Morphological Description and Live Weight Prediction from Body Measurements of Socorro Island Merino Lambs.

The aim of this study was to describe the morphology and estimate live weight from body measurements of Socorro Island Merino lambs. A group of Socorro Island Merino lambs was recorded from birth to year for live weight, rump width, rump length, withers height, body length, cannon bone perimeter, and chest girth, width, and depth. The effect of the lamb type on body measurements and live weight was analyzed using ANOVA, Pearson's correlation analysis was performed to estimate the relationship between body measurements and live weight, multiple linear regressions were fitted to obtain prediction equations of live weight from the body measurements and finally, chest girth was used to generate prediction equations using linear and exponential models. At birth and at year, differences were observed in body measurements, especially those related to the thoracic region, with crossbred males showing the highest values. Live weight was correlated with almost all the body measurements, with the highest coefficients observed with chest girth, chest width, and chest depth. Live weight can be accurately predicted from multiple regression equations using several body measurements, but using only chest girth (CG) as a predictor, the exponential equation W0-365 = 0.9142 exp(0.0462 CG) showed the best accuracy.

Clinical Performance of Self-Collected Nasal Swabs and Antigen Rapid Tests for SARS-CoV-2 Detection in Resource-Poor Settings.

Background: In resource-poor countries, antigen-based rapid tests (Ag-RDTs) performed at primary healthcare and community settings improved access to SARS-CoV-2 diagnostics. However, the technical skills and biosafety requirements inherent to nasopharyngeal and oropharyngeal (OP) specimens limit the scale-up of SARS-CoV-2 testing. The collection of nasal-swabs is programmatically viable, but its performance has not been evaluated in resource-poor settings. Methods: We first evaluated the performance of SteriPack self-collected nasal swabs for the detection of SARS-CoV-2 by real-time PCR in 1498 consecutively enrolled patients with suspected infection. Next, we evaluated the clinical performance of three nasal swab-based Ag-RDTs against real-time PCR on OP specimens. Results: The sensitivity of nasal swabs was 80.6% [95% CI: 75.3−85.2%] compared to OP specimens. There was a good correlation (r = 0.58; p < 0.0001) between Ct values of 213 positive cases obtained using nasal and OP swabs. Our findings show sensitivities of 79.7% [95% CI: 73.3−85.1%] for Panbio COVID-19 Ag-RDT, 59.6% [95% CI: 55.2−63.8%] for COVIOS Ag-RDT, and 78.0% [95% CI: 73.5−82.0%] for the LumiraDx SARS-CoV-2 Ag-RDT. Conclusions: In our setting, the COVIOS Ag-RDT did not meet WHO requirements. Nasal swab-based Ag-RDTs for SARS-CoV-2 detection constitute a viable and accurate diagnostic option in resource-poor settings.

Clinical Performance of Self-Collected Nasal Swabs and Antigen Rapid Tests for SARS-CoV-2 Detection in Resource-Poor Settings

Background: In resource-poor countries, antigen-based rapid tests (Ag-RDTs) performed at primary healthcare and community settings improved access to SARS-CoV-2 diagnostics. However, the technical skills and biosafety requirements inherent to nasopharyngeal and oropharyngeal (OP) specimens limit the scale-up of SARS-CoV-2 testing. The collection of nasal-swabs is programmatically viable, but its performance has not been evaluated in resource-poor settings. Methods: We first evaluated the performance of SteriPack self-collected nasal swabs for the detection of SARS-CoV-2 by real-time PCR in 1498 consecutively enrolled patients with suspected infection. Next, we evaluated the clinical performance of three nasal swab-based Ag-RDTs against real-time PCR on OP specimens. Results: The sensitivity of nasal swabs was 80.6% [95% CI: 75.3−85.2%] compared to OP specimens. There was a good correlation (r = 0.58; p < 0.0001) between Ct values of 213 positive cases obtained using nasal and OP swabs. Our findings show sensitivities of 79.7% [95% CI: 73.3−85.1%] for Panbio COVID-19 Ag-RDT, 59.6% [95% CI: 55.2−63.8%] for COVIOS Ag-RDT, and 78.0% [95% CI: 73.5−82.0%] for the LumiraDx SARS-CoV-2 Ag-RDT. Conclusions: In our setting, the COVIOS Ag-RDT did not meet WHO requirements. Nasal swab-based Ag-RDTs for SARS-CoV-2 detection constitute a viable and accurate diagnostic option in resource-poor settings

IMPACT OF THE COVID-19 PANDEMIC ON SPINE SURGERY IN A TERTIARY HEALTH CARE INSTITUTION.

