Static and dynamic accuracy of a magnetic-inertial measurement unit used to provide racket swing kinematics

Magnetic-inertial measurement units (MIMUs) are becoming more prevalent in sports biomechanics and may be a viable tool to evaluate kinematic parameters. This study examined the accuracy of a MIMU to estimate orientation angles under static conditions and dynamically from a squash racket during a forehand drive shot. A MIMU was mounted onto a goniometer and moved through 0–90°, with static data collected at 10° increments during 10 repetitions of all three axes. Typical error analyses showed the MIMU to be very reliable (TE ≤ 0.03°). MIMU accuracy was determined via intraclass correlation coefficients (ICC) (r > 0.999, p < 0.001). An ordinary least products regression showed no proportional bias and minimal fixed bias for all axes. Dynamic accuracy was assessed by comparing MIMU and optical motion capture data of squash racket swing kinematics. A MIMU was fixed onto a racket and 10 participants each hit 10 forehand shots. Mean orientation angle error at ball impact was <0.50° and ICC showed very high correlations (r ≥ 0.988, p < 0.001) for all orientations. Swing phase root mean squared errors were ≤2.20°. These results indicate that a MIMU could be used to accurately and reliably estimate selected racket swing kinematics.     

Effects of age and spa treatment on match running performance over two consecutive games in highly trained young soccer players

The aim of this study was to examine the effect of age and spa treatment (i.e. combined sauna, cold water immersion, and jacuzzi) on match running performance over two consecutive matches in highly trained young soccer players. Fifteen pre- (age 12.8 ± 0.6 years) and 13 post- (15.9 ± 1 y) peak height velocity (PHV) players played two matches (Matches 1 and 2) within 48 h against the same opposition, with no specific between-match recovery intervention (control). Five post-PHV players also completed another set of two consecutive matches, with spa treatment implemented after the first match. Match running performance was assessed using a global positioning system with very-high-intensity running (> 16.1-19.0 km · h(-1)), sprinting distance (>19 km · h(-1)), and peak match speed determined. Match 2 very-high-intensity running was "possibly" impaired in post-PHV players (-9 ± 33%; ± 90% confidence limits), whereas it was "very likely" improved for the pre-PHV players (+27 ± 22%). The spa treatment had a beneficial impact on Match 2 running performance, with a "likely" rating for sprinting distance (+30 ± 67%) and "almost certain" for peak match speed (+6.4 ± 3%). The results suggest that spa treatment is an effective recovery intervention for post-PHV players, while its value in pre-PHV players is questionable.     

Multidisciplinary graduate training in social research methodology and computer-assisted qualitative data analysis: a hands-on/hands-off course design

Drawing on the experience of training graduate students and researchers in qualitative and mixed-methods analysis since the mid-1990s, the authors reflect on the evolution of a multidisciplinary graduate course developed in a Canadian university since 2007. The hands-on/hands-off course design based on the use of NVivo was developed in parallel with a conceptual and reflexive position on methodology and multidisciplinarity in the context of an action research supported by their institution. This article exposes the four basic components of the course and the constructivist assessment model based on a term-long team analysis of original data created specifically for this purpose. The balance between collective and individual work, in-class and online exchanges, hands-on experience with the software and hands-off reflection is described and compared to recent pedagogical literature on the subject. The interest of this blended approach in fostering the development of the methodological expertise expected from researchers and graduate students, as well as the main issues and challenges facing this type of training in a research environment characterised by new approaches and tools, are discussed.     

Age-related differences in acceleration, maximum running speed, and repeated-sprint performance in young soccer players

We investigated age-related differences in the relationships among acceleration, maximum running speed, and repeated-sprint performance in 61 highly trained young male soccer players (Under 14, n = 14; Under 16, n = 22; Under 18, n = 25). We also examined the possible influence of anthropometry (stature, body mass, fat-free mass) and biological maturation (age at peak height velocity) on performance in those three sprint-running qualities. Players were tested for 10-m sprint (acceleration), flying 20-m sprint (maximum running speed), and 10 × 30-m sprint (repeated-sprint performance) times. Correlations between acceleration, maximum running speed, and repeated-sprint performance were positive and large to almost perfect (r = 0.55-0.96), irrespective of age group. There were age-based differences both in absolute performance in the three sprint-running qualities (Under 18 > Under 16 > Under 14; P < 0.001) and when body mass and fat-free mass were statistically controlled (P < 0.05). In contrast, all between-group differences disappeared after adjustment for age at peak height velocity (P > 0.05). The large correlations among acceleration, maximum running speed, and repeated-sprint performance in all age groups, as well as the disappearance of between-group differences when adjusted for estimated biological maturity, suggest that these physical qualities in young highly trained soccer players might be considered as a general quality, which is likely to be related to qualitative adaptations that accompany maturation.     

Influence of kick frequency on metabolic efficiency and performance at a severe intensity in international monofin-swimmers

The aim of this study was to examine the effect of kick frequency on metabolic efficiency and performance in elite monofin-swimmers at the surface. Seven participants of international calibre were requested to perform three separate time limit exercises conducted at an intensity corresponding to 97.5% of the velocity at the maximal oxygen uptake. The first Time Limit exercise was systematically conducted at a freely chosen kick frequency (FCK(F)) and the other Time Limit exercises were performed in random order at FCK(F)-10% and FCK(F) + 10%. The slow component of oxygen uptake (VO2sc) was identified independently of the Time Limit exercise (ranging from 180 to 243 ml · min(-1), P < 0.05). No significant change in energy cost of aquatic locomotion (ranging from 565 to (596 J · m(-1)) and [VO2sc) responses was observed between the three Time Limit exercises. An increase or decrease of 10% of the FCK(F) was associated with a significant reduction in Time Limit of -47.3% and -49.1%, respectively (P < 0.05). The analysis of the Time Limit exercise indicates that the selection of kick frequency other than FCK(F) is detrimental to overall monofin-swimming performance. Furthermore, the study results showed that the indicators of metabolic efficiency such as energy cost or [VO2sc) do not determine the performance response in elite monofin-swimmers at a severe intensity.     

Contradictions as the driving force of collective and subjective development group employment programmes

This paper explores the role of collective contradictions in the development of participants in a group employment programmes. It presents an analysis, rooted in cultural-historical activity theory, of longitudinal data collected during an intervention aimed at social and professional reintegration of people living a long-term unemployment situation. Notably based on contradictions typology proposed by Y. Engeström and Sannino (2011), our analysis shows a predominance of discursive manifestations of conflicts and critical-conflicts in the transformation of the group’s activity. The contribution to the resolution of contradiction and the mobilization of scientific and systematic conceptual instruments seems to promote the processes of consciousness that allow, on the one hand, a better understanding of what shapes these actions, thoughts and emotions, and on the other hand, a greater control or mastery thereof. This inclusion of conceptual knowledge in the curricula of employment programmes plays a critical role in the empowerment of participants. The analysis of the collective activity of groups aimed at social and professional integration shows the importance of dialectical contradictions as a driving force for development, both in terms of collective and subjective activity. Findings support the benefits of the group context in helping participant’s development towards SPI.