A comparison of two lactate threshold protocols

During a progressive multi-stage running test, heart rate (HR) increases linearly with running speed. However, the HR eventually reaches a speed where it begins to level off. Conconi et al. call the velocity at HR deflection (Vd) and they repot a close agreement (r = 0.99) between Vd and the lactate threshold or LTdiscont (using a test of there own design). Other researchers have compared Vd to continuous LT protocols (LTcont), and have found that Vd overestimates LTcont. In an effort to determine if the discrepancy results from the different LT protocols used, this study compared LTcont to LTdiscont protocols. Additionally, this study compared Vd to LT on continuous and discontinuous tests. Seven trained runners completed four tests each: 1.) a V O2 max test, 2.) a Concom HR test conducted on a 400 m outdoor track with speeds increasing ~ 0.5 km/h every 200 m, 3.) an LTdiscont conducted on a 400 m outdoor track with six runs at predetermined speeds (3 above and 3 below) Vd and 4.) an LTcont protocol with 3-min stages on a treadmill. There were significant differences (P \u3c 0004) between LTdiscont (16.84 ± 1.72 km/h) and LTcont (13 56 ± 2.29 km/h) The correlation between Vd and LTcont was r = 0.86, while a correlation of r = 0.94 was found between Vd and LTdiscont. In conclusion, Conconi’s LTdiscont significantly over-estimates LT as determined by a conventional LT protocol (LTcont). Therefore, the validity of the Conconi test must be questioned and Vd should not be used as an estimate of LT

The reproducibility of measurements of intramuscular magnesium concentrations and muscle oxidative capacity using 31P MRS

31P magnetic resonance spectroscopy (31P MRS) has been used to measure intramuscular magnesium concentrations and muscle metabolism. Abnormal intramuscular magnesium has been reported in several patient populations with suspected metabolic disorders. The purpose of this study was to evaluate our ability to measure intramuscular magnesium and muscle metabolism in the quadriceps muscles of healthy subjects, and to test whether these measurements were influenced by prior exercise. Twelve normal, healthy male volunteers were tested in a 3 Tesla magnet on four separate days. Resting [Mg2+] was calculated from the heights and frequency shifts of the phosphate, phosphocreatine and ATP peaks. Phosphocreatine (PCr) recovery kinetics were measured after 30-39 second bouts of isometric exercise. Thirty minutes prior to the 3rd test session the subjects completed a 2 hour treadmill walk at 40-60% of heart rate reserve. Resting [Mg2+] averaged 0.388 mM and had an interclass correlation coefficient between days (ICC) of 0.352. The mean end exercise PCr was 47.6% and the mean end exercise pH was 6.97. PCr recovery averaged 39 seconds (p = 0.892) and had an ICC of 0.819. Prior long duration exercise did not produce significant alterations in either PCr recovery kinetics or intracellular magnesium levels (p = 0.440). In conclusion, the reproducibility of Resting [Mg2+] was less than that of PCr recovery measurements, and may reflect the sensitivity of these measurements to phasing errors. In addition, prior exercise is unlikely to alter measurements of resting metabolites or muscle metabolism suggesting that rigorous control of physical activity prior to metabolic testing is unnecessary

Locus coeruleus contrast and diffusivity metrics differentially relate to age and memory performance.

Neurocognitive aging researchers are increasingly focused on the locus coeruleus, a neuromodulatory brainstem structure that degrades with age. With this rapid growth, the field will benefit from consensus regarding which magnetic resonance imaging (MRI) metrics of locus coeruleus structure are most sensitive to age and cognition. To address this need, the current study acquired magnetization transfer- and diffusion-weighted MRI images in younger and older adults who also completed a free recall memory task. Results revealed significantly larger differences between younger and older adults for maximum than average magnetization transfer-weighted contrast (MTC), axial than mean or radial single-tensor diffusivity (DTI), and free than restricted multi-compartment diffusion (NODDI) metrics in the locus coeruleus; with maximum MTC being the best predictor of age group. Age effects for all imaging modalities interacted with sex, with larger age group differences in males than females for MTC and NODDI metrics. Age group differences also varied across locus coeruleus subdivision for DTI and NODDI metrics, and across locus coeruleus hemispheres for MTC. Within older adults, however, there were no significant effects of age on MTC or DTI metrics, only an interaction between age and sex for free diffusion. Finally, independent of age and sex, higher restricted diffusion in the locus coeruleus was significantly related to better (lower) recall variability, but not mean recall. Whereas MTC has been widely used in the literature, our comparison between the average and maximum MTC metrics, inclusion of DTI and NODDI metrics, and breakdowns by locus coeruleus subdivision and hemisphere make important and novel contributions to our understanding of the aging of locus coeruleus structure

Economic evaluation of short treatment for multidrugresistant tuberculosis, Ethiopia and South Africa : the STREAM trial

