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.

The purpose of this review was to provide a physiological rationale for the use of eccentric resistance training and to provide an overview of the most commonly prescribed eccentric training methods. Based on the existing literature, there is a strong physiological rationale for the incorporation of eccentric training into a training program for an individual seeking to maximize muscle size, strength, and power. Specific adaptations may include an increase in muscle cross-sectional area, force output, and fiber shortening velocities, all of which have the potential to benefit power production characteristics. Tempo eccentric training, flywheel inertial training, accentuated eccentric loading, and plyometric training are commonly implemented in applied contexts. These methods tend to involve different force absorption characteristics and thus, overload the muscle or musculotendinous unit in different ways during lengthening actions. For this reason, they may produce different magnitudes of improvement in hypertrophy, strength, and power. The constraints to which they are implemented can have a marked effect on the characteristics of force absorption and therefore, could affect the nature of the adaptive response. However, the versatility of the constraints when prescribing these methods mean that they can be effectively implemented to induce these adaptations within a variety of populations.

The purpose of this study was to determine the differences in kinetic, kinematic, and metabolic variables between an acute normal dead stop squat (NDS) protocol and an acute accentuated eccentric loaded squat (AEL) protocol. Eight collegiate weightlifters were performed the 2 squat protocols. Eccentric and concentric kinetic and kinematic data were collected via synchronized force plate and linear position transducer. Metabolic parameters assessed were oxygen consumption (VO2 ) using open circuit spirometry, testosterone (T) and cortisol (C) via blood draw from antecubital vein, and lactate (La) values via finger prick blood draw. The following are major findings of the dissertation. No statistical differences were observed for concentric variables between AEL and NDS work sets or between warm-up at 55% (WUP55) and postset at 55% (POST55) sets. Differences were found in the speed and duration of the eccentric portion of the lifts. Results indicate that there are no meaningful biomechanical differences when performing AEL squats in this manner and that the intensity and volume executed did not result in PAP. Oxygen uptake was statistically different during sets with the additional eccentric load (set 4, 5, 6, 7) and the subsequent down set (set 9). Lactate was greater during AEL squatting than NDS after set 7 and set 8 for the whole group. T exhibited no statistically significant changes. C was greater immediately following the AEL protocol compared to NDS 30 minutes post-AEL squat protocol yielded a statistically significant difference from immediately post and a return to near baseline measures. These acute changes may have meaningful effects on long- term gains in hypertrophy and strength. The findings of this dissertation show the potential benefits of AEL dead-stop squats for long-term hypertrophy and strength development. However, because this dissertation was the first to explore dead-stop squats with an additional eccentric load, further research is required on both the potential benefits of dead-stop squats and typical squats with no dead-stop using an AEL protocol.

