A realização de uma sessão com ações excêntricas provoca dano na estrutura muscular. Durante o processo de recuperação, essa estrutura sofre adaptações que a protegem da ocorrência de dano nas sessões subseqüentes. Essas adaptações são chamadas de Efeito da Carga Repetida (ECR). Esse efeito foi estudado com a realização de apenas duas sessões de exercícios. A velocidade da ação excêntrica também pode contribuir para a variabilidade do dano induzido. O objetivo desse estudo foi investigar através da análise dos indicadores indiretos, creatina quinase (CK), força, dor, circunferência e amplitude de movimento (ADM), o dano induzido por diferentes velocidades da ação excêntrica e o efeito da carga repetida com a realização das diferentes velocidades (60ºs-1 (Exc60) e 180ºs-1 (Exc180)); e verificar se o efeito da carga repetida seria maior com a realização de três sessões de exercícios. Os resultados dos indicadores analisados tiveram alterações semelhantes nos grupos Exc60 e Exc180, sugerindo que as diferentes velocidades parecem não interferir na magnitude do dano induzido. O ECR não foi diferente entre as velocidades, pois o comportamento das variáveis analisadas foi semelhante entre os dois grupos nas duas sessões iniciais. A realização da terceira sessão de exercícios excêntricos não promove o aumento do efeito protetor, visto que não houve diferenças significantes entre a segunda e a terceira sessão. Indicando que o ECR advém principalmente da realização da primeira sessão / Performing a bout of eccentric exercise causes muscle damage. During recovery, some adaptations occur that can protect muscle structure. These adaptations are known as Repeated Bout Effect. However, this phenomenon has been studied with two bouts. Velocity of eccentric action has been referred as one possible factor which can affect the extension of muscle damage. The aim of this study was to investigate muscle damage induced by different velocities, the repeated bout effect with different velocities and to verify if the repeated bout effect could be larger if three bouts of eccentric exercise were performed. Results of indirect markers of muscle damage (CK, DOR, upper-arm circumference, maximal isometric force) showed similar alterations in groups Exc60 and Exc180, suggesting that different velocities do not affect the extension of muscle damage. Repeated bout effect is not different between velocities, because changes in markers were comparable in both groups after the first two bouts. After performing a third bout of eccentric exercise, there was not any significant differences between second and third bouts. It indicates that the first bout is responsible for the adaptations of the repeated bout effect

Accentuated eccentric loading (AEL) prescribes eccentric load magnitude in excess of the concentric prescription using movements that require coupled eccentric and concentric actions, with minimal interruption to natural mechanics. This method has been theorized to potentiate concentric performance through higher eccentric loading and, thus, higher concentric force production. There is also evidence for favorable chronic adaptations, namely shifts to faster myosin heavy chain isoforms and changes in IIx-specific muscle cross-sectional area. However, research concerning the acute and chronic responses to AEL is inconclusive, likely due to inconsistencies in subjects, exercise selection, load prescription, and method of providing AEL. Therefore, the purpose of this review is to summarize: (1) the magnitudes and methods of AEL application; (2) the acute and chronic implications of AEL as a means to enhance force production; (3) the potential mechanisms by which AEL enhances acute and chronic performance; and (4) the limitations of current research and the potential for future study.

Abstract not available

Early strength increase with training is normally attributed to neural adaptations but recent evidence suggests that muscle hypertrophy occurs earlier than previously thought. The purpose of this study was to examine the time course of adaptation through 20 days of training and 5 days of detraining. Twenty-two untrained subjects trained one arm every 2nd day for 20 days. Subjects performed isokinetic eccentric biceps training at 90°/s (6 sets of 8 reps). Muscle thickness (reported in cm) via ultrasound, strength (reported in Nm) and muscle activation (electromyography) were measured before, during and after training (9 time points). Muscle thickness increased after 8 days of training (3.66±0.11 to 3.90±0.12; p<0.05) and remained above baseline until the end of training (3.97±0.12). After 5 days of detraining muscle thickness decreased (3.97±0.12 vs. 3.85±0.11; p<0.05), but remained higher than baseline (p<0.05). Muscle thickness did not change significantly in the untrained arm at any time point. Strength in the trained arm decreased after 8 days of training (65.6±4.1 to 57.5±3.5; p<0.05) and remained suppressed throughout the study. Muscle activation amplitude increased after 14 days of training (p<0.05) and remained elevated throughout the study. In conclusion, biceps muscle thickness increases very rapidly with frequent intense eccentric training although this type of training appears to impair strength. These findings provide additional evidence that muscle hypertrophy may occur much faster than has been generally accepted.

