Effect of different loading conditions on running mechanics at different velocities     

Germán Carretero-Navarro  Doménico Cherubini  Wolfgang Taube 《European Journal of Sport Science》2019,19(5):595-602

Weighted vests are widely used to improve running economy and performance. However, it is not well-studied how running mechanics are adapted to counteract the higher peak vertical ground reaction forces (Fpeak) while running with such a device. Therefore, the present study aimed to investigate the effects of different loading conditions on running mechanics at different velocities. Thirteen subjects participated in two separate sessions one week apart. In the first session, maximal aerobic speed (MAS) was determined through a maximal incremental running test while in the second session, they were instructed to run during one minute under different loading (0%, +10% and +20% of body mass [BM]) and velocity (60%, 80% and 100% of MAS) conditions in a random order. Spatiotemporal data were recorded and then running mechanics modelled using the spring-mass model. The main results indicated that vertical and leg stiffness (Kvert and Kleg, respectively) were increased (P?P?>?.05) when load was changed. At the same time, alterations of the running kinematics were observed such as longer contact times, reduced flight times, stride frequencies and step lengths, as well as an increase of the centre of mass dynamics. Based on these results it is assumed that runners maintain a certain stiffness level for each velocity despite different loading conditions. As a consequence, Fpeak increases and this probably causes spatiotemporal adjustments in the movement kinematics.  相似文献   

The ‘aggressive style’: genesis of an ambiguous resource for Swiss hockey and football players     

Orlan Moret  Alan Traclet  Alain Clémence 《Sport in Society》2019,22(3):399-415

In this study, we investigated what drives players to endorse an aggressive style in Swiss ice hockey and football. We selected a sample of 16 players on the basis of their penalty statistics. We used semi-directed retrospective interviews to collect players’; biographic narratives. The results show a socialization process into an aggressive style, supported by the dominant gender and socialization norms of the sport, which is under the influence of the structure of the sports organization. However, there are large differences between players, with only some of them adopting an aggressive style. Although many studies have underlined the influence of moral disengagement, the present results suggest that time also matters and that the diversity of career paths may explain the diversity in attitudes. Socialization differences in the sports field, bodily capital, a career path marked by thwarted reputation are the key factors that drive players to adopt an aggressive style.  相似文献   

Coeducational and single-sex physical education: students’ situational interest in learning tasks centred on technical skills     

Vanessa Lentillon-Kaestner  Cédric Roure 《Physical Education & Sport Pedagogy》2019,24(3):287-300

Background: A student’s choice to engage in a learning task is highly related to the student’s environmental stimuli and his or her perception of interest. From this perspective, the construct of situational interest (SI) has been used to interpret students’ motivation in task engagement. SI is assumed to be transitory, environmentally activated, and context specific. It has been conceptualized as a multidimensional construct with five dimensions: instant enjoyment, exploration intention, attention demand, novelty, and challenge. Few prior studies have compared SI between girls and boys in physical education (PE) contexts, and these studies have offered contrasting findings. They were conducted in coeducational (coed) or single-sex contexts and used learning tasks centred on a variety of outcomes: technical or tactical skills, creativity and cultural understanding.

Purpose: In the context of the debate on single-sex and coed classes in PE, this study aimed to estimate the effects of single-sex and coed PE classes on students’ situational interest (SI) within learning tasks centred on technical skills. The researchers decided to study learning tasks centred on the development of students’ technical skills, since these tasks are often used by teachers in PE.

Participants: The sample consisted of 177 Swiss secondary school students, aged 11–17 years (M?=?14.07, SD?=?1.41, 96 boys, 81 girls).

Data collection: The students completed the French 15-item SI Scale after practising a technical learning task in single-sex and coed PE contexts. The researchers chose five physical activities (i.e. athletics, basketball, dance, gymnastics, and volleyball), which are commonly taught in the state of Vaud (Switzerland) and provide a balance between masculine and feminine activities.

Data analysis: A two-way repeated-measures MANOVA was performed to examine the main and interaction effects of student sex and class sex composition on the five SI dimensions.

Findings: The results showed a main effect of class sex composition on student SI but no main effect of student sex and no interaction effect of student sex and class sex composition. More precisely, the scores for three SI dimensions (i.e. instant enjoyment, exploration intention, and attention demand) were higher in the coed context than in the single-sex context.