Objectives: To assess postoperative complications, including COVID-19 infection, among patients undergoing surgeries at a tertiary institution during the pandemic, and to develop a local epidemiological profile of spine surgery patients. Methods: Retrospective descriptive study of all patients who underwent spine surgery between March 2020 and 14 January 2021 in a tertiary institution in Latin America. All patients who underwent spine surgery were included, without age restrictions. The main outcomes were postoperative complications, including COVID-19 infection. Results: 74 patients were included in the study, 43 males and 31 females. The average age was 49.6 years. The mean duration of hospitalization was 11.5 days. Urgent surgeries were performed in 60.81% of cases. During hospitalization, only 5 of 74 patients were diagnosed with COVID-19, and only 1 patient had pulmonary involvement estimated to be greater than 50%. On average, 1.9 surgical debridements were required after postoperative surgical site infection. Conclusions: During the hospitalization period, only 6.7% of patients were diagnosed with COVID-19 infection. The COVID-19 infection death rate was 1 in 5 cases. The postoperative surgical site infection rate was 10.8%, similar to the level before the pandemic. Level of Evidence IV; Observational retrospective descriptive study .

Objetivos: Avaliar complicações pós-cirúrgicas, incluindo infecções por COVID-19, entre pacientes cirúrgicos numa instituição terciária de saúde durante a pandemia, e desenvolver um perfil epidemiológico local de pacientes de cirurgias da coluna. Métodos: estudo descritivo e retrospectivo de todos os pacientes que passaram por cirurgias da coluna entre março de 2020 e 14 de janeiro de 2021, numa instituição terciária na América Latina. Todos os pacientes que passaram por cirurgias na coluna foram incluídos, sem restrição de idade. Os principais resultados foram complicações pós-cirúrgicas, incluindo a infecção por COVID-19. Resultados: 74 pacientes foram incluídos no estudo, 43 do sexo masculino e 31 do feminino. A média de idade foi de 49.6 anos. A duração média da hospitalização foi de 11.5 dias. Cirurgias urgentes foram realizadas em 60.81% dos casos. Durante a hospitalização, apenas 5 dos 74 pacientes foram diagnosticados com COVID-19, e apenas 1 deles teve envolvimento pulmonar estimado em mais que 50%. Em média, 1,9 desbridamentos cirúrgicos foram necessários após infecção do sítio cirúrgico. Conclusões: Durante o período de hospitalização, apenas 6,37% dos pacientes foram diagnosticados com infeção por COVID-19. A taxa de mortes devido à infecção por COVID-19 foi de 1 em 5. Infecções do sítio cirúrgico atingiram uma taxa de 10.8%, nível similar àquele prévio à pandemia. Nível de evidência IV ; Estudo observacional retrospectivo descritivo .

Impact of the covid-19 pandemic on spine surgery in a tertiary health care institution / Impacto da pandemia de covid-19 nas cirurgias de coluna em uma instituição terciária de saúde

ABSTRACT Objectives: To assess postoperative complications, including COVID-19 infection, among patients undergoing surgeries at a tertiary institution during the pandemic, and to develop a local epidemiological profile of spine surgery patients. Methods: Retrospective descriptive study of all patients who underwent spine surgery between March 2020 and 14 January 2021 in a tertiary institution in Latin America. All patients who underwent spine surgery were included, without age restrictions. The main outcomes were postoperative complications, including COVID-19 infection. Results: 74 patients were included in the study, 43 males and 31 females. The average age was 49.6 years. The mean duration of hospitalization was 11.5 days. Urgent surgeries were performed in 60.81% of cases. During hospitalization, only 5 of 74 patients were diagnosed with COVID-19, and only 1 patient had pulmonary involvement estimated to be greater than 50%. On average, 1.9 surgical debridements were required after postoperative surgical site infection. Conclusions: During the hospitalization period, only 6.7% of patients were diagnosed with COVID-19 infection. The COVID-19 infection death rate was 1 in 5 cases. The postoperative surgical site infection rate was 10.8%, similar to the level before the pandemic. Level of Evidence IV; Observational retrospective descriptive study .

