Kinetic Quantification of Plyometric Take Off, Flight, and Landing Characteristics

This study assessed the kinetic characteristics of a variety of plyometric exercises and assessed gender differences therein. Twenty-six men and 23 women performed a variety of plyometric exercises including line hops, 15.24 cm cone hops, squat jumps, tuck jumps, countermovement jumps, loaded countermovement jumps equal to 30% of 1 RM squat, depth jumps normalized to the subjects jump height, and single leg jumps. All plyometric exercises were performed on a force platform. Outcome variables associated with the takeoff, airborne, and landing phase of each plyometric were assessed including the peak ground reaction force during takeoff, time to takeoff, jump height, peak power, peak ground reaction force during landing, and landing rate of force development. A number of differences were found between plyometric exercises

Dynamic Stabilization During the Landing Phase of Plyometric Exercises

This study examined the differences in and the reliability of time to stabilization (TTS) of several plyometric exercises. Twenty six men performed a variety of plyometric exercises representing a continuum of intensities of landing instability, including line hops, cone hops, squat jumps, tuck jumps, countermovement jumps, dumbbell countermovement jumps, and single leg countermovement jumps on a force platform. A repeated measures ANOVA with Bonferroni post hoc corrections was used to evaluate the differences in TTS between plyometric exercises. Practitioners who use plyometrics to train dynamic stability and balance should create programs that progress the intensity of the exercises based on the results of this study. This study also demonstrates that TTS reliability is fair to excellent for a variety of jumping conditions

Gender-Based Analysis of Hamstring and Quadriceps Muscle Activation During Jump Landings and Cutting

This study evaluated gender differences in the magnitude and timing of hamstring and quadriceps activation during activities that are believed to cause anterior cruciate ligament (ACL) injuries. Twelve men (age = 21.0 ± 1.2 years; body mass = 81.61 ± 13.3 kg; and jump height = 57.61 ± 10.15 cm) and 12 women (age = 19.91 ± 0.9 years; body mass = 64.36 ± 6.14 kg; and jump height = 43.28 ± 7.5) performed 3 repetitions each of the drop jump (jump) normalized to the subject\u27s vertical jump height, and a sprint and cut at a 45-degree angle (cut). Electromyography (EMG) was used to quantify rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), lateral hamstring (LH), and medial hamstrings (MH) activation, timing, activation ratios, and timing ratios before and after foot contact for the jump and cut and normalized to each subject\u27s hamstring and quadriceps maximum voluntary isometric contraction. Data were analyzed using an analysis of variance with results demonstrating that during the postcontact phase of the cut, men demonstrated greater LH and MH activation than women. In the precontact phase of the jump, men showed earlier activation of the VL and VM, than women. Women produced longer RF and VM muscle bursts during the postcontact phase of the cut. Additionally, men showed a trend toward higher hamstring to quadriceps activation ratio than women for the postcontact phase of the cut. This study provides evidence that men are LH dominant during the postcontact phase of the cut compared with women, whereas women sustain RF activation longer than men during this phase. Men activate quadriceps muscles earlier than women in the precontact phase of the jump. Training interventions may offer the potential for increasing the rate and magnitude of hamstring muscle activation. These outcomes should be evaluated using EMG during movements that are similar to those that cause ACL injuries to determine if gender differences in muscle activation can be reduced

Reliability of Surface Electromyography During Maximal Voluntary Isometric Contractions, Jump Landings, and Cutting

The reliability of electromyographic (EMG) data has been examined for isometric and slow dynamic tasks, but little is known about the repeatability of this data for ballistic movements. The purpose of this study was to examine the within-session, trial-to-trial reliability of a variety of quadriceps and hamstrings muscles during isometric and ballistic activities. Data were analyzed by way of intraclass correlation coefficients (ICC), intersubject coefficients of variation (CVinter), and intrasubject coefficients of variation (CVintra). Twenty-four subjects performed 3 repetitions each of 2 randomly ordered test exercises, including landing from a depth jump (J) and cutting after a 10-m sprint (C). Data were acquired and processed with root mean square EMG for the muscles assessed, and data were analyzed for each exercise using a repeated measures analysis of variance. Results revealed that all ICC values were greater than 0.80, with most values greater than 0.90, CVinter values ranged from 5.4% to 148.7%, and CVintra values ranged from 11.5% to 49.3%. This study indicates that EMG is a reliable method for assessing the reproducibility of both the quadriceps and hamstrings muscle activation during either isometric or ballistic exercises

За кадры. 1973. № 64 (1739)

Митинг солидарности / С. ПивеньКафедра политэкономии / В. Г. ЗавьяловМонография ученогоКиноочерк об институтеНа рубеже сезонов / Р. ГорскаяАктивист / О. СоловьеваУчеба / И. ДмитриевПрофбюро / С. ГоловачевСоревнование / К. СульженкоНа страже интересов студенчества. Спорт / К. С. ШаминовНа страже интересов студенчества. Здоровье / С. СергеенкоНа горе Эттерсберг / Т. Заплавная"Вновь увидеть весну..."Крестьянин я. И есть причина... / И. БилогОсенний дуб / И. Билог"Турнир четырех" / К. С. ШаминовШахматное первенство / В. Ждано

Methoden der Künstlichen Intelligenz für Computerspiele auf Basis semantischer Modelle interaktiver VR/AR-Systeme

Feldmann A, Latoschik ME. Methoden der Künstlichen Intelligenz für Computerspiele auf Basis semantischer Modelle interaktiver VR/AR-Systeme. In: Schumann M, Kuhlen T, eds. Virtuelle und Erweiterte Realität, 5. Workshop of the GI VR & AR special interest group. Shaker Verlag; 2008: 113-124.Methoden der Künstlichen Intelligenz (KI) nehmen einen zentralen Stellenwert in der Entwicklung heutiger Computerspiele ein. Eine explizite lose Koppelung isolierter KI-Module mit benötigten Modulen zur graphischen, physikalischen und auditiven Simulation etc. wird zusehends komplex und stellt eine kritische Schnittstelle innerhalb interaktiver Systeme dar. Dieses Paper dokumentiert eine alternative eng gekoppelte Modellierung einer integrierenden Architektur basierend auf einer generellen semantischen Abstraktionsschicht. Ein semantisches Netz führt in der entworfenen Architektur die verschiedenartigen Simulationsmodule zusammen und stellt die Grundlage für ein einheitliches Entwurfsparadigma "Semantic Reflection" dar. Dieses findet hier für die Realisierung verschiedener benötigter KI-Verfahren im Computerspielekontext Anwendung. Am Beispiel der Pfadplanung, der Entscheidungsfindung, der Verhaltenssteuerung, des Lernens sowie der Anbindung eines Scriptinginferfaces werden die Vorteile dieses Ansatzes illustriert