Single muscle fibre contractile characteristics with lifelong endurance exercise.

KEY POINTS: A hallmark trait of ageing skeletal muscle health is a reduction in size and function, which is most pronounced in the fast muscle fibres. We studied older men (74 ± 4 years) with a history of lifelong (>50 years) endurance exercise to examine potential benefits for slow and fast muscle fibre size and contractile function. Lifelong endurance exercisers had slow muscle fibres that were larger, stronger, faster and more powerful than young exercisers (25 ± 1 years) and age-matched non-exercisers (75 ± 2 years). Limited benefits with lifelong endurance exercise were noted in the fast muscle fibres. These findings suggest that additional exercise modalities (e.g. resistance exercise) or other therapeutic interventions are needed to target fast muscle fibres with age. ABSTRACT: We investigated single muscle fibre size and contractile function among three groups of men: lifelong exercisers (LLE) (n = 21, 74 ± 4 years), old healthy non-exercisers (OH) (n = 10, 75 ± 2 years) and young exercisers (YE) (n = 10, 25 ± 1 years). On average, LLE had exercised ∼5 days week-1 for ∼7 h week-1 over the past 53 ± 6 years. LLE were subdivided based on lifelong exercise intensity into performance (LLE-P) (n = 14) and fitness (LLE-F) (n = 7). Muscle biopsies (vastus lateralis) were examined for myosin heavy chain (MHC) slow (MHC I) and fast (MHC IIa) fibre size and function (strength, speed, power). LLE MHC I size (7624 ± 2765 µm2 ) was 25-40% larger (P < 0.001) than YE (6106 ± 1710 µm2 ) and OH (5476 ± 2467 µm2 ). LLE MHC I fibres were ∼20% stronger, ∼10% faster and ∼30% more powerful than YE and OH (P < 0.05). By contrast, LLE MHC IIa size (6466 ± 2659 µm2 ) was similar to OH (6237 ± 2525 µm2 ; P = 0.854), with both groups ∼20% smaller (P < 0.001) than YE (7860 ± 1930 µm2 ). MHC IIa contractile function was variable across groups, with a hierarchical pattern (OH > LLE > YE; P < 0.05) in normalized power among OH (16.7 ± 6.4 W L-1 ), LLE (13.9 ± 4.5 W L-1 ) and YE (12.4 ± 3.5 W L-1 ). The LLE-P and LLE-F had similar single fibre profiles with MHC I power driven by speed (LLE-P) or force (LLE-F), suggesting exercise intensity impacted slow muscle fibre mechanics. These data suggest that lifelong endurance exercise benefited slow muscle fibre size and function. Comparable fast fibre characteristics between LLE and OH, regardless of training intensity, suggest other exercise modes (e.g. resistance training) or myotherapeutics may be necessary to preserve fast muscle fibre size and performance with age.

The relationship of school climate, teacher defending and friends on students' perceptions of bullying in high school.

The purpose of this study was to examine the relationship of school climate, teacher defending, and friends on bullying and victimization. Participants were 2273 high school students from 3 public schools (an all girls, all boys boarding, and a co-ed day) in Kenya. A structural equation model was used to examine relationships between school climate, teacher behavior toward bullying, and student demographic characteristics, and bullying. Results revealed that a positive school climate was associated with less bullying behavior and victimization. In addition, when students reported that teachers stop bullying by students, bullying behavior and victimization scores were lower. Contrary to previous research these results showed that residents of a boys only boarding school were less likely to report bullying behavior than residents of an all girls school, or students at a co-educational institution. Furthermore, there were no differences in bullying behavior or victimization by gender or grade level. Implications of these results are discussed.

Identification of individuals with ADHD using the Dean-Woodcock sensory motor battery and a boosted tree algorithm.

The accurate and early identification of individuals with pervasive conditions such as attention deficit hyperactivity disorder (ADHD) is crucial to ensuring that they receive appropriate and timely assistance and treatment. Heretofore, identification of such individuals has proven somewhat difficult, typically involving clinical decision making based on descriptions and observations of behavior, in conjunction with the administration of cognitive assessments. The present study reports on the use of a sensory motor battery in conjunction with a recursive partitioning computer algorithm, boosted trees, to develop a prediction heuristic for identifying individuals with ADHD. Results of the study demonstrate that this method is able to do so with accuracy rates of over 95 %, much higher than the popular logistic regression model against which it was compared. Implications of these results for practice are provided.