Conclusions: This study encourages teachers to propose coed PE classes to enhance students’ motivation and engagement when practising learning tasks centred on technical skills. This study offers supplementary evidence of the teacher’s role in promoting student SI. Beyond accounting for students’ dispositional factors (e.g. sex), PE teachers can significantly impact students’ SI in technical learning tasks through instructional choices.  相似文献   

Key somatic variables in young backstroke swimmers     

Senda Sammoud  Alan Michael Nevill  Yassine Negra  Raja Bouguezzi  Chaabene Helmi  Younés Hachana 《Journal of sports sciences》2019,37(10):1162-1167

The purpose of this study was to estimate the optimal body size, limb-segment length, girth or breadth ratios for 100-m backstroke mean speed performance in young swimmers. Sixty-three young swimmers (boys [n = 30; age: 13.98 ± 0.58 years]; girls [n = 33; age: 13.02 ± 1.20 years]) participated in this study. To identify the optimal body size and body composition components associated with 100-m backstroke speed performance, we adopted a multiplicative allometric log-linear regression model, which was refined using backward elimination. The multiplicative allometric model exploring the association between 100-m backstroke mean speed performance and the different somatic measurements estimated that biological age, sitting height, leg length for the lower-limbs, and two girths (forearm and arm relaxed girth) are the key predictors. Stature and body mass did not contribute to the model, suggesting that the advantage of longer levers was limb-specific rather than a general whole-body advantage. In fact, it is only by adopting multiplicative allometric models that the abovementioned ratios could have been derived. These findings highlighted the importance of considering somatic characteristics of young backstroke swimmers and can help swimming coaches to classify their swimmers and enable them to suggest what might be the swimmers’ most appropriate stroke (talent identification).  相似文献   

Systems model and individual simulations of training strategies in elite short-track speed skaters     

Thibaut Méline  Ludovic Mathieu  Fabio Borrani  Robin Candau 《Journal of sports sciences》2019,37(3):347-355

This study aimed to evaluate the effect of simulated training strategies on performance potential in elite short-track speed skaters. Training load and field-based criterion performances from fifteen athletes (10 males, 5 females) were collected over a 3-month training period and the relationship between training loads and performance was computed with a variable dose-response model using a genetic algorithm. Individual simulations of tapers preceded or not preceded by an overload training (OT) were assessed. We obtained a significant correlation between actual and modelled performances (R² = 0.76 ± 0.07). Regarding model parameters, no significant difference was found between males and females but the time to recover performance tended to be lower in females. Simulations in which the taper parameters were free highlighted that an exponential or a step taper were the most effective for increasing performance compared to a linear taper (p < 0.05). Optimal exponential taper duration after OT was 10.7 ± 2.4d and the optimal load reduction was 75.9 ± 3.7%. OT intensity had the greatest influence on the predicted performance, followed by OT duration, taper decay, and to a lesser extent load reduction during taper and taper duration. Thus, a variable dose-response systems model allows the evaluation of different taper strategies and their potential effect on performance changes.  相似文献   

The effects of a calf pump device on second half performance of a simulated soccer match in competitive youth players     

S. Béliard  J. Cassirame  G. Ennequin  G. Coratella  N. Tordi 《Journal of sports sciences》2019,37(6):708-716

During soccer matches, performance decrements have been reported that relate to both physical abilities and technical skills. To investigate the effects of low-frequency electrical stimulation LFES (VeinoplusSport®, Ad Rem Technology, France) administered during half-time recovery on performance alterations during the second half. Twenty-two highly trained young players undertook a soccer-match simulation (SAFT⁹⁰). During half-time, they were randomly assigned to LFES group or Placebo group. Each half was split into 3 bouts of 12 minutes. Following each bout, maximal strike speed (MSS), sprint test (ST), maximal sprint accelerations (MA) and metabolic power (MP) were determined in both groups. Arterial (AF) and venous flows (VF) were measured at rest and at the end of half-time. LEFS group exhibited beneficial effects on performance compared to the Placebo group with a likely effect for MSS, ST, MA, and a possible effect for MP. AF and VF increased statistically more in LEFS group compared to Placebo group. The use of specific calf-pump LFES during half-time of a youth simulated soccer match attenuated the decrease in performance during the second half compared to Placebo group. This effect is most marked at the beginning of the second half with regards to explosive parameters.  相似文献   

Validity and reliability of a low-cost dynamometer to assess maximal isometric strength of upper limb     

Natalia Romero-Franco  Juan C Fernández-Domínguez  Juan A Montaño-Munuera  Javier Romero-Franco  Pedro Jiménez-Reyes 《Journal of sports sciences》2019,37(15):1787-1793

Muscle imbalance and deficit are key parameters for guiding rehabilitation and sports sessions and avoiding injuries. However, the high cost and non-portable nature of most instruments employed for muscle strength assessment frequently hamper an affordable evaluation in field conditions. This study evaluated the validity and reliability of a low-cost digital dynamometer to assess the maximal isometric strength of upper limb muscles. Fourteen physically active volunteers performed the main movements of the upper limb at maximal isometric strength: flexion-extension, internal-external rotation and abduction-adduction of the shoulder; and flexion-extension of both elbow and wrist. Validity was examined by comparing the strength values from the low-cost digital dynamometer and those measured by an isokinetic dynamometer, assumed as the gold standard. The correlation between both devices was perfect (r > 0.913), while Bland-Altman plots showed absolute agreement between both devices, the maximum range of the values of bias was ?0.99–1.00 N in wrist extension. Inter-tester and intra-tester reliability were excellent for all movements (ICC ≥ 0.855). The low-cost digital dynamometer showed strong validity and excellent reliability in assessing maximal isometric strength during the main movements of the upper limb. Professionals may use it for an affordable isometric muscle strength assessment in field situations.  相似文献   

