STUDY OF PERFORMANCE RELATED STRENGTH TESTS FOR COMPETITION LEVEL SPRINTERS

Strength is a performance determining factor in sprinting. This study investigates the significance of a variety of isokinetic tests to control strength requirements for sprinters. Eighteen competition level sprinters &1i0 0 m-time = 10.94 s, = 0.22 s) ran a 40 meter sprint and performed 24 isokinetic strength tests on the PROMETT-system Static, concentric, eccentric and plyometric contractions were executed at velocities between 0 and 300 '1s for knee-extensors, knee flexors and ankle extensors. For each movement the torque at three different joint angles was recorded. As the performance determining factors change in relation to running distance, the correlation between the recorded torques and the running speed is graphically presented in relation to running distance (72 graphs). Per type of contraction the torque with the highest correlation with running speed was selected for further analysis. To interpret these graphs three phases are distinguished in a 40 meter sprint. Phase 1 is the phase of initial acceleration (from 0 to 10 m), phase 2 is the phase of continued acceleration (from 10 to 30 m) and phase 3 is the phase of maximum running speed (30 to 40 m). The common variance in torque and running speed data is quantified by means of the determinationcoefficient. The results indicate that isokinetic strength tests can be used to evaluate sprint related strength requirements at a competition level. 30 to 50 percent of variance in running speed within each of the three phases can be declared by a single isokinetic strength test. It may be concluded that the strength of the knee flexors determines 50 % of the variance within the phase of initial acceleration. Ankle extension torques explain 45 % of the variance in running speed within phase 2, and the strength of the knee extensors determines 33 % of variance in maximum running speed. It is also remarkable that for ankle extension only tests were selected with a high movement velocity (200°/s), while for knee extension tests were selected at lower velocities (65 and 130°/s)

Relationships between lower-limb kinematics and block phase performance in a cross section of sprinters

This study investigated lower-limb kinematics to explain the techniques used to achieve high levels of sprint start performance. A cross-sectional design was used to examine relationships between specific technique variables and horizontal external power production during the block phase. Video data were collected (200 Hz) at the training sessions of 16 sprinters who ranged in 100 m personal best times from 9.98 to 11.6 s. Each sprinter performed three 30 m sprints and reliable (all intraclass correlation coefficients, ICC(2,3) ≥ 0.89) lower-limb kinematic data were obtained through manual digitising. The front leg joints extended in a proximal-to-distal pattern for 15 sprinters, and a moderate positive relationship existed between peak front hip angular velocity and block power (r = 0.49, 90% confidence limits = 0.08–0.76). In the rear leg, there was a high positive relationship between relative push duration and block power (r = 0.53, 90% confidence limits = 0.13–0.78). The rear hip appeared to be important; rear hip angle at block exit was highly related to block power (r = 0.60, 90% confidence limits = 0.23–0.82), and there were moderate positive relationships with block power for its range of motion and peak angular velocity (both r = 0.49, 90% confidence limits = 0.08–0.76). As increased block power production was not associated with any negative aspects of technique in the subsequent stance phase, sprinters should be encouraged to maximise extension at both hips during the block phase

Choice of sprint start performance measure affects the performance-based ranking within a group of sprinters: which is the most appropriate measure?

Sprint start performance has previously been quantified using several different measures. This study aimed to identify whether different measures could influence the performance-based ranking within a group of 12 sprinters, and if so, to identify the most appropriate measure. None of the 10 performance measures ranked all sprinters in the same order; Spearman's rho correlations between different block phase measures ranged from 0.50 to 0.94, and between block phase measures and those obtained beyond block exit from 0.66 to 0.85. Based on the consideration of what each measure quantifies, normalised average horizontal external power was identified as the most appropriate, incorporating both block velocity and the time spent producing this velocity. The accuracy with which these data could be obtained in an externally valid field setting was assessed against force platform criterion data. For an athlete producing 678 ± 40 W of block power, a carefully set-up manual high-speed video analysis protocol produced systematic and random errors of +5 W and ± 24 W, respectively. Since the choice of performance measure could affect the conclusions drawn from a technique analysis, for example the success of an intervention, it is proposed that external power is used to quantify start performance

Combined student ratings and self-assessment provide useful feedback for clinical teachers

