Construct validity and reliability of the 2-Minute Step Test (2MST) in individuals with low back pain.

BACKGROUND: Functional tests are important clinical tools, since they are non-invasive methods, with simple applicability, and low cost. However, there are few tests adapted for individuals with chronic low back pain. Thus, our objective was to evaluate the test-retest and inter-rater reliability of the 2-Minute Step Test in individuals with chronic low back pain and to correlate the test score with measures of pain and physical activity. METHODS: We included patients aged between 18 and 45 years, of both sexes, and with low back pain. The interval between the test and retest was 7 days. We analyzed the data via intra-class correlation coefficient (ICC), confidence interval at 95%, standard error of measurement, and minimum detectable change for reliability. We used the Spearman's correlation coefficient to verify the correlation between 2-Minute Step Test and measures of pain and physical activity (Numerical Pain Scale, Roland-Morris Disability Questionnaire, Pain-Related Catastrophizing Thoughts Scale, Tampa Scale of Kinesiophobia, and Baecke Habitual Physical Activity Questionnaire). RESULTS: Sample is composed of 37 individuals, most of them female, with overweight and low back pain > 60 months. 2-Minute Step Test showed excellent test-retest (ICC = 0.903) and inter-rater (ICC = 0.925) reliability. Sport domain of the Baecke showed a significant correlation with the 2-Minute Step Test (rho = 0.444). CONCLUSION: 2-Minute Step Test is a reliable measure to measure the functional capacity of patients with chronic low back pain considering different times and examiners, as well as being positively correlated with sports practice.

Mechanisms of muscle stretching exercises for reduction of low back pain: narrative review / Mecanismos de exercícios de alongamento muscular para redução de dor lombar: revisão narrativa

ABSTRACT BACKGROUND AND OBJECTIVES: Stretching exercises are present in physical training and muscle rehabilitation programs. Within the context of rehabilitation of patients with low back pain (lombalgy), there is still a gap about the mechanisms that these exercises should reduce pain and disability in these patients. The aim of this study was to investigate what are the possible mechanisms through which muscle stretching exercise could reduce pain in individuals with chronic low back pain.CONTENTS: Pain in the lumbar region is one of the most disabling pains when it comes to limitations for daily functions, so it's necessary to investigate alternatives that provide relief for these patients. As the cause of non-specific chronic low back pain is multifactorial, the treatment of the pathology occurs mainly to reduce the sensation of pain. As an alternative, the flexibility training through stretching exercises can be efficient because they generate biomechanical and sensory changes, which would result in an analgesic effect. Additionally, it's still possible that these two effects occur together to explain the reduction in low back pain after performing stretching exercises. CONCLUSION: There is theoretical basis in the literature to support the performance of stretching exercises as a non-pharmacological strategy for the treatment of chronic low back pain. Biomechanical and neurophysiological mechanisms can be pointed out to explain these benefits.

RESUMO JUSTIFICATIVA E OBJETIVOS: Exercícios de alongamento estão presentes em programas de treinamento físico e reabilitação muscular. Dentro do contexto da reabilitação de indivíduos com dor na região lombar (lombalgia), ainda existe uma lacuna sobre os mecanismos pelos quais esses exercícios reduzem dor e incapacidade nesses pacientes. O objetivo deste estudo foi descrever os possíveis mecanismos pelos quais o exercício de alongamento pode reduzir dor em indivíduos com lombalgia crônica. CONTEÚDO: A dor na região lombar é uma das dores mais incapacitantes quando se trata de limitações para as funções no cotidiano. Por isso, é necessário investigar alternativas que possam proporcionar o seu alívio nesses pacientes. Considerando que a causa da lombalgia crônica não específica é multifatorial, o tratamento desta doença ocorre principalmente na tentativa de reduzir a sensação dolorosa. Como alternativa, o treinamento da flexibilidade por meio de exercícios de alongamento pode agir reduzindo a dor lombar por gerarem alterações biomecânicas e sensoriais que resultam em efeito analgésico. Adicionalmente, ainda é possível que esses dois efeitos possam atuar em conjunto para explicar a redução da dor lombar após a realização de exercícios de alongamento. CONCLUSÃO: Existe suporte teórico na literatura para sustentar a realização dos exercícios de alongamento como estratégia não farmacológica para o tratamento da dor lombar crônica. Mecanismos biomecânicos e neurofisiológicos poderiam ser apontados para explicar tais benefícios.

