Explosive Movement Research Articles

Range Extensions and Rapid Dispersal of Etheostoma blennioides (Teleostei: Percidae) in the Susquehanna River Drainage

An introduced population of Etheostoma blennioides (greenside darter) in the Susquehanna River drainage has rapidly expanded its range since its discovery in the late 1960s. Geochronology of collection data in the Susquehanna River drainage provides evidence for explosive dispersal and long-range movement patterns. We discuss the current status and distribution of E. blennioides in the drainage, and suggest that other Mid-Atlantic Slope drainages with low native-darter diversity are at risk of similar colonization events. Although the long-term effect of these invasive populations is as yet unknown, we suggest that they may pose serious threats to persistence of several unique members of the Atlantic Slope ichthyofauna, especially the critically imperiled Etheostoma sellare (Maryland darter).

Postactivation Potentiation

Complex training is a method of hyper-stimulating the nervous system by performing a heavy resistance exercise (e.g., squat, bench press) prior to performing an explosive movement (e.g., vertical jump, medicine ball put). The heavy resistance exercise causes neural hyper-stimulation which may lead to enhanced force and power production. This neural hyper-stimulation phenomenon is known as Post-Activation Potentiation (PAP). Functional Isometrics (FI) is a form of weight training where a person lifts greater than 100% of their 1RM in a limited range of motion until the weight meets an immoveable object at which point they push and hold the weight for 3–5 seconds. This technique is a method of initiating a PAP which theoretically leads to one's ability to exert increased muscular force and power. PURPOSE: To investigate if untrained males and females performing a FI squat at 150% of their 1RM for 3 seconds would increase counter movement vertical jump (CMJ) height. METHODS: Untrained (no weight training experience) males (n=8, age: 29±6 yrs, mass: 102±23 kg, ht: 177±5 cm) and females (n=8, age: 23+3 yrs, mass: 62±7 kg, ht: 164±6 cm) participated in the study. Day 1: CMJ and 1 RM in the back squat were determined. Subjects practiced a FI squat using only the bar. Day 2: Subjects performed a 3 second FI squat with 150% of their 1RM squat, sat and rested for 4 minutes, performed a CMJ, waited 1 minute and performed another CMJ at 5 minutes post-FI squat. RESULTS: Repeated measures ANOVA procedures failed to reveal a significant increase in CMJ for either group (p>.45) following the FI squat. CONCLUSIONS The results of this study demonstrate no effect of functional isometric squatting on PAP as measured by CMJ in untrained males or females. This is consistent with current theory that untrained individuals fail to exhibit PAP following a hyper-stimulus event to the nervous system.

Explosive-type Strength Training in the Elderly

The age-related decline in muscle power and explosive force capacity (i.e. contractile rate of force development RFD) is as stronger predictor for incidence of falling, motor impairment, self-reported functional status and balance capability in community-dwelling old adults than maximal muscle strength per se. It was therefore recently suggested to develop strength training programmes aimed at maximising maximal muscle power and RFD by implementing explosive concentric movements with training loads of 40–60% of 1RM. However, older individuals often perform weight-bearing motor tasks close to their maximum capability (i.e. 1RM) and above especially during unexpected tasks such as reversing an impending fall. PURPOSE: To investigate the effect of 12-week, twice a week, heavy-resistance strength training (75–80 % of 1RM) with fast-to-explosive execution of the movements on maximal voluntary contraction (MVC), explosive force characteristics (RFD and impulse), muscle power and functional performances in two age-groups of community-dwelling elderly women (TG60, TG80, age-groups 60 and 80, respectively). METHODS: Elderly women from two age-groups, 60 (62.7 2.2 years, n=40) and 80 (81.8 2.7 years, n=25) were randomized (matched) into two training and two control groups (TG60, n=20; TG80, n=12) (CG 60, n=20; CG80, n=13). MVC, RFD and impulse were obtained during a maximal isometric unilateral leg press manuevre. Mechanical performance was assessed as jump height, (JH) and peak power (Ppeak) in a standardized countermovement jump (CMJ) and as mean power (Prigmean). in the Nottingham single-legged power rig. Functional motor performances were i) five-repeated chair rise, ii) 10-m walking test at self selected and maximal speed, and iii) Physical Performance Test (PPT). RESULTS: RFD, impulse, MVC, P peak', JH and Prigmean increased with training in both age-groups. The gains in RFD (50.5%), impulse (41.9%) and MVC (28.1%) for TG 80 were of such a magnitude that the difference observed pre intervention with the age-group 60 was abolished after training. Chair-rise and PPT improved in TG80 and only chair rise in TG60, whereas no improvements occurred in self-selected and maximal 10-meter gait speed. CONCLUSIONS: The present findings indicate that heavy-resistance strength training performed with explosive movement characteristics is highly effective in inducing adaptive neuromuscular changes in selected physiological variables and functional performances commonly associated with risk of falls and disability in aged individuals. This training modality seems to be safe and suitable for healthy women even in the 8th decade of life.