Partner attachment and interpersonal characteristics.

This study investigated partner attachment and interpersonal characteristics in 134 nonclinical couples in long-term marriages. Irrespective of gender, spouses with greater anxiety over abandonment or discomfort with closeness endorsed dysfunctional relationship beliefs to a greater extent. On the anxiety over abandonment dimension, husbands with higher scores were rated less aggressive, less controlling, and more rebellious, whereas wives with higher scores were rated more dependent, more self-critical, and less competitive. Husbands higher on discomfort with closeness were rated less cooperative and responsible and were rated more aggressive and rebellious. Matched secure couples reported lower marital dissatisfaction than matched insecure or mismatched couples. Future research should contrast samples of nonclinical and clinical couples by marital duration to identify specific partner behaviors that are likely to foster marital dissatisfaction within particular attachment pairings. The authors' findings suggest the importance of marital therapists being attuned to the attachment-related beliefs and interpersonal styles uniquely operating within each couple.

Not One Pandemic: A Multilevel Mixture Model Investigation of the Relationship Between Poverty and the Course of the COVID-19 Pandemic Death Rate in the United States.

The COVID-19 pandemic, which began in China in late 2019, and subsequently spread across the world during the first several months of 2020, has had a dramatic impact on all facets of life. At the same time, it has not manifested in the same way in every nation. Some countries experienced a large initial spike in cases and deaths, followed by a rapid decline, whereas others had relatively low rates of both outcomes throughout the first half of 2020. The United States experienced a unique pattern of the virus, with a large initial spike, followed by a moderate decline in cases, followed by second and then third spikes. In addition, research has shown that in the United States the severity of the pandemic has been associated with poverty and access to health care services. This study was designed to examine whether the course of the pandemic has been uniform across America, and if not how it differed, particularly with respect to poverty. Results of a random intercept multilevel mixture model revealed that the pandemic followed four distinct paths in the country. The least ethnically diverse (85.1% white population) and most rural (82.8% rural residents) counties had the lowest death rates (0.06/1000) and the weakest link between deaths due to COVID-19 and poverty (b = 0.03). In contrast, counties with the highest proportion of urban residents (100%), greatest ethnic diversity (48.2% nonwhite), and highest population density (751.4 people per square mile) had the highest COVID-19 death rates (0.33/1000), and strongest relationship between the COVID-19 death rate and poverty (b = 46.21). Given these findings, American policy makers need to consider developing responses to future pandemics that account for local characteristics. These responses must take special account of pandemic responses among people of color, who suffered the highest death rates in the nation.

Comparing the effects of various whole-body vibration accelerations on counter-movement jump performance.

While it seems that whole body vibration (WBV) might be an effective modality to enhance physical performance, the proper prescription of WBV for performance enhancement remains unknown. The purpose of this study was to compare the immediate effect of various WBV accelerations on counter movement jump (CMJ) height, the duration of any effect, and differences between men and women. Forty-four participants (33 men, 11 women) participated in no less than four CMJ familiarization sessions and completed all vibration sessions. Participants performed a pre-test (three maximal CMJs), followed randomly by one of five WBV accelerations; 1g (no-WBV control), 2.16g, 2.80g, 4.87g, and 5.83g. Participants performed three maximal CMJs immediately, five, and 10 minutes following each 45 sec WBV session. The mean of the three performances was used and calculated as a percentage of the pre-vibration mean value. A Repeated Measures Analysis of Variance (ANOVA; acceleration x time x gender) model was used to analyze the data. The two-way interactions of acceleration-gender (p = 0.033) and time-gender (p = 0.050) were significant. Women performed significantly better following the 2.80g (p = 0.0064) and 5.83g (p = 0. 0125) WBV sessions compared to the 1g (control) session. Men, however, did not experience performance enhancing effects following any of the vibration sessions. While significant differences did not occur between time in either gender, the effects of the 45 sec WBV session in women were transient, lasting approximately five minutes. During the prescription of WBV, gender should be considered given that the results of this study seem to indicate that men and women respond differently to WBV. The results of this study suggest that WBV might be a useful modality as applied during the pre-competition warm-up. Key pointsWBV accelerations of 2.80g (40 Hz, 2-4 mm) and 5.83g (50 Hz, 4-6 mm) seem to elicit a performance enhancement effect following short-duration (45 sec) exposure in untrained women.The performance enhancement effect of a short-duration is transient, lasting less than 10 minutes following exposure.Men and women might differ in their response to the WBV stimulus, as measured by countermovement jump.

