-0450 , an author affiliation was not complete. Pedro Bezerra is also with the Research Center in Sports Sciences, Health Sciences and Human Development, CIDESD, Vila Real, Portugal. The online version of this article has been corrected.
Elizabeth J. Durden-Myers, Margaret E. Whitehead, and Niek Pot
nurturing human flourishing. Therefore, the aim of this paper is to discuss the relationship between physical literacy and human flourishing in detail, unveiling what value this connection may hold in promoting physical literacy as an element integral in achieving a full and flourishing life. Human
Samantha L. Winter and John H. Challis
For a physiologically realistic joint range of motion and therefore range of muscle fiber lengths, only part of the whole muscle force-length curve can be used in vivo; that is, only a section of the force-length curve is expressed. Previous work has determined that the expressed section of the force-length curve for individual muscles can vary between subjects; however, the degree of intersubject variability is different for different muscles. This study determined the expressed section of both the rectus femoris and gastrocnemius—muscles with very different ratios of tendon slack length to muscle fiber optimum length—for 28 nonspecifically trained subjects to test the hypothesis that the value of this ratio affects the amount of variability in the expressed section. The force-length curves of the two muscles were reconstructed from moment-angle data using the method of Herzog & ter Keurs (1988). There was no relationship between the expressed sections of the force-length curve for the two muscles. Less variability was found in the expressed section of the gastrocnemius compared with the rectus femoris, supporting the hypothesis. The lack of relationship between the expressed sections of the two muscles has implications for motor control and for training muscle for rehabilitation.
Kristen E. Thomas and Leah R. Bent
The integration of vestibular and somatosensory information for the control of lower limb musculature remains elusive. To determine whether a subthreshold vestibular input influences the cutaneous evoked response, the isometric EMG activity in the posturally inactive soleus muscles of 13 healthy, seated subjects was collected. Vestibular afferents were activated using galvanic vestibular stimulation (GVS; 1.8–2.5mA, 500ms), while percutaneous electrical stimulation was delivered to the distal tibial nerve (11ms train of 3 × 1.0 ms pulses, 200Hz) to activate foot sole skin afferents. GVS elicited responses in soleus both independently and when combined with cutaneous stimulation. The responses to the combined sensory input showed an interaction between the two sensory modalities to influence muscle activation. Of note is the presence of significant muscle modulation in the combined condition, where subthreshold vestibular inputs altered the outcome of the cutaneous reflex response. This finding has implications for individuals with sensory deficiency. In the case of an absent or deficient sensory modality, balance protective reflexes to maintain postural equilibrium may be enhanced with targeted sensory augmentation.
Thomas Haugen, Gøran Paulsen, Stephen Seiler, and Øyvind Sandbakk
Higher, faster, stronger: what are the upper limits of human performance? In a published study from January 2008, Berthelot et al 1 estimated that world records had reached 99% of its asymptotic values and that human upper performance limits in sport would be reached within 1 generation. Only
Marc Monsour, Tanya D. Ivanova, Tim D. Wilson, and S. Jayne Garland
The purpose of this study was to investigate whether application of bipolar galvanic vestibular stimulation (GVS) would influence the common modulation of motor unit discharge rate in bilateral soleus muscles during quiet standing. Soleus motor unit activity was recorded with fine wire electrodes in each leg. Subjects stood, with eyes closed, on two adjacent force platforms to record postural sway with the head facing straight ahead, turned to right, or turned left. Subjects also swayed voluntarily without GVS to the same position as evoked during the GVS. There was no difference in the common drive to bilateral soleus motoneurons during quiet standing and voluntary sway tasks. Common drive was significantly lower during right cathode GVS with the head straight or turned to the right. These results demonstrate that manipulation of vestibular afferent input influences the common modulation of bilateral soleus motor unit pairs during quiet standing.
Christopher M. McLeod and Calvin Nite
currently unable to account for markets depending on exceptional human performance, like sport markets. Therefore, a theory is needed that can account for human capital ecosystems . In a human capital ecosystem, actors are responsible for investing in and capturing returns from human capital. The purpose
of society and even in some corners of the scientific enterprise. But negating or ignoring the underlying biology of human variability does not make it disappear. Human Genomics The exciting field of genomics burst on the scene around 1990 when the Human Genome Project was launched. Spectacular
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.
Neil Chapman, John Whitting, Suzanne Broadbent, Zachary Crowley-McHattan, and Rudi Meir
electrically stimulated in vivo human muscle. 23 However, it is important to note an apparent disparity in magnitude of RFE between electrically stimulated and voluntarily activated contractions. In fact, the magnitude of RFE has been found to vary greatly in vivo voluntarily contracted human muscle. 23