IMPULSE GENERATION AND INITIAL VELOCITY DIFFERENCES IN TWO-FOOT RUNNING JUMPS WITH AND WITHOUT A BASKETBALL

This study aimed to (1) identify the roles of each leg in impulse generation and (2) determine differences in impulse generation and initial centre of mass velocities in two-foot running jumps with and without a ball. Eight recreational to collegiate basketball players performed three to ten repetitions of two-foot running jumps with and without a ball. We found that the first leg generated more backward and vertical impulse than the second leg in both two-foot running jumps with and without a basketball. Two-foot running jumps with a ball resulted in lower jump height and less vertical impulse generated by the second leg vs. jumps without a ball. These different impulse generation strategies and jump heights when jumping with a ball prompt further research to uncover why there are differences and which training practices can address the differences and lead to higher jump heights with a ball

A 3D APPROACH TO BASEBALL PITCHING KINEMATIC SEQUENCE

A proximal-to-distal sequence (PDS) in baseball pitching is theorized to be more efficient and can reduce upper limb joint loads. However, studies investigating PDS using timing of peak segment angular velocity magnitude did not identify the use of “full” PDS from pelvis to hand. This study investigated PDS by comparing the timings of peak angular velocities about each global axis for the pelvis, trunk, upper arm, forearm, and hand during fastballs thrown by professional pitchers (n=4). We found that pitchers demonstrated full PDS about the global left axis (from pitching mound to first base) in 67-100% of their trials, depending on the pitcher. No pitcher demonstrated full PDS about the other two global axes. Similar to prior studies, we also did not observe full PDS when using angular velocity magnitude. This could be explained by differences in body segment rotation sequences between global axes. We also preliminarily uncovered impacts of filtering on the kinematic sequence detected. Analyzing 3D angular velocities with carefully selected filters may advance our understanding of the dynamics of pitching

THE ROLES AND MECHANISMS OF LINEAR AND ANGULAR IMPULSE GENERATION FOR BOTH LEGS IN BASEBALL PITCHING: A WHOLE-BODY PERSPECTIVE

This study compared the role of each leg in generating linear and angular impulse during fastball pitches performed by professional pitchers (n=4). Participants were asked to pitch from an instrumented mound and 6-11 successful fastball pitches were used for the analysis. The results indicate that back leg generated forward linear impulse and the front leg generated backward linear impulse for all pitchers. Back leg ground reaction forces generated significantly larger angular impulse about a horizontal axis passing through the body center of mass from the mound to first base than the front leg in three of four pitchers. Additionally, the mechanisms of moment generation about the axis by each leg differed

L'Auto-vélo : automobilisme, cyclisme, athlétisme, yachting, aérostation, escrime, hippisme / dir. Henri Desgranges

03 juillet 19181918/07/03 (A19,N6372)

Estimating Stair Running Performance Using Inertial Sensors

Stair running, both ascending and descending, is a challenging aerobic exercise that many athletes, recreational runners, and soldiers perform during training. Studying biomechanics of stair running over multiple steps has been limited by the practical challenges presented while using optical-based motion tracking systems. We propose using foot-mounted inertial measurement units (IMUs) as a solution as they enable unrestricted motion capture in any environment and without need for external references. In particular, this paper presents methods for estimating foot velocity and trajectory during stair running using foot-mounted IMUs. Computational methods leverage the stationary periods occurring during the stance phase and known stair geometry to estimate foot orientation and trajectory, ultimately used to calculate stride metrics. These calculations, applied to human participant stair running data, reveal performance trends through timing, trajectory, energy, and force stride metrics. We present the results of our analysis of experimental data collected on eleven subjects. Overall, we determine that for either ascending or descending, the stance time is the strongest predictor of speed as shown by its high correlation with stride time

Method for Estimating Three-Dimensional Knee Rotations Using Two Inertial Measurement Units: Validation with a Coordinate Measurement Machine

Three-dimensional rotations across the human knee serve as important markers of knee health and performance in multiple contexts including human mobility, worker safety and health, athletic performance, and warfighter performance. While knee rotations can be estimated using optical motion capture, that method is largely limited to the laboratory and small capture volumes. These limitations may be overcome by deploying wearable inertial measurement units (IMUs). The objective of this study is to present a new IMU-based method for estimating 3D knee rotations and to benchmark the accuracy of the results using an instrumented mechanical linkage. The method employs data from shank- and thigh-mounted IMUs and a vector constraint for the medial-lateral axis of the knee during periods when the knee joint functions predominantly as a hinge. The method is carefully validated using data from high precision optical encoders in a mechanism that replicates 3D knee rotations spanning (1) pure flexion/extension, (2) pure internal/external rotation, (3) pure abduction/adduction, and (4) combinations of all three rotations. Regardless of the movement type, the IMU-derived estimates of 3D knee rotations replicate the truth data with high confidence (RMS error < 4 ° and correlation coefficient r ≥ 0.94 )

Agility drill time and average turn radius performance metric grouped by agility drill time.

<p>Boxplots of <b>(A)</b> agility drill time and <b>(B)</b> average turn radius for each trial evenly grouped by sorting agility drill time as the performance outcome. Asterisks indicate statistically significant differences between performance groups via post-hoc mean rank test (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188184#pone.0188184.t001" target="_blank">Table 1</a>).</p

Turn phase ground reaction-based performance metrics grouped by agility drill time.

<p>Boxplots of ground reaction-based performance metrics for each trial evenly grouped by sorting agility drill time as the performance outcome. The following metrics are displayed, calculated during turn phases: <b>(A)</b> Average horizontal ground reaction magnitude (body mass normalized), <b>(B)</b> average percent horizontal ground reaction normal to the foot trajectory, <b>(C)</b> cumulative footfall duration, and <b>(D)</b> “force generation” metric. Asterisks indicate statistically significant differences between performance groups via post-hoc mean rank test (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188184#pone.0188184.t001" target="_blank">Table 1</a>).</p

Exemplar average horizontal foot trajectory curvature.

<p>Average foot path curvature as a function of time for an exemplar high performer. Agility drill time is the time that elapses between a performer passing cone 1 and passing cone 5. The approximate time that the performer circumvented each cone is represented with numbered orange circles.</p

Exemplar body speed and tangential acceleration estimates.

<p><b>(A)</b> Body speed and <b>(B)</b> tangential acceleration estimates vs. time for an exemplar high performer. The approximate time that the performer circumvented each cone is represented with numbered orange circles. The tangential acceleration range is represented by the vertical gray bars between successive cones.</p