Clinical Question: Is there sufficient evidence to determine which low back instability tests should be incorporated into a stabilization classification exam for athletes? Clinical Bottom Line: There is moderate level 2 evidence to include, but not to use in isolation, the prone instability test along with other instability tests in a stabilization classification exam.
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Pedro L. Valenzuela, Javier S. Morales, Adrián Castillo-García and Alejandro Lucia
Purpose: To determine the acute effects of ketone supplementation on exercise performance (primary outcome) and physiological and perceptual responses to exercise (secondary outcomes). Methods: A systematic search was conducted in PubMed, Web of Science, and SPORTDiscus (since inception to July 21, 2019) to find randomized controlled trials assessing the effects of acute ketone supplementation compared with a drink containing no ketones (ie, control intervention). The standardized mean difference (Hedges g) between interventions and 95% confidence interval (CI) were computed using a random-effects model. Results: Thirteen studies met all inclusion criteria. No significant differences were observed between interventions for overall exercise performance (Hedges g = −0.05; 95% CI, −0.30 to 0.20; P = .68). Subanalyses revealed no differences between interventions when analyzing endurance time-trial performance (g = −0.04; 95% CI, −0.35 to 0.28; P = .82) or when assessing the separate effects of supplements containing ketone esters (g = −0.07; 95% CI, −0.38 to 0.24; P = .66) or salts (g = −0.02; 95% CI, −0.45 to 0.41; P = .93). All studies reported increases in plasma ketone concentration after acute ketone supplementation, but no consistent effects were reported on the metabolic (plasma lactate and glucose levels), respiratory (respiratory exchange ratio, oxygen uptake, and ventilatory rate), cardiovascular (heart rate), or perceptual responses to exercise (rating of perceived exertion). Conclusions: The present findings suggest that ketone supplementation exerts no clear influence on exercise performance (from sprints to events lasting up to ∼50 min) or metabolic, respiratory, cardiovascular, or perceptual responses to exercise. More research is needed to elucidate if this strategy could provide ergogenic effects on other exercise types (eg, ultraendurance exercise).
Brian Tyo, Rebecca Spataro-Kearns and David R. Bassett Jr.
Purpose: The purpose of this study was twofold: (1) to determine if the Digi-Walker SW-200 (SW-200), New Lifestyles NL-2000 (NL-2000), and Omron HJ-303 (HJ-303) yield similar daily step counts compared to the StepWatch-3; and (2) to determine if pedometer error is influenced by adiposity and/or stepping rate in African American women. Methods: 60 participants (28.0 ± 9.8 y) wore the devices for three weekdays. ANOVAs were performed to determine if body mass index (BMI) and device were related to steps per day, and to determine if BMI and device were related to error. Stepwise linear regressions were performed to determine which variables contributed to pedometer error. Results: StepWatch-3 counted significantly more steps than all other devices within each BMI category (p < .01). The NL-2000 had significantly less error in the normal (−13.4%) and overweight (−14.9%) groups compared to the SW-200 (−26.2% and −33.3%) and HJ-303 (−32.5% ad −31.5%) (p < .05). The SW-200 had significantly more error in the obese group (−50.7%) compared to the NL-2000 (−17.1%) and HJ-303 (−26.0%) (p < .05). NL-2000 error was not related to any variables while the SW-200 error was related to waist circumference (WC) and the HJ-303 error was related to percentage of slow steps. Conclusion: In African American women adiposity is more strongly related to more pedometer error in a device using a spring-levered mechanism (SW-200). Accumulating steps at a slow rate is related to more pedometer error when using a device with a step filter (HJ-303).