Shallow foundations are widely used in different types of soils for supporting the loads from the lightly loaded superstructures of various civil infrastructures both on level and sloping ground. Design of shallow foundations in geotechnical engineering practice is widely based on the principles of saturated soil mechanics because they are relatively simple. However, the soil near the ground surface (i.e., vadose zone) in which the shallow foundations are typically placed is in an unsaturated state. The water content variation in unsaturated soils is influenced by hydrological events such as the snow melt, rainfall infiltration, evaporation, and the plant transpiration. Due to this reason, the hydro-mechanical properties (i.e., coefficient of permeability, shear strength and volume change) of unsaturated soils are sensitive to the variation in soil suction associated with water content changes. These properties in turn have a significant impact on the bearing capacity and settlement behavior of the shallow foundations. Therefore, it is rational to investigate shallow foundations’ behavior extending the principles of unsaturated soil mechanics. During the last two decades, there has been a significant interest towards investigating shallow foundations based on unsaturated soil mechanics. Laboratory, field, and model studies highlight that matric suction variation in unsaturated soils has a significant influence on the bearing capacity and settlement behavior of shallow foundations. However, the focus of most of the presently available studies in the literature consider mostly vertical loading conditions on level soil ground. There are limited studies related to the design of shallow foundations on sloping ground and subjected to inclined and eccentric loading conditions. Also, there are only few studies that consider the effect of the steady state and transient flow conditions on the foundation bearing capacity evaluation. Therefore, one of the key objectives of this thesis is directed toward developing rational tools for investigating shallow foundations considering the steady state and transient flow conditions associated with water infiltration and evaporation in unsaturated soils. Comprehensive investigation studies are undertaken to interpret the influence of the steady state and transient flow conditions on the shallow foundations related to: (i) bearing capacity on the sloping ground in different types of soils including expansive soils, and (ii) bearing capacity under the inclined and eccentric loading conditions with homogeneous soil properties and considering spatial variation of soil properties. Succinct details related to investigated studies are summarized below: (1) An analytical method is proposed for quantifying the bearing capacity of the shallow foundations on unsaturated soil slopes considering different rainfall infiltration conditions. The proposed method is a novel tool for considering the simultaneous influence of several parameters that include the flow rates, the infiltration duration, the foundation set-back distance and the ground water table depth on the foundation bearing capacity. (2) Another analytical method is proposed for evaluating the foundation bearing capacity under inclined and eccentric loading considering both the steady state and transient flow conditions. Semi-empirical equations are proposed for describing the failure envelops in vertical and horizontal (V - H) loading space and in the vertical and moment (V - M) loading space. These equations are capable to describe the variation of failure envelops considering the influence of the groundwater table depth variation, internal friction angles, surface flux boundary conditions and different infiltration durations. (3) The influence of infiltration on the combined performance of both the foundation and the slope in cracked expansive soils is evaluated with the aid of a numerical technique. A semi-empirical model that describes the elastic modulus and the matric suction is implemented into the numerical model. Bimodal soil water characteristic curve is used as a tool for understanding the influence of surface cracks in the numerical study in a simplified manner. The influence of the rainfall intensity, rainfall duration, foundation setback distance and foundation loading on the combined performance of foundation and slope were investigated. Results combined with some suggestions for rational design procedures are presented that can be useful for geotechnical engineers in practice applications. (4) Numerical analyses are conducted for shallow foundations under vertical and combined loading subjected to different flow conditions. A numerical code procedure is exclusively developed as a part of this study to: (i) consider the variation of soil properties along with the matric suction fluctuations in the commercial software ABAQUS with the aid of a user developed subroutine USDFLD; (ii) incorporate the spatial variability of soil properties into the finite element model. Comparisons are provided between the numerical study and other methods such as the experimental investigations, the analytical methods, and the semi-empirical equations for bearing capacity failure envelopes. In addition, comparisons are also made between the failure envelopes and the failure mechanisms contour using the model considering soil spatial variability and homogeneous soil properties. The proposed methods in this thesis are simple to use for evaluating bearing capacity of shallow foundations that are subjected to steady state and transient state flow conditions considering two scenarios: (i) foundation on sloping ground (ii) foundation under inclined and eccentric loading. The results from the above studies reveal that it is the relationship between the soil permeability and the rainfall characteristics that mainly control the water infiltration rates. The soil suction and the effective degree of saturation are influenced by the water infiltration rates and have a significant impact on the foundation as well as the slope behavior. More importantly, the investigations undertaken in this thesis contribute towards addressing the research gaps related to the behavior of foundations in unsaturated soils. Various scenarios considered in this thesis include the influence of unsaturated flow have not been considered earlier in the literature. The results of the studies summarized in this thesis are expected to be useful for practicing geotechnical engineers in the optimal design of shallow foundations extending the principles of unsaturated soil mechanics for various soils. Moreover, the proposed methods can be used for interpreting the foundation behavior for their entire life span service. In addition, these methods can be employed to rationally explain the field-measured data and can also be used in the forensics analyses of failed slopes and shallow foundations.