The 'repeated bout effect'(RBE) is an adaptation whereby a single eccentric (ECC) exercise session protects against muscle damage during subsequent ECC exercise bouts and is characterized by faster strength recovery and a reduction in soreness and inflammation. The purpose was to determine if the protective capacity of the RBE is greater when both bouts of ECC exercise are performed at the same compared to a different velocity of contraction as well as at a fast or slow velocity. Thirty-one right handed participants were randomly assigned to perform an initial unilateral bout of either fast (180°/s) or slow (30°/s) maximal isokinetic ECC elbow flexion. Three weeks later 16 participants completed a repeated bout of ECC exercise at the same velocity as the initial bout (SAME)(FAST-FAST[n=8] and SLOW-SLOW[n=8]), while 15 participants completed a bout at the corresponding different velocity (DIFF) (FAST-SLOW[n=8] and SLOW-FAST[n=7]). Elbow flexor function and damage was measured prior to, immediately after, and at 24, 48, and 72 hours post exercise. Dependant variables included maximal voluntary contraction (MVC) isometric strength (Dynamometer), muscle thickness (MT; Ultrasound), delayed onset muscle soreness (DOMS; Visual Analog Scale), biceps and triceps electromyography (EMG), percent activation (Interpolated twitch), and twitch torque. There were no group differences for height, weight, training experience, or total work performed during the ECC bouts (p>0.05). After the repeated bout, there was a significant reduction in MVC strength, MT, and DOMS at 24, 48, and 72 hours, pooled across participants (p<0.05). After the repeated bout, MVC strength recovered faster only for the SAME group. There were no differences between groups for MT, DOMS, EMG, ITT, and TT. The analysis revealed neither fast nor slow contractions offered greater protection against muscle damage when the repeated bout was not completed at the same velocity. Since a faster recovery of strength is velocity specific this suggests there may be a neural contribution to the repeated bout effect.

The 'repeated bout effect'(RBE) is an adaptation whereby a single eccentric (ECC) exercise session protects against muscle damage during subsequent ECC exercise bouts and is characterized by faster strength recovery and a reduction in soreness and inflammation. The purpose was to determine if the protective capacity of the RBE is greater when both bouts of ECC exercise are performed at the same compared to a different velocity of contraction as well as at a fast or slow velocity. Thirty-one right handed participants were randomly assigned to perform an initial unilateral bout of either fast (180°/s) or slow (30°/s) maximal isokinetic ECC elbow flexion. Three weeks later 16 participants completed a repeated bout of ECC exercise at the same velocity as the initial bout (SAME)(FAST-FAST[n=8] and SLOW-SLOW[n=8]), while 15 participants completed a bout at the corresponding different velocity (DIFF) (FAST-SLOW[n=8] and SLOW-FAST[n=7]). Elbow flexor function and damage was measured prior to, immediately after, and at 24, 48, and 72 hours post exercise. Dependant variables included maximal voluntary contraction (MVC) isometric strength (Dynamometer), muscle thickness (MT; Ultrasound), delayed onset muscle soreness (DOMS; Visual Analog Scale), biceps and triceps electromyography (EMG), percent activation (Interpolated twitch), and twitch torque. There were no group differences for height, weight, training experience, or total work performed during the ECC bouts (p>0.05). After the repeated bout, there was a significant reduction in MVC strength, MT, and DOMS at 24, 48, and 72 hours, pooled across participants (p<0.05). After the repeated bout, MVC strength recovered faster only for the SAME group. There were no differences between groups for MT, DOMS, EMG, ITT, and TT. The analysis revealed neither fast nor slow contractions offered greater protection against muscle damage when the repeated bout was not completed at the same velocity. Since a faster recovery of strength is velocity specific this suggests there may be a neural contribution to the repeated bout effect.

Early strength increase with training is normally attributed to neural adaptations but recent evidence suggests that muscle hypertrophy occurs earlier than previously thought. The purpose of this study was to examine the time course of adaptation through 20 days of training and 5 days of detraining. Twenty-two untrained subjects trained one arm every 2nd day for 20 days. Subjects performed isokinetic eccentric biceps training at 90°/s (6 sets of 8 reps). Muscle thickness (reported in cm) via ultrasound, strength (reported in Nm) and muscle activation (electromyography) were measured before, during and after training (9 time points). Muscle thickness increased after 8 days of training (3.66±0.11 to 3.90±0.12; p<0.05) and remained above baseline until the end of training (3.97±0.12). After 5 days of detraining muscle thickness decreased (3.97±0.12 vs. 3.85±0.11; p<0.05), but remained higher than baseline (p<0.05). Muscle thickness did not change significantly in the untrained arm at any time point. Strength in the trained arm decreased after 8 days of training (65.6±4.1 to 57.5±3.5; p<0.05) and remained suppressed throughout the study. Muscle activation amplitude increased after 14 days of training (p<0.05) and remained elevated throughout the study. In conclusion, biceps muscle thickness increases very rapidly with frequent intense eccentric training although this type of training appears to impair strength. These findings provide additional evidence that muscle hypertrophy may occur much faster than has been generally accepted.

