Using Statistical Simulation to Visualize and Quantify Day-to-Day Measurement Error in Indirect Calorimetry

Please refer to the pdf version of the abstract located adjacent to the title

Exercise-Induced Glycogen Reduction Increases Muscle Activity

International Journal of Exercise Science 9(3): 336-346, 2016. Intramuscular glycogen stores are an important energy source during extended bouts of strenuous exercise. A substantial reduction in glycogen could influence neural muscular drive and result in a decreasing quality of exercise performance and potentially increased injury rates. The aim of this study was to examine the effect of glycogen reduction on motor drive as determined by the surface electromyogram (EMG) amplitude and median frequency during a cycling graded exercise test. Eight trained cyclists performed a discontinuous cycling graded exercise test to exhaustion under both normal and glycogen reduced conditions. EMG was collected from the vastus lateralis. Repeated measures regression models indicated that EMG amplitudes were elevated at cycling workloads higher than 196 Watts and metabolic workloads higher than 40.8 ml/kg/min, corresponding to 77% VO2max. There was no effect of increases in workload or glycogen reduction on EMG median frequency. Changes in mechanical and metabolic workload had a substantial effect on EMG amplitude (Cohen’s f2 = 0.227 and 0.247, respectively), but not median frequency (Cohen’s f2 = 0.026 and 0.033, respectively). Thus, EMG amplitude is a more effective and reliable measure to examine changes in motor drive during variable workload conditions and metabolic perturbations. The results suggest that healthy glycogen reduced humans require higher levels of muscle activity in order to attain a given mechanical and metabolic workload. This may affect the long term performance of professional and military athletes who need to be able to perform at a high level for extended periods of activity

Effects of Cognitive Fatigue on High Intensity Circuit Exercise: Preliminary study

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Thrombospondin-1 is downregulated by anoxia and suppresses tumorigenicity of human glioblastoma cells.

Angiogenesis, the sprouting of new capillaries from preexisting blood vessels, results from a disruption of the balance between stimulatory and inhibitory factors. Here, we show that anoxia reduces expression of thrombospondin-1 (TSP-1), a natural inhibitor of angiogenesis, in glioblastoma cells. This suggests that reduced oxygen tension can promote angiogenesis not only by stimulating the production of inducers, such as vascular endothelial growth factor, but also by reducing the production of inhibitors. This downregulation may significantly contribute to glioblastoma development, since we show that an increase in TSP-1 expression is sufficient to strongly suppress glioblastoma cell tumorigenicity in vivo

Information theory in the study of anisotropic radiation

Information theory is used to perform a thermodynamic study of non equilibrium anisotropic radiation. We limit our analysis to a second-order truncation of the moments, obtaining a distribution function which leads to a natural closure of the hierarchy of radiative transfer equations in the so-called variable Eddington factor scheme. Some Eddington factors appearing in the literature can be recovered as particular cases of our two-parameter Eddington factor. We focus our attention in the study of the thermodynamic properties of such systems and relate it to recent nonequilibrium thermodynamic theories. Finally we comment the possibility of introducing a nonequilibrium chemical potential for photons.Comment: 1 eps figure upon request by e-mail, to appear in Journal of Physics

Nervous system differences between the sexes and across the menstrual cycle

Sex hormones have in vitro effects on the nervous system. Furthermore, the effects of estradiol and progesterone metabolites have neurologic responses on the motor system, evidenced by transcranial magnetic stimulation studies. Sex hormone effects on the nervous system may underlie some of the sex discrepancies seen in athletic performance, injury and cardiovascular events. Investigating sex differences is often complicated by hormonal oscillations across the menstrual cycle; therefore, the aims of this research were to investigate sex and menstrual cycle effects on the motor and cardiovascular systems and the interaction of these two systems. In study 1, motor unit (MU) recruitment patterns of the vastus medialis (VM) and vastus medialis oblique (VMO) were examined in males and females at five menstrual cycle phases. Initial discharge rate between the VM and VMO were different only in females. This VM/VMO discharge discrepancy was only evident in females during the ovulatory and mid luteal menstrual phases. Study 2 examined the frequency domain relationship of the VM and VMO MUs between the sexes and across the menstrual cycle. Males have 256% to 741% greater odds of having coherent MU oscillations in the common drive band than females, indicating a greater common rate modulation. Further evidence indicated MU pairs from the VMO and VM/VMO have 228% and 212% greater odds of having beta band oscillations than the VM, indicating control of those muscle groups has a common cortical modulation. Study 3 looked at changes in the autonomic nervous system across the menstrual cycle via heart rate variability analysis. Heart rate variability decreases from the follicular to the luteal phases of the menstrual cycle, indicating a decrease in parasympathetic control. In study 4, the time and frequency domain relationship between electrocardiogram and MU discharge timing was examined between the sexes and across the menstrual cycle. The time domain relationship indicated that both males and females have MU time lag centered between 20-25 milliseconds, with an apparent modulation of this relationship across the menstrual cycle. The findings from this series of studies indicate that there are differences between the sexes which are often modified by the menstrual cycle in females.Kinesiology and Health Educatio

