High-resolution MEMRI characterizes laminar specific ascending and descending spinal cord pathways in rats.

BACKGROUND: The spinal cord is composed of nine distinct cellular laminae that currently can only be visualized by histological methods. Developing imaging methods that can visualize laminar architecture in-vivo is of significant interest. Manganese enhanced magnetic resonance imaging (MEMRI) yields valuable architectural and functional information about the brain and has great potential in characterizing neural pathways in the spinal cord. Here we apply MEMRI to visualize laminae architecture in the thoracic region of the spinal cord with ultra-high resolution. NEW METHOD: Manganese chloride (MnCl2) was delivered systemically and imaging of the lumbar and thoracic spinal cord levels was acquired in high field, 11.7 T MRI scanner, 48 h following MnCl2 administration. RESULTS: Here we demonstrate laminar specific signal enhancement in the spinal cord of rats administered with MnCl2 with 69 µm in-plane resolution. We also report reduced T1 values over time in MnCl2 groups across laminae IIX. COMPARISONS WITH EXISTING METHODS: This is the first study to demonstrate that MEMRI is capable of identifying spinal laminae at a high resolution of 69 µm in a living animal. This would enable the visualization of architecture and function of distinct regions with improved resolution, in healthy and diseased animal models. CONCLUSIONS: The regions with the largest T1 enhancements were observed to correspond to laminae that contain either high cell density or large motor neurons, making MEMRI an excellent tool for studying spinal cord architecture, physiology and function in different animal models.

Youth Oriented Activity Trackers: Comprehensive Laboratory- and Field-Based Validation.

BACKGROUND: Commercial activity trackers are growing in popularity among adults and some are beginning to be marketed to children. There is, however, a paucity of independent research examining the validity of these devices to detect physical activity of different intensity levels. OBJECTIVES: The purpose of this study was to determine the validity of the output from 3 commercial youth-oriented activity trackers in 3 phases: (1) orbital shaker, (2) structured indoor activities, and (3) 4 days of free-living activity. METHODS: Four units of each activity tracker (Movband [MB], Sqord [SQ], and Zamzee [ZZ]) were tested in an orbital shaker for 5-minutes at three frequencies (1.3, 1.9, and 2.5 Hz). Participants for Phase 2 (N=14) and Phase 3 (N=16) were 6-12 year old children (50% male). For Phase 2, participants completed 9 structured activities while wearing each tracker, the ActiGraph GT3X+ (AG) research accelerometer, and a portable indirect calorimetry system to assess energy expenditure (EE). For Phase 3, participants wore all 4 devices for 4 consecutive days. Correlation coefficients, linear models, and non-parametric statistics evaluated the criterion and construct validity of the activity tracker output. RESULTS: Output from all devices was significantly associated with oscillation frequency (r=.92-.99). During Phase 2, MB and ZZ only differentiated sedentary from light intensity (P<.01), whereas the SQ significantly differentiated among all intensity categories (all comparisons P<.01), similar to AG and EE. During Phase 3, AG counts were significantly associated with activity tracker output (r=.76, .86, and .59 for the MB, SQ, and ZZ, respectively). CONCLUSIONS: Across study phases, the SQ demonstrated stronger validity than the MB and ZZ. The validity of youth-oriented activity trackers may directly impact their effectiveness as behavior modification tools, demonstrating a need for more research on such devices.

Feasibility and Effects of Short Activity Breaks for Increasing Preschool-Age Children's Physical Activity Levels.

BACKGROUND: We examined the effects of short bouts of structured physical activity (SBS-PA) implemented within the classroom setting as part of designated gross-motor playtime on preschoolers PA. METHODS: Preschools were randomized to SBS-PA (centers, N = 5; participants, N = 141) or unstructured free playtime (UPA) (centers, N = 5; participants, N = 150). SBS-PA consisted of structured PA implemented in the classroom during the first 10 minutes of gross-motor playtime followed by 20 minutes of free playtime. UPA consisted of 30 minutes of unstructured free playtime. Teachers implemented both conditions for 5 days/week for 6 months. PA was assessed with accelerometers (preschool-day) and direct observation (30-minute sessions). Generalized linear mixed models were used to examine the impact of the intervention. RESULTS: Regarding the 30-minute sessions, significant group main effects were observed for intervals spent at light (p < .001) and moderate-to-vigorous PA (MVPA, p < .001). Regarding the preschool-day PA, significant group by visit interaction was observed for percent time spent in total preschool-day MVPA (F (2, 254) = 3.54, p = .03). Percent of time spent in MVPA significantly decreased in both groups at 3 months and at 6 months. CONCLUSION: SBS-PA can be implemented in classroom settings; however, further research is needed to examine its impact on preschoolers PA levels.

