Acute effects of an intense strength training sesion under simulated orthostasis

Lower body negative pressure (LBNP) is a gravity independent method to simulate orthostasis. Due to the muscle pump function in exercising leg muscles, an increase in hydrostatic pressure by gravity or LBNP increases the arterio-venous pressure difference and in consequence muscle perfusion (Egaña, Ryan, Warmington, & Green, 2010). This study is the first application of combining a robotic leg press (RBL) that allows free modelled profiles of force and velocity with a LBNP chamber. We tested the hypotheses that LBNP during simulated high-intensity leg press exercises i) increases total haemoglobin content (tHb) and oxygen saturation (SmO₂) for m. vastus lateralis, and ii) reduces the increase in systolic blood pressure (sBP) and elevates cardiac output (CO

EFFECT OF KINESIO TAPING ON PERFORMANCE IN COUNTER-MOVEMENT JUMP

The purpose of this study was to identify the influence of taping with a flexible tape on jumping performance and its effects on the impulse in a stretch-shortening cycle movement. 23 subjects were divided in control group and intervention group. The subjects participated in two trials of vertical counter-movement jumps. In the trial, the knee extensors of the subjects in the intervention group were taped with an activating taping technique. Reaction forces of the jump were measured with an AMTI-force plate. Results showed no significant differences (ANOVA,

Plyometrics can preserve peak power during 2 months of physical inactivity: an RCT including a one-year follow-up

Objective: Inactivity results in a marked loss of muscle function, especially in movements requiring high power, force, and rate of force development. The aim of the present study was to evaluate if jump training can prevent these deteriorating effects of physical inactivity. Methods: Performance and muscle activity during several types of jumps was assessed directly before and after 60 days of bed rest as well as during follow-up visits in 23 male participants. Participants in the jump training group (JUMP, 12 participants) trained 5-6x per week during the bed rest period in a sledge jump system that allows jumps in a horizontal position, whereas the control group (CTRL, 11 participants) did not train. Results: Performance and muscle activity considerably decreased after bed rest in the control group but not in the training group, neither for countermovement jumps (peak power CTRL -31%, JUMP +0%, group × time interaction effect p < 0.001), nor for squat jumps (peak power CTRL -35%, JUMP +1%, p < 0.001) and repetitive hops (peak force CTRL -35%, JUMP -2%, p < 0.001; rate of force development CTRL -53%, JUMP +4%, p < 0.001). The control group\u27s performance had returned to baseline 3 months after bed rest. Conclusion: Despite the short exercise duration, the jump training successfully prevented power and strength losses throughout 2 months of bed rest.Thus, plyometrics can be recommended as an effective and efficient type of exercise for sedentary populations, preventing the deterioration of neuromuscular performance during physical inactivity

Steigerung der Leistung im Dehnungsverkürzungszyklus durch konditionierende Sprünge : Mechanismus, Anwendung und Transfer in den Spitzensport

