Validation of an opto-electronic instrument for the measurement of weighted countermovement jump execution velocity.

The purpose of this study was to analyse the reliability and validity of an opto-electronic sensor system (Velowin) compared to a linear velocity transducer (T-Force System) considered as the gold standard. Mean velocity (MV) and peak velocity (PV) generated in the Smith machine bar placed on the shoulders in counter-movement jump exercise (CMJ) were analysed. The study was conducted with a sample of 21 men with experience in resistance training. Five measurements were analysed for CMJ exercise in concentric phase using a progressive loading increase. Three jumps were made per load with a 3-4 min recovery between loads. The analysis of the variance confirmed that there were no significant differences (p > 0.05) in the execution velocity between Velowin and T-Force with each of the loads. The reliability analysis showed, with each of the loads, high values of the intraclass correlation coefficient (ICC = 0.95-0.99) and a 'substantial' Lin´s concordance coefficient in MV (CCC ≥0.96) and between 'substantial' (CCC = 0.98) and 'almost perfect' (CCC = 0.99) in PV. These results confirm the reliability and validity of the Velowin device is reliable for measuring the execution velocity in loaded CMJ exercise.

Validation of an opto-electronic instrument for the measurement of execution velocity in squat exercise.

The purpose of this study was to analyse the reliability and validity of an opto-electronic sensor system (Velowin) for assessment of the bar-velocity in the deep squat exercise. Mean velocity, mean propulsive velocity and peak velocity generated in the deep squat exercise performed in the Smith machine bar were analysed compared to a linear velocity transducer considered as the gold standard. The study was conducted with a sample of 26 men with experience in resistance training. Six measurements were analysed for squat exercise in concentric phase using a progressive loading increase. Three consecutive repetitions were performed per load with a 3-4 min recovery between loads. Analysis of variance confirmed that there were no significant differences (p > 0.05) for the velocity variables between Velowin and T-Force for each of the loads. The reliability analysis showed high values of the intraclass correlation coefficient (ICC = 0.94-0.99), an 'almost perfect' Lin's concordance coefficient (CCC = 0.99) and a low coefficient of variation (CV <3.4%) for each of the loads and velocities. These results confirm the reliability and validity of the Velowin device for measuring the execution velocity in deep squat exercise.

The Importance of the Coach in Predicting Implicit Beliefs about Skill and Beliefs about the Causes of Success in Handball Players.

The objective of the present study was to determine the predictive capacity of the motivational climate generated by coaches and perceived by handball players on implicit beliefs about ability and beliefs about the causes of success in sport. The sample consisted of 444 youth handball players. These players completed the Beliefs about the Causes of Success in Sport Questionnaire, the Conceptions of the Nature of Athletic Ability Questionnaire, Version Two, and the Perceived Motivational Climate in Sport Questionnaire. The structural regression model showed that the mastery climate positively predicted the belief in incremental ability and that this in turn positively predicts both belief in athletic success through effort and ability. The results reflected the importance of the coach in the formative process of the player and the search for performance in sport.