TL;DR: The results fit in with theories on the existence of generalized motor programs within the central nervous system, the output of which is determined by the setting of parameters such as amplitude and relative timing of control signals.
Abstract: VAN ZANDWIJK, J. P., M. F. BOBBERT, M. MUNNEKE, and P. PAS. Control of maximal and submaximal vertical jumps.Med. Sci. Sports Exerc., Vol. 32, No. 2, pp. 477‐ 485, 2000. Purpose: It was investigated to what extent control signals used by human subjects to perform submaximal vertical jumps are related to control signals used to perform maximal vertical jumps. Methods: Eight subjects performed both maximal and submaximal height jumps from a static squatting position. Kinematic and kinetic data were recorded as well as electromyographic (EMG) signals from eight leg muscles. Principal component analysis was used analyze the shape of smoothed rectified EMG (SREMG) histories. Jumps were also simulated with a forward dynamic model of the musculoskeletal system, comprising four segments and six muscles. First, a maximal height jump was simulated by finding the optimal stimulation pattern, i.e., the pattern resulting in a maximum height of the mass center of the body. Subsequently, submaximal jumps were simulated by adapting the optimal stimulation pattern using strategies derived from the experimental SREMG histories. Results: SREMG histories of maximal and submaximal jumps revealed only minor differences in relative timing of the muscles between maximal and submaximal jumps, but SREMG amplitude was reduced in the biarticular muscles. The shape of the SREMG recordings was not much different between the two conditions, even for the biarticular muscles. The simulated submaximal jump resembled to some extent the submaximal jumps found in the experiment, suggesting that differences in control signals as inferred from the experimental data could indeed be sufficient to get the observed behavior. Conclusions: The results fit in with theories on the existence of generalized motor programs within the central nervous system, the output of which is determined by the setting of parameters such as amplitude and
TL;DR: This book discusses the foundations of Biomechanics and Qualitative Analysis, and its applications in Physical Education, Sports Medicine and Rehabilitation, and Mechanics of the Musculoskeletal System.
Abstract: Preface. Part 1: Introduction. 1. Introduction to the Biomechanics of Human Movement. 2. Fundamentals of Biomechanics and Qualitative Analysis. Part 2: Biological/Structural Bases. 3. Anatomical Description and its Limitations. 4. Mechanics of the Musculoskeletal System. Part 3: Mechanical Bases. 5. Linear and Angular Kinetics. 6. Linear Kinetics. 7. Angular Kinetics. 8. Fluid Mechanics. Part 4: Applications of Biomechanics in Qualitative Analysis. 9. Applying Biomechanics in Physical Education. 10. Applying Biomechanics in Coaching. 11. Applying Biomechanics in Strength and Conditioning. 12. Applying Biomechanics in Sports Medicine and Rehabilitation. References. Appendix A: Glossary. Appendix B: Conversion Factors. Appendix C: Suggested Answers to Selected Review Questions. Appendix D: Right Angle Trigonometry Review. Appendix E: Qualitative Analysis in Biomechanical Principles. Index. Lab Activities. About the Author. Index.
TL;DR: It was suggested that the neural input used in the fatigued condition did not constitute an optimal solution and may have played a role in decreasing maximal jump height achievement.
Abstract: PURPOSE: The aim of this study was to investigate the segmental coordination of vertical jumps under fatigue of the knee extensor and flexor muscles. METHODS: Eleven healthy and active subjects performed maximal vertical jumps with and without fatigue, which was imposed by requesting the subjects to extend/flex their knees continuously in a weight machine, until they could not lift a load corresponding to approximately 50% of their body weight. Knee extensor and flexor isokinetic peak torques were also measured before and after fatigue. Video, ground reaction forces, and electromyographic data were collected simultaneously and used to provide several variables of the jumps. RESULTS: Fatiguing the knee flexor muscles did not reduce the height of the jumps or induce changes in the kinematic, kinetic, and electromyographic profiles. Knee extensor fatigue caused the subjects to adjust several variables of the movement, in which the peak joint angular velocity, peak joint net moment, and power around the knee were reduced and occurred earlier in comparison with the nonfatigued jumps. The electromyographic data analyses indicated that the countermovement jumps were performed similarly, i.e., a single strategy was used, irrespective of which muscle group (extensor or flexors) or the changes imposed on the muscle force-generating characteristics (fatigue or nonfatigue). The subjects executed the movements as if they scaled a robust template motor program, which guided the movement execution in all jump conditions. It was speculated that training programs designed to improve jump height performance should avoid severe fatigue levels, which may cause the subjects to learn and adopt a nonoptimal and nonspecific coordination solution. CONCLUSION: It was suggested that the neural input used in the fatigued condition did not constitute an optimal solution and may have played a role in decreasing maximal jump height achievement.