The Contribution of Maximal Force Production to Explosive Movement Among Young Collegiate Athletes

Critical to multidimensional sport conditioning is a systematic knowledge of the interactions between fitness components, as well as the transference relationships to performance. The purpose of this investigation was to examine the relationships between lower body muscular strength and several fundamental explosive performance measures. Fifty-four men and women collegiate athletes were tested to determine (a) lower-body muscular strength (1 repetition maximum barbell back squat), (b) countermovement vertical jump height and peak power output, (c) standing broad jump distance, (d) agility (cone T-test time), (e) sprint acceleration (m.s(-2)), and (f) sprint velocity (m.s(-1)). Analyses were performed using Pearson r correlations to examine these relationships. Partial correlations tested for relationships between performance measures while controlling for muscular strength. T-tests were performed to assess the difference between men and women. Correlation data demonstrated that significant (p < 0.01) strong linear relationships were indicated between muscular strength and power, as well as every sport-performance field tests. However, when controlling for strength with partial correlation, each of these relationships appreciably diminished. Significant differences (p < 0.05) were found between men and women for each of the performance tests. Muscular strength, peak power output, vertical jumping ability, standing broad jump, agility, sprint acceleration, and sprint velocity were all shown to be very highly related. Further examination demonstrated that body mass-adjusted muscular strength is more highly related to performance measures than is absolute muscular strength. Current correlation data provide a quantified look at the interaction between muscular fitness components, as well as the transfer relationship to several athletic-specific performance measures.

The Acute Effects of Prior Dynamic Resistance Exercise Using Different Loads on Subsequent Upper-Body Explosive Performance in Resistance-Trained Men

The purpose of this study was to determine if explosive upper-body performance could be improved when it was preceded by conditioning contraction protocols that incorporate resistance exercise. Providing that performance was enhanced, it was also the intention to determine the optimal conditioning contraction load for enhancing performance. Eight recreationally trained men completed 4 experimental sessions. Each session consisted of a warm-up, 3 bench press throws (pre), a conditioning protocol, and 3 bench press throws (post). The different conditioning protocols consisted of 5 bench press repetitions using 100, 75, or 50% of 5 repetition maximum (5RM) strength. The fourth protocol, in which no repetitions were completed, acted as a control. Participants performed each conditioning protocol on a different day, and the order in which the protocols were performed was randomized. Average power, assessed during the bench press throws, was determined for the starting segment and the end segment (point of bar release) for each throw. Comparisons in average power, for each segment of the bench press 1RM, were made between the pre- and postconditioning protocol bench press throws. None of the conditioning protocols had an effect on bench press throw performance in either of the 2 segments of the movement. The results suggest there is no performance advantage when explosive upper-body movement is preceded by resistance exercise of varying loads. Alternatively, the performance of a set of resistance exercise did not compromise explosive upper-body performance. Considering this, training methods that combine both resistance exercise and plyometric-like exercise may offer a practical and time-efficient training system.

Post-Activation Potentiation

The response of muscle to volitional or electrically induced stimuli is affected by its contractile history. Fatigue is the most obvious effect of contractile history reflected by the inability of a muscle to generate an expected level of force. However, fatigue can coexist with post-activation potentiation (PAP), which serves to improve muscular performance, especially in endurance exercise and activities involving speed and power. The measured response of muscular performance following some form of contractile activity is the net balance between processes that cause fatigue and the simultaneous processes that result in potentiation. Optimal performance occurs when fatigue has subsided but the potentiated effect still exists. PAP has been demonstrated using electrically induced twitch contractions and attributed to phosphorylation of myosin regulatory light chains, which makes actin and myosin more sensitive to Ca(2+). The potentiated state has also been attributed to an increase in alpha-motoneuron excitability as reflected by changes in the H-reflex. However, the significance of PAP to functional performance has not been well established. A number of recent studies have applied the principles of PAP to short-term motor performance as well as using it as a rationale for producing long-term neuromuscular changes through complex training. Complex training is a training strategy that involves the execution of a heavy resistance exercise (HRE) prior to performing an explosive movement with similar biomechanical characteristics, referred to as a complex pair. The complex pair is then repeated for a number of sets and postulated that over time will produce long-term changes in the ability of a muscle to generate power. The results of these studies are equivocal at this time and, in fact, no training studies have actually been undertaken. The discrepancies among the results of the various studies is due in part to differences in methodology and design, with particular reference to the mode and intensity of the HRE, the length of the rest interval within and between the complex pairs, the type of explosive activity, the training history of the participants, and the nature of the dependent variables. In addition, few of the applied studies have actually included measures of twitch response or H-reflex to determine if the muscles of interest are potentiated. There is clearly more research required in order to clarify the functional significance of PAP and, in particular, the efficacy of complex training in producing long-term neuromuscular adaptations.

