Effects of Practical Durations of Stretching on Hamstrings Range of Motion and Strength

ABSTRACT Stretching is often performed prior to exercise with the intent to improve range of motion (ROM) and athletic performance. However, stretching-induced strength loss has been extensively reported and is believed to be influenced by several factors, including the time under stretch. The majority of previous studies showing stretching-induced strength declines have used stretching routines for durations (8-30 min) considerably longer than those commonly applied in the field. Fewer studies have examined the effects of shorter, more practical durations (≤2 min) of stretching on ROM and muscle strength. PURPOSE: To examine the acute effects of practical stretching durations on hamstrings ROM and muscle strength. METHODS: Eighteen young, healthy females (age = 21±2 years) volunteered for this investigation.Participants visited the laboratory 5 times, separated by 2-7 days at approximately the same time of day (±2 hours). The first visit was a familiarization trial, and the next 4 visits were experimental trials in a randomized order: ((a) control condition and stretching treatment conditions for (b) 30 s, (c) 1 min, and (d) 2 min). For each experimental trial, participants completed 2 passive straight-leg raises (SLRs) and isometric maximal voluntary contractions (MVCs) before and after the treatment condition using an isokinetic dynamometer. The control condition consisted of quiet resting for 5 min. For the SLR assessments, the dynamometer lever arm passively moved the right leg toward the head at 5°·s-1 until the maximal tolerable torque threshold was achieved, which was regarded as the maximum ROM, at which point the leg was immediately returned to the baseline position. For each MVC, participants laid supine and were instructed to extend the right thigh “as hard and fast as possible” for 3-4 s. Isometric MVC peak torque (PT) was determined as the highest mean 500 ms epoch during the entire 3-4 s MVC plateau. The stretching treatments were performed in the same fashion as the SLR assessments; however, when the maximal tolerable torque threshold was reached, it was sustained for 30 s and then released for 20 s. Each stretch was repeated until the specific time under stretch was completed for each condition. RESULTS: ROM increased from pre- to post-stretching for the 30 s(100±21° to 108±22°; P \u3c 0.001), 1 min (100±23º to 109±19º; P \u3c 0.001), and 2 min (103±22º to 113±22º; P \u3c0.001) conditions but not for the control condition (101± 25º to 102± 25º; P = 0.389). PT decreased from pre- to post-stretching for all conditions (collapsed across condition: 231±54Nm to 224±54Nm; P = 0.038). CONCLUSION: These findings demonstrated that the stretching durations of 30 s, 1 min, and 2 min resulted in significant increases (8-10%) in ROM. The similar decreases (1-4%) in PT between conditions indicated that these stretching durations for the hamstrings did not alter muscle strength when compared to the control condition. Because stretching routines for long durations of ≥8 min have been shown to elicit significant reductions (\u3e10%) in muscle strength, it may be advantageous for practitioners who are using pre-exercise stretches as a warm-up, to perform them on their athletes for shorter durations similar to those used in the present study (≤2 min)

Reliability and Relationships between Rectus Femoris Muscle Size and Hip Flexion Maximal and Explosive Strength