TL;DR: EMS combined with plyometric training has proven useful for the improvement of vertical jump ability in volleyball players, with rapid increases of the knee extensors and plantar flexors maximal strength.
Abstract: MAFFIULETTI, N. A., S. DUGNANI, M. FOLZ, E. DI PIERNO, and F. MAURO. Effect of combined electrostimulation and plyometric training on vertical jump height. Med. Sci. Sports Exerc. Vol. 34, No. 10, pp. 1638–1644, 2002.PurposeThis study investigated the influence of a 4-wk combined electromyostimulati
TL;DR: When the aim of EMS resistance training is to enhance vertical jump ability, sport-specific workouts following EMS would enable the central nervous system to optimize the control to neuromuscular properties.
Abstract: The aim of this study was to investigate the influence of a 4-week electromyostimulation (EMS) training program on the vertical jump performance of 12 volleyball players. EMS sessions were incorporated into volleyball sessions 3 times weekly. EMS consisted of 20-22 concomitant stimulations of the knee extensor and plantar flexor muscles and lasted approximately 12 minutes. No significant changes were observed after EMS training for squat jump (SJ) and counter movement jump (CMJ) performance, while the mean height and the mean power maintained during 15 seconds of consecutive CMJs significantly increased by approximately 4% (p < 0.05). Ten days after the end of EMS training, the jumping height significantly (p < 0.05) increased compared with baseline also for single jumps (SJ +6.5%, CMJ +5.4%). When the aim of EMS resistance training is to enhance vertical jump ability, sport-specific workouts following EMS would enable the central nervous system to optimize the control to neuromuscular properties.
Cites background from "Control of maximal and submaximal v..."
...Indeed, the execution of these rapid actions relies heavily on preprogrammed muscle stimulation patterns (6, 26) because afferent feedback can only play a limited role due to short execution time....
...Considering the fact that the execution of maximal vertical jumping relies heavily on preprogrammed muscle stimulation patterns (26), delayed optimization of such templates within the central nervous system can result in delayed development of vertical jump ability after EMS resistance training....
TL;DR: It was indicated that countermovement jumps were performed with a consistent well-timed motion of the segments, and a "common drive," which acts without the knowledge of the muscle properties, was suggested as mediating and controlling the muscle activation timing between agonist-antagonist muscle pairs.
Abstract: PURPOSE: The aim of this study was to investigate the segmental coordination of vertical jumps under fatigue. METHODS: Twelve subjects performed maximal countermovement jumps with and without fatigue, which was imposed by maximal continuous jumps in place until their maximal jump height corresponded to 70% of the nonfatigued condition. Video, ground reaction forces, and electromyographic signals were recorded to analyze the segmental coordination of countermovement jumps before (CMJ1) and after (CMJ2) fatigue. The magnitude of joint extension initiation, peak joint angular velocity, and peak net power around the ankle, knee, and hip joints and their respective times were determined. RESULTS: CMJ2 was characterized by a longer contact time, which was accompanied with an earlier movement initiation and several differences (P < 0.05) in the variables used to describe coordination. When the movement duration was normalized with respect to the contact phase duration, the differences between CMJ1 and CMJ2 were not sustained. A consistent pattern was indicated, in which the segmental coordination did not differ between jump conditions. When the magnitude of the muscle activation was set aside, a remarkably consistent muscle activation time was noticed between conditions. CONCLUSIONS: It was indicated that countermovement jumps were performed with a consistent well-timed motion of the segments. A "common drive," which acts without the knowledge of the muscle properties, was suggested as mediating and controlling the muscle activation timing between agonist-antagonist muscle pairs.
TL;DR: This chapter discusses the evolution of a field of study, methodology for Studying, and methods for studying human information processing and motor learning.
