RADIO-ULNAR PRONATION VS FOREARM EXTENSION: WHICH THE BEST TO REACH THE MAXIMAL BADMINTON RACKET VELOCITY?

Aim. Forearm extension and radio-ulnar pronation are two common components of the final movement during each badminton smash stroke. By coordinating the forearm to produce both extension and pronation at the same time, racket head velocity can be increased. Thus, this study examined maximal velocity and racket deflection during both movements in regard with skill level. Materials and methods. Twenty-two players (8 experts and 14 novices) participated in this study. Wrist, handle and racket head velocity were recorded using high speed cameras (Vicon V8i at a frequency of 250 Hz). Results. The racket head velocity with radio-ulnar pronation was 16 % higher than with forearm extension. This higher velocity resulted from an 8 % higher acceleration and a 70 % higher maximal angular velocity of the end points of the forearm segments during radio-ulnar pronation. In each movement, experts’ maximal velocity was higher than that of novices (p < .001).The maximal velocity of the racket for novices was obtained with elbow extension (20.9 ± 4.8 m/s), with a gain of 47 %, whereas for experts, it was obtained with radio-ulnar pronation (33.9 ± 5.8 m/s), with a gain of 53 %. Conclusion. The difference between the best velocities in both samples is 39 %, obtained respectively by radio-ulnar pronation for experts and an elbow extension for novices. Forearm extension and radio-ulnar pronation acceleration on the handle led to an increase in racket head velocity.

Motivational orientations and performance in penalty throws during elite male team handball games

This study is based on Regulatory Focus Theory and investigates the links between the subjects' motivational orientations for promotion or prevention and their performance in handball penalty throws. In a real-world setting with high stakes, we analyzed 327 penalties taken from 68 closed games. The results of the 7-meter throws constitute the dependent variable (Goal vs Miss). The independent variables are the situational focus ([critical moment (ie, final minute) = pressure] vs [non-critical moment = no pressure]), the reward structure (ie, [thrower's team is behind = losses reward structure] vs [thrower's team is ahead or teams are tied = gains reward structure), and the game location (home vs away). Using logistic regression analysis, the results show that when there is a fit between the situational focus and the reward structure, the thrower's performance is higher than when there is a mismatch (OR = 2.21; P = .004). In the same way, the thrower's performance is higher when there is high fit between the situational focus and the reward structure (OR = 1.78), than when there is a high mismatch (OR = 0.54). These results globally support the Regulatory Fit Theory in an ecological context.

Weightlifting and the actomyosin cycle

How does a human lift a weight? Can we relate the dynamics of the lift to the molecular actin–myosin interactions responsible for muscle contraction? We address these questions with bench press experiments that we analyse with a theoretical model, based on the sliding filament theory. The agreement is fair, and we discuss its possible extension to medical diagnostics.

Age- and gender-related development of stretch shortening cycle during a sub-maximal hopping task

The aim of this study was to analyse the effects of age and gender (and their interaction) on a stretch shortening cycle solicited during a hopping task. For this aim, 147 girls and 148 boys aged 11 to 20 years, who were enrolled in middle school or secondary school with no experience in sport activity, or training less than three times per week, performed 3×5 hops in place. Leg-stiffness, jump-height and reactive-strength indices were assessed using an accelerometer (Myotest). The participants were selected in order to form five age groups: 11 12, 13-14, 15-16, 17-18 and 19-20 years. Regression analysis between force and centre of mass displacement revealed spring-mass behaviour for all groups (r(2)=.73-.89), meaning that beginning at the age of 11 years, children are able to perform complex inter-muscular coordination of the lower limbs, revealing efficient neural control early in childhood. Leg stiffness increased from 24.7 ± 10.6 kN · m(-1) at 11-12 years to 44.1 ± 14 kN · m(-1) in boys, with a small increase until 16 years (+17%) and a large increase between 17 and 20 years (+32.7%). In girls, leg stiffness increased from 26.6 ± 9 kN · m(-1) at 11-12 years to 39.4 ± 10.9 kN · m(-1) at 19-20 years, with a curious decrease in leg stiffness at 17-18 years, probably due to an increase in the percentage of fat at this age (25%). While no gender effect was found, the reactive-strength index revealed that, from 15-16 years onward, boys were better able to produce high levels of force in a shorter time than girls. The age of 15-16 years is a threshold of maturity and gender differentiation, where the boys investigated are more efficient in the stretch shortening cycle.

