Relationships among lateral medicine ball throw test performance, HIP and trunk muscle strength, and lower limb kinematics: A cross-sectional study.

INTRODUCTION: The lateral medicine ball throw (LMBT) test is used to evaluate the throwing action, involving the entire kinetic chain and the principle of force transfer, with association between the strength of the lower limb and trunk muscles and the lower limb kinematics. The LMBT to investigate the association between lower limb kinematics and hip and trunk muscle strength. EXPERIMENTAL: This was a cross-sectional study with 84 healthy and physically active young people. Determinations were made of the maximum isometric strengths of the hip abductor, lateral rotator, extensor, and flexor muscles, and the trunk lateral flexors and extensors. Kinematic analyses (2D) of the hip, knee, and ankle in the sagittal and frontal planes were performed during the countermovement phase of the LMBT, together with quantification of LMBT. Statistical analysis of the associations employed multiple linear regression, with α = 5%. RESULTS: There were significant associations between the LMBT and the independent variables hip extensors strength, trunk flexors strength, valgus angle, and knee flexion angle and gender. The regression model presented adjusted R2 = 0.622. CONCLUSIONS: LMBT was influenced by the trunk flexor and hip extensor muscle strengths, knee flexion kinematics, lower limb valgus in the countermovement phase, and gender.

Reliability of 2D kinematics during landing of volleyball athletes after exhaustion.

INTRODUCTION: It is possible to quantify changes in movement patterns through kinematic analysis of landing, especially to quantify changes in pre and post exhaustion situations, however the reliability of this post exhaustion analysis is not known. OBJECTIVE: To verify the inter and intra-examiner reliability of two-dimensional kinematic analysis during the landing of a vertical jump of volleyball athletes, pre and post exhaustion protocol. EXPERIMENTAL: Thirty volleyball athletes were recruited, and kinematic analysis was performed during landing, pre and post exhaustion protocol. The angular measurements analyzed were: 1) frontal plane: knee valgus and 2) sagittal plane: anterior trunk inclination, knee flexion and tibiotarsal angle, performed by two examiners. The reliability calculation used the intraclass correlation coefficient (ICC), in addition to the error of measurement (SEM), the coefficient of variation (CV) and the minimum detectable difference (MDD). RESULTS: Regarding reliability: ICC = 0.95-0.98 (pre) and ICC = 0.83-0.98 (post exhaustion). The CV presented heterogeneous values for the knee valgus and the inclination of the trunk, both pre and post protocol. The SEM from all angles presented values that varied from 0.74°-2.33° and the MDD ranged from 2.55°-5.54° pre protocol and 2.05°-6.45° post protocol. CONCLUSION: 2D kinematic evaluation can be used during landing, before and after the application of an exhaustion protocol, but professionals should pay attention to the angles of the knee valgus and the inclination of the trunk, as they have a large CV.

Relationship between the strength of the hip and knee stabilizer muscles and the Y balance test performance in adolescent volleyball athletes.

BACKGROUND: Due to the large number of jumping and landing movements, volleyball exerts a high demand on lower limbs, causing a high incidence of injuries. On average, 52% of volleyball injuries occur in lower limbs. Y Balance-test (YBT) is widely used to predict lower limb injury in athletes who jump, so it is important to identify whether the hip and knee stabilizer muscle strength is related to the performance of this test, since muscle strength is important for injury prevention, given the possibility of modifying these factors. The aim of this cross-sectional study was to correlate the strength of the knee and hip stabilizing muscles with YBT in adolescent volleyball athletes. METHODS: A study including 25 young volleyball players (aged 15.3 [0.85] years), was evaluated. The isometric strength of knee extensor muscles, abductors, extensors and lateral hip rotators were assessed by using the manual isometric dynamometer (Lafaytte Instrument Company®, Lafayette, IN, USA). YBT was performed three times on each posterolateral (PL), anterior (ANT) and posteromedial (PM) direction to evaluate the dominant leg. The average of 3 repetitions of isometric strength tests of tested muscles and YBT was analyzed. Pearson's Correlation test was used for the correlation of the variables, considering as strong correlation values (0.5≤r<1), with P≤0.05. RESULTS: A moderate correlation was observed between the knee extensor strength and the ANT direction, and a moderate correlation between the hip extensor strength and the PL direction in YBT. CONCLUSIONS: The strength of knee and hip extensors may be one of the factors that influence the performance of YBT in adolescent volleyball players.