RESUMO Objetivos: Avaliar complicações pós-cirúrgicas, incluindo infecções por COVID-19, entre pacientes cirúrgicos numa instituição terciária de saúde durante a pandemia, e desenvolver um perfil epidemiológico local de pacientes de cirurgias da coluna. Métodos: estudo descritivo e retrospectivo de todos os pacientes que passaram por cirurgias da coluna entre março de 2020 e 14 de janeiro de 2021, numa instituição terciária na América Latina. Todos os pacientes que passaram por cirurgias na coluna foram incluídos, sem restrição de idade. Os principais resultados foram complicações pós-cirúrgicas, incluindo a infecção por COVID-19. Resultados: 74 pacientes foram incluídos no estudo, 43 do sexo masculino e 31 do feminino. A média de idade foi de 49.6 anos. A duração média da hospitalização foi de 11.5 dias. Cirurgias urgentes foram realizadas em 60.81% dos casos. Durante a hospitalização, apenas 5 dos 74 pacientes foram diagnosticados com COVID-19, e apenas 1 deles teve envolvimento pulmonar estimado em mais que 50%. Em média, 1,9 desbridamentos cirúrgicos foram necessários após infecção do sítio cirúrgico. Conclusões: Durante o período de hospitalização, apenas 6,37% dos pacientes foram diagnosticados com infeção por COVID-19. A taxa de mortes devido à infecção por COVID-19 foi de 1 em 5. Infecções do sítio cirúrgico atingiram uma taxa de 10.8%, nível similar àquele prévio à pandemia. Nível de evidência IV ; Estudo observacional retrospectivo descritivo .

Genetic aspects of athletic performance: the African runners phenomenon.

The current dominance of African runners in long-distance running is an intriguing phenomenon that highlights the close relationship between genetics and physical performance. Many factors in the interesting interaction between genotype and phenotype (eg, high cardiorespiratory fitness, higher hemoglobin concentration, good metabolic efficiency, muscle fiber composition, enzyme profile, diet, altitude training, and psychological aspects) have been proposed in the attempt to explain the extraordinary success of these runners. Increasing evidence shows that genetics may be a determining factor in physical and athletic performance. But, could this also be true for African long-distance runners? Based on this question, this brief review proposed the role of genetic factors (mitochondrial deoxyribonucleic acid, the Y chromosome, and the angiotensin-converting enzyme and the alpha-actinin-3 genes) in the amazing athletic performance observed in African runners, especially the Kenyans and Ethiopians, despite their environmental constraints.

Bovine diseases causing neurological signs and death in Mexican feedlots.

The number of large feedlot operations, similar to that of USA and Canada, has notably increased in Mexico in the last three decades. Clinical and laboratory diagnoses of neurological diseases in feedlot cattle are crucial in Mexico and Central America because of the high incidence of bovine paralytic rabies (BPR). Because of its zoonotic potential, BPR must be promptly diagnosed and differentiated from other bovine neurological diseases such as thrombotic meningoencephalitis (TME), polioencephalomalacia (PEM) and botulism. More recently, BPR and botulism have been diagnosed with increasing frequency in Mexican feedlots. Neither BPR nor botulism has relevant gross lesions, thus post-mortem diagnosis without laboratory support is impossible. Herein, we describe five outbreaks of neurological diseases in Mexican feedlots in which BPR, botulism and PEM were diagnosed either independently or in combination. A diagram illustrating the most conspicuous pathologic findings and ancillary laboratory test required to confirm the diagnoses of these neurological diseases in feedlot cattle is proposed.

Descriptive epidemiology of injuries in a Brazilian premier league soccer team.

Soccer, which has a large number of participants, has a high injury incidence that causes both financial and time burdens. Therefore, knowledge about the epidemiology of soccer injuries could allow sports-medicine professionals, such as physicians and physiotherapists, to direct their work in specific preventive programs. Thus, our aim was to conduct an epidemiological survey of injuries sustained by professional soccer players from the same team who participated in the Brazilian championship premier league in 2009. To this end, we evaluated retrospectively player medical records from the team, which included name, date of birth, position, date of injury, mechanism of injury, and type of injury. In the period of study, 95 injuries were recorded: 42 (44.2%) were recorded during matches, and 53 (55.8%) during the training period. Injuries occurred more frequently in midfielders and strikers. All injuries happened in the lower limb, most of the injuries were muscular, and most occurred as the result of collisions with other athletes. In summary, this study demonstrates that there is a need for greater safety awareness in the training environment.