Physiological adaptations were investigated following a strength-endurance (S-E) block prescribed with accentuated eccentric loading (AEL) or traditional resistance training (TRAD). Recreationally trained participants (n = 11 males, 6 females, age = 23.2 ± 4.2 yrs, body mass (BM) = 81.3 ± 22.2 kg, height = 172.1 ± 10 cm) completed a four-week block of concurrent resistance, sprint, and change of direction training. Participants were assigned one of two training conditions, AEL (n = 9) or TRAD (n = 8). Training was identical, except AEL performed 110% eccentric overloading every 1st, 3rd, 5th, 7th, and 9th repetition during back squat (BS) and bench press (BP). Body composition, summated muscle size (ACSAsum) and thickness (MTsum), regional ACSA and MT, and region-specific fascicle angle (FA) and length (FL) were assessed pre- (PRE) and post-training (POST). External work was calculated and exercise displacement was measured to determine the mechanical stimulus provided. Physiological variables were analyzed using multiple mixed analysis of variance (ANOVA). External work and displacement were analyzed with independent Welch’s t-tests. A statistically significant main effect of Time was observed for ACSAsum and ICW (p < 0.05); however, there were no statistically significant Time x Condition interaction effects observed for any dependent variable (p > 0.05). Time x Length interaction effects also failed to reach statistical significance for regional ACSA or regional MT (p > 0.05). Moreover, Time x Position interaction effects were not statistically significant for regional MT (p > 0.05). There were also no statistically significant interaction effects observed for regional FA or FL (p > 0.05). Differences in external work did not reach statistical significance (p > 0.05). A four-week S-E training block, performed with or without AEL, increases muscle size, but results in only minor architectural alterations. Additionally, AEL appears to induce unique region-specific hypertrophy. In contrast, TRAD seems to induce greater increases in ICW, potentially indicating greater sarcoplasmic hypertrophy. Interestingly, 110% eccentric overloading did not lead to statistically greater work performed, although differences may be practically significant when allometrically scaled. Researchers and practitioners should examine region-specific musculoskeletal adaptations, when possible, to more accurately assess training effects.

The purpose of this review is to provide strength and conditioning practitioners with recommendations on how best to implement tempo eccentric training (TEMPO), flywheel inertial training (FIT), accentuated eccentric loading (AEL), and plyometric training (PT) into resistance training programs that seek to improve an athlete’s hypertrophy, strength, and power output. Based on the existing literature, TEMPO may be best implemented with weaker athletes to benefit positional strength and hypertrophy due to the time under tension. FIT may provide an effective hypertrophy, strength, and power stimulus for untrained and weaker individuals; however, stronger individuals may not receive the same eccentric (ECC) overload stimulus. Although AEL may be implemented throughout the training year to benefit hypertrophy, strength, and power output, this strategy is better suited for stronger individuals. When weaker and stronger individuals are exposed to PT, they are exposed to an ECC overload stimulus as a result of increases in the ECC force and ECC rate of force development. In conclusion, when choosing to utilize ECC training methods, the practitioner must integrate these methods into a holistic training program that is designed to improve the athlete’s performance capacity.

No description available.

