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).

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.

Previous studies have reported an association between eccentric strength (ECC-STR) and change of direction (COD) ability. Little is known about how ECC-STR facilitates COD maneuvers. The aim of this study was to examine the role of ECC-STR during a 180° COD task in 18 female soccer players. Each player performed six trials of a 180° COD task whereby three-dimensional motion data from 10 Qualisys Pro-Reflex infrared cameras (240 Hz) and ground reaction forces (GRFs) from two AMTI force platforms (1200 Hz) were collected. Relative eccentric knee extensor (ECC-EXT) and flexor (ECC-FLEX) peak torque was collected from both limbs at 60°·s⁻¹ using a Kin Com isokinetic dynamometer. Large correlations were revealed between COD performance (time to complete 5 m approach, 180° turn, 5 m return) and ECC-EXT (R = −0.674) and ECC-FLEX (R = −0.603). Moderate to large correlations were observed between approach velocity (AV) and COD performance (R = −0.484) and ECC-EXT (R = 0.724). Stronger participants (n = 9) recorded significantly (p < 0.05) faster AV (4.01 ± 0.18 vs. 3.74 ± 0.24 m·s⁻¹, d = 1.27) and a greater reduction in velocity (−1.55 ± 0.17 vs. −1.37 ± 0.21 m·s⁻¹, d = −0.94) during penultimate contact than weaker (n = 9) subjects. Greater ECC-STR is associated with faster COD performance in female soccer players, as stronger players are better able to decelerate during penultimate contact from faster approach velocities.

Background: Cutting actions are associated with non-contact ACL injuries in multidirectional sports due to the propensity to generate large multiplanar knee joint loads (KJLs) that have the capacity to increase ACL loading and strain. Numerous studies have investigated the biomechanical determinants of KJLs in cutting tasks. The aim of this systematic review was to comprehensively review the literature regarding biomechanical determinants of KJLs during cutting, in order to develop a cutting technical framework alongside training recommendations for practitioners regarding KJL mitigation.Methods: Databases (SPORTDiscus, Web of Science and PubMed) were systematically searched using a combination of the following terms: “Biomechanical determinants”, or “Knee abduction moment”, or “Technical determinants”, or “Knee loading”, or “Knee loads”, or “Mechanical determinants”, or “ACL strain”, or “Knee adduction moment”, or “Anterior tibial shear”, or “Knee internal rotation moment”, or “Knee valgus moment” AND “Change of direction”, or “Cutting manoeuvre”, or “Run and cut”, or “Run-and-cut”, or “Sidestepping”, or “Side-stepping”, or “Shuttle run”. Inclusion criteria were as follows: studies examining a cutting task < 110° with a preceding approach run that examined biomechanical determinants of KJLs using three-dimensional motion analysis.Results: The search returned 6404 possibly eligible articles, and 6 identified through other sources. Following duplicate removal, 4421 titles and abstracts were screened, leaving 246 full texts to be screened for inclusion. Twenty-three full texts were deemed eligible for inclusion and identified numerous determinants of KJLs; 11 trunk, 11 hip, 7 knee, 3 multiplanar KJLs, 5 foot/ankle and 7 identifying ground reaction forces (GRFs) as determinants of KJLs.Conclusion: Using the framework developed from the results, cutting KJLs can be mitigated through the following: reducing lateral foot-plant distances, thus lowering hip abduction and orientating the foot closer to neutral with a mid-foot or forefoot placement strategy; minimising knee valgus and hip internal rotation angles and motion at initial contact (IC) and weight acceptance (WA); avoiding and limiting lateral trunk flexion and attempt to maintain an upright trunk position or trunk lean into the intended direction; and finally, reducing GRF magnitude during WA, potentially by attenuation through increased knee flexion and emphasising a greater proportion of braking during the penultimate foot contact (PFC).

Dos'Santos, T, McBurnie, A, Thomas, C, Comfort, P, and Jones, PA. Biomechanical determinants of the modified and traditional 505 change of direction speed test. J Strength Cond Res 34(5): 1285–1296, 2020—The aim of this study was to investigate the whole-body biomechanical determinants of 180° change of direction (COD) performance. Sixty-one male athletes (age: 20.7 ± 3.8 years, height: 1.77 ± 0.06 m, mass: 74.7 ± 10.0 kg) from multiple sports (soccer, rugby, and cricket) completed 6 trials of the modified and traditional 505 on their right leg, whereby 3D motion and ground reaction force data were collected during the COD. Pearson's and Spearman's correlations were used to explore the relationships between biomechanical variables and COD completion time. Independent t-tests and Hedges' g effect sizes were conducted between faster (top 20) and slower (bottom 20) performers to explore differences in biomechanical variables. Key kinetic and kinematic differences were demonstrated between faster and slower performers with statistically significant (p ≤ 0.05) and meaningful differences (g = 0.56–2.70) observed. Faster COD performers displayed greater peak and mean horizontal propulsive forces (PF) in shorter ground contact times, more horizontally orientated peak resultant braking and PFs, greater horizontal to vertical mean and peak braking and PF ratios, greater approach velocities, and displayed greater reductions in velocity over key instances of the COD. In addition, faster performers displayed greater penultimate foot contact (PFC) hip, knee, and ankle dorsi-flexion angles, greater medial trunk lean, and greater internal pelvic and foot rotation. These aforementioned variables were also moderately to very largely (r or ρ = 0.317–0.795, p ≤ 0.013) associated with faster COD performance. Consequently, practitioners should focus not only on developing their athletes' ability to express force rapidly, but also develop their technical ability to apply force horizontally. In addition, practitioners should consider coaching a 180° turning strategy that emphasizes high PFC triple flexion for center of mass lowering while also encouraging whole-body rotation to effectively align the body toward the exit for faster performance.