Effect of Fatigue and Graded Running on Kinematics and Kinetics Parameters in Triathletes.

This study aimed to evaluate the effect of cycling-induced fatigue on subsequent running with different ground inclinations on triathletes. Twenty male triathletes ran on a treadmill at individual speeds, on three inclines: level (0%), 7% uphill (7%), and 7% downhill (-7%). Subsequently, the athletes performed an incremental ramp-to-exhaustion (RTE) protocol on an ergometric bicycle until task failure and repeated the running protocol (POST-RTE). During running and cycling was monitored perceived exertion (RPE) and heart rate (HR). Plantar pressure distribution, peak plantar pressure, total foot area, and ground contact time were measured by an in-shoe sensor. Analysis of variance showed that HR (p=0.001; η2=0.63) and RPE (p=0.001; η2=0.82 large effect) were higher in POST-RTE, without interactions between slopes and fatigue. The heel load showed difference between 0 and 7% and 7 and -7% (p=0.001; η 2=0.44 large effect) with higher value in -7%. The midfoot showed differences between 0 and -7% with higher value in 0% (p=0.03; η 2=0.15 small effect). The contact time showed interactions between fatigue and slopes with a higher value in POST-RTE. Coaches should be aware that training on the uphill and downhill surfaces can alter the plantar load on different foot parts.

Relationship between infrared thermography and muscle damage markers in physically active men after plyometric exercise.

Plyometric training has been used in several sports and fitness programs to improve jumping ability and explosive strength, both in individual and team sports. Eccentric muscle actions, such as those performed during plyometric jumps, induce muscle damage and consequently a rise in skin temperature (Tsk). Thus, the purpose of this study is to assess the response of infrared thermography measurement as an indirect marker of muscle damage after a protocol of plyometric jumps in physically active subjects. Therefore, for the aim of this study ten male subjects with no previous experience in plyometric training participated in the research (age 22.5 ± 3.3 years, weight 71.7 ± 11.0 kg, height 171.1 ± 5.3 cm, and fat mass 15.5 ± 4.7%). To assess the muscle damage, countermovement jump (CMJ), creatine kinase (CK), delayed-onset muscle soreness (DOMS) and infrared thermography (IRT) were measured at 24, 48, and 72 h after plyometric exercise. The acute exercise protocol of plyometric jumps induced muscle damage, as shown by the CK and DOMS (24 and 48 h, p < 0.05) but no statistical difference was shown between the moments analyzed in Tsk (warm zone). Nevertheless, when comparing baseline to 48h, a moderate effect was found in the Tsk (warm zone) for anterior right thigh (ES = 1.1) and posterior left thigh (ES = 0.9) and large effect was found for anterior left thigh (ES = 1.4) and posterior right thigh (ES = 1.3). A moderate effect in the Tsk (warm zone) was found for posterior right and left thigh (ES = 0.9 and ES = 1.1, respectively) when comparing baseline to 72h of IRT. These results suggest that a plyometric jumping session alters CK and DOMS, as well as the thigh's skin temperature in an evident way, bringing up a possible relation with markers of muscle damage.

Distance and Intensity Profiles in Division I Women's Soccer Matches across a Competitive Season.

