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Exercise‐Related Adaptations in Connective Tissue

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BoneTendons and ligamentsMeniscusConcluding commentsReferences

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... This belief is based on earlier studies in which it was suggested that elastic energy could be stored in the tendinous tissues during the downward phase and used during the upward phase to increase force production (12,44). More recently, several researchers have, however, argued that the storage and utilization of elastic energy does not explain the difference in jump height between the CMJ and SJ (1,2,5,7,50,77-79), even though elastic energy enhances force production in both SJ and CMJ performances (30,68,90). More specifically, during the initial upward phase of the SJ and CMJ, a concentric contraction of the muscle fibers stretches the tendinous tissues, which later in the upward phase will recoil in a catapult-like manner to enhance force production. ...
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Two movements that are widely used to monitor athletic performance are the countermovement and squat jump. Countermovement jump performance is almost always better than squat jump performance, and the difference in performance is thought to reflect an effective utilization of the stretch-shortening cycle. However, the mechanisms responsible for the performance enhancing effect of the stretch-shortening cycle are frequently undefined. Uncovering and understanding these mechanism(s) is essential to make an inference regarding the difference between the jumps. Therefore, we will review potential mechanisms that explain the better performance in a countermovement jump as compared to a squat jump. It is concluded that the difference in performance may primarily be related to the greater uptake of muscle slack and the buildup of stimulation during the countermovement in a countermovement jump. Elastic energy may also have a small contribution to enhanced countermovement jump performance. Therefore, a larger difference between the jumps is not necessarily a better indicator of high-intensity sports performance. Although a larger difference may reflect the utilization of elastic energy in a small amplitude countermovement jump as a result of a well-developed capability to co-activate muscles and quickly buildup stimulation, a larger difference may also reflect a poor capability to reduce the degree of muscle slack and buildup stimulation in the squat jump. Because the capability to reduce the degree of muscle slack and quickly buildup stimulation in the squat jump may be especially important to high-intensity sports performance, training protocols might concentrate on attaining a smaller difference between the jumps.
... The exercise stimulus must induce sufficient stress on the body's relevant systems for an adaptation to occur. Important benefits of strength training include the physical aspect, such as adaptations of the connective tissues; stronger tendons and ligaments provide a better capacity to resist injury, and bone has been shown to significantly adapt in strength, mineral content and mineral density if subjected to high enough strains and strain rates (e.g., Kohrt, Bloomfield, Little, Nelson, & Yingling, 2004;Stone & Karatzaferi, 2003;Zernicke & Loitz-Ramage, 2003). In addition, strength training positively affects body composition in that it increases muscle mass relative to body fat. ...
... The exercise stimulus must induce sufficient stress on the body's relevant systems for an adaptation to occur. Important benefits of strength training include the physical aspect, such as adaptations of the connective tissues; stronger tendons and ligaments provide a better capacity to resist injury, and bone has been shown to significantly adapt in strength, mineral content and mineral density if subjected to high enough strains and strain rates (e.g., Kohrt, Bloomfield, Little, Nelson, & Yingling, 2004;Stone & Karatzaferi, 2003;Zernicke & Loitz-Ramage, 2003). In addition, strength training positively affects body composition in that it increases muscle mass relative to body fat. ...
... Deckflächen der Wirbelkörper, Röhrenknochen etc.) erhöht werden (vgl. Brüggemann & Krahl, 2000; Burrows, 2007; Cohen et al., 1995; Conroy et al., 1993; Kemmler et al., 2003; Pettersson et al., 1999; Ryan et al., 2004; Stone, 1992; Zernicke & Loitz, 1992 Conroy et al., 1993; Kemmler et al., 2003; Pettersson et al., 1999; Ryan et al., 2004) bis 13,5-jährigen Mädchen und bei 13-bis 15- jährigen Jungen am höchsten, was die Wichtigkeit eines Krafttrainings in dieser Alters spanne unterstreichen würde. " The fear that resistance exercise is detrimental to bone growth appears inappropriate. ...
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In diesem Beitrag werden aktuelle Aspekte des Krafttrainings bei Kindern und Jugendlichen diskutiert. Einleitend werden aus historischer Perspektive Entwicklungen zum Krafttraining bei Heranwachsenden skizziert. Aufbauend auf Ontogenese und motorischer Entwicklung werden Krafttrainingseffekte bei Kindern und Jugendlichen spezifiziert. Danach werden Krafttrainingseffekte auf Muskulatur, anaboles und neuromuskuläres System sowie auf den passiven Bewegungsapparat beschrieben. Verletzungen und Schädigungen durch Krafttrainingsinterventionen werden ebenso diskutiert wie Effekte in der Therapie sowie bei Übergewicht. Abschließend werden pädagogische Hinweise und Trainingsempfehlungen für das Krafttraining, speziell das apparative Training, ausgesprochen
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Training-induced adaptations in the neuromuscular and endocrine systems were investigated in seven females during prolonged power type strength training. Great (p less than 0.05) changes occurred primarily during the earlier weeks of the 16-week training especially in the time of force production (from 161 +/- 107 to 93 +/- 65 ms to produce a 500 N force) and, correspondingly, in the average forces in the earlier positions of the (absolute) force-time curve of the leg extensor muscles. These changes were accompanied by significant (p less than 0.05) increases in the neural activation of the trained muscles in the earliest positions of the IEMG-time curve. Hypertrophic changes, as judged from muscle fibre area data of both FT and ST types, were only slight (ns.) during the entire training period. No statistically significant changes occurred during the training in mean concentrations of serum testosterone, free testosterone, follicle stimulating hormone (FSH), luteinizing hormone (LH), cortisol, progesterone, estradiol (E2) or sex hormone-binding globulin (SHBG). However, the individual mean serum levels of both total and free testosterone correlated significantly (r = .81-.95, p less than 0.05-0.01) with the individual changes during the training in the time of force production and in the forces in the force-time curve of the trained muscles. The present results in female subjects indicate the important role of training-induced adaptations in the nervous system for muscular power development. In females testosterone may be of great importance for muscular power and/or strength development during prolonged training and an important indicator of the trainability of an individual.