Anantha Narayanan, Farzanah Desai, Tom Stewart, Scott Duncan and Lisa Mackay
Background: Application of machine learning for classifying human behavior is increasingly common as access to raw accelerometer data improves. The aims of this scoping review are (1) to examine if machine-learning techniques can accurately identify human activity behaviors from raw accelerometer data and (2) to summarize the practical implications of these machine-learning techniques for future work. Methods: Keyword searches were performed in Scopus, Web of Science, and EBSCO databases in 2018. Studies that applied supervised machine-learning techniques to raw accelerometer data and estimated components of physical activity were included. Information on study characteristics, machine-learning techniques, and key study findings were extracted from included studies. Results: Of the 53 studies included in the review, 75% were published in the last 5 years. Most studies predicted postures and activity type, rather than intensity, and were conducted in controlled environments using 1 or 2 devices. The most common models were support vector machine, random forest, and artificial neural network. Overall, classification accuracy ranged from 62% to 99.8%, although nearly 80% of studies achieved an overall accuracy above 85%. Conclusions: Machine-learning algorithms demonstrate good accuracy when predicting physical activity components; however, their application to free-living settings is currently uncertain.
Matthieu Dagenais, Nancy M. Salbach, Dina Brooks and Kelly K. O’Brien
Purpose: To assess the criterion and construct validity of the Fitbit Zip® to measure physical activity among adults living with HIV. Methods: Participants were video recorded completing 2 walk tests while wearing the Fitbit Zip® and completed 3 self-reported physical activity questionnaires 1 week later. The authors calculated intraclass correlation coefficients (ICCs) to determine agreement between the number of steps taken and distance walked (Fitbit Zip®) with the visual count of number of steps taken and actual distance walked (walk tests). The authors tested 15 a priori hypotheses about predicted associations between questionnaire scores and physical activity measured by the Fitbit Zip®. Results: Among the 34 participants, there was “excellent” agreement between the number of steps taken measured by the Fitbit Zip® and visually counted number of steps taken (ICC = .99) and number of steps taken at slow (ICC = .75), moderate (ICC = .85), and fast (ICC = .78) walking speeds. There was “poor” agreement between the Fitbit Zip® recorded distance and actual determined distance walked (ICC = .20). Three (20%) construct validity hypotheses were confirmed. Conclusions: The Fitbit Zip® demonstrated criterion validity for its ability to measure number of steps taken but not distance walked, and did not demonstrate construct validity for measuring physical activity among adults with HIV.
James J. Annesi
Background: Physical activity (PA)–related mood improvement is important because it positively affects predictors of weight-management behaviors. Methods: Decline in PA, mood, and exercise self-efficacy after an initial 6 months of gains were assessed in 93 women in a behavioral obesity treatment. Results: Reduction in change in PA during months 6 to 24, but not actual PA, significantly predicted increased negative mood. For participants whose negative mood increased, their 7 days per week PA regimens were reduced by ∼2.5 days per week versus ∼1 day per week without an increase. Exercise self-efficacy significantly mediated the PA–mood change relationship. Conclusions: Mood-related benefits of sustaining PA beyond initial treatment months were clarified.
Carl Foster, Jos J. de Koning, Christian Thiel, Bram Versteeg, Daniel A. Boullosa, Daniel Bok and John P. Porcari
Background: Pacing studies suggest the distribution of effort for optimizing performance. Cross-sectional studies of 1-mile world records (WRs) suggest that WR progression includes a smaller coefficient of variation of velocity. Purpose: This study evaluates whether intraindividual pacing used by elite runners to break their own WR (1 mile, 5 km, and 10 km) is related to the evolution of pacing strategy. We provide supportive data from analysis in subelite runners. Methods: Men’s WR performances (with 400-m or 1-km splits) in 1 mile, 5 km, and 10 km were retrieved from the IAAF database (from 1924 to present). Data were analyzed relative to pacing pattern when a runner improved their own WR. Similar analyses are presented for 10-km performance in subelite runners before and after intensified training. Results: WR performance was improved in 1 mile (mean [SD]: 3:59.4 [11.2] to 3:57.2 [8.6]), 5 km (13:27 [0:33] to 13:21 [0:33]), and 10 km (28:35 [1:27] to 28:21 [1:21]). The average coefficient of variation did not change in the 1 mile (3.4% [1.8%] to 3.6% [1.6%]), 5 km (2.4% [0.9%] to 2.2% [0.8%]), or 10 km (1.4% [0.1%] to 1.5% [0.6%]) with improved WR. When velocity was normalized to the percentage mean velocity for each race, the pacing pattern was almost identical. Very similar patterns were observed in subelite runners in the 10 km. When time improved from 49:20 (5:30) to 45:56 (4:58), normalized velocity was similar, terminal RPE increased (8.4 [1.6] to 9.1 [0.8]), coefficient of variation was unchanged (4.4% [1.1%] to 4.8% [2.1%]), and VO2max increased (49.8 [7.4] to 55.3 [8.8] mL·min−1·kg−1). Conclusion: The results suggest that when runners break their own best performances, they employ the same pacing pattern, which is different from when WRs are improved in cross-sectional data.
