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17 pages, 8900 KiB

Open AccessArticle

Modes of Vibration in Basketball Rims and Backboards and the Energy Rebound Testing Device

by Daniel Winarski, Kip P. Nygren and Tyson Winarski

Vibration 2023, 6(4), 726-742; https://doi.org/10.3390/vibration6040045 - 22 Sep 2023

Viewed by 1304

Abstract

Six mode shapes, including bending and torsion, were documented for five different basketball rims and backboards at the United States Military Academy, West Point, New York, NY, USA. The frequency and damping ratio of each mode shape were also determined. The empirical process began with the time-domain excitation and response of each rim-backboard system. The impulse of excitation came from an impact hammer separately applied sequentially to each node. The sinusoidal response was gathered from an accelerometer at a fixed location (node 1). Each time-domain excitation response was then converted to a frequency-domain Bode plot for each node by a Brüel & Kjær 2034 Signal Analyzer, giving transfer functions of output/input versus frequency. Structural Measurements System (SMS) StarStruc software was used to fit mode shapes to the Bode plots. Each of the six mode shapes was fitted to the Bode plots of each node at a specific modal frequency. Each of the six mode shapes was a function of the locations of the nodes, and the Bode plots gathered at each node. The first and second modes were critical for showing that the Energy Rebound Testing Device statistically correlated with the energy transferred to the rim and backboard. A known perturbation mass was selectively attached to the rim to help isolate the dynamic masses and spring rates for the rim and backboard and to ascertain that the kinetic energy transferred to the rim had a 95.67% inverse correlation with rim stiffness. Full article

(This article belongs to the Special Issue Vibrations in Sports)

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15 pages, 1354 KiB

Open AccessArticle

Using Wearable Accelerometers to Develop a Vertical Ground Reaction Force Prediction Model during Running: A Sensitivity Study

by Thomas Provot, Samaneh Choupani, Maxime Bourgain, Laura Valdes-Tamayo and Delphine Chadefaux

Vibration 2023, 6(3), 680-694; https://doi.org/10.3390/vibration6030042 - 12 Sep 2023

Viewed by 1191

Abstract

The estimation of vertical ground reaction forces (VGRFs) during running is necessary to understand running mechanisms. For this purpose, the use of force platforms is fundamental. However, to extend the study of VGRFs to real conditions, wearable accelerometers are a promising alternative to force platforms, whose use is often limited to the laboratory environment. The objective of this study was to develop a VGRF model using wearable accelerometers and a stepwise regression algorithm. Several models were developed and validated using the VGRFs and acceleration signals collected during 100 stances performed by one participant. The validated models were tested on eight participants. In a sensitivity study, the strongest correlations were observed at cut-off frequencies of ≤25 Hz and in models developed with 30 to 90 stances. After the validation phase, the 10 best models had, on average, low relative differences (≤10%) in the estimation of discrete VGRF parameters, i.e., the passive peak (

|ε_{p p}| = 6.26 %

), active peak (

|ε_{a p}| = 2.22 %)

, and loading rate (

|ε_{l r}| = 2.17 %

). The results indicate that the development of personalized models is more suitable for achieving the best estimates. The proposed methodology opens many perspectives for monitoring VGRFs under real conditions using a limited number of wearable sensors. Full article

(This article belongs to the Special Issue Vibrations in Sports)

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8 pages, 603 KiB

Open AccessArticle

Acute Effects of Whole-Body Vibration on Quadriceps Isometric Muscular Endurance in Middle-Aged Adults: A Pilot Study

by Francesca Greco, Federico Quinzi, Katia Folino, Marco Spadafora, Loretta Francesca Cosco, Maria Grazia Tarsitano and Gian Pietro Emerenziani

Vibration 2023, 6(2), 399-406; https://doi.org/10.3390/vibration6020024 - 22 Apr 2023

Cited by 1 | Viewed by 1588

Abstract

This study analysed the acute effects of whole-body vibration (WBV) on quadriceps isometric muscular endurance. Fifteen healthy middle-aged males performed an endurance isometric strength test after three different warm-up conditions: static half squat plus WBV (HSV), static half squat without WBV (HS), and control condition (CC). The endurance isometric strength test consisted of 10 maximal isometric contractions held for 4 s and interspersed by 2 s of rest between each repetition. Rate of Perceived Exertion (RPE) was assessed after warm-up (RPE₁) and at the end of the testing session (RPE₂). During each testing session, participant’s heart rate (HR) was continuously recorded. For each trial, the mean force across the 10 repetitions and fatigue index were evaluated. Mean force was significantly higher (p < 0.01) in CC than in the other two conditions. Both RPE₁ and RPE₂ were significantly lower (p < 0.01) in CC than HSV and HS condition. Warm-up HR and the mean testing session HR were significantly lower in CC than the other two conditions (p < 0.01). No significant differences were observed in fatigue index between conditions (p > 0.05) or in HR during the endurance protocol. Performing half-squat with or without vibration stimuli does not increase isometric muscular endurance and does not influence fatigue index. Full article

(This article belongs to the Special Issue Vibrations in Sports)

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