scholarly journals Spatiotemporal inflection points in human running: Effects of training level and athletic modality

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0258709
Author(s):  
Yuta Goto ◽  
Tetsuya Ogawa ◽  
Gaku Kakehata ◽  
Naoya Sazuka ◽  
Atsushi Okubo ◽  
...  

The effect of the different training regimes and histories on the spatiotemporal characteristics of human running was evaluated in four groups of subjects who had different histories of engagement in running-specific training; sprinters, distance runners, active athletes, and sedentary individuals. Subjects ran at a variety of velocities, ranging from slowest to fastest, over 30 trials in a random order. Group averages of maximal running velocities, ranked from fastest to slowest, were: sprinters, distance runners, active athletes, and sedentary individuals. The velocity-cadence-step length (V-C-S) relationship, made by plotting step length against cadence at each velocity tested, was analyzed with the segmented regression method, utilizing two regression lines. In all subject groups, there was a critical velocity, defined as the inflection point, in the relationship. In the velocity ranges below and above the inflection point (slower and faster velocity ranges), velocity was modulated primarily by altering step length and by altering cadence, respectively. This pattern was commonly observed in all four groups, not only in sprinters and distance runners, as has already been reported, but also in active athletes and sedentary individuals. This pattern may reflect an energy saving strategy. When the data from all groups were combined, there were significant correlations between maximal running velocity and both running velocity and step length at the inflection point. In spite of the wide variety of athletic experience of the subjects, as well as their maximum running velocities, the inflection point appeared at a similar cadence (3.0 ± 0.2 steps/s) and at a similar relative velocity (65–70%Vmax). These results imply that the influence of running-specific training on the inflection point is minimal.

2021 ◽  
Vol 12 ◽  
Author(s):  
Zhiyan Chen ◽  
Duoduo Zhang ◽  
Zhengyi Sun ◽  
Qi Yu

We aimed to investigate the relationship between testosterone (T) levels and pregnancy outcomes in patients with tubal or male infertility at different times during in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) cycles. Patients with tubal or male infertility and normal androgen levels undergoing IVF/ICSI were consecutively recruited. We performed a longitudinal analysis of T levels at three time points (i.e., T0: baseline, T1: trigger day, and T2: day after the trigger day) in three groups with different pregnancy outcomes (i.e., group 1: no pregnancy; group 2: clinical pregnancy but no live birth; and group 3: live birth) as repeated measurement data using linear mixed-effects models. We also plotted fitted curves depicting the relationship between T levels and a number of oocytes retrieved at different time points and identified the inflection points of the curves. In total, 3,012 patients were recruited. Groups 1 and 3 had improvements in T levels at the three time points. After refitting, the slope in group 3 was significantly higher than that in group 1 (P = 0.000). Curves that reflected the association between T levels and numbers of retrieved oocytes presented an upward trend before a certain inflection point, after which the curves had no obvious changes or fell with increasing T levels. The inflection points for T0, T1, and T2 were calculated as 0.45, 0.94, and 1.09, respectively. A faster upward trend in T levels might be associated with better pregnancy outcomes. Within a range lower than a T level inflection point, more oocytes and embryos could be obtained with increasing T levels.


2017 ◽  
Vol 13 (2) ◽  
pp. 73
Author(s):  
Ridwan Pandiya ◽  
Ismail Bin Mohd

For long periods of time, mathematics researchers struggled in obtaining the appropriate starting point when implementing root finding methods, and one of the most famous and applicable is Newton’s method. This iterative method produces sequence that converges to a desired solution with the assumption that the starting point is close enough to a solution. The word “close enough” indicates that we actually do not have any idea how close the initial point needed so that this point can bring into a convergent iteration. This paper comes to answer that question through analyzing the relationship between inflection points of one-dimensional non-linear function with the convergence of Newton’s method. Our purpose is to illustrate that the neighborhood of an inflection point of a function never fails to bring the Newton’s method convergent to a desired solution


