Influence of force-vector and force application plyometric training in young elite basketball players

Plyometric training composed by unilateral exercises with horizontal jumping direction seems to be an effective way to improve physical performance in athletes. The present study aimed to compare the influence of a combined jumping direction and force application (horizontal-unilateral vs. vertical-bilateral) plyometric training on linear sprinting, jumping, change of direction (COD) and dynamic balance in young elite basketball players. Twenty young (U-13 to U-14) male basketball players (age: 13.2?±?0.7 years, body mass: 59.5?±?12.7?kg, height: 172.9?±?7.9?cm) were randomly assigned either to a unilateral-horizontal (UH, n?=?10) or bilateral-vertical (BV, n?=?10) plyometric group, twice a week for 6-wk. Both groups performed between 60 and 100 jumps/session. UH executed all jumps unilaterally with horizontal direction, while jumps in the BV were bilaterally with vertical direction. Performance was assessed by a linear sprinting test, vertical and horizontal jumping tests, COD tests (V-cut and 5+5?m with a 180°COD test), an ankle dorsiflexion test and dynamic balance tests (anterior and postero-lateral directions). Within-group differences showed substantial improvements (Effect size (ES):0.31–1.01) in unilateral vertical and horizontal jumping, V-cut test and postero-lateral direction with right leg after both training interventions. Furthermore, UH group also substantially improved (ES:0.33–0.78) all sprinting times and postero-lateral direction with left leg, while BV enhanced anterior direction with left leg (ES:0.25). Between-group analyses showed substantially greater improvements (ES:0.33) in 10-m and V-cut test in UH than in BV. The likely beneficial effect (small ES) achieved in sprinting abilities suggests the combination of unilateral-horizontal jumps to improve such abilities.     

Comparison of centre of gravity and centre of pressure patterns in the golf swing

Analysing the centre of pressure (COP) and centre of gravity (COG) could reveal stabilising strategies used by golfers throughout the golf swing. This study identified and compared golfers’ COP and COG patterns throughout the golf swing in medial–lateral (ML) and anterior–posterior (AP) directions using principal component analysis (PCA) and examined their relationship to clubhead velocity. Three-dimensional marker trajectories were collected using Vicon motion analysis and force plate data from two Kistler force plates for 22 low-handicap golfers during drives. Golfers’ COG and COP were expressed as a percentage distance between their feet. PCA was performed on COG and COP in ML and AP directions. Relationships between principal component (PC) scores were examined using Pearson correlation and regression analysis used to examine the relationship with clubhead velocity. ML COP movements varied in magnitude (PC1), rate of change and timing (PC2 and PC3). The COP and COG PC1 scores were strongly correlated in both directions (ML: r?=?0.90, P?<?.05; AP: r?=?0.81, P?<?.05). Clubhead velocity, explained by three PCs (74%), related to timing and rate of change in COP_ML near downswing (PC2 and PC3) and timing of COG_ML late backswing (PC2). The relationship between COP_ML and COG_ML PC1 scores identified extremes of COP and COG patterns in golfers and could indicate a golfer’s dynamic balance. Golfers with earlier movement of COP to the front foot (PC2) and rate of change (PC3) patterns in ML COP, prior to the downswing, may be more likely to generate higher clubhead velocity.     

Personality and burnout among school psychologists

Personality factors along with organizational factors and interpersonal factors have commonly been thought to contribute to the experience of burnout among human services workers, including school psychologists. This study validates the relationship of personality characteristics as measured by the California Psychological Inventory (CPI) and burnout as measured by the Maslach Burnout Inventory. School psychologists with well-integrated personalities (high Factor 3 scores on the CPI) are less prone to burnout than others.     

Changes in jump performance and muscle activity following soccer-specific exercise

The jump performance of ten youth soccer players (mean age 15.8 years, s= 0.4) was assessed before and after 42 min of soccer-specific exercise performed on a non-motorized treadmill. A squat, countermovement, and drop jump were performed on a force platform and simultaneously surface EMG activity of four lower limb muscles was collected. Jump height deteriorated across all conditions with mean reductions of - 1.4 cm (s = 1.6; P < 0.05), - 3.0 cm (s = 2.9; P < 0.05), and -2.3 cm (s = 1.7; P < 0.01) in the squat, countermovement, and drop jump respectively. The impact force in the drop jump was the only force variable to show a significant change with fatigue (P < 0.05). Following the prolonged exercise, reductions in total muscle activity were non-significant for the squat jump, approached significance for the counter-ovement jump (P = 0.07), and achieved significance for the drop jump (P < 0.05). The results showed that completing soccer-specific exercise reduced performance in all jump tasks. Reductions in muscle activity were greatest for the drop jump, suggesting an influence of muscle stretch and loading on reduced muscle activity when fatigued.