KINEMATIC ANALYSES OF THE DISCUS THROWING COMPETITIONS AT THE WORLD ATHLETICS CHAMPIONSHIPS 1993

Purpose of the paper This paper wants to discus possibilities and limitations of applied kinematic performance diagnostics of discus throwing as an example for other athletic disciplines. On the basis of kinematic analyses of the finalists at the WAC 94 added to a data base including 260 throws of world class athletes the applicability of traditional kinematic approaches is called into question. &f&& Analyses were performed with a PEAK PERFORMANCE motion analysis system. The video fields were digitized manually. 17 body landmarks were taken to define the locations of 12 body segments. Timing Parameters The analysis of phase durations is a good indicator for the stability of individual movement rhythm and timing. Highest importance is usually awarded to the last three phases of the throw. 11 is true that the often formulated demand for a possibly short airborne phase can be supported by mechanical considerations but individual variations (see table 2) avoid a significant correlation between this parameter and throwing distance (r= -.0076, p= ,919) as well as release velocity (I= ,0193, p= ,891) . The same comes true for transition and delivery phase. No significant correlation to release parameters could be identified. These variations occur interindividually with astonishing uniform individual timing patterns. If we compare the men's medallists we find a high constancy in individual movement patterns as far as timing is concerned. Release Characteristics Of all release parameters velocity oi release appears to be the most important. The assumption of a direct linear relation between release velocity and throwing distance cannot be maintained. Quadratic regressions indicate an area for release velocities and not as expected for maximum velocities. If we summarize all data available on release velocity and throwing distance the correlation turns out to be r=.55. Correcting throwing distance for the influence of wind by calculating ballistic distance increases the correlation to I= .90. The negative coefficient for velocity and the difference between ballistic and official distance (r=-64) indicates a decreasing influence of the wind conditions with increasing release velocities. Thus increasing throwing distance by increasing release velocity is primarily an intraindividual problem of movement coordination on a high speed level. This result comes true not only for discus throwing but can also be observed in other throwing events and even athletic jumping events as well. Nevertheless individual styles profed to be rather repeatable and typical for a specific athlete. Discussion The present kinematic analysis of discus throwing increased the existing data base of the discipline. Timing Characteristics how extreme interindividual variabilities but high intraindividual constancy without significant relations to throwing distance. None of the timing variations can be recommended as the best solution. Release parameters revealed no further insights into throwing techniques. As release velocity contributes about 80% to the variance-of the ballistic distance it is the most important release parameter. The influence of the wind conditions appears to decrease statistically with increasing release velocity on the one hand but on the other hand avoids a higher correlation between release velocity and the official distance. Regression analysis revealed that release velocity must rather be optimized than maximized. This might be due to the individual athletes' ability to control the discus release at high velocities. History of the discus' acceleration described as change of discus velocity during the crucial phases of the turn again revealed interindividual variations without showing a common tendency or even a solution to be called the best. It must be questioned whether a kinematic analysis of top level athletes' techniques leads to further insights into the discipline itself. The kinematic data are nothing else than a descriptions of the athletes' movements in a more objective way. Those analyses did not yet identify the ideal technique. This means a dilemma for any trainer as he has no criteria to separate between mistakes and individual variations of movement technique

ANALYSIS OF FACTORS INFLUENCING THE START PUSH IN WHEELCHAIR RACING

The purpose of this study was (1) to identify muscle strength potentials of wheelchair racing athletes of different performance levels and (2) to identify factors which determine the successful initial push during start. Kinematic and force data were sampled for analysis. Initial acceleration was found to be dependent on the length of the propulsion path as well as on the position of the hands on the hand rim. Favourable handrim positions could be identified for the start. Hand positions preferred by the athletes produced comparable force values but highest power output compared to alternative positions given through the protocol!. The stiffness of the wrist joint prior to release contributed considerably to the acceleration of the wheelchair-athlete system

REFLEX RESPONSES TO LOCAL SOLEUS MUSCLE VIBRATION

The aims of the present work was i. to investigate the acute effects of prolonged vibratory stimulation on short-latency stretch reflexes (SLR) of soleus muscle, ii. to assess effects of vibration on parameters of the H-reflex and M-wave stimulus-response curves. There were no changes in the EMG of SLR. During vibration H-reflex amplitudes decreased but H-reflex threshold current increased. None of the H-reflex parameters showed timedependent changes. In contrast, maximum M-wave magnitude (MMAX) decreased after 30min of sustained vibration. The analysis suggests differential effects of presynaptic inhibition on ��-motoneurons. The vibration parameters have no effect on excitability of afferent and efferent fibers. The depression of the MMAX after vibratory stimulation may be related to neuromuscular transmission failure and/or reduced sarcolemmal excitability

