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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Movement variability is defined as the normal variations in motor performance across multiple repetitions of a task. However, the term “movement variability” can mean different things depending on context, and when used by itself does not capture the specifics of what has been investigated. Within sport, complex movements are performed repeatedly under a variety of different constraints (e.g. different situations, presence of defenders, time pressure). Movement variability has implications for sport performance and injury risk management. Given the importance of movement variability, it is important to understand the terms used to measure and describe it. This broad term of “movement variability” does not specify the different types of movement variability that are currently being assessed in the sporting literature. We conducted a scoping review (1) to assess the current terms and definitions used to describe movement variability within sporting tasks and (2) to utilise the results of the review for a proposed framework that distinguishes and defines the different types of movement variability within sporting tasks. To be considered eligible, sources must have assessed a sporting movement or skill and had at least one quantifiable measure of movement variability. A total of 43 peer-reviewed journal article sources were included in the scoping review. A total of 280 terms relating to movement variability terminology were extracted using a data-charting form jointly developed by two reviewers. One source out of 43 (2%) supplied definitions for all types of movement variability discussed. Moreover, 169 of 280 terms (60%) were undefined in the source material. Our proposed theoretical framework explains three types of movement variability: strategic, execution, and outcome. Strategic variability describes the different approaches or methods of movement used to complete a task. Execution variability describes the intentional and unintentional adjustments of the body between repetitions within the same strategy. Outcome variability describes the differences in the result or product of a movement. These types emerged from broader frameworks in motor control and were adapted to fit the movement variability needs in sports literature. By providing specific terms with explicit definitions, our proposed framework can ensure like-to-like comparisons of previous terms used in the literature. The practical goal of this framework is to aid athletes, coaches, and support staff to gain a better understanding of how the different types of movement variability within sporting tasks contribute to performance. The framework may allow training methods to be tailored to optimise the specific aspects of movement variability that contribute to success. This review was retrospectively registered using the Open Science Framework (OSF) Registries (
The objective of the study was to explore coaches’ philosophies regarding strength training (repetitive muscle actions against high loads) and the transfer of strength training to sports performance. Thirteen world class coaches and athletes from track cycling, Bicycle Moto-Cross (BMX), sprint kayaking, rowing and athletics sprinting were interviewed using an open-ended, semi-structured approach. Participants were asked about their coaching philosophies, design of athlete training programmes, strength training and its transfer to sports performance. A thematic analysis was conducted. Data trustworthiness was enhanced by methods of member checking and analyst triangulation. Coaches believed that task-specific strength is essential for sports performance. They reported that non-specific strength training (‘traditional’ gym-based strength exercises that are not specific to a sport movement) is important for increasing athletes’ muscle size and strength. This is typically used in conjunction with resisted sport movement training (for example, increased resistance running, pedalling or rowing), believed to achieve an effective transfer of enhanced muscle strength to sports performance. Coaches described the transfer process as complex, with factors associated with fatigue and coordination having particular significance. The importance that coaches place on coordination is supported by a theoretical model that demonstrates increases in muscle strength from strength training may need to be accompanied with a change in inter-muscular coordination to improve sport performance. The idea that each athlete needs to adapt intermuscular coordination in response to a change in his/her unique set of ‘organism constraints’ (e.g. muscle strength) is well described by the theory of ecological dynamics and Newell’s model of constraints.
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Four Olympic-style weightlifters and six athletes from other sports volunteered to perform maximal and submaximal vertical jumps with countermovement and/or snatch lifts on a Kistler force plate to compare the kinetics of the two activities at different levels of effort. Parameters studied included maximum vertical ground reaction force generated during a snatch lift or jump for both maximal and submaximal efforts and force duration at magnitudes greater than 50, 80 and 90 percent of max during the propulsion phase of each activity. Results indicated that in both activities, as the level of performance (intensity) increased, maximal propulsion force magnitudes generally decreased, whereas the duration of force at higher percentages of maximum increased. Qualitative similarities in the temporal pattern of vertical ground reaction force for each activity were observed in both unweighting and propulsion phases. Use of a double knee bend lifting technique accounted for an unweighting phase during the snatch lifts. Data indicated that the athletes used adjustments in temporal pattern of propulsive force application, rather than an increase in the magnitude of force generated for maximal versus submaximal efforts in both activities. Athletes who require improved jumping ability may benefit from utilizing Olympic lifting movements as part of their strength training program due to the applied overload and the similarities found between the propulsive force patterns of each activity. (C) 1992 National Strength and Conditioning Association
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Skeletal muscle undergoes substantial adaptation when it is subjected to a strength training regimen. At one extreme, these effects are manifested as profound morphological changes, such as those exemplified by bodybuilders. However, it is possible to increase strength without any change in muscle size. This dissociation underscores the notion that strength is not solely a property of muscle but rather it is a property of the motor system. The nervous system seems to be of paramount importance for the expression and development of strength. Indeed, it is probable that increases in strength can be achieved without morphological changes in muscle but not without neural adaptations. This review focuses on the role of the nervous system in the development of strength. In the strength literature, 3 topics exemplify the importance of the nervous system in strength development. These 3 topics are considered in detail in the review: electromyostimulation, cross-training effects, and EMG-force relationships. Evidence is presented from several different paradigms emphasising the significant contribution of neural mechanisms to the gains in strength with short term training. Although little is known about the specific neural mechanisms associated with strength training adaptations, the literature emphasises that the measure of human performance known as strength can be influenced by a variety of neurophysiological processes.
Overtraining is an imbalance between training and recovery. Short term overtraining or ‘over-reaching’ is reversible within days to weeks. Fatigue accompanied by a number of physical and psychological symptoms in the athlete is an indication of ‘stateness’ or ‘overtraining syndrome’. Staleness is a dysfunction of the neuroendocrine system, localised at hypothalamic level. Staleness may occur when physical and emotional stress exceeds the individual coping capacity. However, the precise mechanism has yet to be established. Clinically the syndrome can be divided into the sympathetic and parasympathetic types, based upon the predominance of sympathetic or parasympathetic activity, respectively. The syndrome and its clinical manifestation can be explained as a stress response. At present, no sensitive and specific tests are available to prevent or diagnose overtraining. The diagnosis is based on the medical history and the clinical presentation. Complete recovery may take weeks to months.
There are obvious differences in appearance between men and women, which account for differences in sports performance and injury incidence and location. The recent greater exposure of women to high-level sports has produced an increase in the absolute numbers of injuries in women. However, there are marked anatomic differences between men and women in the musculoskeletal system. For example, women naturally have more subcutaneous fat than men, in a characteristic distribution over the buttocks and thighs and behind the upper arms, giving them a more rounded appearance. Skeletal differences are evident in the pelvis, which has larger inlet and outlet to allow for childbirth. Muscle size and muscle development is less in women, due to the physiologic effects of sex hormones. Relaxin in women plays a role in ligament and tendon laxity, allowing women to be generally more supple than men. At times, these anatomic differences are accentuated by feminine fashion, and by the wearing of dress shoes with high heels.
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.
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.
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)
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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