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Paolo Bardella Irene Carrasquilla García Marco Pozzo Julio Tous-Fajardo Eduardo Saez de Villareal 《Sports biomechanics / International Society of Biomechanics in Sports》2017,16(1):102-114
The purpose of this study was to analyse the raw lifting speed collected during four different resistance training exercises to assess the optimal sampling frequency. Eight physically active participants performed sets of Squat Jumps, Countermovement Jumps, Squats and Bench Presses at a maximal lifting speed. A linear encoder was used to measure the instantaneous speed at a 200 Hz sampling rate. Subsequently, the power spectrum of the signal was computed by evaluating its Discrete Fourier Transform. The sampling frequency needed to reconstruct the signals with an error of less than 0.1% was f99.9 = 11.615 ± 2.680 Hz for the exercise exhibiting the largest bandwidth, with the absolute highest individual value being 17.467 Hz. There was no difference between sets in any of the exercises. Using the closest integer sampling frequency value (25 Hz) yielded a reconstruction of the signal up to 99.975 ± 0.025% of its total in the worst case. In conclusion, a sampling rate of 25 Hz or above is more than adequate to record raw speed data and compute power during resistance training exercises, even under the most extreme circumstances during explosive exercises. Higher sampling frequencies provide no increase in the recording precision and may instead have adverse effects on the overall data quality. 相似文献
63.
Asier Mañas Borja del Pozo-Cruz Francisco José García-García Amelia Guadalupe-Grau 《European Journal of Sport Science》2017,17(7):940-953
Sedentary behaviour (SB) has recently emerged as an independent risk factor for different health outcomes. Older adults accumulate long time in SB. Understanding the role that SB plays on health is crucial for a successful aging. This short systematic review summarizes the current evidence related to the effects of objectively measured SB on frailty, physical performance and mortality in adults ≥60?years old. The literature search produced 271 records for physical performance (n?=?119), frailty (n?=?31), and mortality (n?=?121). Finally, only 13 articles fulfilled the inclusion criteria and were included in this review. All articles but one included in the physical performance section (n?=?9) showed a negative association between longer time spent in SB and physical performance. A significant association of SB with higher odds of frailty was found, however this association disappeared after adjusting for cognitive status. Lastly, two of the three included studies showed positive associations between SB and mortality, but this effect decreased or even disappeared in the more adjusted models. In conclusion, there is consistency that SB is negatively associated with physical performance. However, the relationship between objectively measured SB and frailty incidence and mortality rates remains unclear and deserves further research. The use of homogenous criteria to assess SB and the inclusion of more robust research designs will help clarifying the independent effects that SB could have on physical performance, frailty, and mortality. This will ultimately help designing more efficient and comprehensive physical activity guidelines for older adults. 相似文献
64.
Leandro de Carvalho da Silva Carla Ferro Pereira-Monfredini 《Journal of sports sciences》2017,35(18):1825-1830
This study aimed at assessing the interaction between subjective error estimation and frequency of extrinsic feedback in the learning of the basketball free shooting pattern by children. 10- to 12-year olds were assigned to 1 of 4 groups combining subjective error estimation and relative frequency of extrinsic feedback (33% × 100%). Analysis of performance was based on quality of movement pattern. Analysis showed superior learning of the group combining error estimation and 100% feedback frequency, both groups receiving feedback on 33% of trials achieved intermediate results, and the group combining no requirement of error estimation and 100% feedback frequency had the poorest learning. Our results show the benefit of subjective error estimation in association with high frequency of extrinsic feedback in children’s motor learning of a sport motor pattern. 相似文献
65.
Previous studies have distinguished cognitive, occupational status and network mechanisms in the relation between education and ethnocentrism. Hypotheses on these mediating mechanisms are derived from socialization theory, realistic group threat and contact theory. In the current study we use structural equation modeling to investigate the explanatory power of these three mechanisms simultaneously. The analysis is based on a representative population survey from the Netherlands (NELLS 2009, n = 1910). The results show that more than half of the initial association between education and ethnocentrism can be attributed to cognitive ability and occupational status mechanisms. The remaining part of the overall association, however, still has to be modeled as a direct relationship between education and ethnocentrism. This direct association can be attributed either to social desirability or to a direct liberalizing effect of education on social and political attitudes. Our analysis tentatively suggests that the rise of average education levels in Western societies might lead to less ethnocentric attitudes via the cognitive sophistication mechanism. 相似文献
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Cadore E Lhullier F Brentano M Silva E Ambrosini M Spinelli R Silva R Kruel L 《Journal of sports sciences》2008,26(10):1067-1072
The aim of present study was to examine the relationships between serum and salivary values of free testosterone, dehydroepiandrosterone, and cortisol before and after a session of resistance exercise. Twenty-eight healthy men (mean age 40 years, s = 4) participated in the present study. Serum and salivary samples were collected at rest and after a multiple-sets resistance exercise protocol, of approximately 25 minutes duration. Concentrations of free testosterone, dehydroepiandrosterone, and cortisol were measured using radioimmunoassay kits. No significant correlation was observed between serum free testosterone and salivary testosterone (r = 0.22 to 0.26, P > 0.05). Serum cortisol was significantly correlated with salivary cortisol before (r = 0.52, P = 0.005) and after (r = 0.62, P = 0.001) the exercise protocol. Serum and salivary concentrations of dehydroepiandrosterone were significantly correlated before (r = 0.68, P < 0.001) and after (r = 0.7, P < 0.001) exercise. The results of the present study suggest that even under exercise conditions, the salivary values of cortisol and dehydroepiandrosterone can reflect the behaviour of these hormones in blood. However, further studies are necessary to verify if salivary testosterone reflects the behaviour of serum free testosterone during resistance exercise. 相似文献
69.
70.
Preparatory heart rate deceleration occurs in tasks with an external focus of attention and is often assumed to facilitate balance performance. However, its effects upon sport-related complex balance movements have not been studied. Heart rate patterns during the preparation period of an acrobatic element (flic-flac) on the balance beam were studied in 14 female gymnasts (M age 13.2 years). A significant heart rate deceleration was found in attempts with a fall in the consecutive acrobatic element, but not in attempts without a fall. These data suggest that preparatory heart rate deceleration may be detrimental to the performance of complex movements on the balance beam. 相似文献