Ultrasound assessments of muscle cross-sectional area (CSA) are commonly used to evaluate muscle size in young adults. It has been hypothesized that the CSA of the rectus femoris (RF) may be an important contributor to hip flexion maximal and explosive strength capacities. However, limited data exist regarding the reliability of RF CSA and how it relates to maximal and explosive strength of the hip flexors in young adults. PURPOSE: To examine the reliability of RF CSA and its relationships with hip flexion isometric maximal and explosive strength. METHODS: Nineteen young, healthy females (age = 21±2 years; mass = 61±7 kg; height = 163±6 cm) volunteered for this study. Participants visited the laboratory 2 times, separated by 2-7 days at approximately the same time of day (±2 hours). During each visit, participants underwent 2 diagnostic ultrasound assessments followed by 2 isometric maximal voluntary contractions (MVCs) of the hip flexors using an isokinetic dynamometer. CSA (cm2) of the RF was measured on the right leg using a portable B-mode ultrasound imaging device and linear-array probe. For each ultrasound assessment, participants laid supine with the knee resting comfortably in extension near the natural resting position of 10°. All ultrasound images were taken in the transverse plane using a panoramic ultrasound imaging technique, which consisted of the investigator moving the probe manually at a slow and continuous rate along the surface of the skin from the lateral to medial sides of the muscle. For each MVC, participants laid supine and were instructed to flex the right thigh “as hard and fast as possible” for 3-4 s. Isometric MVC peak torque (PT; Nm) was determined as the highest mean 500 ms epoch during the entire 3-4 s MVC plateau. Rate of torque development (RTD; Nm·s-1) was determined from the linear slope of the torque-time curve over the time interval of 0-200 ms. The intraclass correlation coefficient (ICC) and standard error of measurement expressed as a percentage of the mean (SEM%) were calculated across visits to assess reliability for RF CSA and hip flexion PT and RTD. The relationships between these variables were determined by Pearson product-moment correlation coefficients (r). RESULTS: Mean±SD values (averaged across both visits) were 9.38±1.69 cm2, 136.58±23.88 Nm, and 772.86±170.91 Nm·s-1, ICCs were 0.95, 0.90, and 0.82, and SEM% values were 5.85, 5.68, and 10.03% for the CSA, PT, and RTD data, respectively. Significant positive relationships were observed between CSA and PT (r = 0.605, P = 0.006) and RTD (r = 0.462, P = 0.046). CONCLUSION: These findings demonstrated that CSA, PT, and RTD may be reliable measures for assessing RF muscle size and maximal and explosive strength capacities of the hip flexors in young, healthy adults. The significant relationships observed between CSA and PT and RTD perhaps suggest that the size of the RF may play an important role in hip flexion maximal and explosive strength. As a result, practitioners may consider implementing training programs aimed at increasing the size of the RF in younger adults which may be beneficial for improving the maximal and explosive strength capacities of the hip flexors

Construction of a comparative genetic map in faba bean (Vicia faba L.); conservation of genome structure with Lens culinaris

Background The development of genetic markers is complex and costly in species with little pre-existing genomic information. Faba bean possesses one of the largest and least studied genomes among cultivated crop plants and no gene-based genetic maps exist. Gene-based orthologous markers allow chromosomal regions and levels of synteny to be characterised between species, reveal phylogenetic relationships and chromosomal evolution, and enable targeted identification of markers for crop breeding. In this study orthologous codominant cross-species markers have been deployed to produce the first exclusively gene-based genetic linkage map of faba bean (Vicia faba), using an F6 population developed from a cross between the lines Vf6 (equina type) and Vf27 (paucijuga type). Results Of 796 intron-targeted amplified polymorphic (ITAP) markers screened, 151 markers could be used to construct a comparative genetic map. Linkage analysis revealed seven major and five small linkage groups (LGs), one pair and 12 unlinked markers. Each LG was comprised of three to 30 markers and varied in length from 23.6 cM to 324.8 cM. The map spanned a total length of 1685.8 cM. A simple and direct macrosyntenic relationship between faba bean and Medicago truncatula was evident, while faba bean and lentil shared a common rearrangement relative to M. truncatula. One hundred and four of the 127 mapped markers in the 12 LGs, which were previously assigned to M. truncatula genetic and physical maps, were found in regions syntenic between the faba bean and M. truncatula genomes. However chromosomal rearrangements were observed that could explain the difference in chromosome numbers between these three legume species. These rearrangements suggested high conservation of M. truncatula chromosomes 1, 5 and 8; moderate conservation of chromosomes 2, 3, 4 and 7 and no conservation with M. truncatula chromosome 6. Multiple PCR amplicons and comparative mapping were suggestive of small-scale duplication events in faba bean. This study also provides a preliminary indication for finer scale macrosynteny between M. truncatula, lentil and faba bean. Markers originally designed from genes on the same M. truncatula BACs were found to be grouped together in corresponding syntenic areas in lentil and faba bean. Conclusion Despite the large size of the faba bean genome, comparative mapping did not reveal evidence for polyploidisation, segmental duplication, or significant rearrangements compared to M. truncatula, although a bias in the use of single locus markers may have limited the detection of duplications. Non-coding repetitive DNA or transposable element content provides a possible explanation for the difference in genome sizes. Similar patterns of rearrangements in faba bean and lentil compared to M. truncatula support phylogenetic studies dividing these species into the tribes Viceae and Trifoliae. However, substantial macrosynteny was apparent between faba bean and M. truncatula, with the exception of chromosome 6 where no orthologous markers were found, confirming previous investigations suggesting chromosome 6 is atypical. The composite map, anchored with orthologous markers mapped in M. truncatula, provides a central reference map for future use of genomic and genetic information in faba bean genetic analysis and breeding

