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Ilkka Heinonen, Jukka Kemppainen, Toshihiko Fujimoto, Juhani Knuuti and Kari K. Kalliokoski

-Czernik, 2012 ). Human bone marrow circulation responds to acute exercise ( Heinonen et al., 2013a , 2013b ) and local heat stress ( Heinonen et al., 2011a ), although to a lesser degree than in contracting skeletal muscles ( Heinonen et al., 2007 , 2010a , 2011b , 2015 ). In addition to its perfusion, the

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Maarten F. Bobbert, Han Houdijk, Jos J. de Koning and Gert de Groot

To gain a better understanding of push-off mechanics in speed skating, forward simulations were performed with a model comprising four body segments and six muscles. We started with a simulated maximum height one-legged jump, obtained by optimization of muscle stimulation time histories. The simulated jump was very similar to one-legged jumps produced by a human, indicating that the model was realistic. We subsequently studied how performance was affected by introducing four conditions characteristic of speed skating: (a) We changed the initial position from that in jumping to that at the start of the push-off phase in skating. This change was accommodated by a delay in stimulation onset of the plantar flexors in the optimal solution. (b) The friction between foot and ground was reduced to zero. As a result, maximum jump height decreased by 1.2 cm and performance became more sensitive to errors in muscle stimulation. The reason is that without surface friction, the foot had to be prevented from slipping away, which constrained the solution space and reduced the tolerance to errors in stimulation. (c) We introduced the requirement to maintain the upper body in a more or less horizontal position. This change could be accommodated by a delay in stimulation onset of the hamstrings, which inevitably caused a reduction in maximum jump height by 11.6 cm. (d) We increased the effective foot length from 16.5 cm, representative of jumping, to 20.5 cm, representative of skating with klapskates. At the 20.5-cm foot length, rotation of the foot did not start during the buildup of plantar flexion moment as it did at smaller foot lengths, but was delayed until hip and knee extension moments decreased. This caused an unbalanced increase in segment angular velocities and muscle shortening velocities, leading to a decrease in muscle force and muscle work and a further decrease in maximum jump height by approximately 5 cm. Qualitatively, these findings help clarify why and how performance of speed skaters depends on the location of the hinge of their skate.

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Daniel P. Ferris and Bryan R. Schlink

Robotic exoskeletons and bionic prostheses have moved from science fiction to science reality in the last decade. These robotic devices for assisting human movement are now technically feasible given recent advancements in robotic actuators, sensors, and computer processors. However, despite the ability to build robotic hardware that is wearable by humans, we still do not have optimal controllers to allow humans to move with coordination and grace in synergy with the robotic devices. We consider the history of robotic exoskeletons and bionic limb prostheses to provide a better assessment of the roadblocks that have been overcome and to gauge the roadblocks that still remain. There is a strong need for kinesiologists to work with engineers to better assess the performance of robotic movement assistance devices. In addition, the identification of new performance metrics that can objectively assess multiple dimensions of human performance with robotic exoskeletons and bionic prostheses would aid in moving the field forward. We discuss potential control approaches for these robotic devices, with a preference for incorporating feedforward neural signals from human users to provide a wider repertoire of discrete and adaptive rhythmic movements.

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Adrián Hernández-Vicente, Alejandro Santos-Lozano, Carmen Mayolas-Pi, Gabriel Rodríguez-Romo, Helios Pareja-Galeano, Natalia Bustamante, Eva M. Gómez-Trullén, Alejandro Lucia and Nuria Garatachea

The population of centenarians (≥100 years) is steadily increasing globally ( Byass, 2008 ) being the paradigm of human extreme longevity and healthy aging because they have postponed, if not avoided, major age-related diseases, for example, cancer, cardiovascular disease, or neurodegeneration

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Richard E.A. Van Emmerik, Michael T. Rosenstein, William J. McDermott and Joseph Hamill

Nonlinear dynamics and dynamical systems approaches and methodologies are increasingly being implemented in biomechanics and human movement research. Based on the early insights of Nicolai Bernstein (1967), a significantly different outlook on the movement control “problem” over the last few decades has emerged. From a focus on relatively simple movements has arisen a research focus with the primary goal to study movement in context, allowing the complexity of patterns to emerge. The approach taken is that the control of multiple degrees-of-freedom systems is not necessarily more difficult or complex than that of systems only comprising a few degrees of freedom. Complex patterns and dynamics might not require complex control structures. In this paper we present a tutorial overview of the mathematical underpinnings of nonlinear dynamics and some of its basic analysis tools. This should provide the reader with a basic level of understanding about the mathematical principles and concepts underlying pattern stability and change. This will be followed by an overview of dynamical systems approaches in the study of human movement. Finally, we discuss recent progress in the application of nonlinear dynamical techniques to the study of human locomotion, with particular focus on relative phase techniques for the assessment of coordination.