Abstract: Chapter 1. Evolution of a Field of Study Chapter 2. Methodology for Studying Chapter 3. Human Information Processing Chapter 4. Attention and Performance Chapter 5. Sensory Contributions to Motor Control Chapter 6. Central Contributions to Motor Control Chapter 7. Principles of Speed and Accuracy Chapter 8. Coordination Chapter 9. Individual Differences and Capabilities Chapter 10. Motor Learning Concepts and Research Methods.
"Control of maximal and submaximal v..." refers background in this paper
...An elegant alternative which circumvents the storage and novelty problem is based on the concept of generalized motor programs (9)....
"Control of maximal and submaximal v..." refers methods in this paper
...Electromyographic signals (EMG signals) of eight muscles of one leg were recorded during the execution of the jumps using pairs of surface electrodes (Meditrace ECE 1801) after standard skin preparation techniques (2)....
TL;DR: It was concluded that muscle properties constitute a peripheral feedback system that has the advantage of zero time delay, and reduces the effect of perturbations during human vertical jumping to such a degree that the task may be performed successfully without any adaptation of the muscle stimulation pattern.
Abstract: Explosive movements such as throwing, kicking, and jumping are characterized by high velocity and short movement time. Due to the fact that latencies of neural feedback loops are long in comparison to movement times, correction of deviations cannot be achieved on the basis of neural feedback. In other words, the control signals must be largely preprogrammed. Furthermore, in many explosive movements the skeletal system is mechanically analogous to an inverted pendulum; in such a system, disturbances tend to be amplified as time proceeds. It is difficult to understand how an inverted-pendulum-like system can be controlled on the basis of some form of open loop control (albeit during a finite period of time only). To investigate if actuator properties, specifically the force-length-velocity relationship of muscle, reduce the control problem associated with explosive movement tasks such as human vertical jumping, a direct dynamics modeling and simulation approach was adopted. In order to identify the role of muscle properties, two types of open loop control signals were applied: STIM(t), representing the stimulation of muscles, and MOM(t), representing net joint moments. In case of STIM control, muscle properties influence the joint moments exerted on the skeleton; in case of MOM control, these moments are directly prescribed. By applying perturbations and comparing the deviations from a reference movement for both types of control, the reduction of the effect of disturbances due to muscle properties was calculated. It was found that the system is very sensitive to perturbations in case of MOM control; the sensitivity to perturbations is markedly less in case of STIM control. It was concluded that muscle properties constitute a peripheral feedback system that has the advantage of zero time delay. This feedback system reduces the effect of perturbations during human vertical jumping to such a degree that when perturbations are not too large, the task may be performed successfully without any adaptation of the muscle stimulation pattern.
TL;DR: A relatively simple control strategy for mechanically complex arm movements is suggested: neural circuits produce a common phasic and tonic activation waveform that is scaled in amplitude and delayed in time, depending on the desired movement direction.
Abstract: Little is known about the patterns of muscle activation that subserve arm movement in three-dimensional space. In this study, activation patterns of seven arm muscles were related to the spatial direction of human arm movement. Twenty movement directions defined two orthogonal vertical planes in space. The arm movements were moderately paced; each movement lasted approximately 500 msec. New techniques of EMG analysis were developed to describe the temporal pattern of muscle activation. For each muscle, a principal component analysis revealed a common phasic and tonic waveform for all directions of movement, within one plane. A temporal shifting procedure based on best covariance values revealed activation delays associated with different movement directions. The results show a consistent pattern of temporal shifting of the common waveform for movements in different directions. Coupled with past results showing that activation amplitude is a function of the cosine angle of movement or force direction, the present results suggest a relatively simple control strategy for mechanically complex arm movements: neural circuits produce a common phasic and tonic activation waveform that is scaled in amplitude and delayed in time, depending on the desired movement direction.
"Control of maximal and submaximal v..." refers background or result in this paper
...Since the fractions of explained variance by the first PC found in this study are somewhat higher than those reported in (3), it seems likely that for each muscle a single waveform is involved in the control of vertical jumping....
...Flanders (3) reported for pointing movements that the first PC often accounted for over 80% of the variance of a set of EMG traces for each muscle....