Women's participation in soccer has increased rapidly. The purpose of this study was to evaluate the physiological demands imposed on women's NCAA Division I soccer players across a season according to speed, total distance traveled, and numbers of sprints measured via GPS (Polar Team Pro®). Eighteen athletes (19.2 ± 1.1 years, 50.5 ± 6.5 mL/kg/min and 23.4 ± 3.6% fat) participated in this study. The analysis was obtained through 13 official matches. Speed zones were defined as Zone 1 (1.0 to 5.99 km·h-1), Zone 2 (6.0 to 10.99 km·h-1), Zone 3 (11.0 to 15.49 km·h-1), Zone 4 (15.5 to 19.9 km·h-1) and Zone 5 (sprint > 20 km·h-1), with Zones 4-5 considered as high intensity running. Individual differences in playing time and total distance were highly variable due to substitutions. Average distance traveled per game in quartiles was 3.9 km, 5.6 km and 7.4 km in the 25th, 50th, and 75th quartiles, respectively. Relative to playing time, players travelled an average of 113.64 ± 17.12 m/min (range: 93.7 to 143.5 m/min) and ran one sprint every 4.12 ± 2.06 min. When distance was summated and analyzed for the entire team, significant difference between halves was found for speed Zones 2, 3 and 4, with greater values found in the first half. Total distance, high intensity running and sprint distance were significantly less than previously recorded in professional players. These findings suggest that coaches should consider the unique physiological demands and recovery opportunities present in NCAA play when constructing practices and conditioning programs.

Thermoregulatory and metabolic responses to a half-marathon run in hot, humid conditions.

This study describes the thermoregulatory and metabolic responses during a simulated half-marathon (21 km) run performed outdoors in a hot, humid environment. Ten male runners were recruited for the study, The run was carried out individually under solar radiation on a predetermined path in the following environmental conditions (ambient temperature: 27.96 ± 1.70 °C, globe temperature: 28.52 ± 2.51 °C, relative humidity: 76.88 ± 7.49%, wet bulb globe temperature: 25.80 ± 1.18 °C). Core temperature, skin temperature, head temperature, heat storage, heart rate, expired gases, rating of perceived exertion, and speed were measured or calculated before the start, every 3 km, and immediately following the run. Comparisons were made for each dependent variable using one-way repeated measures analysis of variance tests, and a Bonferroni test. Average run time and pace were 101:00 ± 9:52 min and 4:48 ± 00:16 min km-1, respectively. Participants significantly reduced their running speed, oxygen consumption, and heat storage at 9 km (p < 0.05). While core temperature was significantly increased at 6 km (p < 0.05) before plateauing for the remainder of the run. The key finding was that most of the runners reduced their pace when a Tcore of 39 °C was reached which occurred between 6 and 9 km of the run, yet runners were able to increase their speed demonstrating an "end-spurt" near the end of the run.

Effects of puberty on jump and sprint performance in young futsal players / Efeitos da puberdade no desempenho de saltos e sprints em jogadores jovens de futsal / Efectos de la pubertad en el desempeño de saltos y sprints en jugadores jóvenes de futsal

ABSTRACT Futsal is a sport that involves motor actions with high intensity and short duration, especially vertical jumps and sprints, which require fast application of strength and speed. The evaluation and training of these physical capacities is a routine practice of coaches, especially in the base categories, which are the entry point for many children and adolescents aiming for a professional career in futsal. With regard to the training of this public, puberty is a factor that must be considered, as a natural biological process involving several bodily transformations that can influence the performance of these physical capacities, especially considering that the categories are divided by chronological age, which does not always correspond to pubertal age. The objective of this study was to conduct a literature review of body modifications during puberty, and how these can affect the aspects that determine good performance in jumps and sprints. It was verified that this phase is associated with hormonal changes, an increase in muscle mass, and anthropometric aspects, as well as the maturation of the neuromuscular functions and refinement of the more complex motor activities, such as locomotion. Together, these factors can favor the fast application of force, and better performance of these players in terms of motor activities. However, it is important to emphasize that although these factors increase and naturally favor the players' performance in terms of strength and speed, it is a phase in which specific types of training focused on the aspects that determine good performance are fundamental to increase these capacities and diminish other aspects that also occur with the bodily development, such as a transient decrease in motor coordination and balance due to the rapid growth spurt, and tissue stiffness, which can sometimes occur during this period. Level of evidence V; Expert Opinion.

