Browsing by Author "Kim, Youngdeok (TTU)"
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Item Does l-citrulline supplementation improve exercise blood flow in older adults?(2017) Gonzales, Joaquin U. (TTU); Raymond, Andrea (TTU); Ashley, John (TTU); Kim, Youngdeok (TTU)New Findings: What is the central question of this study? Does short-term supplementation with l-citrulline in order to increase l-arginine improve exercise blood flow and peripheral dilatation responses to exercise in older adults? What is the main finding and its importance? l-Citrulline increased femoral blood flow by 11% and vascular conductance by 14% during lower-limb exercise in older men, whereas no changes were observed in older women. This modest improvement in bulk muscle blood flow in older men has implications for altering muscle metabolism that may result in enhanced exercise tolerance in older adults. l-Citrulline (Cit) increases l-arginine (Arg), the primary substrate for nitric oxide biosynthesis. We tested the hypothesis that muscle blood flow during exercise would be enhanced by Cit supplementation in older adults. Femoral artery blood flow was measured during calf exercise using Doppler ultrasound, and vascular conductance (FVC) was calculated in 25 older adults (13 women and 12 men) before and after 14 days of Cit (6 g day−1) and placebo (maltodextrin) in a randomized, double-blind, crossover study. Plasma [Arg] and resting blood pressure were also measured before and after each condition. Women and men were analysed separately because of significant sex-by-condition interactions for the change in exercise blood flow and FVC. Plasma [Arg] was increased by 30 and 35% after Cit (P < 0.01) in women and men, respectively, with no change after placebo. Citrulline lowered diastolic blood pressure in men (75 ± 9 versus 71 ± 6 mmHg, P = 0.02), but this variable remained unchanged in women. Blood flow and FVC during exercise at higher workloads were increased after Cit in men (flow, 521 ± 134 versus 584 ± 166 ml min−1, P = 0.04; FVC, 5.0 ± 1.5 versus 5.8 ± 1.7 m, min mmHg−1, P = 0.01) but were not different after placebo. These variables were not altered by Cit in women. Adjusting for baseline diastolic blood pressure removed (P = 0.10) the difference in FBF and FVC following Cit in men. These results indicate that l-citrulline has a modest effect of improving muscle blood flow during submaximal exercise in older men.Item Extracting objective estimates of sedentary behavior from accelerometer data: Measurement considerations for surveillance and research applications(2015) Kim, Youngdeok (TTU); Welk, Gregory J.; Braun, Saori I.; Kang, MinsooBackground Accelerometer-based activity monitors are widely used in research and surveillance applications for quantifying sedentary behavior (SB) and physical activity (PA). Considerable research has been done to refine methods for assessing PA, but relatively little attention has been given to operationalizing SB parameters (i.e., sedentary time and breaks) from accelerometer data - particularly in relation to health outcomes. This study investigated: (a) the accrued patterns of sedentary time and breaks; and (b) the associations of sedentary time and breaks in different bout durations with cardiovascular risk factors. Methods Accelerometer data on 5,917 adults from the National Health Examination and Nutrition Survey (NHANES) 2003-2006 were used. Sedentary time and breaks at different bout durations (i.e., 1, 2-4, 5-9, 10-14, 15-19, 20-24, 25-29, and -≥ 30-min) were obtained using a threshold of < 100 counts per minute. Sedentary time and breaks were regressed on cardiovascular risk factors (waist circumference, triglyceride, and high-density lipoprotein cholesterol) and body mass index across bout durations. Results The results revealed that the majority of sedentary time occurred within relatively short bout durations (≈ 70% and ≈ 85% for <5-min and <10-min, respectively). The associations of sedentary time and breaks with health outcomes varied depending on how bout time was defined. Estimates of SB parameters based on bout durations of 5 min or shorter were associated with reduced cardiovascular risk factors while durations longer than 10-min were generally associated with increased risk factors. Conclusions The present study demonstrates that the duration of sedentary bouts should be further considered when operationalizing the SB parameters from accelerometer data. The threshold of 5 minutes to define a bout is defensible, but a 10 minute threshold would provide a more conservative estimate to clearly capture the prolonged nature of sedentary behavior. Additional research is needed to determine the relative sensitivity and specificity of these thresholds.Item Gender differences in the prevalence of chronic pain and leisure time physical activity among US adults: A NHANES study(2019) Umeda, Masataka; Kim, Youngdeok (TTU)Gender disparities in chronic pain are well documented in the literature. However, little is known regarding the relationship between physical activity (PA) and gender disparities in chronic pain. This study described gender differences in prevalence of chronic pain and PA, and identified a type of leisure time PA that individuals frequently chose in a nationally representative sample of US adults (N = 14,449). Data from the National Health Nutrition Examination Survey 1999–2004 were analyzed. Individuals were categorized into no chronic pain (NCP), localized chronic pain (LCP), and widespread chronic pain (WCP) groups based on responses to a pain questionnaire. A self-report PA questionnaire was used to estimate the time spent in different types of PA. Women showed higher prevalence of LCP and WCP compared to men. Men spent more hours per week for leisure time PA compared to women, but men and women showed similar prevalence of sufficient PA to meet a PA recommendation (≥150 min/week of moderate-to-vigorous intensity PA) across chronic pain categories. However, the prevalence of sufficient PA was substantially higher among men and women with NCP compared to men and women with LCP and WCP. Additionally, both men and women chose walking as the primary type of leisure time PA. Together, gender disparities exist in the prevalence of chronic pain and hours spent for leisure time PA. More