Abstract des Autors

Die aktuelle Dissertation bestand aus drei verschiedenen Forschungsstufen, die in chronologischer Reihenfolge und inhaltlich organisiert wurden. Das Ziel der ersten Studie war es, die Reliabilität der Tensiomyographie (TMG) kontraktilen Eigenschaften zu analysieren. Der Zweck der zweiten Studie war es, die TMG-Sensitivität gegenüber Emüdung unter Verwendung von TMG-Muskeleigenschaften nach verschiedenen Kraftprotokollen zu analysieren. Schließlich war das Ziel der dritten Studie, die Ermüdung nach einem einwöchigen intensiven Kraft- oder Ausdauertraining zu überwachen. Darüber hinaus wurde die TMG-Sensitivität zur Differenzierung zwischen Kraft- und Ausdauersportlern untersucht. Die Ergebnisse zeigen, dass TMG als Instrument reliabel ist und sensibel für Ermüdungsdetektion ist. Es könnte ein nützliches Instrument sein, um zwischen Kraft- und Ausdauersportlern zu unterscheiden und Ermüdung sowie Erholung nach intensiven Trainingsphasen, insbesondere bei Kraftathleten, zu überwachen.

Abstract des Autors

The knowledge of the effects of physical training on fatigue and recovery demands is essential for an effective training load prescription. The extent of muscle fatigue and the effects of physical training have been investigated in relation to several physiological markers and neuromuscular function. However, most of these measurements commonly available in the applied field are not suitable. A large amount of these procedures are either invasive or motivation dependent, not standardized, and highly demanding for the athletes. Muscle contractile properties have been used as an alternative for monitoring fatigue and recovery, and for estimating the degree and type of fatigue. Accordingly, the tensiomyography (TMG), which allows muscular function evaluation through the assessment of specific muscle contractile properties during a twitch contraction evoked by electrical stimulation, could be a useful procedure. Therefore, the purpose of the current doctoral thesis was to analyse fatigue and recovery demands of strength and endurance training based on TMG measurements, and to verify if TMG is sensitive for distinguishing between strength and endurance athletes, as well. The current doctoral thesis was composed of three distinct research stages, which were carefully organized in a chronological order and in terms of content. They focus on their respective and specific aims, and complement each other. The aim of the first study was to analyze the inter-day reliability of TMG muscle contractile properties under different intensities of electric stimuli. Maximal radial deformation of the muscle belly (Dm); delay time (Td), determined from the onset of electrical stimulus to 10% Dm; contraction time (Tc), determined from 10 to 90% Dm; sustain time (Ts), determined as the time between 50% Dm during muscle contraction and relaxation; relaxation time (Tr), determined from time of fall from 90 to 50% Dm; mean velocities of the muscle belly deformation until 10% Dm (V10), and until 90% Dm (V90) were examined. The muscles rectus femoris (RF), biceps femoris (BF), and gastrocnemius lateralis (GL), from 20 male sport students were tested two times over one-week period. Maximal electrical stimuli exhibited higher level of reliability in all muscles evaluated. In most of the cases, TMG properties Tc, Td, Dm, V10, and V90 showed ICC scores > 0.8 and CV < 10%, confirming the efficacy of the TMG method for muscle contractile assessment. Higher repeatability of Tc, Td, Dm, V10, and V90 in comparison with Tr and Ts was also exhibited under submaximal condition. In some cases, Tr (RF, CV = 32.8%; BF, CV = 20.6%; GL, CV = 12.6%; BF, ICC = 0.7) and Ts (RF, CV = 21.3%) showed poor reliability or have not been repeatable even for high electric stimuli. It seems that TMG contractile properties Tr and Ts are not reliable variables for assessing muscle function. 61 The purpose of the second study was to analyze TMG sensitivity to changes in muscle force and muscular function of the RF using TMG muscle properties after 5 different lower-limb
strength training protocols (MS = multiple sets; DS = drop sets; EO = eccentric overload; FW = flywheel; PL = plyometrics). After baseline measurements, 14 male strength trained athletes completed 1 squat training protocol per week over a 5-week period in a randomized controlled order. Maximal voluntary isometric contraction (MVIC) and TMG measurements of Dm, Tc, V10, and V90 were analyzed up to 0.5 (post-train), 24 (post-24), and 48 hours (post-48) after the training interventions. It was observed significant reductions (p < 0.01) for Dm in MS, DS, EO, and FW from baseline to post-train. Dm remained decreased (p < 0.01) 24 and 48 h after FW and DS, respectively. It has been shown significant decrements (p < 0.01) for V10 and V90 from baseline to post-train in DS and FW and those reductions in contractile velocities were still observed 24 and 48 h after FW and DS, respectively. Furthermore, MVIC decreased (p <0.01) after DS, EO, and FW. Dm and V10 post-train values were significantly lower after protocols DS and FW compared with protocol PL (p = 0.032 and 0.012, respectively). Dm, V10, and V90 decrements correlated significantly to decreases in MVIC (r = 0.64–0.67, p <0.05). The aim of the third study was to investigate whether TMG is sensitive to differentiate between strength and endurance athletes, and to monitor fatigue after either one-week of
intensive strength (ST) or endurance (END) training. 14 strength (24.1 ± 2.0 years) and 11 endurance athletes (25.5 ± 4.8 years) performed an intensive training period of 6 days of ST or END, respectively. ST and END groups completed specific performance tests as well as TMG measurements of Dm, Tc, V10, and V90, before (baseline), after training period (post1), and after 72 h of recovery (post2). Specific performance of both groups decreased from baseline to post1 (p < 0.05) and returned to baseline values at post2 (p < 0.05). The ST group showed higher countermovement jump (p < 0.05) and shorter Tc (p < 0.05) at baseline. After training, Dm, V10, and V90 were reduced in the ST (p < 0.05) while TMG changes were less pronounced in the END. TMG is reliable to assess muscle contractile properties particularly within maximal electric stimuli. Especially the parameters Tc, Td, Dm, V10, and V90 may be used for evaluation of
muscle groups of different morphological characteristics. TMG muscle properties Dm, V10, and V90 are sensitive for fatigue detection, and different lower-limb strength training protocols lead to distinct responses of muscular function. Strength training protocols involving elevated number of repetitions performed under high intensities using eccentric overload may induce higher levels of peripheral fatigue and recovery demands as well. TMG 62
could be a useful tool to differentiate between strength and endurance athletes, and to monitor fatigue and recovery after a short-term intensive training period, especially in strength athletes.