THE COUNTERMOVEMENT JUMP (CMJ) TEST IS COMMONLY CONDUCTED TO ASSESS NEUROMUSCULAR FUNCTION AND IS BEING INCREASINGLY PERFORMED USING FORCE PLATFORMS. COMPREHENSIVE INSIGHT INTO ATHLETES' NEUROMUSCULAR FUNCTION CAN BE GAINED THROUGH DETAILED ANALYSES OF FORCE-TIME CURVES THROUGHOUT SPECIFIC PHASES OF THE CMJ, BEYOND JUMP HEIGHT ALONE. CONFUSINGLY, HOWEVER, MANY DIFFERENT TERMS AND METHODS HAVE BEEN USED TO DESCRIBE THE DIFFERENT PHASES OF THE CMJ. THIS ARTICLE DESCRIBES HOW 6 KEY PHASES OF THE CMJ (WEIGHING, UNWEIGHTING, BRAKING, PROPULSION, FLIGHT, AND LANDING) CAN BE DERIVED FROM FORCE-TIME RECORDS TO FACILITATE RESEARCHERS' AND PRACTITIONERS' UNDERSTANDING AND APPLICATION TO THEIR OWN PRACTICE.

Changes of direction (CODs) are key manoeuvres linked to decisive moments in sport and are also key actions associated with lower limb injuries. During sport athletes perform a diverse range of CODs, from various approach velocities and angles, thus the ability to change direction safely and quickly is of great interest. To our knowledge, a comprehensive review examining the influence of angle and velocity on change of direction (COD) biomechanics does not exist. Findings of previous research indicate the biomechanical demands of CODs are ‘angle’ and ‘velocity’ dependent and are both critical factors that affect the technical execution of directional changes, deceleration and reacceleration requirements, knee joint loading, and lower limb muscle activity. Thus, these two factors regulate the progression and regression in COD intensity. Specifically, faster and sharper CODs elevate the relative risk of injury due to the greater associative knee joint loading; however, faster and sharper directional changes are key manoeuvres for successful performance in multidirectional sport, which subsequently creates a ‘performance-injury conflict’ for practitioners and athletes. This conflict, however, may be mediated by an athlete’s physical capacity (i.e. ability to rapidly produce force and neuromuscular control). Furthermore, an ‘angle-velocity trade-off’ exists during CODs, whereby faster approaches compromise the execution of the intended COD; this is influenced by an athlete’s physical capacity. Therefore, practitioners and researchers should acknowledge and understand the implications of angle and velocity on COD biomechanics when: (1) interpreting biomechanical research; (2) coaching COD technique; (3) designing and prescribing COD training and injury reduction programs; (4) conditioning athletes to tolerate the physical demands of directional changes; (5) screening COD technique; and (6) progressing and regressing COD intensity, specifically when working with novice or previously injured athletes rehabilitating from an injury.

THE ISOMETRIC MIDTHIGH PULL (IMTP) IS COMMONLY USED TO ASSESS AN ATHLETE'S FORCE GENERATION ABILITY. THIS TEST IS HIGHLY RELIABLE AND IS SIMPLE AND RELATIVELY QUICK TO PERFORM. THE DATA THAT CAN BE DETERMINED FROM THE FORCE–TIME CURVES GENERATED BY THE TEST HAVE BEEN SHOWN TO BE CLOSELY RELATED TO PERFORMANCE CAPACITIES IN A VARIETY OF DYNAMIC ATHLETIC TASKS. HOWEVER, WITHIN THE SCIENTIFIC LITERATURE, THERE ARE INCONSISTENCIES IN THE DATA COLLECTION PROCEDURES AND METHODS USED FOR DATA ANALYSIS THAT MAY IMPACT THE RESULTANT OUTPUT AND THE ABILITY TO COMPARE AND GENERALIZE RESULTS. THEREFORE, THE PRIMARY AIM OF THIS REVIEW IS TO IDENTIFY THE DIFFERENCES IN IMTP TESTING PROCEDURES AND DATA ANALYSIS TECHNIQUES, WHEREAS IDENTIFYING THE POTENTIAL IMPACT THIS MAY HAVE ON THE DATA COLLECTED. THE SECONDARY AIM IS TO PROVIDE RECOMMENDATIONS FOR THE STANDARDIZATION OF TESTING PROCEDURES TO ENSURE THAT FUTURE IMTP DATA ARE OF MAXIMAL BENEFIT TO PRACTITIONERS AND RESEARCHERS. FOR A VIDEO ABSTRACT OF THIS ARTICLE, SEE SUPPLEMENTAL DIGITAL CONTENT 1 (SEE VIDEO, HTTP://LINKS.LWW.COM/SCJ/A249).

Performance in adult athletes; however, this relationship in younger athletes has been less extensively studied. The aim of this study, therefore, was to determine the relationships between strength, sprint, and jump performances in well-trained youth soccer players. Thirty-four young male soccer players (17.2 ± 0.6 years; body mass, 72.62 ± 7.42 kg; height, 179.27 ± 6.58 cm) performed a predicted maximal squat test, 20-m sprints, squat jumps (SJs), and countermovement jumps (CMJs). Absolute strength showed the strongest correlations with 5-m sprint times (r = −0.596, p < 0.001, power = 0.99), SJ height (r = 0.762, p < 0.001, power = 1.00), and CMJ height (r = 0.760, p < 0.001, power = 1.00), whereas relative strength demonstrated the strongest correlation with 20-m sprint times (r = −0.672, p < 0.001, power = 0.99). The results of this study illustrate the importance of developing high levels of lower-body strength to enhance sprint and jump performance in youth soccer players, with stronger athletes demonstrating superior sprint and jump performances....

Dos'Santos, T, Thomas, C, Jones, PA, and Comfort, P. Mechanical determinants of faster change of direction speed performance in male athletes. J Strength Cond Res 31(3): 696–705, 2017—Mechanical variables during change of directions, for example, braking and propulsive forces, impulses, and ground contact times (GCT) have been identified as determinants of faster change of direction speed (CODS) performance. The purpose of this study was to investigate the mechanical determinants of 180° CODS performance with mechanical characteristic comparisons between faster and slower performers; while exploring the role of the penultimate foot contact (PEN) during the change of direction. Forty multidirectional male athletes performed 6 modified 505 (mod505) trials (3 left and right), and ground reaction forces were collected across the PEN and final foot contact (FINAL) during the change of direction. Pearson's correlation coefficients and coefficients of determination were used to explore the relationship between mechanical variables and mod505 completion time. Independent T-tests and Cohen's d effect sizes (ES) were conducted between faster (n = 10) and slower (n = 10) mod505 performers to explore differences in mechanical variables. Faster CODS performance was associated (p ≤ 0.05) with shorter GCTs (r = 0.701–0.757), greater horizontal propulsive forces (HPF) (r = −0.572 to −0.611), greater horizontal braking forces (HBF) in the PEN (r = −0.337), lower HBF ratios (r = −0.429), and lower FINAL vertical impact forces (VIF) (r = 0.449–0.559). Faster athletes demonstrated significantly (p ≤ 0.05, ES = 1.08–2.54) shorter FINAL GCTs, produced lower VIF, lower HBF ratios, and greater HPF in comparison to slower athletes. These findings suggest that different mechanical properties are required to produce faster CODS performance, with differences in mechanical properties observed between fast and slower performers. Furthermore, applying a greater proportion of braking force during the PEN relative to the FINAL may be advantageous for turning performance.