Es ist bekannt, dass die maximale Leistung sportlicher Bewegungen durch unmittelbar zuvor ausgeführte maximale oder nahezu maximale Muskelkontraktionen – sogenannte Konditionierungen – kurzfristig gesteigert werden kann. Dies ist für Athleten aus Sportarten, deren Erfolg unmittelbar durch eine maximale Kraft oder eine maximale Leistung bestimmt ist von besonderem Interesse. Eine Vielzahl an Studien untersuchte die Wirksamkeit von diversen Konditionierungsaktivitäten im Hinblick auf Leistungssteigerungen sportlicher Bewegungen. Die optimale Konditionierung in verschiedenen sportlichen Disziplinen ist jedoch unklar. Dies ist darauf zurückzuführen, dass die Mechanismen der potenzierten Bewegungsleistung nach wie vor nicht eindeutig bestimmt sind. Gegenstand dieser Arbeit ist die Untersuchung des Mechanismus, der reaktiven Sprüngen als Konditionierung zur Steigerung der Leistung im Dehnungsverkürzungszyklus zugrunde liegt. Anschließend werden daraus Anwendungen für den Spitzensport abgeleitet und evaluiert. In Studie I wurde die Muskelsehneneinheit des M. triceps surae im Hinblick auf ihre Arbeitsweise im Dehnungsverkürzungszyklus während eines durch Konditionierungssprünge potenzierten Sprungs untersucht und mit einem Kontrollsprung verglichen. Bei 32 Studienteilnehmern wurde in zwei Teilexperimenten während der Sprungtests mittels bildgebendem Ultraschall die Faszikellänge des M. gastrocnemius medialis, des M. soleus sowie die Längenänderung der Achillessehne bestimmt. Kürzere Faszikellängen werden durch eine höhere Kraft des M. gastrocnemius medialis bedingt. Sie ermöglichen eine höhere Dehnung der Achillessehne während der exzentrischen Muskelkontraktion. Dadurch kann mehr elastische Energie aufgenommen und in der konzentrischen Phase abgegeben werden. Eine gesteigerte tendo-neuromuskuläre Leistung im konditionierten Sprung ist die Folge. Die unveränderte neuronale Aktivierung deutet daraufhin, dass diese Anpassung durch intrinsische Mechanismen im Muskel verursacht wird. Dehnen reduziert die reaktive Bewegungsleistung und die isometrische Kraft des gedehnten Muskels. In Studie II wurde untersucht, ob dieser Reduktion mithilfe von reaktiven Sprüngen entgegengewirkt werden kann. Bei 20 männlichen Studienteilnehmern wurde die reaktive Sprungleistung unter einer Kontrollbedingung und unmittelbar nach vier verschiedenen Konditionierungen erfasst. Diese beinhalteten ein statisches Dehnen des M. triceps surae über 20 s, zehn repetitive reaktive Sprünge, die Kombination von reaktiven Sprüngen mit anschließendem Dehnen, sowie die umgekehrte Reihenfolge. Es wurden elektrisch evozierte isometrische Muskelkontraktionen des M. triceps surae verwendet, um den Effekt der verschieden Konditionierungen auf die Muskelkraft zu bestimmen. Zehn repetitive Sprünge wirken einer durch Dehnen verursachten Reduktion der reaktiven Bewegungsleistung entgegen. Das gleiche Ergebnis zeichnete sich in den elektrisch evozierten Muskelkontraktionen ab und weist daraufhin, dass die reziproken Effekte von Dehnen und reaktiven Sprüngen auf muskulärer Ebene erfolgen.In Studie III wurde der Einsatz von reaktiven Sprüngen im Spitzensport evaluiert. Als Probanden dienten Kaderathleten des deutschen Bob- und Schlittenverbandes. Die Bewegungsleistung wurde in einem reaktiven Sprungtest und in einem sportartspezifischen Sprinttest über eine Distanz von 30 m erfasst. Zehn reaktive Sprünge wurden unmittelbar vor den Tests. als Konditionierung durchgeführt. Im Vergleich zu den Kontrollsprüngen steigerten alle Athleten unmittelbar nach der Konditionierung ihre maximale Sprunghöhe. Die Sprintzeiten blieben nach der Konditionierung unverändert. Die Ergebnisse zeigen, dass auch Spitzenathleten von reaktiven Sprüngen profitieren. Der Transfer der Leistungspotenzierung auf sportartspezifische Bewegungen ist jedoch limitiert. Fazit: Die wesentliche Erkenntnis dieser Arbeit ist, dass eine veränderte Mechanik der Muskelsehneneinheit des M. triceps surae die Ursache der Leistungspotenzierung nach zehn reaktiven Sprüngen ist. Die veränderte Mechanik äußert sich in einer höheren Muskelkraft bei vergleichbarer Aktivierung. Sie bewirkt eine Steigerung der tendo-neuromuskulären Leistung im Dehnungsverkürzungszyklus des Muskels. Dehnen wird in einigen Sportarten als Wettkampfvorbereitung eingesetzt, um ein hohes Maß an Beweglichkeit zu realisieren. Konditionierungen bieten eine effektive Möglichkeit, um den leistungsmindernden Effekten von Dehnen auf muskulärer Ebene entgegenzuwirken. Die leistungssteigernden Effekte treten auch bei hochtrainierten Athleten auf. Der Transfer auf sportartspezifische Bewegungen scheint bisher jedoch ein Problem darzustellen, wie das Beispiel der Sprints zeigt. Der Einsatz von reaktiven Sprüngen ist dennoch potenziell für den Spitzensport geeignet.publishe

Robotic guidance induces long-lasting changes in the movement pattern of a novel sport-specific motor task

Facilitating the learning or relearning of motor tasks is one of the main goals of coaches, teachers and therapists. One promising way to achieve this goal is guiding the learner through the correct movement trajectory with the help of a robotic device. The aim of this study was to investigate if haptic guidance can induce long-lasting changes in the movement pattern of a complex sport-specific motor task. For this purpose, 31 subjects were assigned to one of three groups: EA (early angle, n=10), LA (late angle, n=11) and CON (control, n=10). EA and LA successfully completed five training sessions, which consisted of 50 robot-guided golf swings and 10 free swings each, whereas CON had no training. The EA group was guided through the movement with the wrist being bent early during backswing, whereas in the LA group it was bent late. The participants of EA and LA were not told about this difference in the movement patterns. To assess if the robot-guided training was successful in shaping the movement pattern, the timing of the wrist bending during the backswing in free swings was measured before (PRE), one day after (POST), and 7days after (FUP) the five training sessions. The ANOVA (time×group×angle) showed that during POST and FUP, the participants of the EA group bent their wrist significantly earlier during the backswing than the other groups. Post-hoc analyses revealed that this interaction effect was mainly due to the differences in the wrist angle progression during the first 5° of the backswing. The robot-guided training was successful in shaping the movement pattern, and these changes persisted even after 7days without further practice. This might have implications for the learning of complex motor tasks in general, as haptic guidance might quickly provide the beginner with an internal model of the correct movement pattern without having to direct the learner's attention towards the key points of the correct movement pattern