Heart rate response during a simulated Olympic boxing match is predominantly above ventilatory threshold 2: a cross sectional study.

The present study aimed to describe heart rate (HR) responses during a simulated Olympic boxing match and examine physiological parameters of boxing athletes. Ten highly trained Olympic boxing athletes (six men and four women) performed a maximal graded exercise test on a motorized treadmill to determine maximal oxygen uptake (52.2 mL · kg(-1) · min(-1) ± 7.2 mL · kg(-1) · min(-1)) and ventilatory thresholds 1 and 2. Ventilatory thresholds 1 and 2 were used to classify the intensity of exercise based on respective HR during a boxing match. In addition, oxygen uptake (V̇O2) was estimated during the match based on the HR response and the HR-V̇O2 relationship obtained from a maximal graded exercise test for each participant. On a separate day, participants performed a boxing match lasting three rounds, 2 minutes each, with a 1-minute recovery period between each round, during which HR was measured. In this context, HR and V̇O2 were above ventilatory threshold 2 during 219.8 seconds ± 67.4 seconds. There was an increase in HR and V̇O2 as a function of round (round 3 < round 2 < round 1, P < 0.0001). These findings may direct individual training programs for boxing practitioners and other athletes.

Effect of supplemental yeast culture and physiological factors on colostrum and milk composition of Pelibuey ewes.

The effects of supplemental yeast culture, litter size, stage and number of lactation on milk composition were studied in Pelibuey ewes. Twenty ewes were randomly assigned to one of two dietary treatments. Ten control ewes grazed on guinea grass (Panicum maximum) and were supplemented with concentrate. A further ten ewes received the same diet with 14 g/head/day of yeast culture (Saccharomyces cerevisiae). Colostrum was collected within 24 h after parturition, and subsequently, milk samples were collected at fortnightly intervals (7, 21, 35, and 49 days). Total solids content averaged 32% in colostrum and 12.5% in milk. Colostrum of primiparous ewes had higher total solids content than that of ewes with more than five lactations. However, ewes with more than five lactations produced milk with higher net energy, total solids, protein, and casein than ewes with fewer lactations. Milk at 7 days had a significantly higher content of energy, total solids, and fat than milk at 21, 35, and 49 days. Total solids content was lower for ewes rearing one lamb than larger litter sizes. Supplementation with yeast culture did not affect the composition of colostrum and milk, which was mainly affected by the stage and number of lactation.

Incidencia de las discrepancias sérico globulares del grupo sanguíneo A en pacientes con leucemia mieloide aguda de novo en el Servicio de Hematología Clínica del Hospital Nacional Edgardo Rebagliati Martins Lima - Perú durante el periodo 2011 / Incidence of discrepancies globular serum-blood in patients group

En el presente estudio se determino la incidencia de las discrepancias sérico-globulares en pacientes del grupo sanguíneo "A" con leucemia mieloide aguda de novo del Servicio de Hematología del Hospital Nacional Edgardo Rebagliati Matins durante el periodo 2011. Se presentaron un total de 20 pacientes con diagnostico de leucemia mieloide aguda de los cuales 13 fueron del grupo sanguíneo "O", 01 era de grupo sanguíneo "B" y 06 del grupo sanguíneo "A". Se confirmo el grupo sanguíneo en tubo (sérico-globular) a los pacientes del grupo sanguíneo "A", de los cuales cinco de ellos presento una lectura de 4+ (cuatro cruces) en la prueba globular y no se encontró discrepancia con la prueba sérica. Solo un paciente de sexo masculino presento una lectura de 2+ (dos cruces) en la prueba globular y la prueba sérica dio una lectura de 4+. Además se recolectaron los informes del cariotipo de cada paciente, cuyos resultados fueron normales, a excepción del paciente con discrepancia del grupo sanguíneo que presento un cariotipo de 46XY t (9;22) lo que estaría acorde con los reportes de otros estudios sobre la discrepancias sérico-globulares, donde se menciona que la pérdida de expresión de antígenos del grupo sanguíneo son causadas por alteraciones genéticas como translocaciones, delecciones, mutaciones y metilaciones del ADN que afecten el gen del grupo sanguíneo ABO localizado en el cromosoma 9.