2017 ◽  
Vol 13 (2) ◽  
pp. 73
Author(s):  
Ridwan Pandiya ◽  
Ismail Bin Mohd

For long periods of time, mathematics researchers struggled in obtaining the appropriate starting point when implementing root finding methods, and one of the most famous and applicable is Newton’s method. This iterative method produces sequence that converges to a desired solution with the assumption that the starting point is close enough to a solution. The word “close enough” indicates that we actually do not have any idea how close the initial point needed so that this point can bring into a convergent iteration. This paper comes to answer that question through analyzing the relationship between inflection points of one-dimensional non-linear function with the convergence of Newton’s method. Our purpose is to illustrate that the neighborhood of an inflection point of a function never fails to bring the Newton’s method convergent to a desired solution


2020 ◽  
Vol 60 (2) ◽  
pp. 252-262
Author(s):  
Benhammou Saddek ◽  
Jérémy B.J. Coquart ◽  
Laurent Mourot ◽  
Belkadi Adel ◽  
Mokkedes Moulay Idriss ◽  
...  

SummaryThe aims of this study were (a): to compare maximal physiological responses (maximal heart rate: HRmax and blood lactate concentration: [La-]) and maximal aerobic speed (MAS) achieved during a gold standard test (T-VAM) to those during a new test entitled: the 150-50 Intermittent Test (150-50IT), and (b): to test the reliability of the 150-50IT. Eighteen middle-distance runners performed, in a random order, the T-VAM and the 150-50IT. Moreover, the runners performed a second 150-50IT (retest). The results of this study showed that the MAS obtained during 150-50IT were significantly higher than the MAS during the T-VAM (19.1 ± 0.9 vs. 17.9 ± 0.9 km.h−1, p < 0.001). There was also significant higher values in HRmax (193 ± 4 vs. 191 ± 2 bpm, p = 0.011), [La-] (11.4 ± 0.4 vs. 11.0 ± 0.5 mmol.L−1, p = 0.039) during the 150-50IT. Nevertheless, significant correlations were noted for MAS (r = 0.71, p = 0.001) and HRmax (r = 0.63, p = 0.007). MAS obtained during the first 150-50IT and the retest were not significantly different (p = 0.76) and were significantly correlated (r = 0.94, p < 0.001, intraclass correlation coefficient = 0.93 and coefficient of variation = 6.8 %). In conclusion, the 150-50IT is highly reproducible, but the maximal physiological responses derived from both tests cannot be interchangeable in the design of training programs.


2021 ◽  
pp. 154596832110010
Author(s):  
Margaret A. French ◽  
Matthew L. Cohen ◽  
Ryan T. Pohlig ◽  
Darcy S. Reisman

Background There is significant variability in poststroke locomotor learning that is poorly understood and affects individual responses to rehabilitation interventions. Cognitive abilities relate to upper extremity motor learning in neurologically intact adults, but have not been studied in poststroke locomotor learning. Objective To understand the relationship between locomotor learning and retention and cognition after stroke. Methods Participants with chronic (>6 months) stroke participated in 3 testing sessions. During the first session, participants walked on a treadmill and learned a new walking pattern through visual feedback about their step length. During the second session, participants walked on a treadmill and 24-hour retention was assessed. Physical and cognitive tests, including the Fugl-Meyer-Lower Extremity (FM-LE), Fluid Cognition Composite Score (FCCS) from the NIH Toolbox -Cognition Battery, and Spatial Addition from the Wechsler Memory Scale-IV, were completed in the third session. Two sequential regression models were completed: one with learning and one with retention as the dependent variables. Age, physical impairment (ie, FM-LE), and cognitive measures (ie, FCCS and Spatial Addition) were the independent variables. Results Forty-nine and 34 participants were included in the learning and retention models, respectively. After accounting for age and FM-LE, cognitive measures explained a significant portion of variability in learning ( R2 = 0.17, P = .008; overall model R2 = 0.31, P = .002) and retention (Δ R2 = 0.17, P = .023; overall model R2 = 0.44, P = .002). Conclusions Cognitive abilities appear to be an important factor for understanding locomotor learning and retention after stroke. This has significant implications for incorporating locomotor learning principles into the development of personalized rehabilitation interventions after stroke.