Effect of a Brazilian Jiu-jitsu-simulated tournament on strength parameters and perceptual responses     

Daniele Detanico  Rodolfo André Dellagrana  Marina Saldanha da Silva Athayde  Rafael Lima Kons  Angel Góes 《Sports biomechanics / International Society of Biomechanics in Sports》2017,16(1):115-126

This study aimed to analyse the effects of a simulated Brazilian jiu-jitsu (BJJ) tournament on vertical jump performance, grip strength test and perceived effort responses. 22 male BJJ athletes participated in a simulated tournament consisting of three 7 min matches separated by 14 min of rest. Kimono grip strength test (KGST), counter movement jump (CMJ) and rate of perceived exertion (RPE) were measured before and after each match, while RPE of specific areas was assessed after three matches. ANOVA for repeated measures was used to compare strength parameters after each match with the level of significance set at 5%. The key results showed a significant decrease of jump height (p = 0.001) and net vertical impulse in the CMJ (p = 0.031), as well as a reduction of the number of reps in the KGST (p < 0.001). A significant increase of RPE was found throughout the matches (p < 0.001). Considering the RPE in specific areas, no differences were observed between the upper and lower body (p = 0.743). We conclude that the BJJ simulated tournament generated a decrease of performance in both upper and lower limbs and provoked a progressive increase in the effort perception over the matches.  相似文献   

‘Playing with space’: a conceptual basis for investigating active sport tourism practices     

Valérian Geffroy 《Journal of Sport Tourism》2017,21(2):95-113

ABSTRACT

This paper proposes a conceptual tool, the expression ‘playing with space’, for the analysis of active sport tourism as a meaningful social practice. The expression issues from practice theories and pragmatic understandings of space, which emphasize the processual and contextual dimensions of human action and seek to seize altogether the corporealities and shared conceptions that constitute action. On such views, sport tourists are considered as reflexive and embodied beings, enjoying sensations, mobilities and places, and constantly (re)making sense of their own practices. I argue that the notion of ‘play’ allows for a comprehensive understanding of the ways active sport tourists engage with space, where space is viewed as an object or material for this play. Three major dimensions of active sport tourism are then identified: a set of playful and game-like practices with global space resulting in shared imaginaries and large-scale mobilities; a kinaesthetic play, based on freedom and sensations and deeply engaged in the materiality of the places and the omnipresent media practices that support the other dimensions of play while being fully integrated into the experience of sport tourism. This conceptual framework is a way to better understand the motives and practices of sport tourists; it is also a way to underline wider trends of contemporary leisure cultures: such cultures are increasingly integrated into the daily spheres of activity, increasingly playful and increasingly mediatized.  相似文献   

Assessment of leg muscles mechanical capacities: Which jump,loading, and variable type provide the most reliable outcomes?     

Amador García-Ramos  Belén Feriche  Alejandro Pérez-Castilla  Paulino Padial  Slobodan Jaric 《European Journal of Sport Science》2017,17(6):690-698

This study aimed to explore the strength of the force–velocity (F–V) relationship of lower limb muscles and the reliability of its parameters (maximum force [F₀], slope [a], maximum velocity [V₀], and maximum power [P₀]). Twenty-three men were tested in two different jump types (squat and countermovement jump: SJ and CMJ), performed under two different loading conditions (free weight and Smith machine: Free and Smith) with 0, 17, 30, 45, 60, and 75?kg loads. The maximum and averaged values of F and V were obtained for the F–V relationship modelling. All F–V relationships were strong and linear independently whether observed from the averaged across the participants (r?≥?0.98) or individual data (r?=?0.94–0.98), while their parameters were generally highly reliable (F₀ [CV: 4.85%, ICC: 0.87], V₀ [CV: 6.10%, ICC: 0.82], a [CV: 10.5%, ICC: 0.81], and P₀ [CV: 3.5%, ICC: 0.93]). Both the strength of the F–V relationships and the reliability of their parameters were significantly higher for (1) the CMJ over the SJ, (2) the Free over the Smith loading type, and (3) the maximum over the averaged F and V variables. In conclusion, although the F–V relationships obtained from all the jumps tested were linear and generally highly reliable, the less appropriate choice for testing the F–V relationship could be through the averaged F and V data obtained from the SJ performed either in a Free weight or in a Smith machine. Insubstantial differences exist among the other combinations tested.  相似文献