This randomized, double-blind study examined the effects of rehydration per se and rehydration plus carbohydrate (CHO) ingestion during recovery (REC) on subsequent endurance running capacity. Nine men ran at 70% V̇O2max on a level treadmill for 90 min (Tl) on two occasions, followed by a 4 hour REC and a further exhaustive run at the same speed (T2). During the first 3 hours of REC, subjects drank either a 6.9% CHO-electrolyte solution (CE) or a CHO- and electrolyte-free sweetened placebo (PL) every 30 min. Volumes prescribed were 200% of the fluid lost after Tl. but the actual volume of fluid ingested during the REC ranged from 113–200% and 88.5–200% of the body mass lost for the CE and PL trials (NS). However, positive fluid balance was found in both trials after REC. During T2. run time was 24.3 ± 4.4 min longer in the CE trial (69.3 ± 5.5 vs. 45.0 ± 4.2 min; p < .05). Higher blood glucose concentrations were observed throughout REC in the CE trial. These results suggest that ingesting a CHO-electrolyte solution is more effective in restoring endurance capacity compared to the same large volume of placebo, even though complete rehydration was achieved in both trials.
Stephen H. Wong, Clyde Williams, and Neville Adams
Wendy Y. Huang, Stephen H. Wong, and Gang He
This study investigated the association between a change in travel mode to school and one-year changes in physical activity (PA) among children in Hong Kong. Data from 677 children aged 7–10 years (56% boys) who participated in the Understanding Children’s Activity and Nutrition (UCAN) study were analyzed. During the 2010/11 and 2011/12 school years, the children wore an accelerometer for a week and their parents completed a questionnaire about the children’s modes of travel to school and nonschool destinations. Associations between a change in the mode of travel to school and changes in moderate-to-vigorous PA (MVPA) were determined using linear mixed models, adjusting for covariates. Compared with children who consistently used passive travel modes, a change from passive to active travel to school was positively associated with changes in the percentage of time spent in MVPA (b = 1.32, 95% CI = 0.63, 2.02) and MVPA min/day (b = 10.97, 95% CI = 5.26, 16.68) on weekdays. Similar results were found for weekly MVPA. Promoting active travel to school may help to combat age-related decline in PA for some Chinese children. However, maintaining active travel to school may not be sufficient to halt the decreasing trend in MVPA with age.
Y.J. Huang, Stephen H.S. Wong, and Jo Salmon
This study aimed to examine the reliability and validity of the modified Children’s Leisure Activities Study Survey (CLASS) Chinese-version questionnaire in assessing physical activity among Hong Kong Chinese Children. Test-retest reliability was examined in 84 boys and 136 girls aged 9–12 years by comparing data from two administrations of the survey conducted one week apart. Validity was determined by comparing data from the second administration with accelerometer estimates. The results suggested that the questionnaire provided reliable and valid estimates in overall physical activity patterns in Hong Kong Chinese children. However, substantial overestimation was observed in vigorous activity.
Wendy Y. Huang, Stephen H.S. Wong, Cindy H.P. Sit, Martin C.S. Wong, Raymond K.W. Sum, Sam W.S. Wong, and Jane J. Yu
Ya Jun Chen, Stephen H. Wong, Chun Kwok Wong, Ching Wan Lam, Ya Jun Huang, and Parco M. Siu
This study examined the effect of ingesting 3 isocaloric meals with different glycemic indices (GI) and glycemic loads (GL) 2 hr before exercise on metabolic responses and endurance running performance. Eight male runners completed 3 trials in a randomized order, separated by at least 7 days. Carbohydrate (CHO) content (%), GI, and GL were, respectively, 65%, 79, and 82 for the high-GI/high-GL meal (H-H); 65%, 40, and 42 for the low-GI/low-GL meal (L-L); and 36%, 78, and 44 for the high-GI/low-GL meal (H-L). Each trial consisted of a 1-hr run at 70% VO2max, followed by a 10-km performance run. Low-GL diets (H-L and L-L) were found to induce smaller metabolic changes during the postprandial period and during exercise, which were characterized by a lower CHO oxidation in the 2 trials (p < .05) and a concomitant, higher glycerol and free-fatty-acid concentration in the H-L trial (p < .05). There was no difference, however, in time to complete the preloaded 10-km performance run between trials. This suggests that the GL of the preexercise meal has an important role in determining subsequent metabolic responses.
Stephen H.S Wong, Oi Won Chan, Ya Jun Chen, Heng Long Hu, Ching Wan Lam, and Pak Kwong Chung
This study examined the effect of consuming carbohydrate- (CHO) electrolyte solution on running performance after different-glycemic-index (GI) meals.
Nine men completed 3 trials in a randomized counterbalanced order, with trials separated by at least 7 days. Two hours before the run after an overnight fast, each participant consumed a high-GI (GI = 83) or low-GI (GI = 36) CHO meal or low-energy sugar-free Jell-O (GI = 0, control). The 2 isocaloric GI meals provided 1.5 g available CHO/kg body mass. During each trial, 2 ml/kg body mass of a 6.6% CHO-electrolyte solution was provided immediately before exercise and every 2.5 km after the start of running. Each trial consisted of a 21-km performance run on a level treadmill. The participants were required to run at 70% VO2max during the first 5 km of the run. They then completed the remaining 16 km as fast as possible.