Genus ◽  
2021 ◽  
Vol 77 (1) ◽  
Author(s):  
Andrea Priulla ◽  
Nicoletta D’Angelo ◽  
Massimo Attanasio

AbstractThis paper investigates gender differences in university performances in Science, Technology, Engineering and Mathematics (STEM) courses in Italy, proposing a novel application through the segmented regression models. The analysis concerns freshmen students enrolled at a 3-year STEM degree in Italian universities in the last decade, with a focus on the relationship between the number of university credits earned during the first year (a good predictor of the regularity of the career) and the probability of getting the bachelor degree within 4 years. Data is provided by the Italian Ministry of University and Research (MIUR). Our analysis confirms that first-year performance is strongly correlated to obtaining a degree within 4 years. Furthermore, our findings show that gender differences vary among STEM courses, in accordance with the care-oriented and technical-oriented dichotomy. Males outperform females in mathematics, physics, chemistry and computer science, while females are slightly better than males in biology. In engineering, female performance seems to follow the male stream. Finally, accounting for other important covariates regarding students, we point out the importance of high school background and students’ demographic characteristics.


2021 ◽  
Author(s):  
Jiří Mihola

The monograph develops the theory of production functions and their systematic typology. It looks at the relationship between inputs and outputs as a universal relationship that is used not only in economics but also in other disciplines. In addition to the static production function, special attention is paid to the dynamization of individual quantities and the issue of expressing the effect of changes in these quantities on the change in production. It is explained why in the aggregate production function expressed through aggregate factor input and aggregate factor productivity it is necessary to use a multiplicative relationship, why the multiplicative link is also suitable in terms of total input factor and why the share of weights in labor and capital should be the same. The use of the production function is demonstrated on the development of the economies of the USA, China and India and on the ten largest economies of the world in terms of absolute GDP, on cryptocurrencies and on the so-called farming role.In addition to a comprehensive overview of production functions, the monograph also enriches new ideas that arose during long-term computational and analytical activities of economic and business. Particularly innovative is the generalization of the production function to any system with variable inputs and outputs. The production function can thus be recognized in many identities. The original intention of the research was to examine the intensity of economic development, but it turned out that it is closely related to production functions. The impetus for this research comes from Prof. Ing. František Brabec, DrSc. a genius mathematician, designer, economist and manager, former general director of Škoda in Pilsen and later rector of ČVÚT.The presented typology of production functions is not limited to one area of economics, but goes beyond it. The monograph respects the definition of the static production function as the maximum amount of production that can be produced with a given number of production factors. On this function, which can be effectively displayed using polynomial functions of different orders,significant points can be systematically defined, ie the inflection point, the point of maximum efficiency, the point of maximum profit and the point of maximum production. The purpose is to optimize the number of inserted production factors. The text is preferred the point with the greatest effectiveness. If this quantity does not correspond, for example, to demand, it is possible to choose another technology, which will be reflected in a shift in the static production function. At the same time, the important points of these functions describe the trajectory, which has the nature of a dynamic production function. For a dynamic production function, the crucial question is how the change in individual factors contributes to the overall change in output. If the production function is expressed through inputs and their efficiency, dynamic parameters of extensibility and intensity can be defined, which exactly express the effect of changes in inputs and the effect of changes in efficiency on changes in outputs for all possible situations. Special attention is paid to the aggregate production function. It explains why it should be expressed as the product of the aggregate input factor (TIF) and aggregate factor productivity (TFP), or why the term TIF should be expressed as a weighted product of labor and capital, in which the value of labor and capital weights could be and identical. The monograph here surpasses the traditional additive view of the multi-factor production function by proposing a multiplicative link, which also allows the derivation of growth accounting, but with a new interpretation of weights and (1-), which do not need to be calculated for each subject and each year.The time production function is used to forecast the GDP development of the US, China and India economies until 2030 and 2050, respectively. It is also predicted an increase in the absolute GDP of Indonesia, a stable position of Russia and the loss of the elite position of Japan and Germany.The monograph also deals with the hitherto unresolved question of whether, even in economics, it is also necessary in certain circumstances to take into account a phenomenon called quantization in physics. It turns out that quantization is a common thing in economics, which is documented on specific forms of production functions that respect quantization in economics.The monograph also deals with the relationship between the efficiency of an individual given the use of a certain point on a specific static production function and common efficiency, ie all actors together. These examples assume limited resources. The sum of the outputs of all actors depends on how the actors share these limited resources. It can be expected that there will be at least one method of distribution that will bring the highest sum of outputs (products, crops) of all actors. This result, however, also depends on the shape of the production functions. This is investigated using EDM, i.e.elementary distribution models. EDM for polynomial production functions of the 2nd to 5th order are not yet published in summary. Of the new findings, they are the most interesting. When using two polynomial production functions, the EDM boundary becomes linear if the inflection point is used for both production functions. If we are above the inflection point, the EDM is properly concave. It turned out that the "bending" of the production function in the region of the inflection point can be modeled using a quantity of the order of the respective polynomial. The higher the order of the polynomial, the higher the deflection can be achieved. This proved to be a very important finding in modeling specific production functions. This effect cannot be achieved by combining other parameters.