Determinant factors in climbing ability: Influence of strength, anthropometry, and neuromuscular fatigue

The goal of this study was to (i) assess the physical and anthropometric differences between three levels of climbers and (ii) predict climbing ability by using a multiple regression model. The participants were divided into novice (n = 15), skilled (n = 16), and elite (n = 10) climbers. Anthropometric characteristics such as height, weight, percentage of body fat and muscle, bi-acromial breath, arm span, and ape index were measured. General and specific strength were assessed through an arm jump test, a bench press test, and a hand and finger grip strength test in maximal and endurance conditions. All variables were combined into components via a principal component analysis (PCA) and the components used in a multiple regression analysis. The major finding of this study is that climbing ability is more related to specific rather than general strength. Only finger grip strength shows a higher level of initial strength between all samples while the arm jump test discriminates between climbers and non-climbers. The PCA reveals three components, labeled as training, muscle, and anthropometry, which together explain 64.22% of the variance. The regression model indicates that trainable variables explained 46% of the total variance in climbing ability, whereas anthropometry and muscle characteristics explain fewer than 4%.

Bench press exercise: the key points

The bench press exercise (BPE) is receiving increasing interest as a field testing, training/therapeutic modality to improve neuromuscular performance or to increase bone mass density. Several studies have been performed using BPE as a standard for increasing upper-limb strength. For this purpose, the position of the bar, the loads, the sets, the number of repetitions, the recovery time in-between sets, the movement speed, the muscular work and the use of the determination of the one repetition maximum (1-RM) are the classical tools investigated in the literature that have been shown to affect the BPE effect on neuromuscular. The goal of the present short review is to make a picture of the current knowledge on the bench press exercise, which could be very helpful for a better understanding of this standard movement and its effects. Based on the related literature, several recommendations on these key points are presented here.

Reliability and validity of an accele-rometric system for assessing vertical jumping performance

The validity of an accelerometric system (Myotest©) for assessing vertical jump height, vertical force and power, leg stiffness and reactivity index was examined. 20 healthy males performed 3ד5 hops in place”, 3ד1 squat jump” and 3× “1 countermovement jump” during 2 test-retest sessions. The variables were simultaneously assessed using an accelerometer and a force platform at a frequency of 0.5 and 1 kHz, respectively. Both reliability and validity of the accelerometric system were studied. No significant differences between test and retest data were found (p < 0.05), showing a high level of reliability. Besides, moderate to high intraclass correlation coefficients (ICCs) (from 0.74 to 0.96) were obtained for all variables whereas weak to moderate ICCs (from 0.29 to 0.79) were obtained for force and power during the countermovement jump. With regards to validity, the difference between the two devices was not significant for 5 hops in place height (1.8 cm), force during squat (-1.4 N · kg⁻¹) and countermovement (0.1 N · kg⁻¹) jumps, leg stiffness (7.8 kN · m⁻¹) and reactivity index (0.4). So, the measurements of these variables with this accelerometer are valid, which is not the case for the other variables. The main causes of non-validity for velocity, power and contact time assessment are temporal biases of the takeoff and touchdown moments detection.

Principal Component Structure and Sport-Specific Differences in the Running One-Leg Vertical Jump

The aim of this study is to identify the kinetic principal components involved in one-leg running vertical jumps, as well as the potential differences between specialists from different sports. The sample was composed of 25 regional skilled athletes who play different jumping sports (volleyball players, handball players, basketball players, high jumpers and novices), who performed a running one-leg jump. A principal component analysis was performed on the data obtained from the 200 tested jumps in order to identify the principal components summarizing the six variables extracted from the force-time curve. Two principal components including six variables accounted for 78 % of the variance in jump height. Running one-leg vertical jump performance was predicted by a temporal component (that brings together impulse time, eccentric time and vertical displacement of the center of mass) and a force component (who brings together relative peak of force and power, and rate of force development). A comparison made among athletes revealed a temporal-prevailing profile for volleyball players, and a force-dominant profile for Fosbury high jumpers. Novices showed an ineffective utilization of the force component, while handball and basketball players showed heterogeneous and neutral component profiles. Participants will use a jumping strategy in which variables related to either the magnitude or timing of force production will be closely coupled; athletes from different sporting backgrounds will use a jumping strategy that reflects the inherent demands of their chosen sport.

Upper-limb motion and drop jump: effect of expertise

AIM

In this study, the role of arm motion in a drop jump was investigated in skilled and unskilled subjects.

METHODS

Nine skilled volleyball players and 8 novice individuals performed a series of jumps from two different heights: 30 cm and 60 cm. Free and restricted arm motion were used to determine the effect of arm motion on the vertical jump. Participants were instructed to land on a force plate and jump as high as possible. The ground reaction force was measured with an AMTI force plate (500 Hz). The kinematics of the jumps was recorded with two digital cameras (50 Hz).

RESULTS

The motion of the arms during the jumps was found to increase the jump height by 15% for the volleyball players and 12% for unskilled jumpers. Volleyball players performed better in the 60 cm than in 30 cm drop height (+8.5%). In the volleyball players, the peak vertical ground reaction force during take-off increased by 7%, the peak power increased by 10.6% while the peak impact force decreased by 6.3%.

CONCLUSIONS

Skilled jumpers were found to have a better use of arm motion than novices in (i) increasing the vertical jump performance, (ii) controlling the balance of the body at take-off (iii) leaving the ground with an optimal body orientation.