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Construction of a High-Pass Digital Filter from a Low-Pass Digital Filter

Stephen D. Murphy and D. Gordon E. Robertson

To remove low-frequency noise from data such as DC-bias from electromyo-grams (EMGs) or drift from force transducers, a high-pass filter was constructed from a low-pass filter of known characteristics. A summary of the necessary steps required to transform the low-pass digital were developed. Contaminated EMG and force platform data were used to test the filter. The high-pass filter successfully removed the low-frequency noise from the EMG signals. The high-pass filter was then cascaded with the low-pass filter to produce a band-pass filter to enable simultaneous high- and low-frequency noise reduction.

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The Dietary Flavonoid Quercetin Increases VO2max and Endurance Capacity

J. Mark Davis, Catherine J. Carlstedt, Stephen Chen, Martin D. Carmichael, and E. Angela Murphy

Quercetin, a natural polyphenolic flavonoid substance present in a variety of food plants, has been shown in vitro and in animal studies to have widespread health and performance benefits resulting from a combination of biological properties, including antioxidant and anti-inflammatory activity, as well as the ability to increase mitochondrial biogenesis. Little is known about these effects in humans, however, especially with respect to exercise performance. The authors determined whether quercetin ingestion would enhance maximal aerobic capacity and delay fatigue during prolonged exercise in healthy but untrained participants. Twelve volunteers were randomly assigned to 1 of 2 treatments: (a) 500 mg of quercetin twice daily dissolved in vitamin-enriched Tang or (b) a nondistinguishable placebo (Tang). Baseline VO2max and bike-ride times to fatigue were established. Treatments were administered for a period of 7 days using a randomized, double-blind, placebo-controlled, crossover study design. After treatment both VO2max and ride time to fatigue were determined. Seven days of quercetin feedings were associated with a modest increase in VO2max (3.9% vs. placebo; p < .05) along with a substantial (13.2%) increase in ride time to fatigue (p < .05). These data suggest that as little as 7 days of quercetin supplementation can increase endurance without exercise training in untrained participants. These benefits of quercetin may have important implications for enhancement of athletic and military performance. This apparent increase in fitness without exercise training may have implications beyond that of performance enhancement to health promotion and disease prevention.

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Global Matrix 4.0 Physical Activity Report Card Grades for Children and Adolescents: Results and Analyses From 57 Countries

Salomé Aubert, Joel D. Barnes, Iryna Demchenko, Myranda Hawthorne, Chalchisa Abdeta, Patrick Abi Nader, José Carmelo Adsuar Sala, Nicolas Aguilar-Farias, Susana Aznar, Peter Bakalár, Jasmin Bhawra, Javier Brazo-Sayavera, Mikel Bringas, Jonathan Y. Cagas, Angela Carlin, Chen-Kang Chang, Bozhi Chen, Lars Breum Christiansen, Candice Jo-Anne Christie, Gabriela Fernanda De Roia, Christine Delisle Nyström, Yolanda Demetriou, Visnja Djordjic, Arunas Emeljanovas, Liri Findling Endy, Aleš Gába, Karla I. Galaviz, Silvia A. González, Kylie D. Hesketh, Wendy Yajun Huang, Omphile Hubona, Justin Y. Jeon, Danijel Jurakić, Jaak Jürimäe, Tarun Reddy Katapally, Piyawat Katewongsa, Peter T. Katzmarzyk, Yeon-Soo Kim, Estelle Victoria Lambert, Eun-Young Lee, Sharon Levi, Pablo Lobo, Marie Löf, Tom Loney, José Francisco López-Gil, Juan López-Taylor, Evelin Mäestu, Agus Mahendra, Daga Makaza, Marla Frances T. Mallari, Taru Manyanga, Bojan Masanovic, Shawnda A. Morrison, Jorge Mota, Falk Müller-Riemenschneider, Laura Muñoz Bermejo, Marie H. Murphy, Rowena Naidoo, Phuong Nguyen, Susan Paudel, Željko Pedišić, Jorge Pérez-Gómez, John J. Reilly, Anne Kerstin Reimers, Amie B. Richards, Diego Augusto Santos Silva, Pairoj Saonuam, Olga L. Sarmiento, Vedrana Sember, Mohd Razif Shahril, Melody Smith, Martyn Standage, Gareth Stratton, Narayan Subedi, Tuija H. Tammelin, Chiaki Tanaka, Riki Tesler, David Thivel, Dawn Mahube Tladi, Lenka Tlučáková, Leigh M. Vanderloo, Alun Williams, Stephen Heung Sang Wong, Ching-Lin Wu, Paweł Zembura, and Mark S. Tremblay

Background: The Global Matrix 4.0 on physical activity (PA) for children and adolescents was developed to achieve a comprehensive understanding of the global variation in children’s and adolescents’ (5–17 y) PA, related measures, and key sources of influence. The objectives of this article were (1) to summarize the findings from the Global Matrix 4.0 Report Cards, (2) to compare indicators across countries, and (3) to explore trends related to the Human Development Index and geo-cultural regions. Methods: A total of 57 Report Card teams followed a harmonized process to grade the 10 common PA indicators. An online survey was conducted to collect Report Card Leaders’ top 3 priorities for each PA indicator and their opinions on how the COVID-19 pandemic impacted child and adolescent PA indicators in their country. Results: Overall Physical Activity was the indicator with the lowest global average grade (D), while School and Community and Environment were the indicators with the highest global average grade (C+). An overview of the global situation in terms of surveillance and prevalence is provided for all 10 common PA indicators, followed by priorities and examples to support the development of strategies and policies internationally. Conclusions: The Global Matrix 4.0 represents the largest compilation of children’s and adolescents’ PA indicators to date. While variation in data sources informing the grades across countries was observed, this initiative highlighted low PA levels in children and adolescents globally. Measures to contain the COVID-19 pandemic, local/international conflicts, climate change, and economic change threaten to worsen this situation.