RESUMO O futsal é um esporte que envolve ações motoras de alta intensidade e curta duração, principalmente, saltos verticais e sprints que exigem rápida aplicação de força e velocidade. A avaliação e o treinamento dessas capacidades físicas fazem parte de uma prática rotineira de treinadores, especialmente, das categorias de base, em que há o ingresso de muitas crianças e adolescentes que pretendem seguir uma carreira profissional no futsal. Em relação ao treinamento desse público, a puberdade é um fator que deve ser considerado como um processo biológico natural envolvendo diversas transformações corporais que podem influenciar no desempenho dessas capacidades físicas, principalmente, considerando que as categorias são divididas pela idade cronológica que nem sempre corresponde à idade puberal. O objetivo desse estudo consistiu em realizar uma revisão da literatura em relação às modificações corporais durante a puberdade e como as mesmas podem afetar os aspectos que determinam o bom desempenho em saltos e sprints. Foi verificado que essa fase está associada a alterações hormonais, aumento da massa muscular e aspectos antropométricos, assim como o amadurecimento das funções neuromusculares e refinamento das atividades motoras mais complexas como a locomoção. Juntos, esses fatores podem favorecer a rápida aplicação de força e maior rendimento desses jogadores quanto às atividades motoras. Entretanto, é importante ressaltar que, embora esses fatores aumentem e favoreçam naturalmente o desempenho de força e velocidade dos jogadores, essa é uma fase em que tipos específicos de treinamento focados em aspectos que determinam o bom rendimento são fundamentais para aumentar essas capacidades e diminuir outros aspectos que também podem ocorrer com o desenvolvimento corporal, como por exemplo, a diminuição temporária da coordenação motora e equilíbrio devido ao pico de crescimento e a rigidez tecidual que, algumas vezes, podem ocorrer durante esse período. Nível de evidência V; Opinião de Especialista.

RESUMEN El futsal es un deporte que abarca acciones motoras de alta intensidad y corta duración, principalmente, saltos verticales y sprints, que exigen rápida aplicación de fuerza y velocidad. La evaluación y entrenamiento de estas capacidades físicas forman parte de una práctica rutinaria de entrenadores, especialmente de las categorías de base, en que hay ingreso de muchos niños y adolescentes que pretenden seguir una carrera profesional en el futsal. Con relación al entrenamiento de ese público, la pubertad es un factor que debe ser considerado como un proceso biológico natural involucrando diversas transformaciones corporales que pueden influenciar en el desempeño de esas capacidades físicas, principalmente, considerando que las categorías son divididas por la edad cronológica que no siempre corresponde a la edad puberal. El objetivo de este estudio consistió en realizar una revisión de la literatura con relación a las modificaciones corporales durante la pubertad y cómo pueden las mismas afectar los aspectos que determinan el buen desempeño en saltos y sprints. Se verificó que esta fase está asociada a alteraciones hormonales, aumento de la masa muscular y aspectos antropométricos, así como la madurez de las funciones neuromusculares y refinamiento de las actividades motoras más complejas como la locomoción. Juntos, estos factores pueden favorecer la rápida aplicación de fuerza y mayor rendimiento de estos jugadores cuanto a las actividades motoras. Entretanto, es importante resaltar que, aunque estos factores aumenten y favorezcan naturalmente el desempeño de fuerza y velocidad de los jugadores, esta es una fase en que tipos específicos de entrenamiento enfocados en aspectos que determinan el buen rendimiento son fundamentales para aumentar esas capacidades y disminuir otros aspectos que también pueden ocurrir con el desarrollo corporal, como por ejemplo, la disminución transitoria de la coordinación motora y el equilibrio debido al pico de crecimiento, además de la rigidez tisular que, algunas veces, pueden ocurrir durante ese período. Nivel de evidencia V; Opinión de Especialista.