There was no difference in the time to complete the 21-km run (high-GI vs. low-GI vs. control: 91.1 ± 2.0 vs. 91.8 ± 2.2 vs. 92.9 ± 2.0 min, n.s.). There were no differences in total CHO and fat oxidation throughout the trials, despite differences in preexercise blood glucose, serum insulin, and serum free-fatty-acid concentrations.
When a CHO-electrolyte solution is consumed during a 21-km run, the GI of the preexercise CHO meal makes no difference in running performance.
Salomé Aubert, Joel D. Barnes, Nicolas Aguilar-Farias, Greet Cardon, Chen-Kang Chang, Christine Delisle Nyström, Yolanda Demetriou, Lowri Edwards, Arunas Emeljanovas, Aleš Gába, Wendy Y. Huang, Izzeldin A.E. Ibrahim, Jaak Jürimäe, Peter T. Katzmarzyk, Agata Korcz, Yeon Soo Kim, Eun-Young Lee, Marie Löf, Tom Loney, Shawnda A. Morrison, Jorge Mota, John J. Reilly, Blanca Roman-Viñas, Natasha Schranz, John Scriven, Jan Seghers, Thomas Skovgaard, Melody Smith, Martyn Standage, Gregor Starc, Gareth Stratton, Tim Takken, Tuija Tammelin, Chiaki Tanaka, David Thivel, Richard Tyler, Alun Williams, Stephen H.S. Wong, Paweł Zembura, and Mark S. Tremblay
Background: To better understand the childhood physical inactivity crisis, Report Cards on physical activity of children and youth were prepared concurrently in 30 very high Human Development Index countries. The aim of this article was to present, describe, and compare the findings from these Report Cards. Methods: The Report Cards were developed using a harmonized process for data gathering, assessing, and assigning grades to 10 common physical activity indicators. Descriptive statistics were calculated after converting letter grades to interval variables, and correlational analyses between the 10 common indicators were performed using Spearman’s rank correlation coefficients. Results: A matrix of 300 grades was obtained with substantial variations within and between countries. Low grades were observed for behavioral indicators, and higher grades were observed for sources of influence indicators, indicating a disconnect between supports and desired behaviors. Conclusion: This analysis summarizes the level and context of the physical activity of children and youth among very high Human Development Index countries, and provides additional evidence that the situation regarding physical activity in children and youth is very concerning. Unless a major shift to a more active lifestyle happens soon, a high rate of noncommunicable diseases can be anticipated when this generation of children reaches adulthood.
Salomé Aubert, Joel D. Barnes, Chalchisa Abdeta, Patrick Abi Nader, Ade F. Adeniyi, Nicolas Aguilar-Farias, Dolores S. Andrade Tenesaca, Jasmin Bhawra, Javier Brazo-Sayavera, Greet Cardon, Chen-Kang Chang, Christine Delisle Nyström, Yolanda Demetriou, Catherine E. Draper, Lowri Edwards, Arunas Emeljanovas, Aleš Gába, Karla I. Galaviz, Silvia A. González, Marianella Herrera-Cuenca, Wendy Y. Huang, Izzeldin A.E. Ibrahim, Jaak Jürimäe, Katariina Kämppi, Tarun R. Katapally, Piyawat Katewongsa, Peter T. Katzmarzyk, Asaduzzaman Khan, Agata Korcz, Yeon Soo Kim, Estelle Lambert, Eun-Young Lee, Marie Löf, Tom Loney, Juan López-Taylor, Yang Liu, Daga Makaza, Taru Manyanga, Bilyana Mileva, Shawnda A. Morrison, Jorge Mota, Vida K. Nyawornota, Reginald Ocansey, John J. Reilly, Blanca Roman-Viñas, Diego Augusto Santos Silva, Pairoj Saonuam, John Scriven, Jan Seghers, Natasha Schranz, Thomas Skovgaard, Melody Smith, Martyn Standage, Gregor Starc, Gareth Stratton, Narayan Subedi, Tim Takken, Tuija Tammelin, Chiaki Tanaka, David Thivel, Dawn Tladi, Richard Tyler, Riaz Uddin, Alun Williams, Stephen H.S. Wong, Ching-Lin Wu, Paweł Zembura, and Mark S. Tremblay
Background: Accumulating sufficient moderate to vigorous physical activity is recognized as a key determinant of physical, physiological, developmental, mental, cognitive, and social health among children and youth (aged 5–17 y). The Global Matrix 3.0 of Report Card grades on physical activity was developed to achieve a better understanding of the global variation in child and youth physical activity and associated supports. Methods: Work groups from 49 countries followed harmonized procedures to develop their Report Cards by grading 10 common indicators using the best available data. The participating countries were divided into 3 categories using the United Nations’ human development index (HDI) classification (low or medium, high, and very high HDI). Results: A total of 490 grades, including 369 letter grades and 121 incomplete grades, were assigned by the 49 work groups. Overall, an average grade of “C-,” “D+,” and “C-” was obtained for the low and medium HDI countries, high HDI countries, and very high HDI countries, respectively. Conclusions: The present study provides rich new evidence showing that the situation regarding the physical activity of children and youth is a concern worldwide. Strategic public investments to implement effective interventions to increase physical activity opportunities are needed.