The theoretical limits to the power output of a muscle-tendon complex with inertial and gravitational loads.

When a muscle delivers power to an inertial load through a spring, the peak power can exceed the maximum that the muscle alone could produce. Using normalized differential equations relating dimensionless quantities we show, by solving the equations either analytically or numerically, that one dimensionless constant (Xi), representing the inertial load, is sufficient to specify the behaviour during shortening of a muscle-tendon complex with linear force-velocity and force-extension properties. In the presence of gravity, an additional constant (Gamma), representing the gravitational acceleration, is required. Nonlinear force-velocity and force-extension relationships each introduce an additional constant, representing their curvature. In the absence of gravity the power output delivered to an inertial load is limited to approximately 1.4 times the maximum power of the muscle alone, and when gravity is present the power delivered is limited to approximately twice the power of muscle alone. These limits are found for the purely inertial load at Xi ca. 1 and with gravity acting at XiGamma = 0.5 with Xi arbitrarily small. The effects of nonlinear muscle and tendon properties tend to cancel each other out and do not produce large deviations from these optima. A lever system of constant ratio between muscle and load does not alter these limits. Cams and catches are required to exceed these limits and attain the high power outputs sometimes observed during explosive animal movement.

PILOT STUDY: EFFECTS OF VIRAL UPPER RESPIRATORY ILINESS ON PHYSICAL PERFORMANCE

1589 The purpose of this study was to assess the impact of a URI on physical performance. Seven young adult subjects (mean age = 19.9) with naturally-acquired moderate/severe colds were screened and selected into the illness group (ILL). As feasible, subjects' URI episodes were confirmed through laboratory diagnosis. A control group (CRL) of 7 subjects was also examined. Aerobic performance was measured by assessing the subjects' treadmill running time to exhaustion. Prior to the exhaustion run, the subjects completed five bouts of ten minute interval treadmill running. The treadmill work loads were adjusted for each runner to achieve a heart rate response of approximately 80% of age-predicted maximal heart rate (PMHR). The subject's run to exhaustion work load was 90% of PMHR. During the running tests (five running bouts of ten minutes each and one run to exhaustion), Heart Rate Monitors were utilized to record the subjects' heart rates. In addition, the subjects' perceived exertion was recorded. Anaerobic performance was measured through mechanical power as the subjects performed intermittent vertical jumps (selected because they require explosive total body movement). A force plate was used to measure the reaction forces. The vertical jumps were performed prior to and between the five running bouts. A shuttered video camera positioned perpendicular to the treadmill and the primary plane of movement recorded the segment movement during the five running bouts. Differences between time to exhaustion were evaluated with a t-test. A MANOVA with repeated measures was employed to identify differences between stride length and stride frequency data. Perceived exertion differences were analyzed using Chi-square procedures. No alterations in physical performance during a URI were identified as compared to controls. This study supports many physicians' current practice of allowing athletes to train/compete under certain conditions during a URI. Other viral URI studies have revealed minimal changes in running gait and shown that physiological responses to pulmonary function testing and submaximal and maximal exercise do not appear altered by a URI.

Built for Jumping: the Design of the Frog Muscular System

Frogs must generate a high level of mechanical power when they jump. The muscular system of frogs that jump is presumably designed to deliver these high powers. The length changes and activation pattern that muscles undergo during jumping were measured, and isolated muscle bundles were driven through this in vivo pattern. During jumping, muscles generated maximum power. Specifically, the muscle fibers (i) operated at optimal sarcomere lengths, (ii) operated at optimal shortening velocities, and (iii) were maximally activated during power generation. Thus, many different parameters must have evolved in concert to produce a system capable of this explosive jumping movement.

The contribution of muscle properties in the control of explosive movements.

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 movements. 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.

