KINEMATIC ANALYSIS OF KNEE VALGUS DURING DROP VERTICAL JUMP AND FORWARD STEP-UP IN YOUNG BASKETBALL PLAYERS

Purpose/Background

Lower limb asymmetry between dominant and nondominant limbs is often associated with injuries. However, there is a lack of evidence about frontal plane projection angle (FPPA) of the knee joint (knee valgus) during drop vertical jump (DVJ) and forward step-up tasks (FSUP) in young basketball players. Therefore, the purpose of this study was to assess the FPPA (i.e., dynamic knee valgus) via 2D video analysis during DVJ and FSUP tasks in the dominant and nondominant limbs of young male basketball players.

Methods

Twenty seven young male basketball players (age 14.5 ± 1.3 y, height 161.1 ± 4.1 cm, weight 64.2 ± 10.2 kg) participated in this study. The participants were asked to perform a bilateral DVJ and unilateral FSUP tasks. Kinematic analysis of FPPA was completed via a two-dimensional (2D) examination in order to evaluate the knee valgus alignment during the beginning of the concentric phase of each task. Knee valgus alignment was computed considering the angle between the line formed between the markers at the anterior superior iliac spine and middle of the tibiofemoral joint and the line formed from the markers on the middle of the tibiofemoral joint to the middle of the ankle mortise. Paired t-tests were used to evaluate differences in tasks. Standard error of measurement (SEM) was calculated to establish random error scores.

Results

There was no difference in knee valgus angle during the DVJ task between dominant (20.2 ± 4.4 º) and nondominant legs (20 ± 4.1 º; p = 0.067). However, a significant difference was noted during FSUP between the non-dominant limb (18.7 ± 3.4 º) when compared to the dominant (21.7 ± 3.5 º; p = 0.001) limb.

Conclusion

Two dimensional kinematic analysis of knee FPPA may help coaches and other professionals to detect asymmetries between dominant and nondominant limbs, and to develop training programs with the goal of reducing overall lower extremity injury risk.

Level of evidence

2b     

Plasma volume reduction and hematological fluctuations in high‐level athletes after an increased training load

The time course of plasma volume (PV) reduction following an increased training load period is unknown and was investigated. The accompanying fluctuations in [Hb] and OFF‐hr score were analyzed in the Athlete Biological Passport. Further, whether fluctuations in plasma albumin, soluble transferrin receptors (sTfR), and pro‐atrial natriuretic peptide (proANP) concentrations correlate with PV fluctuations was investigated. Eleven high‐level competitive cyclists were investigated for 3 weeks. After initial measurements in week 1, training load was increased ~250% in week 2 followed by a reversion to baseline training load in week 3. PV and hematological variables were determined frequently during all weeks. The higher training load in week 2 increased (P<.001) PV 10%, while [Hb] and OFF‐hr score decreased ~6% (P<.01) and ~16% (P<.001), respectively. PV and [Hb] returned to baseline within 2 and 4 days after week 2, respectively, while OFF‐hr score remained reduced for 6 days. Further, one and three atypical blood profiles of the ABP occurred during weeks 2 and 3, respectively. Individual changes in albumin, sTfR, and proANP only correlated weakly (R²<.20) with PV fluctuations. In conclusion, PV and [Hb] fluctuations caused by an elevated training load period were reverted within 2 and 4 days after returning to baseline training load, respectively, while OFF‐hr remained altered for 6 days. Furthermore, some atypical blood profiles were induced during and subsequent to the increased training load, demonstrating the importance of knowledge on naturally occurring hematological fluctuations. Finally, concentrations of albumin, sTfR, and proANP could not explain PV fluctuations.     

关于改进运动员睡眠床垫的研究

目的：研究优秀跳高运动员黄海强现有睡眠床垫的压力分布情况,设计一套改进的睡眠方案。方法：应用X-SEN—SOR压力床垫式检测系统,对黄海强现有两种床垫进行检测,分析后设计新的人机工学床垫,再进行效果评定。结果：原平板床与平面弹簧网海绵床垫平均压力,新设计的床垫能有效分散人体压力,新的床垫显示黄海强仰卧位平均压力为14．7mmHg,最大压力（臀部）为31．7mmHg,远低于以前的床垫。结论：针对黄海强体形设计睡眠床,能有效分散臀部与后背部压力,改善其睡眠状况。