Comparison of Methods for Factor Invariance Testing of a 1-Factor Model With Small Samples and Skewed Latent Traits.

A primary underlying assumption for researchers using a psychological scale is that scores are comparable across individuals from different subgroups within the population. In the absence of invariance, the validity of these scores for inferences about individuals may be questionable. Factor invariance testing refers to the methodological approach to assessing whether specific factor model parameters are indeed equivalent across groups. Though much research has investigated the performance of several techniques for assessing invariance, very little work has examined how methods perform under small sample size, and non-normally distributed latent trait conditions. Therefore, the purpose of this simulation study was to compare invariance assessment Type I error and power rates between (a) the normal based maximum likelihood estimator, (b) a skewed-t distribution maximum likelihood estimator, (c) Bayesian estimation, and (d) the generalized structured component analysis model. The study focused on a 1-factor model. Results of the study demonstrated that the maximum likelihood estimator was robust to violations of normality of the latent trait, and that the Bayesian and generalized component models may be useful in particular situations. Implications of these findings for research and practice are discussed.

Cardiorespiratory Fitness Is Inversely Associated With Clustering of Metabolic Syndrome Risk Factors: The Ball State Adult Fitness Program Longitudinal Lifestyle Study.

OBJECTIVE: The focus of this study was the association between the metabolic syndrome (MetSyn) and cardiorespiratory fitness (CRF) defined as maximal oxygen uptake (VO2max). Although previous research has shown a relationship between MetSyn and CRF, most studies are based on less objective measures of CRF and different cardiometabolic risk factor thresholds from earlier guidelines. PARTICIPANTS AND METHODS: The metabolic markers included in the present study were central obesity, elevated plasma triglycerides, elevated fasting high-density lipoprotein cholesterol, impaired fasting plasma glucose, hypertension, or pharmacologic treatment for diagnosed hypertension, hypertriglyceridemia, low high-density lipoprotein cholesterol, or diabetes. A cohort of 3636 adults (1629 women, 2007 men; mean ± SD age, 44.7±12.3 years) completed CRF and metabolic risk factor assessment between January 1, 1971, and November 1, 2016. The CRF was defined as a measured VO2max from a cardiopulmonary exercise test on a treadmill, with a respiratory exchange ratio value of 1.0 or more. RESULTS: Prevalence of MetSyn (≥3 factors) was 26% (n=953) in the cohort, with men having a greater likelihood for MetSyn compared with women (P<.001). The difference in VO2max between those individuals with MetSyn and those without was approximately 2.3 (2.0-2.5) metabolic equivalents. Logistic regression analyses showed a significant inverse and graded association between quartiles of CRF and MetSyn for the group overall (P<.001), with odds ratios (95% CI) using the lowest fitness group as the referent group of 0.67 (0.55-0.81), 0.41 (0.34-0.51), and 0.10 (0.07-0.14) for VO2max (P<.001). The sex-specific odds ratios were 0.25 (0.18-0.34), 0.05 (0.02-0.10), and 0.02 (0.01-0.09) for women and 0.43 (0.31-0.59), 0.19 (0.14-0.27), and 0.03 (0.02-0.05) for men (P<.001). CONCLUSION: These results with current risk factor thresholds and a large number of women demonstrate that low VO2max is associated with MetSyn.

Reference standards for lean mass measures using GE dual energy x-ray absorptiometry in Caucasian adults.

OBJECTIVE: To develop reference values by age and sex for LM measures using GE-Healthcare DXA systems. METHODS: A de-identified sample was obtained from Ball State University's Clinical Exercise Physiology Laboratory and University of Wisconsin-Milwaukee's Physical Activity & Health Research Laboratory. DXA scans of 2,076 women and 1,251 men were completed using a GE Lunar Prodigy or iDXA. Percentiles (%ile) were calculated for all variables of interest (LM, LMI, %LM, and ALMI) and a factorial ANOVA was used to assess differences for each variable between 10-year age groups and sex, as well as the interaction between age and sex. RESULTS: Men had higher mean total LM, %LM, LMI, and ALMI than women (p<0.01), across all age groups. All LM variables decreased significantly over the 5 decades in men, however in women only total LM, %LM, and ALMI decreased from the youngest to oldest age groups (p<0.01). CONCLUSION: These reference values provide for a more accurate interpretation of GE-Healthcare DXA-derived LM measurements offering clinicians and researchers with an initial resource to aid in the early detection and assessment of LM deficits.