Strength and Power in Sport

List of Contributors. Preface. Units of Measurement and Terminology. Part 1: Definitions. 1 Basic Definitions for Exercise. H.G. KNUTTGEN AND P.V. KOMI. . Part 2: Biological Basis for Strength and Power. 2 Neuronal control of functional movement. VOLKER DIETZ. 3 Motor Unit and Motor Neuron Excitability during Explosive Movement. TOSHIO MORITANI. 4 Muscular Basis of Strength. R. BILLETER AND H. HOPPELER. 5 Hormonal Mechanisms Related to the Expression of Muscular Strength and Power. WILLIAM J. KRAEMER AND SCOTT A. MAZZETTI. 6 Exercise--related Adaptations in Connective Tissue. RONALD F. ZERNICKE AND BARBARA LOITZ--RAMAGE. 7 Contractile Performance of Skeletal Muscle Fibres. K.A. PAUL EDMAN. 8 Skeletal Muscle and Motor Unit Architecture: Effect on Performance. RONALD R. ROY, RYAN J. MONTI, ALEX LAI AND V. REGGIE EDGERTON. 9 Mechanical Muscle Models and Their Application to Force and Power Production. WALTER HERZOG. 10 Stretch--shortening Cyle. PAAVO V. KOMI. 11 Stretch--shortening Cycle Fatigue and its Influence on Force and Power Production. CAROLINE NICOL AND PAAVO. V. KOMI. . Part 3: Mechanism for Adaptation in Strength and Power Training. 12 Cellular and Molecular Aspects of Adaptation in Skeletal Muscle. GEOFFREY GOLDSPINK AND STEPHEN HARRIDGE. 13 Hypertrophy and Hyperplasia. J. DUNCAN MACDOUGALL. 14 Acute and Chronic Muscle Metabolic Adaptations to Strength Training. PER A. TESCH AND BJORN A. ALKNER. 15 Neural Adaptation to Strength Training. DIGBY G. SALE. 16 Mechanism of Muscle and Motor Unit Adaptation to Explosive Power Training. JACQUES DUCHATEAU AND KARL HAINAUT. 17 Proprocetive Training: Considerations for Strength and Power Production. ALBERT GOLLHOFER. 18 Connective Tissue and Bone Response to Strength Training. MICHAEL H. STONE AND CHRISTINA KARATZAFERI. 19 Endocrine Responses and Adaptations to Strength and Power Training. WILLIAM KRAEMER AND NICHOLASS A. RATAMESS. 20 Cardiovascular Responses to Training. STEVEN J. FLECK. . Part 4: Special Problems in Strength and Power Training. 21 Aging and Neuromuscular Adaptation to Strength Training. KEIJO HAKKINEN. 22 Use of Electrical Stimulation in Strength and Power Training. GARY A. DUDLEY AND SCOTT W. STEVENSON. Part 5: Strength and Power Training for Sports. 23 Biomechanics of Strength and Strength Training. VLADIMIR M. ZATSIORSKY. 24 Vibration Loads: Potential for Strength and Power Development. JOACHIM MESTER P.(?) SPITZENPFEIL AND ZENGYOUAN YUE. 25 Training for Weightlifting. JOHN GARHAMMER AND BOB TAKANO

Structural Lags and Stability in International Macromodels

One of the features of many popular international macromodels that is troublesome is their apparent sensitivity to very slight changes in assumptions and intial conditions. This is especially the case for models with an asset sector in which hodlings depend on the instantaneous expected rate of change of a variable, such as the exchange rate, and in which asset holders are taken to exhibit "myopic perfect foresight" in making their forecasts. Typically these models are only conditionally stable -- i.e., if they are distrubed from equilibrium, some free variable (often the current exchange rate) must accomplish a discrete, exactly correct jump so as to put the system on its unique stable trajectory to the new equilibrium. In the strict version of these models, even the slightest deviation from this path or the smallest error in this jump will lead -- in the absence of the intervention or other bounds of the system -- to its collapse through an explosive movement of the exchange rate and other related variables.

運動動作発現時における胸腔内圧変動と呼吸位相

Relationships were examined between the following variables: respiratory phase (R.P.) and intrathoracic pressure (I.T.P.); exercise intensity and I.T.P.; and whole body reaction movement and I.T.P., R.P. Intraesophageal balloon method was used to record the changes of I.T.P. The subjects were six young male volunteers. The following observations were made: 1)In accordance with the type of body movement, not only the positive but also the negative pressure changes were observed during dynamic body movements (situps, trunk extension, throwing, jumping and pressing). 2)A positive correlation was found between the exercise intensity and the amplitude of I.T.P. change. 3)Under the condition of unintentional respiration, breathholding after inspiration was the common phase of respiration at the commencement of a dynamic movement. 4)For the condition of waiting for signal, the shorter reaction time and movement time in whole body reaction movement were recorded in inspiratory breathholding state than in expiratory breathholding state. 5)During the whole body reaction movement commenced by the waiting condition of inspiratory breathholding, the changes of I.T.P. showed high amplitude in positive direction. When the signal was waited in expiratory breathholding state, I.T.P. change in negative direction preceded immediately before the pressure Change in positive direction. 6)These results suggested that the sharp positive change in I.T.P. is an essential factor for the commencement of an explosive movement mobilizing the large muscles of the body.