EVALUATION OF PASSIVELY INDUCED SHOULDER STRETCH REFLEX USING AN ISOKINETIC DYNAMOMETER IN MEN

The purpose of the current study was to determine shoulder internal rotator muscles\u27 reflex latencies (SLR) under variable conditions in 20 healthy, specifically trained male participants. Sets of different external shoulder rotation stretches were applied via an isokinetic dynamometer. SLR latencies were determined from sEMG readings as the time from external shoulder rotation stretches application to onset of muscle activity. The amount of muscular response to the perturbation was evaluated via a peak-to-peak analysis. SLR latencies and amplitudes of the pectoral muscle and the anterior deltoid were affected by the investigated muscle and the level of pre-innervation torque. Our results indicated faster muscular stretch response than reported in previous studies which can be attributed to training induced adaptions of the shoulder muscles and capsule

Interactive processes link the multiple symptoms of fatigue in sport competition

Muscle physiologists often describe fatigue simply as a decline of muscle force and infer this causes an athlete to slow down. In contrast, exercise scientists describe fatigue during sport competition more holistically as an exercise-induced impairment of performance. The aim of this review is to reconcile the different views by evaluating the many performance symptoms/measures and mechanisms of fatigue. We describe how fatigue is assessed with muscle, exercise or competition performance measures. Muscle performance (single muscle test measures) declines due to peripheral fatigue (reduced muscle cell force) and/or central fatigue (reduced motor drive from the CNS). Peak muscle force seldom falls by >30% during sport but is often exacerbated during electrical stimulation and laboratory exercise tasks. Exercise performance (whole-body exercise test measures) reveals impaired physical/technical abilities and subjective fatigue sensations. Exercise intensity is initially sustained by recruitment of new motor units and help from synergistic muscles before it declines. Technique/motor skill execution deviates as exercise proceeds to maintain outcomes before they deteriorate, e.g. reduced accuracy or velocity. The sensation of fatigue incorporates an elevated rating of perceived exertion (RPE) during submaximal tasks, due to a combination of peripheral and higher CNS inputs. Competition performance (sport symptoms) is affected more by decision-making and psychological aspects, since there are opponents and a greater importance on the result. Laboratory based decision making is generally faster or unimpaired. Motivation, self-efficacy and anxiety can change during exercise to modify RPE and, hence, alter physical performance. Symptoms of fatigue during racing, team-game or racquet sports are largely anecdotal, but sometimes assessed with time-motion analysis. Fatigue during brief all-out racing is described biomechanically as a decline of peak velocity, along with altered kinematic components. Longer sport events involve pacing strategies, central and peripheral fatigue contributions and elevated RPE. During match play, the work rate can decline late in a match (or tournament) and/or transiently after intense exercise bursts. Repeated sprint ability, agility and leg strength become slightly impaired. Technique outcomes, such as velocity and accuracy for throwing, passing, hitting and kicking, can deteriorate. Physical and subjective changes are both less severe in real rather than simulated sport activities. Little objective evidence exists to support exercise-induced mental lapses during sport. A model depicting mind-body interactions during sport competition shows that the RPE centre-motor cortex-working muscle sequence drives overall performance levels and, hence, fatigue symptoms. The sporting outputs from this sequence can be modulated by interactions with muscle afferent and circulatory feedback, psychological and decision-making inputs. Importantly, compensatory processes exist at many levels to protect against performance decrements. Small changes of putative fatigue factors can also be protective. We show that individual fatigue factors including diminished carbohydrate availability, elevated serotonin, hypoxia, acidosis, hyperkalaemia, hyperthermia, dehydration and reactive oxygen species, each contribute to several fatigue symptoms. Thus, multiple symptoms of fatigue can occur simultaneously and the underlying mechanisms overlap and interact. Based on this understanding, we reinforce the proposal that fatigue is best described globally as an exercise-induced decline of performance as this is inclusive of all viewpoints

Comparison of EMG Activity between Single-Leg Deadlift and Conventional Bilateral Deadlift in Trained Amateur Athletes - An Empirical Analysis