Effect of kinesio taping on performance in counter-movement jump

The purpose of this study was to identify the influence of taping with a flexible tape on jumping performance and its effects on the impulse in a stretch-shortening cycle movement. 23 subjects were divided in control group and intervention group. The subjects participated in two trials of vertical counter-movement jumps. In the trial, the knee extensors of the subjects in the intervention group were taped with an activating taping technique. Reaction forces of the jump were measured with an AMTI-force plate. Results showed no significant differences (ANOVA, p<0.05) between the two groups in both trials. Mean jumping height in Trial 1 was 0.38 ± 0.11 m (control) and 0.33 ± 0.05 m (intervention) compared to 0.35 ± 0.10 m (control) and 0.33 ± 0.05 m (intervention) in Trial 2. No improvements in jumping performance could be detected

Conditioning hops increase triceps surae muscle force and Achilles tendon strain energy in the stretch-shortening cycle

Postactivation potentiation can improve athletic performance, but the underlying mechanisms are poorly understood. This study investigated the effect of conditioning hops on triceps surae muscle force and tendon strain and its contribution to potentiated stretch-shortening cycle (SSC) performance. Thirty-two subjects participated in two experiments. In both experiments, subjects performed three drop jumps (DJs) after prior conditioning with 10 maximal hops, three unconditioned DJs served as control. Ground reaction forces, kinematics, and triceps surae electromyographic activity were recorded. Ultrasound imaging was used to determine fascicle lengths (FASC) of the gastrocnemius (GM) and soleus muscles (experiment 1) and the length of the Achilles tendon (experiment 2) during the DJs. DJ height after the conditioning hops was significantly higher compared to control DJs (experiment 1: +12% and experiment 2: +19%). A significantly shorter GM FASC during the DJs performed after the conditioning hops coincided with an increased force acting on the triceps surae muscle. Moreover, the triceps surae muscle-tendon unit (MTU) showed increased energy absorption during the eccentric phase of the DJs and increased energy release during the concentric phase. The second experiment revealed a higher Achilles tendon strain in DJs performed after the conditioning hops compared to control DJs. No significant differences in muscle activities were observed. The shorter FASC in GM and the larger Achilles tendon strain facilitated MTU energy transfer from the eccentric to the concentric phase during the DJ. Thereby, conditioning hops improved SSC efficacy and DJ performance.peerReviewe

Effects of conditioning hops on drop jump and sprint performance : a randomized crossover pilot study in elite athletes

It has previously been shown that conditioning activities consisting of repetitive hops have the potential to induce better drop jump (DJ) performance in recreationally active individuals. In the present pilot study, we investigated whether repetitive conditioning hops can also increase reactive jump and sprint performance in sprint-trained elite athletes competing at an international level.publishe

Motion sickness symptoms during jumping exercise on a short-arm centrifuge

Artificial gravity elicited through short-arm human centrifugation combined with physical exercise, such as jumping, is promising in maintaining health and performance during space travel. However, motion sickness symptoms could limit the tolerability of the approach. Therefore, we determined the feasibility and tolerability, particularly occurrence of motion sickness symptoms, during reactive jumping exercises on a short-arm centrifuge. In 15 healthy men, we assessed motion sickness induced by jumping exercises during short-arm centrifugation at constant +1Gz or randomized variable +0.5, +0.75, +1, +1.25 and +1.5 Gz along the body axis referenced to center of mass. Jumping in the upright position served as control intervention. Test sessions were conducted on separate days in a randomized and cross-over fashion. All participants tolerated jumping exercises against terrestrial gravity and on the short-arm centrifuge during 1 Gz or variable Gz at the center of mass without disabling motion sickness symptoms. While head movements markedly differed, motion sickness scores were only modestly increased with jumping on the short-arm centrifuge compared with vertical jumps. Our study demonstrates that repetitive jumping exercises are feasible and tolerable during short-arm centrifugation. Since jumping exercises maintain muscle and bone mass, our study enables further development of exercise countermeasures in artificial gravity

Training data.

<p>Exemplary ground reaction forces and position signal from one series of 13 hops during one participant’s training session in the SJS.</p