Acute effects of small changes in crank length on gross efficiency and pedalling technique during submaximal cycling

ABSTRACT

The main purpose of this study was to assess the acute effects of small changes in crank length (assumable by competitive cyclists) on metabolic cost and pedalling technique during submaximal cycling. Twelve amateur road cyclists performed three sets of submaximal pedalling (150, 200 and 250 W) at a constant cadence (91.3 ± 0.8 rpm) in a randomised order with three commonly used crank lengths, preferred (172.5–175 mm), +5 mm and ?5 mm. Energy cost of pedalling, kinetic and kinematic variables were simultaneously registered. Changes in crank length had no significant effect on heart rate (144 ± 13, 145 ± 12 and 145 ± 13 bpm, respectively) and gross efficiency (GE) (20.4 ± 2.1, 20.1 ± 2.2 and 20.3 ± 2.4%, respectively). A longer crank induced a significant (P < 0.05) reduction of positive impulse proportion (PIP) (0.9–1.9%) due to a greater maximum (1.0–2.3 N · m) and minimum torque (1.0–2.2 N · m). At the same time, the maximum flexion and range of motion of the hip and knee joints were significantly increased (1.8–3.4° and P < 0.05), whereas the ankle joint was not affected. In conclusion, the biomechanical changes due to a longer crank did not alter the metabolic cost of pedalling, although they could have long-term adverse effects. Therefore, in case of doubt between two lengths, the shorter one might be recommended.     

Amid Progress and Wilderness: Early Reception of Georges Hébert’s Naturist Ideas in Brazil During the First Half of the Twentieth Century

Abstract

This paper aims at analyzing how Hébert’s naturist ideas were received and assimilated in Brazil based on the perusal of sources such as Azevedo (1915, 1920, 1931), Miranda (1945) as well as some broadsheets and periodicals, for example Correio da Manhã, O Paiz, Gazeta de Noticias, and Fon-Fon! (1913–1928). Furthermore, it investigates by what means Hébert’s conception of nature integrated the mindset of Brazilian sanitarians in the first half of the twentieth century. Evidence suggests that there must have been some intertwinement of points of view that brought together Hebert’s Natural Method and the French Naturist Perspective at the time of the arrival of the latter in Brazil. Hébert’s thoughts on the concept of Nature reached Brazil early in the 1910s, and were incorporated in the shaping of a new approach to therapeutic treatments focused on preserving the patient’s welfare. As a result, this study has enabled us to properly understand the reception of Hébert’s works in Brazil, and come to terms with the historical connection between French gymnastic practices based on the Natural Method and their subsequent acclimatized Brazilian variants.     

Football and justice devices: hybrid ethical narratives,sanctions and legitimacy of interests

The concept of justice has gradually colonized sports’ narratives in general and professional football ones in particular. Discourses on justice often give rise to ambiguous, unclear narrations with a great deal of noise and opportunism. The aim of this article is to apply the concept of justice devices to clarify the range of measures used and link these to the diverse agents that attempt to gain legitimacy and power through them. In an initial characterisation, we highlight conventional and post-conventional models of ethics of justice. Subsequently, we compare these models to the systems of justice employed by football’s governing institutions, FIFA and UEFA. Finally, we analyse a paradigmatic event of judicial interpretation by various actors using the case of ‘Luiz Adriano’. In this article, we reveal some of the specific uses, settings and strategic aims of justice devices employed by the main actors involved in international football.     

Metabolic demand and muscle damage induced by eccentric cycling of knee extensor and flexor muscles

The aim of this study was to examine the metabolic demand and extent of muscle damage of eccentric cycling targeting knee flexor (FLEX) and knee extensor (EXT) muscles. Methods: Eight sedentary men (23.3?±?0.7?y) underwent two eccentric cycling sessions (EXT and FLEX) of 30?min each, at 60% of the maximum power output. Oxygen consumption (VO₂), heart rate (HR) and rated perceived exertion (RPE) were measured during cycling. Countermovement and squat jumps (CMJ and SJ), muscle flexibility, muscle soreness and pain pressure threshold (PPT) of knee extensor and flexor muscles were measured before, immediately after and 1–4 days after cycling. Results: FLEX showed greater VO₂ (+23%), HR (+14%) and RPE (+18%) than EXT. CMJ and SJ performance decreased similarly after cycling. Muscle soreness increased more after EXT than FLEX and PPT decreased in knee extensor muscles after EXT and decreased in knee flexor muscles after FLEX. Greater loss of muscle flexibility in knee flexor muscles after FLEX was observed. Conclusion: Eccentric cycling of knee flexor muscles is metabolically more demanding than that of knee extensors, however muscle damage induced is similar. Knee flexors experienced greater loss of muscle flexibility possibly due to increased muscle stiffness following eccentric contractions.     