Assessment of acute physiological demand for soccer / Avaliação da demanda fisiológica aguda no futebol

Soccer is a sport practiced worldwide, on all continents. It is considered an intermittent activity of high intensity and long duration, in which movements that require great strength and speed, such as jumps and sprints, result in high levels of muscle microtrauma, hampering athletes' training and recovery. The present study aimed to evaluate the magnitude of changes in different markers of physiological demand resulting from a soccer match in healthy individuals. Ten healthy male physical education students participated in the study and were evaluated in two matches: the semi-final and final games of the college tournament at the federal university where they studied. Blood samples were collected from each volunteer pre- and post-match. Cortisol, IL-6 and CK concentrations were increased after the match (p < 0.05). Testosterone and alpha-actin concentrations did not change. Our results indicate that changes in some of the acute response markers evaluated in players before and after competitive soccer matches provide important information for planning training or recovery, as well as nutritional strategies for improving performance.

O futebol é um esporte de abrangência mundial praticado em todos os continentes.É considerada uma atividade intermitente, de alta intensidade e longa duração, na qual as ações de grande força e velocidade como saltos e sprints implicam altos níveis de microtrauma muscular, atrapalhando o treinamento e a recuperação dos atletas. O propósito deste trabalho foi avaliar a magnitude das alterações de diferentes marcadores da demanda fisiológica em indivíduos saudáveis decorrentes de um jogo de futebol. Participaram do estudo, dez homens considerados saudáveis, estudantes de Educação Física. Os indivíduos foram avaliados em dois jogos, sendo a semifinal e a final do torneio universitário da universidade federal onde estudavam. A amostra sanguínea foi retirada de cada voluntário nos momentos pré e pós-jogo. Resultados: As concentrações de Cortisol, IL-6 e CK, apresentaram aumento pós-jogo (p<0,05). As concentrações de Testosterona e alfa-actina não se alteraram. Pode-se concluir que as alterações em parte dos marcadores das respostas agudas avaliados em jogos competitivos de futebol fornecem informações importantes para o planejamento de métodos de treinamento, recuperação ou estratégias nutricionais para o aperfeiçoamento do esporte.

The ACTN3 genotype in soccer players in response to acute eccentric training.

Genetic factors can interfere with sporting performance. The identification of genetic predisposition of soccer players brings important information to trainers and coaches for individual training loads adjustment. Different responses to eccentric training could be observed by the genotype referred to as α-actinin-3 (ACTN3) in biomarkers of muscle damage, hormones and inflammatory responses. The aim of this study was to compare acute inflammatory responses, muscle damage and hormonal variations according to the eccentric training in soccer professional athletes with different genetic profiles of ACTN3 (XX, RX and RR). 37 soccer professional athletes (9 XX, 13 RX, 15 RR) were randomly divided into five stations associated to eccentric muscle contraction and plyometrics. Blood samples were taken from athletes pre-eccentric training, immediately after (post), 2- and 4-h post-eccentric training to determine hormone responses (cortisol and testosterone), muscle damage (CK and α-actin), and inflammatory responses (IL-6). After eccentric training, athletes XX presented higher levels for CK (4-h post), α-actin (post and 2-h post) and cortisol (post) compared to RR and RX athletes. However, RR and RX athletes presented higher levels of testosterone (post) and IL-6 (2 h post and 4 h post) compared to athletes XX. The main conclusion of this study is that professional soccer athletes homozygous to ACTN3XX gene are more susceptible to eccentric damage and present a higher catabolic state, demonstrated by metabolic, hormonal and immune responses post an eccentric training, in comparison to ACTN3RR and ACTN3RX groups.