2017 ◽  
Vol 29 (2) ◽  
pp. 43-66
Author(s):  
Geoffrey Hill ◽  
Pratim Datta ◽  
Candice Vander Weerdt

The open-source software (OSS) movement is often analogized as a commons, where products are developed by and consumed in an open community. However, does a larger commons automatically beget success or does the phenomenon fall prey to the tragedy of the commons? This research forwards and empirically investigates the curvilinear relationship between developers and OSS project quality and a project's download volume. Using segmented regression on over 12,000 SourceForge OSS projects, findings suggest an inflection point in the number of contributing developers on download volume – suggesting increasing and diminishing returns to scale from adding developers to OSS projects. Findings support the economic principle of the tragedy of the commons, a concept where an over-allocated (large number) of developers, even in an open-source environment, can lead to resource mismanagement and reduce the benefit of a public good, i.e. the OSS project.


2019 ◽  
Vol 28 ◽  
pp. 2633366X1989227 ◽  
Author(s):  
Jian Chen ◽  
Zhengcai Fu ◽  
Yang Zhao

It is difficult to monitor lightning damage to carbon fibre-reinforced polymers (CFRPs) online. This work experimentally investigates the changes associated with the electrical resistance of CFRPs subjected to lightning strikes. Two kinds of simulated lightning currents with different amplitudes in the range of 10–80 kA were injected into the CFRP samples. By measuring and comparing the changes in the struck-side (front) surface resistance, the surface resistance of the side opposite to the struck-side (back) and the oblique resistance of each sample before and after the lightning strike, it was observed that inflection points exist in the curve of the resistance change rate. The resistance decreases with increasing peak currents before the inflection point and increases when the peak current goes beyond the inflection point. The change rate of the front surface resistance is more sensitive to the lightning damage than are those of the back surface resistance and the oblique resistance. Different simulated lightning currents have approximately the same action integrals at the inflection points of resistance change rate. The characteristics indicate that resistance change detection could be a possible method for the online monitoring of CFRP lightning damage.


1979 ◽  
Vol 134 (4) ◽  
pp. 356-359 ◽  
Author(s):  
D. R. Rutter

SummaryA suggestion that schizophrenic speech may be harder to understand than normal speech was tested by a technique of reconstruction. Ten schizophrenic and ten normal passages were typed onto cards, one sentence per card. Each passage was then presented with the sentences in random order, and students were asked to reconstruct what they believed was the original order. Fewer correct strings of three or more sentences were achieved for the schizophrenic material than the normal material. It is concluded that thereisa detectable abnormality in the structure of schizophrenic speech, but that it stems from the relationshipbetweensentences rather than the content of individual sentences.


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