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The purpose of this brief review is to examine resistance training responses of selected hormones related to acute stress and growth promoting actions. Hormonal mechanisms appear to be involved with both short-term homeostatic control and long-term cellular adaptations. Few studies have modeled the exercise stimulus in resistance training to determine the role of different exercise variables to the hormonal response. A variety of resistance exercise protocols result in increases in peripheral hormonal concentrations. It appears that single factor variables such as the intensity (% of RM) of exercise and amount of muscle mass utilized in the exercise protocol are important determinants of hormonal responses. The volume (sets x repetitions x intensity) of exercise also appears to be an important determinant of hormonal response. Still, little is known with regard to other single and multiple factor variables (e.g., rest period length) and their relationships to peripheral hormonal alterations. Collectively, such information will allow greater understanding concerning the nature of the exercise stimulus and its relationship to training adaptations resulting from heavy resistance exercise.
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A follow-up study of 1 year was performed on 11 male elite weight lifters. Several parameters including training volume, weight lifting performance, and serum hormone concentrations were measured during seven test occasions. In addition, the same measurements were repeated three times during a 6-week period preceding the primary competition, which took place about 5 months after beginning of the follow-up. The primary findings were observed during the 6-week period from which the first 2 weeks of stressful training was associated with significant decreases (P less than 0.01-0.001) in serum testosterone concentration, in testosterone/cortisol and in testosterone/SHBG ratios, and with a significant (P less than 0.001) increase in serum LH concentration. The individual changes during the stressful training in serum testosterone/SHBG ratio were related (r = .63; P less than 0.05) to the individual changes in the weight lifting result in the clean and jerk lift. During the following "normal" 2-week and reduced 2-week training periods, the concentration of serum testosterone remained unaltered, but serum cortisol and serum LH decreased significantly (P less than 0.05-0.01). During these periods, the serum testosterone/SHBG ratio increased (P less than 0.01). The individual changes during this preparatory 4-week training before the primary competition in serum testosterone/SHBG ratio and the individual changes in the weight lifting result in the clean and jerk lift correlated significantly with each other (r = .68; P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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Daily adaptive responses in the neuromuscular and endocrine systems to a 1-week very intensive strength training period with two training sessions per day were investigated in eight elite weight lifters. The morning and the afternoon sessions resulted in acute decreases (P less than 0.05-0.01) in maximal isometric strength and in the maximal neural activation (iEMG) of the leg extensor muscles, but the basic levels remained unaltered during the entire training period. Significant (P less than 0.05-0.01) acute increases in serum total and free testosterone levels were found during the afternoon sessions. During the 1-week training period, serum total and free testosterone concentrations decreased gradually (P less than 0.05-0.001) as observed in the basic morning values before the sessions, but after 1 day of rest serum total and free testosterone reached (P less than 0.01 and 0.05) the pretraining level. The sessions resulted also in acute changes (P less than 0.05-0.01) in serum cortisol and somatotropin concentrations, but the basic morning levels did not change during the training period. The present findings suggest that during a short period of intense strength training the changes especially in serum testosterone concentrations indicate the magnitude of physiologic stress of training. The acute changes in serum hormone concentrations during a period of a few days do not, however, necessarily directly imply the changes in performance capacity. A longer period of follow-up lasting a few weeks is probably needed if an individual trainability status of a strength athlete is to be evaluated on the basis of the hormone determinations.
Acute neuromuscular and endocrine adaptations to weight-lifting were investigated during two successive high intensity training sessions in the same day. Both the morning (I) (from 9.00 to 11.00 hours) and the afternoon (II) (from 15.00 hours to 17.00 hours) training sessions resulted in decreases in maximal isometric strength (p less than 0.01 and less than 0.05), shifts (worsening) in the force-time curve in the absolute scale (p less than 0.05 and ns.) and in decreases in the maximal integrated EMG (p less than 0.01 and less than 0.05) of the selected leg extensor muscles. Increases in serum total (p less than 0.05) and free testosterone (p less than 0.01) and in cortisol (p less than 0.01) concentrations were found during training session II. These were followed by decreases (p less than 0.001 and p less than 0.01 and ns.) in the levels of these hormones one hour after the termination of the session. The responses during the morning training session were different with regard to the decreases in serum total testosterone (p less than 0.05), free testosterone (ns.) and cortisol (p less than 0.05). Only slight changes were observed in the levels of luteinizing hormone and sex hormone-binding globulin during the training sessions. Increases (p less than 0.01) took place in somatotropin during both training sessions. The present findings suggest that high intensity strengthening exercises may result in acute adaptive responses in both the neuromuscular and endocrine systems. The diurnal variations may, however, partly mask the exercise-induced acute endocrinological adaptations in the morning.(ABSTRACT TRUNCATED AT 250 WORDS)
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