research is needed to explore the role of increasing leisure time PA, such as walking, in reducing gender disparities in chronic pain.Item Longitudinal trajectories of physical activity in women using latent class growth analysis: The WIN Study(2016) Kim, Youngdeok (TTU); Kang, Minsoo; Tacón, Anna M. (TTU); Morrow, James R.Purpose This study aimed (1) to examine the longitudinal trajectories in objectively measured physical activity (PA); (2) to identify unknown (i.e., latent) subgroups with distinct trajectories; and (3) to examine the correlates of latent subgroups among community dwelling women. Methods The study sample included a total of 669 women from the Women's Injury Study, a 5-year prospective cohort study conducted from 2007 in the Southwest Central region of the US. Pedometer-based step-count data across 18 consecutive months were fitted to a latent growth model (LGM) and a latent class growth model (LCGM). Baseline characteristics were regressed on latent class membership. Results The longitudinal change in PA was best fit to a piecewise LGM with seasonal transitions. Significantly increased and decreased levels of PA were observed during the spring, fall, and winter, respectively (p < 0.001). Three latent subgroups with distinct PA trajectories were identified (low-active (46.8%), somewhat-active (41.3%), and active (11.9%)). Age and body fat percentage at the baseline significantly explained the likelihoods of being in low-active subgroup. Conclusion Seasonal variations in PA among women were observed but may not be practically significant. A relatively large portion of the sample showed low levels of PA for long periods. Intervention strategies should be considered for women who are overweight or obese, and aged >40 years old to promote PA during the life course.Item Physical activity, screen-based sedentary behavior, and sleep duration in adolescents: Youth risk behavior survey, 2011-2013(2016) Kim, Youngdeok (TTU); Umeda, Masataka; Lochbaum, Marc (TTU); Stegemeier, Steven (TTU)This study examined the concurrent associations of physical activity and screen-based sedentary behavior with sleep duration among adolescents by using data from the national Youth Risk Behavior Survey 2011-2013. Using latent class analysis, we identified 4 latent subgroups of adolescents with various levels of physical activity and screen-based sedentary behavior. The subgroup with high levels of physical activity and low levels of sedentary behavior generally showed greater odds of having sufficient sleep (≥8 hours/night) than the other subgroups. Findings imply that concurrent achievement of a high level of physical activity and low level of screen-based sedentary behavior is necessary to promote sufficient sleep among adolescents.Item Sedentary behavior patterns in non-pregnant and pregnant women(2017) Hawkins, Marquis; Kim, Youngdeok (TTU); Gabriel, Kelley Pettee; Rockette-Wagner, Bonny Jane; Chasan-Taber, LisaSedentary behavior has been associated with adverse health outcomes among pregnant women; however, few studies have characterized sedentary behavior patterns in this population. We described patterns of accelerometer-determined indicators of sedentary behavior among a national sample of US pregnant (n = 234) women and non-pregnant (n = 1146) women participating in the NHANES 2003-06 cycles. We included women with ≥ 4 days of accelerometer wear of ≥ 10 h/day. A count threshold of < 100 cpm was used to describe sedentary behavior as: 1) total accumulated sedentary time by bout length categories; 2) accumulated sedentary time within discrete bout length categories; 3) mean, median, and usual bout length; and 4) and bout frequency. Both non-pregnant and pregnant women spent up to 60% of their accelerometer wear time in sedentary behavior depending on the minimum bout threshold applied. Sedentary time was higher among pregnant women compared to non-pregnant women when lower bout thresholds (i.e. 10 min or less) were applied. The majority of total sedentary time was accumulated in bouts lasting < 10 min. The women averaged less than two prolonged sedentary bouts (i.e., ≥ 30 min) per day, which accounted for nearly 20% of total accumulated sedentary time. When applying a minimum threshold of at least 15 min, sedentary time increased across pregnancy trimesters, while sedentary time was similar across trimesters when using lower thresholds. These findings provide the first characterization of accelerometer-determined indicators of sedentary behavior in pregnant women. The minimum bout threshold applied influenced estimates of sedentary time and patterns sedentary time accumulation across pregnancy trimesters.Item The influence of a consumer-wearable activity tracker on sedentary time and prolonged sedentary bouts: Secondary analysis of a randomized controlled trial NCT01855776 NCT(2018) Sloan, Robert A.; Kim, Youngdeok (TTU); Sahasranaman, Aarti; Müller-Riemenschneider, Falk; Biddle, Stuart J.H.; Finkelstein, Eric A.Objective: A recent meta-analysis surmised pedometers were a useful panacea to independently reduce sedentary time (ST). To further test and expand on this deduction, we analyzed the ability of a consumer-wearable activity tracker to reduce ST and prolonged sedentary bouts (PSB). We originally conducted a 12-month randomized control trial where 800 employees from 13 organizations were assigned to control, activity tracker, or one of two activity tracker plus incentive groups designed to increase step count. The primary outcome was accelerometer measured moderate-to-vigorous physical activity. Results: We conducted a secondary analysis on accelerometer measured daily ST and PSB bouts. A general linear mixed model was used to examine changes in ST and prolonged sedentary bouts, followed by between-group pairwise comparisons. Regression analyses were conducted to examine the association of changes in step counts with ST and PSB. The changes in ST and PSB were not statistically significant and not different between the groups (P < 0.05). Increases in step counts were concomitantly associated with decreases in ST and PSB, regardless of intervention (P < 0.05). Caution should be taken when considering consumer-wearable activity trackers as a means to reduce sedentary behavior. Trial registration NCT01855776 Registered: August 8, 2012