Reference standards for body fat measures using GE dual energy x-ray absorptiometry in Caucasian adults.

BACKGROUND: Dual energy x-ray absorptiometry (DXA) is an established technique for the measurement of body composition. Reference values for these variables, particularly those related to fat mass, are necessary for interpretation and accurate classification of those at risk for obesity-related health complications and in need of lifestyle modifications (diet, physical activity, etc.). Currently, there are no reference values available for GE-Healthcare DXA systems and it is known that whole-body and regional fat mass measures differ by DXA manufacturer. OBJECTIVE: To develop reference values by age and sex for DXA-derived fat mass measurements with GE-Healthcare systems. METHODS: A de-identified sample of 3,327 participants (2,076 women, 1,251 men) was obtained from Ball State University's Clinical Exercise Physiology Laboratory and University of Wisconsin-Milwaukee's Physical Activity & Health Research Laboratory. All scans were completed using a GE Lunar Prodigy or iDXA and data reported included percent body fat (%BF), fat mass index (FMI), and ratios of android-to-gynoid (A/G), trunk/limb, and trunk/leg fat measurements. Percentiles were calculated and a factorial ANOVA was used to determine differences in the mean values for each variable between age and sex. RESULTS: Normative reference values for fat mass variables from DXA measurements obtained from GE-Healthcare DXA systems are presented as percentiles for both women and men in 10-year age groups. Women had higher (p<0.01) mean %BF and FMI than men, whereas men had higher (p<0.01) mean ratios of A/G, trunk/limb, and trunk/leg fat measurements than women. CONCLUSION: These reference values provide clinicians and researchers with a resource for interpretation of DXA-derived fat mass measurements specific to use with GE-Healthcare DXA systems.

Rasch Model Parameter Estimation in the Presence of a Nonnormal Latent Trait Using a Nonparametric Bayesian Approach.

Standard approaches for estimating item response theory (IRT) model parameters generally work under the assumption that the latent trait being measured by a set of items follows the normal distribution. Estimation of IRT parameters in the presence of nonnormal latent traits has been shown to generate biased person and item parameter estimates. A number of methods, including Ramsay curve item response theory, have been developed to reduce such bias, and have been shown to work well for relatively large samples and long assessments. An alternative approach to the nonnormal latent trait and IRT parameter estimation problem, nonparametric Bayesian estimation approach, has recently been introduced into the literature. Very early work with this method has shown that it could be an excellent option for use when fitting the Rasch model when assumptions cannot be made about the distribution of the model parameters. The current simulation study was designed to extend research in this area by expanding the simulation conditions under which it is examined and to compare the nonparametric Bayesian estimation approach to the Ramsay curve item response theory, marginal maximum likelihood, maximum a posteriori, and the Bayesian Markov chain Monte Carlo estimation method. Results of the current study support that the nonparametric Bayesian estimation approach may be a preferred option when fitting a Rasch model in the presence of nonnormal latent traits and item difficulties, as it proved to be most accurate in virtually all scenarios that were simulated in this study.

Cortical and subcortical constructs of the dean-woodcock sensory motor battery: a construct validity study.

The factor structure of the Dean-Woodcock Sensory Motor Battery was examined using exploratory factor analysis with promax rotation. Participants (n = 1,651) were composed of 701 neurologically impaired individuals and 950 normal individuals. Three factors, accounting for almost 58.2% of the total test variation, emerged from the data and were labeled Simple Sensory Skills, Motor and Complex Sensory Skills, and Subcortical Motor Skills and Auditory/Visual Acuity. Hypothesized cross loadings were present, especially between the first two factors, which highlighted the parallel nature of sensory-motor skills. The third factor demonstrated the least amount of cross loadings, which reinforced the demarcation of cortical and subcortical motor skills measured by the DWSMB. The results also indicated that the factors were separated by the complexity of the cortical sensory-motor tasks. The factor structure, combined with an analysis of the interfactor correlations, provides evidence for construct validity of the DWSMB.