Cognitive Fatigue Influences Time-On-Task during Bodyweight Resistance Training Exercise

Prior investigations have shown measurable performance impairments on continuous physical performance tasks when preceded by a cognitively fatiguing task. However, the effect of cognitive fatigue on bodyweight resistance training exercise task performance is unknown. In the current investigation 18 amateur athletes completed a full body exercise task preceded by either a cognitive fatiguing or control intervention. In a randomized repeated measure design, each participant completed the same exercise task preceded by a 52 minute cognitively fatiguing intervention (vigilance) or control intervention (video). Data collection sessions were separated by 1 week. Participants rated the fatigue intervention as being significantly more mentally demanding than the control intervention (p .05). There was no statistical difference for heart rate or metabolic expenditure as a function of fatigue intervention during exercise. Cognitively fatigued athletes have decreased time-on-task in bodyweight resistance training exercise tasks

A Critical Review of Phyiotherapy Editor’s Comments on Statistical Practice

Recently, a group of editors from physiotherapy journals wrote a joint editorial on the use of statistics. The editors, who were not statistical experts themselves, put forth numerous recommendations to physiotherapy researchers on how to analyze and report their statistical analyses. This editorial unfortunately suffers from numerous mischaracterizations or outright falsehoods regarding statistics. After a thorough review, two major issues appear throughout the editorial. First, the editors incorrectly state that the use of confidence intervals (CI) would alleviate some of the issues with significance testing. Second, the editors incorrectly assume “smallest worthwhile change” statistics are immutable facts related to some ground truth of treatment effects. In this critical review, we briefly outline some of the problematic statements made by the editors and offer some simple alternatives that we believe are statistical sound and easy for the average physiotherapy researcher to implement

Athlete Health and Human Performance Will Not Improve Without Transdisciplinary Collaboration and Data Sharing in Elite Sport

There are two largely competing models for an athletics organization at both the collegiate and professional levels: the High Performance Model and the Medical Model. The High Performance Model arises from international Football perspective that places a “Performance Director” at the center of teams supporting the athletes. The Medical Model, supported by both the National Athletic Trainers Association and the NCAA, separates off medical staff (athletic trainers, physical therapists, and physicians, predominantly) and emphasizes the autonomy of medical decisions. The Medical Model has left clinicians in a “medical silo”, limiting our ability to care for the individual athletes as holistic people and limits our wider impact in the field of athlete health and injury mitigation. We argue that Medical Model is consistent with the High Performance Model only if we reject the notion that the “Performance Director” is an administrative person and instead conceptualize this as a “Health and Performance Information Hub” which facilitates transdisciplinary collaboration. This Commentary details how a data broker system can be used to accelerate transdisciplinary collaboration within an athletic organization, leading to better healthcare for athletes and improved team and individual performance. Furthermore, a transdisciplinary organization with data sharing is able to turn real-world data into real-world evidence, enhancing the care and performance of athletes locally as well as facilitating the creation of generalizable knowledge in the area of sports medicine and human performance

Improving Real-World Data Analysis: Revisiting Claims that Gender Meaningfully Impacts Marathon Pacing

The use of real-world data in sport is increasing but without a commensurate increase in analytical rigor or interpretation. This study reexamines a seminal analysis which claims to show gender differences in marathon pacing are “robust.” The earlier work suffers from serious methodological flaws common to real-world data analysis: 1) lack of quality control in the raw data; 2) overuse and misuse of ratio-based metrics; 3) failure to validate the assumptions of statistical models. A proper and valid analysis of the exact same real-world data indicates that there are some potentially interesting differences in pacing between genders, but the differences are only evident in younger and slower runners. While the previous, invalid analysis has been used to suggest there is some sort of biological mechanism for a gender difference in marathon pacing, our valid analysis is more suggestive of a social or motivational difference in this large cohort of recreational marathon runners. This case highlights the need for researchers to prioritize the quality, not just the quantity, of real-world data analyses. Moreover, researchers should avoid defaulting to sensational interpretations when more cautious, grounded explanations may be equally—if not more—plausible