OBJECTIVE STREAM was a phase-III non-inferiority randomised controlled trial (RCT) to evaluate a shortened regimen for multi-drug resistant tuberculosis (MDR-TB), and included the first-ever within-trial economic evaluation of such regimens, reported here. METHODS We compared the costs of ‘Long’ (20-22 months) and ‘Short’ (9-11 months) regimens in Ethiopia and South Africa. Cost data were collected from trial participants, and health system costs estimated using ‘bottom-up’ and ‘top-down’ costing approaches. A cost-effectiveness analysis was conducted with the trial primary outcome as the measure of effectiveness, including a probabilistic sensitivity analysis (PSA) to illustrate decision uncertainty. FINDINGS The Short-regimen reduced healthcare costs per case by 21% in South Africa (US$8,341 Long vs US$6,619 Short) and 25% in Ethiopia (US$6,097 Long vs US$4,552 Short). The largest component of this saving was medication in South Africa (67%) and social support in Ethiopia (35%). In Ethiopia, participants on the Short-regimen reported reductions in dietary supplementation expenditure (US$225 per case (95$13 (95%CI 11-14), South Africa US$64 (95$19,000 (Ethiopia) or <US$14,500 (South Africa). CONCLUSION The Short-regimen provided substantial health system cost savings and reduced financial burden on participants. Shorter regimens are likely to be cost-effective in most settings, and an effective strategy to support the WHO goal of eliminating catastrophic costs in T

Pre- and Post-Activity Stretching Practices of Collegiate Soccer Coaches in the United States

International Journal of Exercise Science 13(6): 260-272, 2020. Current pre- and post-activity stretching guidelines are designed to optimize performance and reduce injury risk. However, it is unclear whether soccer coaches adhere to these recommendations. The purpose of this study was to determine if collegiate soccer coaches’ perceptions and practices align with current scientific recommendations. A total of 781 questionnaires were electronically distributed to soccer coaches from NCAA Division I and III universities.The questionnaire obtained demographic, professional, and educational information, as well as stretching practices. Statistical analysis consisted of computing frequency counts and means where applicable. Pearson\u27s Chi-square tests were performed to assess the potential differences in stretching perceptions and practices among the cohort of soccer coaches. Results suggest that soccer coaches are choosing some forms of stretching more frequently than other coaches (χ2= 342.7, p\u3c 0.001). Further analysis failed to determine significant associations between stretching type and coaching certification, level, sex, years of experience, and age. Of the 209 respondents, 84.9% believed pre-activity stretching to be of greater than average importance on a seven-point Likert scale. Dynamic stretching (68.7%) or a combination of static and ballistic stretching (18.0%) prior to athletic events was the most typical stretching prescribed. Current post-activity practices demonstrate that most coaches (95.4%) are using some form of a general cool-down following practice or competition. This study is an important assessment of the extent to which collegiate coaches administer appropriate stretching techniques. Most coaches adhere to current recommendations; however, they should continue to evaluate their practices against ongoing research and the practices of their peers

Mass Reduction Patterning of Silicon-on-oxide-based Micromirrors

It has long been recognized in the design of micromirror-based optical systems that balancing static flatness of the mirror surface through structural design with the system’s mechanical dynamic response is challenging. Although a variety of mass reduction approaches have been presented in the literature to address this performance trade, there has been little quantifiable comparison reported. In this work, different mass reduction approaches, some unique to the work, are quantifiably compared with solid plate thinning in both curvature and mass using commercial finite element simulation of a specific square silicon-on-insulator–based micromirror geometry. Other important considerations for micromirror surfaces, including surface profile and smoothness, are also discussed. Fabrication of one of these geometries, a two-dimensional tessellated square pattern, was performed in the presence of a 400-μm-tall central post structure using a simple single mask process. Limited experimental curvature measurements of fabricated samples are shown to correspond well with properly characterized simulation results and indicate ∼67% improvement in radius of curvature in comparison to a solid plate design of equivalent mass

Health workers perception of the shorter regimen in MDR-TB treatment. Qualitative evidence from Ethiopia

BACKGROUND: Ethiopia has recently adopted the 9-month MDR-TB treatment regimen within its national TB control programme. The aim of this study is to identify and understand country specific gaps between policy and practice. We also identify concerns relating to the shorter regimen (compared to the standard regimen), from a health worker, patient, and health system perspective. Understanding these issues will be useful for programmes implementing shorter TB regimens. METHODS: Health workers managing patients enrolled into the randomised clinical trial were selected from St. Peters and AHRI hospitals, Addis Ababa, Ethiopia. A snowball sampling technique was used to recruit key informants from each staff category (clinicians and nurses) along the clinical treatment pathway. In-depth interviews were conducted with 14 health workers using a semi-structured interview guide. Thematic data analysis was performed using Atlas.ti software. RESULTS: Health workers perceived the benefits of the shorter treatment for patients to include returning to work sooner, fewer side effects, reduced pill-burden and fewer health facility visits. The low pill-burden, mild side effects and the shorter duration of the regimen were perceived to reduce patients’ psychological distress and increase their adherence to treatment. There were benefits for staff from workload reduction and reduced patient exposure while the health system benefited from resource savings. CONCLUSION: Most respondents considered the advantages of the shorter regimen to outweigh the disadvantages. Health workers’ satisfaction was high due to the decrease in workload, resulting from the shorter nature of the regimen, fewer side effects and better patient compliance. Building strong collaboration between the local government and partners was identified as key to ensuring affordability and sustainability of the new regimen. Ongoing training to strengthen the staff capacity in managing the regimen will be required