Control of blood pressure in the cold: differentiation of skin and skeletal muscle vascular resistance.

NEW FINDINGS: What is the central question of this study? Why does blood pressure increases during cold air exposure? Specifically, what is the contribution of skin and skeletal muscle vascular resistance during whole body versus isolated face cooling? What is the main finding and its importance? Whole-body cooling caused an increase in blood pressure through an increase in skeletal muscle and cutaneous vascular resistance. However, isolated mild face cooling caused an increase in blood pressure predominately via an increase in cutaneous vasoconstriction. ABSTRACT: The primary aim of this investigation was to determine the individual contribution of the cutaneous and skeletal muscle circulations to the cold-induced pressor response. To address this, we examined local vascular resistances in the cutaneous and skeletal muscle of the arm and leg. Thirty-four healthy individuals underwent three different protocols, whereby cold air to clamp skin temperature (27°C) was passed over (1) the whole-body, (2) the whole-body, but with the forearm pre-cooled to clamp cutaneous vascular resistance, and (3) the face. Cold exposure applied to the whole body or isolated to the face increased mean arterial pressure (all, P < 0.001) and total peripheral resistance (all, P < 0.047) compared to thermal neutral baseline. Whole-body cooling increased femoral (P < 0.005) and brachial artery resistance (P < 0.003) compared to thermoneutral baseline. Moreover, when the forearm was pre-cooled to remove the contribution of cutaneous resistance (P = 0.991), there was a further increase in lower arm vasoconstriction (P = 0.036) when whole-body cooling was superimposed. Face cooling also caused a reflex increase in lower arm cutaneous (P = 0.009) and brachial resistance (P = 0.050), yet there was no change in femoral resistance (P = 0.815) despite a reflex increase in leg cutaneous resistance (P = 0.010). Cold stress causes an increase in blood pressure through a change in total peripheral resistance that is largely due to cutaneous vasoconstriction with face cooling, but there is additional vasoconstriction in the skeletal muscle vasculature with whole-body cooling.

Implications of Optimal Feedback Control Theory for Sport Coaching and Motor Learning: A Systematic Review.

Best practice in skill acquisition has been informed by motor control theories. The main aim of this study is to screen existing literature on a relatively novel theory, Optimal Feedback Control Theory (OFCT), and to assess how OFCT concepts can be applied in sports and motor learning research. Based on 51 included studies with on average a high methodological quality, we found that different types of training seem to appeal to different control processes within OFCT. The minimum intervention principle (founded in OFCT) was used in many of the reviewed studies, and further investigation might lead to further improvements in sport skill acquisition. However, considering the homogenous nature of the tasks included in the reviewed studies, these ideas and their generalizability should be tested in future studies.

Sex-Specific Hip Movement Is Correlated With Pelvis and Upper Body Rotation During Running.

There is a sex bias for common overuse running injuries that are associated with sex-specific hip kinematics. Gait retraining programs aimed at altering hip kinematics may be more efficient if they incorporated an understanding of how hip kinematics are correlated with the movement of the remaining body segments. We applied a principal component analysis to structure the whole-body running kinematics of 23 runners (12 ♀) into k = 12 principal movements (PMk), describing correlated patterns of upper and lower body movements. We compared the time-dependent movement amplitudes with respect to each PMk between males and females using a waveform analysis and interpreted our findings according to stick figure animations. The movement amplitudes of two PMs (PM6 and PM8) showed statistically significant effects of "sex," which were independent of running speed. According to PM8, females showed more hip adduction, which correlated with increased transverse rotation of the pelvis and upper body compared to men. We propose that increased hip adduction and upper body rotation in female runners may be a strategy to compensate for a less efficient arm and upper body swing compared to men. Gait interventions aimed at reducing hip adduction and running-related injuries in female runners should consider instructions for both upper and lower body to maximize training efficacy.

Shoot flammability of vascular plants is phylogenetically conserved and related to habitat fire-proneness and growth form.

Terrestrial plants and fire have interacted for at least 420 million years1. Whether recurrent fire drives plants to evolve higher flammability and what the evolutionary pattern of plant flammability is remain unclear2-7. Here, we show that phylogeny, the susceptibility of a habitat to have recurrent fires (that is, fire-proneness) and growth form are important predictors of the shoot flammability of 194 indigenous and introduced vascular plant species (Tracheophyta) from New Zealand. The phylogenetic signal of the flammability components and the variation in flammability among phylogenetic groups (families and higher taxonomic level clades) demonstrate that shoot flammability is phylogenetically conserved. Some closely related species, such as in Dracophyllum (Ericaceae), vary in flammability, indicating that flammability exhibits evolutionary flexibility. Species in fire-prone ecosystems tend to be more flammable than species from non-fire-prone ecosystems, suggesting that fire may have an important role in the evolution of plant flammability. Growth form also influenced flammability-forbs were less flammable than grasses, trees and shrubs; by contrast, grasses had higher biomass consumption by fire than other groups. The results show that shoot flammability of plants is largely correlated with phylogenetic relatedness, and high flammability may result in parallel evolution driven by environmental factors, such as fire regime.