Physiological responses in different intensities of resistance exercise – Critical load and the effects of aging process     

Vivian Maria Arakelian  Cássia da Luz Goulart  Renata Gonçalves Mendes  Nuno Manoel de Sousa  Renata Trimer  Solange Guizilini 《Journal of sports sciences》2019,37(12):1420-1428

Aim was to identify critical load (CL) in young and elderly apparently healthy male cohorts. To contrast the metabolic, cardiovascular and perceptual responses on CL according to age. We evaluated 12 young (23 ± 3 years) and 10 elderly (70 ± 2 years) apparently healthy active males, who underwent: (1) 1 repetition maximum (1RM) test on a 45° Leg Press; (2) on different days, three high-intensity resistance exercise constant load tests (60%, 75% and 90% 1RM) until fatigue (Tlim). Absolute values of both the CL asymptote and curvature constant (kg) were significantly lower in elderly subjects (P < 0.05). In contrast, elderly subjects demonstrated a significantly higher number of repetitions at CL when compared with young subjects (P < 0.05). As expected, oxygen uptake (VO₂) and heart rate (HR) during maximal aerobic exercise testing were significantly reduced in older subjects. However, percent-predicted aerobic capacity were higher in older subjects (P < 0.05). In addition, blood lactate ([La^?]) corrected to Tlim and rating of perceived exertion values were greater in younger subjects at all intensities (P < 0.05). These findings, despite reduced force production in older subjects, endurance-related parameters are well preserved according to age-adjusted percent-predicted values in apparently healthy males.  相似文献   

Optimal sampling frequency in recording of resistance training exercises     

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 f_99.9 = 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   

A novel sleep optimisation programme to improve athletes’ well-being and performance     

Emer Van Ryswyk  Richard Weeks  Laura Bandick  Michaela O’Keefe  Andrew Vakulin  Peter Catcheside 《European Journal of Sport Science》2017,17(2):144-151

Objectives: To improve well-being and performance indicators in a group of Australian Football League (AFL) players via a six-week sleep optimisation programme. Design: Prospective intervention study following observations suggestive of reduced sleep and excessive daytime sleepiness in an AFL group. Methods: Athletes from the Adelaide Football Club were invited to participate if they had played AFL senior-level football for 1–5 years, or if they had excessive daytime sleepiness (Epworth Sleepiness Scale [ESS] >10), measured via ESS. An initial education session explained normal sleep needs, and how to achieve increased sleep duration and quality. Participants (n?=?25) received ongoing feedback on their sleep, and a mid-programme education and feedback session. Sleep duration, quality and related outcomes were measured during week one and at the conclusion of the six-week intervention period using sleep diaries, actigraphy, ESS, Pittsburgh Sleep Quality Index, Profile of Mood States, Training Distress Scale, Perceived Stress Scale and the Psychomotor Vigilance Task. Results: Sleep diaries demonstrated an increase in total sleep time of approximately 20?min (498.8?±?53.8 to 518.7?±?34.3; p?<?.05) and a 2% increase in sleep efficiency (p?<?0.05). There was a corresponding increase in vigour (p?<?0.001) and decrease in fatigue (p?<?0.05). Conclusions: Improvements in measures of sleep efficiency, fatigue and vigour indicate that a sleep optimisation programme may improve athletes’ well-being. More research is required into the effects of sleep optimisation on athletic performance.  相似文献   

Improved children’s motor learning of the basketball free shooting pattern by associating subjective error estimation and extrinsic feedback     

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   

Is there really an eccentric action of the hamstrings during the swing phase of high-speed running? part I: A critical review of the literature     

Bas Van Hooren  Frans Bosch 《Journal of sports sciences》2017,35(23):2313-2321

It is widely assumed that there is an eccentric hamstring muscle fibre action during the swing phase of high-speed running. However, animal and modelling studies in humans show that the increasing distance between musculotendinous attachment points during forward swing is primarily due to passive lengthening associated with the take-up of muscle slack. Later in the swing phase, the contractile element (CE) maintains a near isometric action while the series elastic (tendinous) element first stretches as the knee extends, and then recoils causing the swing leg to forcefully retract prior to ground contact. Although modelling studies showed some active lengthening of the contractile (muscular) element during the mid-swing phase of high-speed running, we argue that the increasing distance between the attachment points should not be interpreted as an eccentric action of the CE due to the effects of muscle slack. Therefore, there may actually be no significant eccentric, but rather predominantly an isometric action of the hamstrings CE during the swing phase of high-speed running when the attachment points of the hamstrings are moving apart. Based on this, we propose that isometric rather than eccentric exercises are a more specific way of conditioning the hamstrings for high-speed running.  相似文献   

How does education have an impact on ethnocentrism? A structural equation analysis of cognitive,occupational status and network mechanisms     

Cecil Meeusen  Thomas de Vroome  Marc Hooghe 《Int J Intercult Relat》2013

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   

Her Day in Court. Women's Property Rights in Fifteenth-Century Granada     

Cristina de la Puente 《Al-Masaq: Islam & the Medieval Mediterranean》2009,21(3):338-340

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On the substitution of the native sulphate of magnesia for salphuric acid in the manufacture of hydrochloric acid,sulphate of soda,nitric acid,and chlorine     

M. Ramon de Luna 《Journal of The Franklin Institute》1840,30(5):351-352

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The weakening of steam boilers by cutting holes in the shell for domes and necks     

W. Barnet Le Van 《Journal of The Franklin Institute》1880,110(5):313-323

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Dust showers     

Washington Jones  W Barnet Le Van  Tinius Olsen  William M Henderson  Wm.D Marks 《Journal of The Franklin Institute》1880,110(2):106-114

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