Many evaluation instruments have been developed to provide feedback to physicians on their clinical teaching but written feedback alone is not always effective. We explored whether feedback effectiveness improved when teachers’ self-assessment was added to written feedback based on student ratings. 37 physicians (10 residents, 27 attending physicians) from different specialties (Internal Medicine, Surgery, Obstetrics/Gynecology, Pediatrics, Neurology, Dermatology, Ophthalmology, ENT, and Psychiatry) were invited to fill out a self-assessment questionnaire on their teaching skills. Students completed an almost identical questionnaire to evaluate the same teachers based on their experiences during clerkships. After receiving written feedback incorporating their self-assessment and the student ratings, the teachers indicated their perceptions of the self-assessment exercise and the written feedback in a questionnaire (five-point Likert scale items) and next, in more detail, in semi-structured interviews with a purposive sample of 12 of the participating teachers. 25 physicians participated (67%). The results showed that self-assessment and student feedback were both perceived as useful (3.7, SD 1.0) but the latter was considered more effective. The physicians we interviewed considered the combination of self-assessment with student ratings more effective than either self-assessment or written feedback alone. Notably, discrepancies between student ratings and self-assessment were deemed a strong incentive for change. We conclude that self-assessment can be a useful tool to stimulate improvement of clinical teaching when it is combined with written feedback based on student ratings. Future research among larger groups is needed to confirm our findings and examine whether these combined tools actually lead to improved teaching

Gene expression profiling of alveolar soft-part sarcoma (ASPS)

<p>Abstract</p> <p>Background</p> <p>Alveolar soft-part sarcoma (ASPS) is an extremely rare, highly vascular soft tissue sarcoma affecting predominantly adolescents and young adults. In an attempt to gain insight into the pathobiology of this enigmatic tumor, we performed the first genome-wide gene expression profiling study.</p> <p>Methods</p> <p>For seven patients with confirmed primary or metastatic ASPS, RNA samples were isolated immediately following surgery, reverse transcribed to cDNA and each sample hybridized to duplicate high-density human U133 plus 2.0 microarrays. Array data was then analyzed relative to arrays hybridized to universal RNA to generate an unbiased transcriptome. Subsequent gene ontology analysis was used to identify transcripts with therapeutic or diagnostic potential. A subset of the most interesting genes was then validated using quantitative RT-PCR and immunohistochemistry.</p> <p>Results</p> <p>Analysis of patient array data versus universal RNA identified elevated expression of transcripts related to angiogenesis (ANGPTL2, HIF-1 alpha, MDK, c-MET, VEGF, TIMP-2), cell proliferation (PRL, IGFBP1, NTSR2, PCSK1), metastasis (ADAM9, ECM1, POSTN) and steroid biosynthesis (CYP17A1 and STS). A number of muscle-restricted transcripts (ITGB1BP3/MIBP, MYF5, MYF6 and TRIM63) were also identified, strengthening the case for a muscle cell progenitor as the origin of disease. Transcript differentials were validated using real-time PCR and subsequent immunohistochemical analysis confirmed protein expression for several of the most interesting changes (MDK, c-MET, VEGF, POSTN, CYP17A1, ITGB1BP3/MIBP and TRIM63).</p> <p>Conclusion</p> <p>Results from this first comprehensive study of ASPS gene expression identifies several targets involved in angiogenesis, metastasis and myogenic differentiation. These efforts represent the first step towards defining the cellular origin, pathogenesis and effective treatment strategies for this atypical malignancy.</p

A comparative study between latent class binomial segmentation and mixed-effects logistic regression to explore between-respondent variability in visual preference for horticultural products

A methodological concept is proposed to study between-respondent variability in visual preference for horticultural products using quantitative imaging techniques. Chicory, a typical Belgian vegetable, serves as a model product. Eight image sequences of high-quality chicory, each representing a different combination of two factor levels of length, width and ovality, were constructed to satisfy a 23 factorial design by using quantitative imaging techniques. The image sequences were pair-wise visualized using a computer-based image system to study visual preference. Twenty respondents chose which of two samples was preferred in all 28 pair-wise combinations of the eight constructed image sequences. The consistency of the respondents and the agreement between respondents was evaluated. The poor fit of a traditional binomial logit model that relates preference with quality descriptors was due to the low agreement in preference between respondents. Therefore, latent class binomial segmentation is compared to mixed-effects logistic regression. Both approaches relax the traditional assumption that the same model holds for all respondents by recognizing the typical between-respondent variability inherent in preference studies. Where the latent class model simultaneously estimates different logit models for different consumer segments, the mixed-effects model recognizes between-respondent variability by incorporating random effects varying by respondent in model formulation.Chicory, latent class, logistic, mixed model, pair-wise comparison, variability,