Facilitators, barriers, and components of a culturally tailored afterschool physical activity program in preadolescent African American girls and their mothers.

OBJECTIVES: Traditional physical activity (PA) programs have not been effective in increasing PA in African American girls. Currently, there is limited information regarding the components of PA programs that drive participation in African American girls. The purpose of our investigation was to describe the facilitators, barriers, and components of a culturally tailored afterschool PA program that will potentially inspire the participation of African American mother-daughter dyads. METHODS: Six focus groups (n=12 mother-daughter dyads; daughters, 7-10 yrs in age) were conducted between March and May 2012. Focus group semi-structured interviews were transcribed, coded, and systematically analyzed using NVivo. RESULTS: Mothers reported a preference for non-traditional (dancing, household chores) types of PA. While daughters preferred to participate in both dance-based and traditional types (walking, riding bikes) of PA. Participants felt that the use of a culturally tailored dance program would be appealing because it highlights the cultural and historical legacy of the African American culture. Mothers wanted programs that would allow them time to spend with their daughters. Top three dance styles that mothers wanted to participate in were African, hip-hop, and Salsa/samba, while daughters reported that they would enjoy participating in hip-hop, African, and jazz. The most common responses given for resources needed for participating in a culturally tailored afterschool dance program were the location of the program, transportation, and childcare for siblings. CONCLUSIONS: Our investigation highlights some cultural factors related to facilitators and barriers of PA that should be addressed in designing PA studies for African American girls and their mothers.

Effects of locomotor skill program on minority preschoolers' physical activity levels.

This pilot study examined the effects of a teacher-taught, locomotor skill (LMS)-based physical activity (PA) program on the LMS and PA levels of minority preschooler-aged children. Eight low-socioeconomic status preschool classrooms were randomized into LMS-PA (LMS-oriented lesson plans) or control group (supervised free playtime). Interventions were delivered for 30 min/day, five days/week for six months. Changes in PA (accelerometer) and LMS variables were assessed with MANCOVA. LMS-PA group exhibited a significant reduction in during-preschool (F (1,16) = 6.34, p = .02, d = 0.02) and total daily (F (1,16) = 9.78, p = .01, d = 0.30) percent time spent in sedentary activity. LMS-PA group also exhibited significant improvement in leaping skills, F (1, 51) = 7.18, p = .01, d = 0.80). No other, significant changes were observed. The implementation of a teacher-taught, LMS-based PA program could potentially improve LMS and reduce sedentary time of minority preschoolers.

Design and baseline characteristics of the Short bouTs of Exercise for Preschoolers (STEP) study.

BACKGROUND: Most preschool centers provide two 30-min sessions of gross-motor/outdoor playtime per preschool day. Within this time frame, children accumulate most of their activity within the first 10 min. This paper describes the design and baseline participant characteristics of the Short bouTs of Exercise for Preschoolers (STEP) study. The STEP study is a cluster randomized controlled study designed to examine the effects of short bouts of structured physical activity (SBS-PA) implemented within the classroom setting as part of designated gross-motor playtime on during-school physical activity (PA) in preschoolers. METHODS/DESIGN: Ten preschool centers serving low-income families were randomized into SBS-PA versus unstructured PA (UPA). SBS-PA schools were asked to implement age-appropriate 10 min structured PA routines within the classroom setting, twice daily, followed by 20 min of usual unstructured playtime. UPA intervention consisted of 30 min of supervised unstructured free playtime twice daily. Interventions were implemented during the morning and afternoon designated gross-motor playtime for 30 min/session, five days/week for six months. Outcome measures were between group difference in during-preschool PA (accelerometers and direct observation) over six-months. Ten preschool centers, representing 34 classrooms and 315 children, enrolled in the study. The average age and BMI percentile for the participants was 4.1 ± 0.8 years and 69th percentile, respectively. Participants spent 74% and 6% of their preschool day engaged in sedentary and MVPA, respectively. DISCUSSION: Results from the STEP intervention could provide evidence that a PA policy that exposes preschoolers to shorter bouts of structured PA throughout the preschool day could potentially increase preschoolers' PA levels.