Steven Salaga, Scott Tainsky and Michael Mondello
The authors demonstrate that betting market outcomes are a statistically significant and economically relevant driver of local market television viewership in the National Basketball Association. Ratings are higher when the local market team covers the point spread and when point spread outcome uncertainty is increased. They further illustrate that point spread market outcomes have a larger relative impact on viewership in less-popular games and when the local market team is expected to perform poorly. This suggests wagering market access serves as insurance to the league and its franchises against reduced viewership in games that are less appealing to consumers. The results assess the degree to which wagering interest has driven past revenues as well as how the legalization of sports wagering may influence future revenues.
David Morawetz, Tobias Dünnwald, Martin Faulhaber, Hannes Gatterer, Lukas Höllrigl, Christian Raschner and Wolfgang Schobersberger
Background: The altering effects of hypoxia on aerobic/anaerobic performance are well documented and form the basis of this study. Application of hyperoxic gases (inspiratory fraction of oxygen [FiO2] > 0.2095) prior to competition or training (hyperoxic preconditioning) can compensate for the negative influence of acute hypoxia. Purpose: To investigate whether oxygen supplementation immediately prior to exercise (FiO2 = 1.0) improves all-out exercise performance in normobaric hypoxia (3500 m) in highly skilled skiers. Methods: In this single-blind, randomized, crossover study, 17 subjects performed a 60-second constant-load, all-out test in a normobaric hypoxic chamber. After a short period of adaptation to hypoxia (60 min), they received either pure oxygen or chamber air for 5 minutes prior to the all-out test (hyperoxic preconditioning vs nonhyperoxic preconditioning). Capillary blood was collected 3 times, and muscle oxygenation was assessed with near-infrared spectroscopy. Results: Absolute and relative peak power (P = .073 vs P = .103) as well as mean power (P = .330 vs P = .569) did not significantly differ after the hyperoxic preconditioning phase. PaO2 increased from 51.3 (3) to 451.9 (89.0) mm Hg, and SaO2 increased from 88.2% (1.7%) to 100% (0.2%) and dropped to 83.8% (4.2%) after the all-out test. Deoxygenation (P = .700) and reoxygenation rates (P = .185) did not significantly differ for both preconditioned settings. Conclusions: Therefore, the authors conclude that hyperoxic preconditioning did not enhance 60-second all-out exercise performance in acute hypoxia (3500 m).
Yan Shi, Wendy Yajun Huang, Cindy Hui-Ping Sit and Stephen Heung-Sang Wong
Background: This study examined the compliance with the 24-Hour Movement Guidelines among Hong Kong adolescents and its associations with body mass index (BMI). Methods: A total of 1039 adolescents (11–18 y) wore the activPAL™ for 24 hours for 7 consecutive days to assess physical activity (PA) and sleep duration. Screen time was measured using the Children’s Leisure Activities Study Survey (Chinese version). Linear mixed models were performed for analysis. Results: The analytic sample consisted of 692 adolescents (53% girls). Only 1.0% of the adolescents met all of the recommendations. The proportions of adolescents who met the recommendation for PA, screen time, and sleep were 9.1%, 31.2%, and 38.6%, respectively. Adolescent boys who did not meet the PA recommendation (β = 3.36; 95% CI, 1.04 to 5.68; P = .001) and those who did not meet the combination of PA and sleep recommendations (β = 2.10, 95% CI, 0.64 to 3.56; P = .01) had a higher body mass index than those who met the respective recommendations. Conclusions: Compliance with the 24-Hour Movement Guidelines was alarmingly low among Hong Kong adolescents. Meeting the PA recommendation or the combination of PA and sleep recommendations was associated with a healthier body weight in boys.