Tumor‐stroma interactions differentially alter drug sensitivity based on the origin of stromal cells

Due to tumor heterogeneity, most believe that effective treatments should be tailored to the features of an individual tumor or tumor subclass. It is still unclear, however, what information should be considered for optimal disease stratification, and most prior work focuses on tumor genomics. Here, we focus on the tumor microenvironment. Using a large‐scale coculture assay optimized to measure drug‐induced cell death, we identify tumor–stroma interactions that modulate drug sensitivity. Our data show that the chemo‐insensitivity typically associated with aggressive subtypes of breast cancer is not observed if these cells are grown in 2D or 3D monoculture, but is manifested when these cells are cocultured with stromal cells, such as fibroblasts. Furthermore, we find that fibroblasts influence drug responses in two distinct and divergent manners, associated with the tissue from which the fibroblasts were harvested. These divergent phenotypes occur regardless of the drug tested and result from modulation of apoptotic priming within tumor cells. Our study highlights unexpected diversity in tumor–stroma interactions, and we reveal new principles that dictate how fibroblasts alter tumor drug responses

Does the Presence of Foreign Investors Affect Financial Reporting Quality in Philippine Publicly Listed Firms?

Reinstate accounting conservatism in the Conceptual Framework – Our findings should be of interest to accounting standard setters, given the ongoing debate on the necessity for accounting conservatism as a characteristic for useful financial statements after its initial removal from the conceptual framework in 2010. While there are arguments that conservatism violates the neutrality of financial reports, further discussions show that conservatism can give a more faithful representation of firm performance (Cooper, 2015; International Accounting Standards Board, 2018)

Near-Infrared Observations of BL Lacertae Host Galaxies

Multi-band near-infrared images of twelve BL Lacertae objects were obtained with the 2.5m telescope at the Las Campanas Observatory in order to determine the properties of their underlying host galaxies. Resolved emission was clearly detected in eight of the lowest redshift targets (up to z~0.3), and was modeled with a de Vaucouleurs r^{1/4} surface brightness law. We find that the morphologies match the elliptical galaxy profiles well, and that the BL Lac objects reside in large and luminous, but otherwise normal hosts -- consistent with previous studies done predominantly at optical wavelengths. The median absolute K-band magnitude of the galaxies in this study is -26.2, the average half-light radius is 4.2 +/- 2.3 kpc, and their average integrated R-K color is 2.7 +/- 0.3 mag. These are well within the range of values measured previously in the H-band by Kotilainen et al. and Scarpa et al. in a comparable number of targets. Taking their data together with our results, we find a best-fit K-band Kormendy relation of \mu_{e} = 4.3 log_{10} (r_{e}/kpc) + 14.2 mag arcsec^{-2}, virtually identical to that obtained for normal ellipticals. Finally, the near-infrared colors determined for five galaxies (average J-K = 0.8 +/- 0.3 mag) are the first such measurements for BL Lac hosts, and match those expected from old stellar populations at the BL Lac redshifts.Comment: 10 pages, includes 4 figures and 3 tables. ApJ, accepte

Prospecting in ultracool dwarfs : Measuring the metallicities of mid- and late-m dwarfs

