; Lieberman et al., 2010; Lovell, Sirotic, Impellizzeri, & Coutts, 2013; Nurse & Nigg, 2001). Repetitive external loads are imposed to the human body during locomotion, due to its interaction with the environment. The Ground Reaction Force (GRF) is a relevant indicator of this external force and mechanical effort imposed during locomotion tasks, and has been considered the main representative and most adequate measure of the impact received by lower-extremity musculoskeletal system (Milner, Ferber, Pollard, Hamill, & Davis, 2006; Zadpoor & Nikooyan, 2011). Additionally, excessive impact has been reported as a possible cause of injury during sport activities (Gabbett, 2004; Hewett et al., 2005; Milner et al., 2006; Tonoli, Cumps, Aerts, Verhagen, & Meeusen, 2010; van Gent et al., 2007; Videbaek, Bueno, Nielsen, & Rasmussen, 2015). The ability to attenuate this external load as a strategy to control mechanical efforts depends on varied and complex mechanisms, including to perceive this impact force (Bastiaanse et al., 2000; Chu et al., 2015; Dietz & Duysens, 2000; Duysens et al., 2000).