International Journal of Exercise Science 14(1): 187-201, 2021. The purpose of the study was to compare the normalized-electromyographic (NEMG) activity of the gluteus maximus (GMAX), gluteus medius (GMED), biceps femoris (BF) and erector spinae (ES) muscles during the single-leg deadlift (SLDL) and the conventional-deadlift (DL). Additionally, a potential influence of body height on the NEMG activity was examined. Fifteen training-experienced male subjects completed the study. SLDL showed significantly higher average concentric NEMG values of the GMED (77.6% vs. 59.3% [p = 0.002, ES = 1.0]) and BF (82.1% vs. 74.2% [p = 0.041, ES = 0.6]). Significantly lower NEMG levels were found only in the left strand of the ES muscle (67.2% vs. 82.7% [p = 0.004, ES = 0.9]). A significant influence of body height on EMG activity was also observed for all muscles, with the exception of the GMED, during the SLDL. Body height correlated negatively with the concentric EMG activity of the ES (r = –0.54 to –0.58), the BF (r = –0.63) and the GMAX (r = –0.85). In the DL there was a negative correlation only in the BF (r = –0.59) and the GMAX (r = –0.7). This means that subjects with a lower body height showed a higher NEMG activity in corresponding muscles. The results of this study indicate that the SLDL is preferable to the DL in training the BF, and GMED. In addition, coaches should be aware that athletes body height can influence the extent to which the respective muscles are activated

Efficacy of foam rolling with additional vibration stimulation on the mobility of the thoracolumbar fascia : An observational study

Introduction Observations show that foam rolling improves joint movements. Likewise, it can be stated that a vibration stimulation of the tissue leads to improved joint mobility. Method This study investigates whether the combination of foam rolling and vibrations (31 Hz) can influence the sliding of the thoracolumbar fascia more effectively than normal foam rolling. 45 subjects participated in the study and were divided into a foam roll with additional vibration group (FRV), a foam roll group (FR) and a control group (CG). The intervention groups rolled out the gluteal muscles, the lateral trunk and the upper and lower back. Mobility measures were taken pre and post the respective intervention. Subsequent cross correlation software analysis quantified the sliding of the fascia and calculated its shear strain mobility (SSM). Results The sliding of the thoracolumbar fascia improved significantly within the FRV by 2.83 mm (SD ± 1.08/p < .001), in the FR by 0.96 mm (SD ± 0.43/p < .001) and in the CG decreased the sliding by 0.1401 mm (SD ± 0.28/p = .076). The fascia/fascia SSM increased in the FRV by 22.61% (SD ± 15.64/p < .001), in the FR by 11.41% (SD ± 20.38/p = .056) and in the CG decreased the SSM by 0.9473% (SD ± 11.35/p < .751). The lumbar movement increased in both intervention groups, but showed no significant result. Conclusion The use of a foam roll with additional vibration and standard intervention have increased thoracolumbar fascia sliding and lumbar movements. The improved shear strain mobility can be attributed to the multi-activity of mechanoreceptors, such as Pacini- and Ruffini-Bodies

Feasibility of monitoring muscle health in microgravity environments using Myoton technology

Physical exercise is important for people living under extreme environmental conditions to stay healthy. Particularly in space, exercise can partially counteract the loss of muscle mass and muscle strength caused by microgravity. Monitoring the adaptation of the musculoskeletal system to assess muscle quality and devise individual training programmes is highly desirable but is restricted by practical, technical and time constraints on board the International Space Station. This study aimed to test the feasibility of using myometric measurements to monitor the mechanical properties of skeletal muscles and tendons in weightlessness during parabolic flights. The mechanical properties (frequency, decrement, stiffness relaxation time and creep) of the m. gastrocnemius, m. erector spinae and Achilles tendon were assessed using the hand-held MyotonPRO device in 11 healthy participants (aged 47 +/- A 9 years) in normal gravity as well as in microgravity during two parabolic flight campaigns. Results showed significant (p < .05-.001) changes in all mechanical properties of both muscles and the Achilles tendon, indicating a more relaxed tissue state in microgravity. Recordings from a phantom rubber material with the device in a test rig confirmed that the device itself was not affected by gravity, as changes between gravity conditions that were too small (< 1 %) to explain the changes observed in the tissues. It is concluded that myometric measurements are a feasible, easy-to-use and non-invasive approach to monitor muscle health in extreme conditions that prohibit many other methods. Real-time assessment of the quality of a muscle being exposed to the negative effect of microgravity and also the positive effects of muscular training could be achieved using Myoton technology