© 2014. The American Astronomical Society. All rights reserved.Metallicity is a fundamental parameter that contributes to the physical characteristics of a star. The low temperatures and complex molecules present in M dwarf atmospheres make it difficult to measure their metallicities using techniques that have been commonly used for Sun-like stars. Although there has been significant progress in developing empirical methods to measure M dwarf metallicities over the last few years, these techniques have been developed primarily for early- to mid-M dwarfs. We present a method to measure the metallicity of mid- to late-M dwarfs from moderate resolution (R ∼ 2000) K-band (≃ 2.2 μm) spectra. We calibrate our formula using 44 wide binaries containing an F, G, K, or early-M primary of known metallicity and a mid- to late-M dwarf companion. We show that similar features and techniques used for early-M dwarfs are still effective for late-M dwarfs. Our revised calibration is accurate to ∼0.07 dex for M4.5-M9.5 dwarfs with -0.58 <[Fe/H] <+0.56 and shows no systematic trends with spectral type, metallicity, or the method used to determine the primary star metallicity. We show that our method gives consistent metallicities for the components of M+M wide binaries. We verify that our new formula works for unresolved binaries by combining spectra of single stars. Lastly, we show that our calibration gives consistent metallicities with the Mann et al. study for overlapping (M4-M5) stars, establishing that the two calibrations can be used in combination to determine metallicities across the entire M dwarf sequence.Peer reviewe

The HST Survey of BL~Lacertae Objects. IV. Infrared Imaging of Host Galaxies

The HST NICMOS Camera 2 was used for H-band imaging of 12 BL Lacertae objects taken from the larger sample observed with the WFPC2 in the R band (Urry et al. 2000; Scarpa et al. 2000). Ten of the 12 BL Lacs are clearly resolved, and the detected host galaxies are large, bright ellipticals with average H-band absolute magnitude M=-26.2+-0.45 mag and effective radius 10+-5 kpc. The rest-frame integrated color of the host galaxies is on average R-H=2.3+-0.3, consistent with the value for both radio galaxies and normal, non-active elliptical galaxies, and indicating the dominant stellar population is old. The host galaxies tend to be bluer in their outer regions than in their cores, with average color gradient Delta(R-H)/Delta(log r)=-0.2 mag, again consistent with results for normal non-active elliptical galaxies. The infrared Kormendy relation, derived for the first time for BL Lac host galaxies, is m(e) = 3.8*log(R)+14.8 (where m(e) is the surface brightness at the effective radius R), fully in agreement with the relation for normal ellipticals. The close similarity between BL Lac host galaxies and normal ellipticals suggests the active nucleus has surprisingly little effect on the host galaxy. This supports a picture in which all elliptical galaxies harbor black holes which can be actively accreting for some fraction of their lifetime.Comment: Accepted for publication on ApJ. 25 pages, 7 figure

Evaluation of Typhoid Conjugate Vaccine Effectiveness in Ghana (TyVEGHA) Using a Cluster-Randomized Controlled Phase IV Trial: Trial Design and Population Baseline Characteristics.

Typhoid fever remains a significant health problem in sub-Saharan Africa, with incidence rates of >100 cases per 100,000 person-years of observation. Despite the prequalification of safe and effective typhoid conjugate vaccines (TCV), some uncertainties remain around future demand. Real-life effectiveness data, which inform public health programs on the impact of TCVs in reducing typhoid-related mortality and morbidity, from an African setting may help encourage the introduction of TCVs in high-burden settings. Here, we describe a cluster-randomized trial to investigate population-level protection of TYPBAR-TCV®, a Vi-polysaccharide conjugated to a tetanus-toxoid protein carrier (Vi-TT) against blood-culture-confirmed typhoid fever, and the synthesis of health economic evidence to inform policy decisions. A total of 80 geographically distinct clusters are delineated within the Agogo district of the Asante Akim region in Ghana. Clusters are randomized to the intervention arm receiving Vi-TT or a control arm receiving the meningococcal A conjugate vaccine. The primary study endpoint is the total protection of Vi-TT against blood-culture-confirmed typhoid fever. Total, direct, and indirect protection are measured as secondary outcomes. Blood-culture-based enhanced surveillance enables the estimation of incidence rates in the intervention and control clusters. Evaluation of the real-world impact of TCVs and evidence synthesis improve the uptake of prequalified/licensed safe and effective typhoid vaccines in public health programs of high burden settings. This trial is registered at the Pan African Clinical Trial Registry, accessible at Pan African Clinical Trials Registry (ID: PACTR202011804563392)