Lesões cervicais não cariosas têm etiologia multifatorial, com ênfase na ação de ácidos, abrasivos e cargas mecânicas aplicadas à distância do local da lesão, mas que concentram tensão na região cervical, que é o local da lesão. O mecanismo de ação das cargas aplicadas à distância não foi ainda elucidado. Pensou-se que seria mediado por micro fraturas que fariam se desprender fragmentos de tecido (abfração); mas isto não explicaria a formação de lesões produzidas na presença de compressão, mesmo concentrada, nem a interação sinérgica na presença de ácidos. Além disso, as fraturas nunca foram localizadas no tecido. Uma outra hipótese considera os tecidos dentários como esponjas rígidas, deformáveis, capazes de expelir a sua própria água quando comprimidos ou absorver fluidos circundantes quando tracionados. Quando a carga fosse removida e o tecido recuperasse sua forma original, o fluido faria o caminho inverso. Assim, a ciclagem mecânica forçaria a circulação de fluidos circundantes no tecido e, se fossem ácidos, facilitaria a dissolução do tecido, tanto sob tração quanto sob compressão. A proposta do estudo foi avaliar a penetração de fluido traçador (nitrato de prata a 10 %) no esmalte de espécimes submetidos ou não a cargas cíclicas excêntricas que provocam compressão ou tração. Os espécimes foram construídos a partir de incisivos bovinos, cortados em paralelepípedos de 3x3x8,2 mm, com entalhe na dentina para formar um pescoço de 2x2 mm de seção transversal. Os espécimes, exceto uma faixa central do esmalte vestibular de 1,5x5 mm foram protegidos da penetração do traçador com verniz. Foram aplicados 1.200 ciclos mecânicos de carga excêntrica para produzir tensões de tração ou compressão no esmalte, com 5 s de carga de 40 N e 25 s sem carga. Um grupo controle não recebeu nem carga nem exposição ao traçador; outro controle recebeu apenas exposição ao traçador, sem carga; outros dois grupos controles receberam carga (de tração ou compressão) enquanto imersos em água e, imediatamente depois, foram expostos ao traçador durante 600 min. Os dois grupos teste foram expostos simultaneamente aos ciclos de carga (de tração ou de compressão) e ao traçador. A prata do traçador foi precipitada por exposição a fixador radiográfico e, posteriormente, à luz de fotopolimerizador (5 min). Para localizar o traçador os espécimes foram micro tomografados, radiografados e, posteriormente, foram cortados longitudinalmente para obter uma fatia central de 1 mm de espessura para avaliação em lupa, com luz refletida ou transmitida. A micro tomografia foi ineficaz devido aos artefatos formados. As radiografias marcaram apenas as regiões de maior concentração do traçador. A avaliação dos cortes em lupa binocular permitiu concluir que existem variações de padrão de coloração natural do esmalte de incisivos bovinos, que todos os espécimes expostos ao traçador, independentemente do grupo experimental, apresentaram alguma infiltração, pelo menos numa camada fina e uniforme da superfície exposta. Além da fina camada marcada, existe variação de padrões de penetração do traçador, mesmo entre os que receberam um mesmo tratamento experimental, o que pode ser devido a variações inevitáveis no histórico de cada dente. Isto, apesar de se tornar um inconveniente para identificar um possível efeito de bombeamento, poderia ser identificado também como um indicador de que podem existir diferenças na velocidade e profundidade de penetração no esmalte de outras moléculas como, por exemplo, as dos ácidos. Em resumo, o corante traçador penetrou no esmalte dos espécimes de incisivos bovinos sem diferenças claras de padrão de penetração entre os diferentes grupos e pode ser um método eficaz para comprovar a hipótese de circulação forçada, mas exigirá novos estudos. / Non-carious cervical lesions have a multifactorial aetiology, with emphasis on the action of acids, abrasives and mechanical loads applied at a distance from the site of the lesion, which concentrates tension at the lesion site. The mechanism of action of loads applied at a distance has not yet been elucidated. It was thought that it would be mediated by microfractures that would cause fragments of tissue (abfração) to be released, but this would not explain the formation of lesions produced in the presence of compression, even concentrated, nor the synergistic interaction in the presence of acids. Also, no fractures were located in the tissue. Another hypothesis considers dental tissues as rigid, deformable sponges capable of expelling their water when compressed or absorbing surrounding fluids under traction. When the load was removed, and the tissue regained its original shape, the fluid would do the reverse way. Thus, mechanical cycling would force the circulation of surrounding fluids into the tissue and, if they were acidic, would facilitate dissolution of the tissue, both under traction and under compression. The study aimed to evaluate the penetration of tracer fluid (10% silver nitrate) in the enamel of specimens subjected or not to eccentric cyclic loads that cause compression or traction. The specimens were constructed from bovine incisors, cut in parallelepipeds of 3x3x8.2 mm, with a notch in dentin to form a neck of 2x2 mm cross-section. The specimens, except a central vestibular enamel strip of 1.5x5 mm, were protected from penetration of the tracer with varnish. 1,200 eccentric load mechanical cycles were applied to produce tension or compression in the enamel, with 5 s of 40 N load and 25 s without load. A control group received neither load nor exposure to the tracer; another control received only exposure to the tracer, without load; two other control groups received loading (tensile or compression) while immersed in water and immediately exposed to the tracer for 600 min. The two test groups were exposed simultaneously to the load (traction or compression) cycles and the tracer. The silver from the tracer was precipitated by exposure to a radiographic fixer and, subsequently, by the light of a curing light source (5 min). To locate the tracer the specimens were micro-scanned, radiographed and later cut longitudinally to obtain a central slice of 1 mm thickness for evaluation in a magnifying glass, light reflected or transmitted. Microtomography was ineffective due to artefacts formed. The radiographs marked only the regions with the highest concentration of the tracer. The evaluation with stereo microscopy allowed to conclude that there are variations in the natural staining pattern of bovine incisor enamel; that all the specimens exposed to the tracer, independently of the experimental group, showed some infiltration, at least in a thin and uniform layer of the exposed surface. In addition to the thin layer marked, there is a variation of tracer penetration patterns, even among those who received the same experimental treatment, which may be due to inevitable variations in the history of each tooth. This fact, although an inconvenience to identify a possible pumping effect, could also be identified as an indicator that there may be differences in the speed and depth of enamel penetration of other molecules, such as those of acids. In summary, tracer dye penetrated the enamel of bovine incisor specimens without clear differences in penetration pattern between the different groups and may be an effective method to prove the hypothesis of forced circulation, but will require further studies.