In the present study we determined the incidence of discrepancies globular serum-blood in patients group "A" with de novo acute myeloid leukemia Hematology Service of the National Hospital Edgardo Rebagliati Matins during 2011. There were a total of 20 patients diagnosed with acute myeloid leukemia which 13 were blood group "O", 01 were blood group "B" and 06 blood group "A". Blood group was confirmed in tube (serum-globular) to patients of blood group "A", of which five of them presented a reading of 4+ (four crosses) in the globular test and found no discrepancies with the test serum. Only one male patient presented a reading of 2+ (two crosses) in the globular test and serum test gave a reading of 4+. It also collected the reports of the karyotype of each patient, the results were normal, except for the patient with blood group discrepancy that showed a karyotype of 46XY t (9;22) which would be consistent with reports from other studies on the discrepancíes serum-globular, which mentions that the loss of expression of blood group antigens are caused by genetic alterations such as translocations, deletions, mutations and DNA methylation affecting the ABO blood group gene on chromosome 9.

Comportamento da força em resposta ao alongamento e encurtamento muscular / Force behavior in response to muscle stretch and shortening

Alguns fenômenos relacionados à produção de força na fibra muscular não podem ser perfeitamente explicados pela teoria das pontes cruzadas; dentre eles, podemos citar o comportamento da força durante e após mudanças de comprimento muscular. Investigando a força durante estas mudanças, notou-se que o aumento e a diminuição da mesma durante o alongamento e encurtamento têm algumas características em comum com relação à forma do traçado da força: ambos apresentam duas fases (I e II), com duas mudanças de inclinação (P1 e P2). Apesar dessas similaridades, existem particularidades: quando diferentes velocidades são aplicadas, os comportamentos de P1 e P2 durante alogamento diferem ligeiramente dos seus homólogos durante o encurtamento. Distintos mecanismos moleculares tentam explicar essas particularidades: durante o alongamento P1 ocorre devido à reversão do curso de alavancagem das pontes cruzadas, ao passo que durante o encurtamento, as mesmas seguem seu curso normal. Em ambas as condições, P2 está relacionado ao ponto onde as pontes cruzadas se destacam; mas como este ponto ocorre em diferentes sentidos, resulta em diferentes estados moleculares finais. Ademais, P1 e P2 têm sido usados para se analisar o comportamento da força durante as mudanças de comprimento. Existem três mecanismos aceitos para explicar o ganho de força durante o alongamento 1) um aumento no número de pontes cruzadas; 2) um aumento na força gerada por cada ponte cruzada e 3) pontes cruzadas operando em estado de pré-curso-de-alavancagem. Já com relação à diminuição da força acredita-se que há uma perda da força média produzida por cada ponte cruzada, quando estas são “empurradas” para um estado molecular de menor tensão...

Some phenomena related to force production in muscle fibers cannot be fully explained by the crossbridge theory; among them we can cite the force behaviour during and after length changes. Investigating force during these changes, it was noted that the increase and decrease in force during stretchand shortening have some characteristics in common with respect to their force trace: both have twophases (I and II), with two changes in slope (P1 and P2). Despite these similarities, there are particularities: when different velocities are applied, P1 and P2 behaviours during stretch differ slightly from their counterpart during shortening. Distinct molecular mechanisms try to explain these particularities: during stretch, P1 occurs due to a reversal of powerstroke, where as during shortening, crossbridges follow the normal powerstroke course. In both conditions, P2 is related to the point where the cross-bridges detach; but as it happens in different directions, it results in different final molecular states. Furthermore, P1 e P2 have been used for force behaviour analyses during length changes. There are three accepted mechanisms to explain force enhancement during stretch: 1) an increase in the number of crossbridges, 2) an increase in force generated per crossbridge and 3) crossbridges operating in prepowerstroke. On the other hand, concerning force depression, it is believed there is a loss in the force produced per crossbridge, while they are "pushed" to a molecular state of lower strain...

Desempenho de basquetebolistas no salto vertical: comparação em diferentes momentos da partida / Basketball player's performance in vertical jump: a comparison at different times of the match

