ECSS Paris 2023: CP-BM14
INTRODUCTION: Lateral ankle sprains (LAS) are a common musculoskeletal injury, particularly in sports that involve jump landings and rapid changes in direction [1]. Chronic ankle instability (CAI) affects the biomechanics and neuromuscular patterns of the ankle as well as the knee and hip, and these findings suggest that the mechanics of CAI may be multifactorial [2]. Consequently, this study aimed to investigate these factors by expanding the analysis to the upper limbs. METHODS: Subjects who scored less than 25 on the CAIT and greater than 10 on the identification of functional ankle instability (IdFAI) were classified into the CAI group (n=11), and those who did not qualify the criteria were included in the control group (n=12). Participants performed a forward horizontal jump from a starting position set at 40 % of their height, landing with their right foot on the force plate, and then immediately jumping to the left with their right foot and landing. Kinematic data defined initial contact (IC) as the point when the ground reaction force (GRF) exceeded 10 N, toe-off as the point when the GRF fell below 10 N, and landing as the point when the ankle angle returned to neutral position. The interval from IC to one second after landing was normalized to 100 %. To evaluate the magnitude of the difference between groups, Cohens D effect sizes (d) were computed as the absolute mean difference between groups divided by the pooled standard deviation (SD). A frame-by-frame two-sample t-test using Statistical Parametric Mapping (SPM1D) was conducted in MATLAB (Math Works Inc., MA, USA) to analyze the group differences in mean values from IC (0%) to 1 second after Landing (100%). To address the issue of multiple comparisons, a Bonferroni correction was applied, and the statistical significance level was set to a = 0.05 / 100 (number of frames). RESULTS: The significant differences between the two groups primarily occurred from IC (0%) to Toe off (26.72%). Based on the CAI group, Neck left oblique (p <.0005), Neck anterior tilt (p <.0005), Neck left rotation (p <.0005), Pelvic left oblique (p <.0005), Pelvic left rotation (p <.0005), Right knee valgus (p <.0005), Right knee internal rotation (p < 0.0005) were small. While Trunk left oblique (p <.0005), Trunk anterior tilt (p <.0005), Trunk left rotation (p <.0005), Pelvic anterior tilt (p <.0005), Right Hip flexion (p <.0005), Right hip internal rotation (p <.0005), Right knee flexion (p <.0005), Right ankle external rotation (p <.0005), and Right ankle eversion (p <.0005) were large. CONCLUSION: The results of this study suggest that CAI movements involving rapid changes in direction may influence the kinematics of both the lower and upper extremity joints. This indicates that the upper extremity may be a contributing factor in the CAI mechanism.
Read CV Chanki KimECSS Paris 2023: CP-BM14
INTRODUCTION: Unstable load is widely used in the fitness field, and the load is often made unstable by using flexible barbells. More unstable movements are generally believed to increase stabilizer muscle activation and strengthen these muscles more effectively than stable loads. Previous studies have mainly focused on investigating muscle activation during unstable and stable shoulder press exercises [1]. The differences in scapular kinematics between unstable and stable shoulder presses have not yet been studied. This pilot study aimed to analyze the differences in scapular kinematics during unstable and stable shoulder presses in recreationally active people. METHODS: This pilot study recruited six recreationally active men with currently regular resistance training. The participants performed both unstable and stable shoulder press exercises in a randomized order. The unstable load was applied using a Bandbell Bar with weight plates suspended by resistance bands on the bar. Unstable and stable shoulder presses each used their respective 15-repetition maximum (RM). During these movements, the electromagnetic motion capture system was used to analyze the scapular upward/downward rotation, anterior/posterior tilt, and external/internal rotation. The scapular kinematics were analyzed at 30°, 60°, 90°, and 120° of shoulder presses during both raising and lowering phases. Both types of shoulder press were tested five times, and the average value was calculated. The Mann-Whitney U test was used to compare differences between the two conditions. RESULTS: The 15 RM of stable and unstable loads in six participants were 28.75 ± 2.09 and 22.47 ± 3.01 kilograms, respectively. The results indicated that shoulder press with unstable loads exhibited a significantly greater upward rotation at 120° of the raising phase compared to stable loads (p = 0.020). No statistically significant differences were observed in the other scapular kinematics. CONCLUSION: Shoulder presses with unstable loads may exhibit greater scapular upward rotation at 120° of the raising phase compared to stable loads. Shoulder presses with unstable loads may be an effective re-education exercise for people with insufficient scapular upward rotation. More participants should be recruited to confirm the findings.
Read CV Yi-Chung TsaiECSS Paris 2023: CP-BM14
INTRODUCTION: Quantifying barbell motion during the back squat is a valid and reliable approach to monitor training performance[1]. When contrasted with force-velocity metrics obtained via integration of vertical ground reaction force (vGRF) from a force plate, the bar trajectory demonstrates a strong positive correlation in the vertical plane[2]. Whilst movement of the centre of pressure (COP), the point of application of the vGRF in the horizontal plane, is reflective of stability[3], there is a paucity of research considering the insight horizontal plane motion of the bar may afford. This study evaluated the similarity between the bar and COP to quantify horizontal plane motion during the back squat. METHODS: Ten participants (age = 31.0 ± 10.1 years; mass = 82.7 ± 12.2 kg; height = 173.5 ± 7.82 cm; 1RM = 116.98 ± 18.32 kg) completed 3 sets of 8 full-depth back squat repetitions at 80%1RM emphasising maximal intent and velocity[1]. COP was derived from a Kistler 9281EA force plate sampling at 1000Hz synchronised to 8 Oqus 300 Qualisys cameras at 100Hz to quantify motion of the bar trajectory, defined as the midpoint between markers positioned on the bar ends. A 10Hz lowpass filter was applied to the bar trajectory with a bandpass filter applied to the COP within Visual3D. The concentric phase of each repetition[4] was extracted for analysis within Python 3.12, with horizontal plane motion defined by the range in the anterior/posterior (AP-Range) and medial/lateral (ML-Range) directions. Procrustes analysis[5] using Scipy.spatial assessed the similarity of horizontal plane motion between the bar and COP trajectories. Procrustes analysis applies an optimised transformation to minimise the distance between datasets with the associated dissimilarity measure implying the degree of similarity (0) or dissimilarity (1). Following exclusion of outliers (mean ± 3SD), statistical analysis was undertaken using descriptive statistics and Student’s t-tests (p=0.05) using Scipy.stats. RESULTS: From 234 back squat repetitions analysed, significant (p<0.001) differences with small-medium (AP-Range: bar = 8.87 ± 3.15cm, COP = 7.92 ± 2.57cm; d=0.337) and large effect (ML-Range: bar = 1.83 ± 0.97cm, COP = 6.52 ± 2.85cm; d= -1.816) were identified. Bar and COP trajectories had a dissimilarity score of 0.54 ± 0.24. CONCLUSION: Horizontal plane motion was significantly different for both AP-Range and ML-Range with Procrustes analysis establishing a lack of similarity between the bar and COP trajectories during the concentric phase of the back squat. Whilst the practical suitability of vertical plane motion of the bar to monitor training performance during the back squat is accepted [1], further research is required to elucidate horizontal plane contributions with results identifying that such motion should not be considered reflective of the COP or therefore stability during a back squat. 1.Thompson et al (2020) 2.Rahmani et al (2000) 3.Kohn et al (2021) 4.McMahon et al. (2018) 5.Krzanowski, W (2000)
Read CV Kathleen Anne ShorterECSS Paris 2023: CP-BM14