Effects of dynamic resistance training on fascicle length and isometric strength

The aims of this study were to assess changes in muscle architecture, isometric and dynamic strength of the leg extensor muscles, resulting from dynamic resistance training, and the relationships between strength and muscle architecture variables. The participants (n = 30) were randomly assigned to one of two groups. The training group (n = 16; age 21.8 +/- 2.3 years, body mass 74.8 +/- 9.2 kg, height 1.75 +/- 0.08 m) performed dynamic resistance training for 13 weeks. The control group (n = 14; age 19.9 +/- 1.5 years, body mass 74.0 +/- 8.5 kg, height 1.76 +/- 0.05 m) did not perform any resistance training. Maximal dynamic and isometric strength were tested in both groups, before and after the training period. The members of the training group used the free-weight squat lift (90 degrees ) as their training exercise. The concentric phase of the squat was performed explosively. Skeletal muscle architecture of the vastus lateralis was visualized using ultrasonography. At the end of the study, significant increases in vastus lateralis muscle thickness (+6.9%, P < 0.001), fascicle length (+10.3%, P < 0.05), one-repetition maximum (+8.2%, P < 0.05), rate of force development (+23.8%, P < 0.05) and average force produced in the first 500 ms (+11.7%, P < 0.05) were seen only in the training group. Adaptations to the muscle architecture in the training group limited the loss of fibre force, and improved the capacity for developing higher velocities of contraction. The architectural changes in the training group were similar to those seen in studies where high-speed training was performed. In conclusion, dynamic resistance training with light loads leads to increases in muscle thickness and fascicle length, which might be related to a more efficient transmission of fibre force to the tendon.     

Low-dose exercise training does not influence cardiac autonomic control in healthy sedentary men aged 55-75 years

The purpose of this study was to evaluate the effects of a realistic, feasible, and commonly used fitness training programme on cardiac autonomic control in 14 sedentary men aged 62.0 +/- 6.1 years (mean +/- s). All participants performed a one-year fitness training programme in which training intensity and frequency were specifically chosen to be compliant for the majority of the participants (2-3 sessions per week at moderate intensity). At the same time, a reference group consisting of 15 sedentary age-matched men (age 64.2 +/- 6.5 years) did not change their habitual physical activity. Measurements were performed before and after the training intervention. Cardiac autonomic control was inferred from resting values (supine and standing) of heart rate variability (HRV) computed in the frequency domain over 10-min intervals. Endurance capacity was evaluated during a maximal incremental bicycle ergometer test. In spite of an increase in peak oxygen consumption (VO2peak) by 6.4% after training, heart rate in the training group remained unchanged at rest and at the same metabolic demand. No changes in resting parameters of HRV were shown for either groups or positions. Results from this study provide no evidence of a clinically meaningful increase in the vagal modulation to the sinus node at rest after one year of low-volume and moderate-intensity fitness training in men aged 55-75 years.     

Evaluation of Neuroanatomy Web Resources for Undergraduate Education: Educators’ and Students’ Perspectives

Despite the development of novel teaching strategies and the abundance of adjunct teaching web resources, students and early career physicians have continuously reported difficulties in learning and clinically applying neuroanatomy. Differences in instructional design of these resources, the lack of assessment of their capacity to meet intended educational goals, and a poor understanding of the user’s perspective may have hindered their success in increasing understanding and retention of neuroanatomical knowledge. To decipher the limitations of existing web resources, an online search for neuroanatomy web resources was performed and distilled through a strict filtration rubric. A selection of resources were analyzed by a panel of educators and rated using Likert scales, focusing on the identification of features influencing their usefulness in learning the anatomy of the spinal pathways. The top three ranked web resources were subsequently evaluated by a panel of medical and neuroscience students to assess how specific features aided in their learning of the subject. This detailed analysis has identified features of neuroanatomy web resources that are valued by both educators and users with regard to instructional design. One resource was rated highest by end users and educators on a series of Likert scale questions in terms of clarity of explanation, step-wise teaching design, summarization of information, control of instructional-pace, integration with neurophysiology, neuroradiology and clinical correlates, deployment of a wide array of pedagogical tools, and factors for visualizing neuroanatomical inter-relationships. These results have provided a novel user perspective on the influence of specific elements of neuroanatomy web resources to improve instructional design and enhance learner performance.     

现代互联网环境下茶学文献的高效获取

综述了获取茶学文献的传统方法和现代网络条件下的新途径。高效率的现代文献检索和获取途径主要包括:利用网络搜索引擎途径、电子出版物的计算机光盘检索途径、大型文献数据库的联机检索途径。文章还介绍了一些科技文献资料的网络数据库资源以及通过这些资源获取茶学文献的具体方法。     

How does one recognize contextual mitigating factors (CMFs) as a basis to understand and arrive at better approaches to research designs?

Cultural Studies of Science Education - In this paper we introduce the concept of contextual mitigating factors (CMFs) as an analytical tool for interrogating the contextual landscapes that situate...