Force–velocity characteristics of upper limb extension during maximal wheelchair sprinting performed by healthy able-bodied females

The aim of this study was to determine the relationship between force and velocity parameters during a specific multi-articular upper limb movement – namely, hand rim propulsion on a wheelchair ergometer. Seventeen healthy able-bodied females performed nine maximal sprints of 8?s duration with friction torques varying from 0 to 4?N?·?m. The wheelchair ergometer system allows measurement of forces exerted on the wheels and linear velocity of the wheel at 100 Hz. These data were averaged for the duration of each arm cycle. Peak force and the corresponding maximal velocity were determined during three consecutive arm cycles for each sprint condition. Individual force–velocity relationships were established for peak force and velocity using data for the nine sprints. In line with the results of previous studies on leg cycling or arm cranking, the force–velocity relationship was linear in all participants (r?=??0.798 to ?0.983, P?<0.01). The maximal power output (mean 1.28?W?·?kg^?1) and the corresponding optimal velocity (1.49?m?·?s^?1) and optimal force (52.3?N) calculated from the individual force–velocity regression were comparable with values reported in the literature during 20 or 30?s wheelchair sprints, but lower than those obtained during maximal arm cranking. A positive linear relationship (r?=?0.678, P?<0.01) was found between maximal power and optimal velocity. Our findings suggest that although absolute values of force, velocity and power depend on the type of movement, the force–velocity relationship obtained in multi-articular limb action is similar to that obtained in wheelchair locomotion, cycling and arm cranking.     

Urinary creatine and methylamine excretion following 4 × 5 g · day−1 or 20 × 1 g · day−1 of creatine monohydrate for 5 days

Abstract

In this study, we examined the effect of two creatine monohydrate supplementation regimes on 24-h urinary creatine and methylamine excretion. Nine male participants completed two trials, separated by 6 weeks. Participants ingested 4 × 5 g · day^?1 creatine monohydrate for 5 days in one trial and 20 × 1 g · day^?1 for 5 days in the other. We collected 24-h urine samples on 2 baseline days (days 1–2), during 5 days of supplementation (days 3–7), and for 2 days post-supplementation (days 8–9). Urine was assayed for creatine using high-performance liquid chromatography and methylamine using gas chromatography. Less creatine was excreted following the 20 × 1 g · day^?1 regime (49.25 ± 10.53 g) than the 4 × 5 g · day^?1 regime (62.32 ± 9.36 g) (mean ± s; P < 0.05). Mean total excretion of methylamine (n = 6) over days 3–7 was 8.61 ± 7.58 mg and 24.81 ± 25.76 mg on the 20 × 1 g · day^?1 and 4 × 5 g · day^?1 regimes, respectively (P < 0.05). The lower excretion of creatine using 20 × 1 g · day^?1 doses suggests a greater retention in the body and most probably in the muscle. Lower and more frequent doses of creatine monohydrate appear to further attenuate formation of methylamine.     

Book reviews

Ohne Zusammenfassung

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Book reviews

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Analyses Bibliographiques

     

Complex Education Systems: from steering change to governance

The theories and approaches of steering/monitoring a process of change within education systems have evolved over the last 20 years or so as a result of many factors such as globalisation and decentralisation, a faster pace of change, increasing expectations and demands from various stakeholders (parents, employers, teacher unions, etc.) and the growing influence of OECD and of the EU in the field of education because of some more or less explicit standards and policy recommendations. All these evolutions contributed to increase the complexity of the education systems and of the instruments and procedures required to establish some coherence between the initiatives of a large number of more autonomous stakeholders. Our main objective here is to describe how the previous notions and concepts used in analysing the conditions for steering education systems have been gradually integrated within a larger paradigm: the ‘governance of multi‐level complex education systems’.