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Salomé Aubert, Joel D. Barnes, Nicolas Aguilar-Farias, Greet Cardon, Chen-Kang Chang, Christine Delisle Nyström, Yolanda Demetriou, Lowri Edwards, Arunas Emeljanovas, Aleš Gába, Wendy Y. Huang, Izzeldin A.E. Ibrahim, Jaak Jürimäe, Peter T. Katzmarzyk, Agata Korcz, Yeon Soo Kim, Eun-Young Lee, Marie Löf, Tom Loney, Shawnda A. Morrison, Jorge Mota, John J. Reilly, Blanca Roman-Viñas, Natasha Schranz, John Scriven, Jan Seghers, Thomas Skovgaard, Melody Smith, Martyn Standage, Gregor Starc, Gareth Stratton, Tim Takken, Tuija Tammelin, Chiaki Tanaka, David Thivel, Richard Tyler, Alun Williams, Stephen H.S. Wong, Paweł Zembura and Mark S. Tremblay

physical, mental, social, and cognitive health outcomes. 4 – 7 The Human Development Index (HDI) is a composite index, ranging from 0 to 1, calculated using education, life expectancy, and per capita income. 8 This index was created by the United Nations Development Programme to rank countries on a scale

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Michael J. Grey, Charles W. Pierce, Theodore E. Milner and Thomas Sinkjaer

The modulation and strength of the human soleus short latency stretch reflex was investigated by mechanically perturbing the ankle during an unconstrained pedaling task. Eight subjects pedaled at 60 rpm against a preload of 10 Nm. A torque pulse was applied to the crank at various positions during the crank cycle, producing ankle dorsiflexion perturbations of similar trajectory. The stretch reflex was greatest during the power phase of the crank cycle and was decreased to the level of background EMG during recovery. Matched perturbations were induced under static conditions at the same crank angle and background soleus EMG as recorded during the power phase of active pedaling. The magnitude of the stretch reflex during the dynamic condition was not statistically different from that during the static condition throughout the power phase of the movement. The results of this study indicate that the stretch reflex is not depressed during active cycling as has been shown with the H-reflex. This lack of depression may reflect a decreased susceptibility of the stretch reflex to inhibition, possibly originating from presynaptic mechanisms.

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Chester R. Kyle and Vincent j. Caiozzo

A comparison of six methods of measuring maximal human power output is given. The methods are as follows: the standard bicycle ergometer and modified bicycle ergometer (revised so that a standard racing bicycle and a higher applied torque could be used); a bicycle ridden on a treadmill; an unbraked flywheel bicycle ergometer; power using bicycle wind and rolling resistance measurements; running up stairs with weights; and running up a ramp with weights. Power output was. measured for time periods varying from less than 1 sec to 20 min. Power from the different methods agreed quite well. Example data are given for leg exercise, arm and leg exercise, and cycling in the prone, supine, and standard cycling positions.

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Nicole C. George, Charles Kahelin, Timothy A. Burkhart and David M. Andrews

Traditional rigid-link segment biomechanical models are unable to accurately represent the impact response of the musculoskeletal system of living humans because they lack separate wobbling mass (fat mass and lean mass) components, which have been shown to influence the magnitude of forces

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Shyh-Chour Huang

This paper presents a description of a general -purpose nonlinear model of the human body. The model is developed to simulate human response to high force and high acceleration as typically experienced in vehicle accidents. The model is composed of connected bodies of segments representing the torso and limbs of the human frame. Nonlinear springs and dampers are used at the connection joints to represent human anatomical characteristics and limits imposed by muscles, ligaments, and soft tissue. The governing dynamical equations are developed using Kane's equations (Kane <&: Levin-son, 1985) and multibody dynamics analysis procedures developed by Huston et al. (1974, 1975, 1978). These equations and procedures form the basis for the algorithms of a computer code. The equations are solved numerically using a fourth-order Runge-Kutta integrator. The results of several accident simulations are also presented.