Introdução: O basquetebol é uma modalidade que se caracteriza pelo predomínio do metabolismo anaeróbio no fornecimento de energia com destaque para potência na realização dos diferentes fundamentos, principalmente na habilidade do salto. Com ações intermitentes no jogo, a produção de fadiga e a queda no desempenho dos atletas é um fator a ser investigado. Objetivo: o objetivo do estudo foi analisar e comparar saltos verticais de atletas de basquetebol, em diferentes quartos de jogo e posições, em duas partidas. Método: Participaram 11 atletas homens (idade de 22,8±3,7 anos, massa corporal de 94,15±13,9 kg, estatura de 196±9,1 cm) em diferentes posições e a avaliação da força explosiva de membros inferiores foi realizada com a técnica de Counter Movement Jump com auxílio dos braços. Os jogadores foram avaliados no início da partida e ao final dos quartos de jogo. Para análise dos dados utilizou-se média e desvio-padrão, teste de Kruskal-Wallis para normalidade, T de Student para dados pareados, na comparação entre as posições. Resultados: Os principais resultados dos valores de salto apontam para a proximidade quantos aos dados iniciais durante todos os quartos de jogo, nas duas partidas avaliadas e, em relação às posições do jogo e o tempo de participação, os armadores se destacam pelas diferenças significativas (p<0,05) avaliadas ao final do segundo e terceiro quarto. Conclusão: Os resultados assemelham-se a achados de outros autores, levando a crer que a fadiga de membros inferiores no salto não ocorre devido à relação com ações fisiológicas e da quantidade de saltos durante as partidas.

Introduction: Basketball is a sport that is characterized by the predominance of anaerobic metabolism in providing energy with the importance of power on the different fundamentals, especially in the ability of jump. With intermittent actions in the game, the production of fatigue and decline in athletes? performance is a factor to be investigated. Objective: The objective of the study was to analyze vertical jumps of basketball athletes, playing in different quarters and positions, in two matches. Methods: Study participants were 11 male athletes (age 22.8 ± 3.7 years, body mass 94.15 ± 13.9 kg, height of 196 ± 9.1 cm) in different positions and evaluation of explosive strength of lower limbs was performed with the technique of Counter Movement Jump with the help of arms. The players were evaluated at the beginning of the match and at the end of all quarters. For data analysis we used mean and standard deviation, the Kruskal-Wallis test for normality, Studen' s T for paired data, comparing the positions. Results: The main results of the jumps indicates to the homogeneity of the initial data for all quarters of the game in both matches and in relation to the playing time and participation, the guards shown significant differences (p <0 , 05) at the jumps evaluated at the second and third quarter, of game 2 and 1, respectively. Conclusion: The results are in accordance with findings of other studies, implying that the lack of fatigue in lower limbs in the act of jumping could be linked to the physiological responses and the number of jumps during the matches.

Periodização do treinamento de força: uma revisão crítica / Periodized strength training: a critical review

Originária da Alemanha e da antiga União das Repúblicas Socialistas Soviéticas (URSS), a teoria da periodização do treinamento se desenvolveu em meados do século XX, no chamado período científi co, baseada na teoria da Síndrome Geral da Adaptação (SGA). A literatura científi ca pertinente ao treinamento de força entende a periodização como a variação sistemática da intensidade e do volume com a fi nalidade de se desenvolver de forma efi ciente uma ou mais capacidades físicas. O presente trabalho teve por objetivo analisar o efeito da periodização sobre o treinamento de força com relação às suas adaptações específi cas e comparar os modelos mais recorrentes (fi xo, linear e ondulado). Para tanto, foi feito um levantamento bibliográfi co sobre as variáveis utilizadas para a prescrição do treinamento resistido, assim como uma revisão sistemática de artigos encontrados nas seguintes bases de dados: Pubmed e Scielo. A constatação principal da presente revisão foi que o modelo ondulado é o mais efi ciente para o aumento de força máxima e potência, seguido pelo linear e por último o fi xo, embora sejam necessárias mais investigações enfocando resistência de força e hipertrofi a muscular.

Originating from Germany and former Union of Soviet Socialist Republics (USSR), the training periodization theory was developed in the middle of the 20th Century, the so-called scientifi c period, based on the General Adaptation Syndrome theory (GAS). The scientifi c literature on strength training understands periodization as the systematic variation of intensity and volume aiming at more effi ciently developing one or more physical abilities. This paper aimed at analyzing the effect of periodization on strength training as related to its specifi c adaptations and comparing the most recurrent models (fi xed, linear, and undulating). For that, a bibliographic survey on the training variables used to prescript resistance training was carried out, as well as a systematic review of the articles found in the following databases: Pubmed and Scielo. The main fi nding of this review was that the undulated model is the most effective one for increasing maximum strength and power, followed by the linear one, and lastly by the fi xed one, although more investigation focusing on strength resistance and muscle hypertrophy is required.