We evaluated the efficacy of treating eccentric muscle damage with IGF-1 PEGylated to a fibrin biomatrix. With one injection, delivered one hour after the induction of eccentric muscle damage we saw an attenuation of force loss early in recovery, maintenance of muscle weight, and progression to the repair/regeneration of the damaged fibers at a greater speed and magnitude in the first week of recovery. As opposed to introducing an unbound bolus of IGF-1, we believe the ability of the PEGylated-fibrin to stabilize and sustain delivery of the molecule results in significantly better recovery. Coupling IGF-1, which has multiple beneficial effects in tissue repair, with this system of delivery provides a simple and easy to administer treatment for eccentric muscle damage. With this form of damage being the most prevalent of all skeletal muscle damage types, since it is underlies all muscle strain, a simple and effective treatment is important for increasing functional recovery after injury. / text

The hypothesis. We supposed the fatigue and its residual phenomena generated by eccentric load to have effect on the changes in vegetative indices, the slow component during exercise of high aerobic intensity in particular. The aim of the research was to establish the residual effect of eccentric load on the changes in vegetative indices during exercise of high intensity. The tasks set were as follows: 1. To estimate the residual effect of eccentric load on the fast component of changes in vegetative indices during exercise of high intensity. 2. To estimate the residual effect of eccentric load on the slow component of changes in vegetative indices during exercise of high intensity. The subjects were 8 students of the Lithuanian University of Agriculture, members of the university basketball team, who gave their informed consent to take part in the experiments within the present study. The age of the subjects was 19,5 ± 0,53 years, height – 191,0 ± 5,8 cm and body mass – 86,5 ± 9,78 kg respectively. The methods used were as follows: changes in the values of VO2, VCO2, heart rate (HR) and Ve indices of the subjects were established applying the test of continuously increased load and the test of constant load when pedalling the veloergometer. After testing blood of the subjects to establish lactate concentration in the blood was taken. To evaluate the level of intensity of the exercise performed by the subjects the evaluation scale of perceptible efforts (intensity of... [to full text]

Stay-in-place (SIP) formwork has been used as an alternative to the conventional formwork system. The systems are mainly assembled on site, hence simplifying the construction process and reducing the construction time as the removal procedure has been eliminated. SIP formwork systems can be divided into two main categories; structural and non-structural formwork, based on their contribution to resist applied loads. The structural formwork provides the same advantages as the non-structural formwork, in addition to its contribution to resist the applied loads. As a result, the cross section and the reinforcement of the structural member can be reduced. Recently, polyvinyl chloride (PVC) has been used as a stay-in-place formwork because of its lower cost compared to other materials, durability, and ease to assemble. The PVC SIP formwork consists of interconnected elements; panels and connectors that serve as permanent formwork for the concrete walls. In this study, the behaviour of the PVC encased reinforced concrete walls under eccentric compression loading was investigated. The variables in this study were the type of the specimen (PVC encased or control), the longitudinal reinforcement (4-10M or 4-15M rebars) and the eccentricity of the applied compression load (33.87 mm, 67.73 mm and 101.6 mm). Generally, the control walls (without PVC encasement) failed by yielding of the steel followed by crushing of the concrete, or by crushing of the concrete without yielding of the steel. For the PVC encased walls, buckling of the PVC occurred after the concrete crushed. The PVC encased specimens showed a higher peak load than their peer control walls. The effect of the PVC on increasing the ultimate capacity at a given eccentricity was more significant for the walls reinforced with 4-10M than the walls reinforced with 4-15M. For the lowest reinforcement ratio (4-10M), the PVC encased specimens showed an increase in peak load by 37.2% and 17.1% at an eccentricity of 67.73 mm and 101.6 mm, respectively. When the reinforcement was increased to 4-15 M, the increase in the peak load dropped at all eccentricities to 10%. For the vertical and the mid-span deflection, the PVC encased specimens and the control specimens showed the same values. Also, the test results showed an increase in the energy absorption capacity for the PVC encased specimens compared to the controls specimens, where the effect for the walls reinforced with 4-10M was higher than the walls reinforced with 4-15M at a given eccentricity. An analytical model was developed to predict the ultimate load capacity of the specimens taking into consideration the effect of the PVC on the load carrying capacity of the walls. The provision was derived based on the moment magnification factor method in which the effect of secondary stresses associated with the column deformations was taken into consideration. The calculated capacities of the PVC encased specimens showed a conservative error of 5.9% on average.