Dissociation of heart rate variability and heart rate recovery in well-trained athletes.

The purpose of this investigation was to examine the relationships between aerobic fitness, volume of physical activity (PA), heart rate variability (HRV), and heart rate recovery (HRR) in a group of well-trained endurance athletes. Nineteen endurance athletes participated in this study and had aerobic capacities that placed them above the 99th percentile based on normative values (VO(2max): 67.1 ± 2 ml kg(-1) min(-1)). HRV was obtained via an EKG collected during supine rest and reported as high-frequency (HF), low-frequency (LF), and total power (TP). Natural log (ln) transformation was applied when variables violated assumptions of normality. HRR recovery was reported as the reduction in heart rate from peak exercise to the heart rate 1 min after cessation of exercise and PA was estimated from a questionnaire. HRR was significantly correlated with PA and VO(2max) (r = 0.67, P = 0.003 and 0.51, P = 0.039, respectively), but not with any index of HRV. Age was significantly correlated with lnHF (r = -0.49, P = 0.033), lnLF/lnHF (r = 0.48, P = 0.037), and normalized units (NU) of LF (r = 0.47, P = 0.042) and HF (r = -0.47, P = 0.042). Stepwise regression revealed that the strongest predictor of HRR was PA (R (2) = 0.45) and that VO(2max) did not add significant predictive value to the model. The relationship between HRV and age is evident in well-trained endurance athletes, whereas the relationship between HRV and PA/aerobic fitness is not. The maintained relationship between HRR and PA/aerobic fitness suggests that HRR may be a better marker of fitness-related differences in autonomic control in this population.

Accuracy of an infrared LED device to measure heart rate and energy expenditure during rest and exercise.

The purpose of this study was to examine the accuracy of the ePulse Personal Fitness Assistant, a forearm-worn device that provides measures of heart rate and estimates energy expenditure. Forty-six participants engaged in 4-minute periods of standing, 2.0 mph walking, 3.5 mph walking, 4.5 mph jogging, and 6.0 mph running. Heart rate and energy expenditure were simultaneously recorded at 60-second intervals using the ePulse, an electrocardiogram (EKG), and indirect calorimetry. The heart rates obtained from the ePulse were highly correlated (intraclass correlation coefficients [ICCs] ≥0.85) with those from the EKG during all conditions. The typical errors progressively increased with increasing exercise intensity but were <5 bpm only during rest and 2.0 mph. Energy expenditure from the ePulse was poorly correlated with indirect calorimetry (ICCs: 0.01-0.36) and the typical errors for energy expenditure ranged from 0.69-2.97 kcal · min(-1), progressively increasing with exercise intensity. These data suggest that the ePulse Personal Fitness Assistant is a valid device for monitoring heart rate at rest and low-intensity exercise, but becomes less accurate as exercise intensity increases. However, it does not appear to be a valid device to estimate energy expenditure during exercise.

Novel polarization-sensitive micropulse lidar measurement technique.

Polarization-sensitive detection of elastic backscattered light is useful for detection of cloud phase and depolarizing aerosols. The U.S. Department of Energy's Atmospheric Radiation Measurement Program has deployed micropulse lidar (MPL) for over a decade, but without polarized detection. Adding an actively-controlled liquid crystal retarder provides the capability to identify depolarizing particles by alternately transmitting linearly and circularly polarized light. This represents a departure from established techniques, which transmit exclusively linear polarization or exclusively circular polarization. Mueller matrix calculations yield simple relationships between the well-known linear depolarization ratio delta(linear), the circular depolarization ratio delta(circ), and this MPL depolarization ratio delta(MPL).