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

Transformation of local Ca(2+) spikes to global Ca(2+) transients: the combinatorial roles of multiple Ca(2+) releasing messengers

In pancreatic acinar cells, low, threshold concentrations of acetylcholine (ACh) or cholecystokinin (CCK) induce repetitive local cytosolic Ca(2+) spikes in the apical pole, while higher concentrations elicit global signals. We have investigated the process that transforms local Ca(2+) spikes to global Ca(2+) transients, focusing on the interactions of multiple intracellular messengers. ACh-elicited local Ca(2+) spikes were transformed into a global sustained Ca(2+) response by cyclic ADP-ribose (cADPR) or nicotinic acid adenine dinucleotide phosphate (NAADP), whereas inositol 1,4,5-trisphosphate (IP(3)) had a much weaker effect. In contrast, the response elicited by a low CCK concentration was strongly potentiated by IP(3), whereas cADPR and NAADP had little effect. Experiments with messenger mixtures revealed a local interaction between IP(3) and NAADP and a stronger global potentiating interaction between cADPR and NAADP. NAADP strongly amplified the local Ca(2+) release evoked by a cADPR/IP(3) mixture eliciting a vigorous global Ca(2+) response. Different combinations of Ca(2+) releasing messengers can shape the spatio-temporal patterns of cytosolic Ca(2+) signals. NAADP and cADPR are emerging as key messengers in the globalization of Ca(2+) signals