Flávio Antônio de Souza Castro

Electromyography for Assessment of Pain in Low Back Muscles

Background and Purpose: Pain is currently evaluated with “subjective” methods (eg, patient self-report). This study aimed to test whether fatigue indexes are able to accurately discriminate between subjects with and subjects without low back pain. Subjects: Sixty subjects separated into 2 groups—a group with low back pain (n=30) and a group without low back pain (n=30)—participated in this study. Methods: Electromyographic (EMG) and force data were obtained during a muscle fatigue test. The same test was repeated to monitor recovery. Linear regression analysis was used to obtain fatigue indexes. Results: Subjects with pain produced significantly lower force values than those without pain. The use of fatigue indexes and force values permitted accurate classification in 89.5% of cases. Discussion and Conclusion: The results confirm that subjects with pain show early myoelectrical manifestations of muscle fatigue and that EMG can be a useful tool in the evaluation of low back pain.

Acute responses of biomechanical parameters to different sizes of hand paddles in front-crawl stroke

Abstract This study investigated the acute effects of different sizes of paddles on the force-time curve during tethered swimming and swimming velocity in front-crawl stroke. Fourteen male swimmers (20.0 ± 3.7 years; 100-m best time: 53.70 ± 0.87 s) performed two 10-s maximal efforts in tethered swimming to obtain peak force, average force, impulse, rate of force development, stroke duration and time to peak force. Swimming velocity, stroke rate and stroke length were obtained from two 25-m maximal swims. Both tests were repeated in five conditions: free swimming, wearing small (280 cm 2 ), medium (352 cm 2 ), large (462 cm 2 ) and extra-large (552 cm 2 ) hand paddles. Compared to free swimming, paddles provided significant increases of peak force (medium: 11.5%, large: 16.7%, extra-large: 21.7%), impulse (medium: 15.2%, large: 22.4%, extra-large: 30.9%), average force (medium: 5.1%, large: 7.5%), rate of force development (extra-large: 11.3%), stroke duration (medium: 9.3%, large: 11.8%, extra-large: 18.5%), time to peak force (medium: 11.1%, large: 15.9%, extra-large: 22.1%), swimming velocity (medium: 2.2%, large: 3.2%, extra-large: 3.7%) and stroke length (medium: 9.0%, large: 9.0%, extra-large: 14.8%), while stroke rate decreased (medium: –6.2%, large: –5.5%, extra-large: –9.5%). It is concluded that medium, large and extra-large paddles influence the force-time curve and change swimming velocity, suggesting these sizes may be useful for force development in water.

The Reliability of a Functional Agility Test for Water Polo

Abstract Few functional agility tests for water polo take into consideration its specific characteristics. The preliminary objective of this study was to evaluate the reliability of an agility test for water polo players. Fifteen players (16.3 ± 1.8 years old) with a minimum of two years of competitive experience were evaluated. A Functional Test for Agility Performance (FTAP) was designed to represent the context of this sport. Several trials were performed to familiarize the athlete with the movement. Two experienced coaches measured three repetitions of the FTAP. Descriptive statistics, repeated measures analysis of variance (ANOVA), 95% limit of agreement (LOA), intraclass correlation coefficient (ICC) and standard error of measurements (SEM) were used for data analysis. It was considered that certain criteria of reliability measures were met. There was no significant difference between the repetitions, which may be explained by an effect of the evaluator, the ability of the players or fatigue (p > 0.05). The ICC average from evaluators was high (0.88). The SEM varied between 0.13 s and 0.49 s. The CV average considering each individual was near 6-7%. These values depended on the condition of measurement. As the FTAP contains some characteristics that create a degree of unpredictability, the same athlete may reach different performance results, increasing variability. An adjustment in the sample, familiarization and careful selection of subjects help to improve this situation and enhance the reliability of the indicators.

Validity of a portable force platform for assessing biomechanical parameters in three different tasks

Abstract The aim of this study was to determine the precision and accuracy of the vertical and anterior–posterior force components of the portable PASCO PS-2142 force plate. Impulse, peak force, and time to peak force were assessed and compared to a gold standard force plate in three different tasks: vertical jump, forward jump, and sprint start. Two healthy male participants performed ten trials for each task, resulting in 60 trials. Data analyses revealed good precision and accuracy for the vertical component of the portable force plate, with relative bias and root mean square (RMS) error values nearly the same in all tasks for the impulse, time to peak force, and peak force parameters. Precision and accuracy of the anterior–posterior component were lower for the impulse and time to peak force, with relative bias and RMS error values nearly the same between tasks. Despite the lower precision and accuracy of the anterior–posterior component of the portable force plate, these errors were systematic, reflecting a good repeatability of the measure. In addition, all variables presented good agreement between the portable and gold standard platforms. Our results provide a good perspective for using the aforementioned portable force plate in sports and clinical biomechanics.

Estruturas elásticas e fadiga muscular

Muscle weakness can be defined as the inability to keep a certain task over time; neuromuscular and metabolic mechanisms involved in muscle contraction are directly associated with this physical process. This bibliographical study seeks to describe the changes in contractile and elastic elements involved in muscle contraction and its relation to performance in locomotion. The contractile structures are those that develop active force with metabolic energy expenditure - a mechanism of cross-bridges, the elastic ones are those that offer mechanical resistance to stretching at no energy cost - passive force - and keep energy to a new elastic contraction. Therefore muscle weakness is associated with the function of contractile and elastic structures.Muscle weakness can be defined as the inability to keep a certain task over time; neuromuscular and metabolic mechanisms involved in muscle contraction are directly associated with this physical process. This bibliographical study seeks to describe the changes in contractile and elastic elements involved in muscle contraction and its relation to performance in locomotion. The contractile structures are those that develop active force with metabolic energy expenditure - a mechanism of cross-bridges, the elastic ones are those that offer mechanical resistance to stretching at no energy cost - passive force - and keep energy to a new elastic contraction. Therefore muscle weakness is associated with the function of contractile and elastic structures.

Electromyography and economy of walking in chronic heart failure and heart transplant patients

Background Patients with chronic heart failure frequently report intolerance to exercise and present with changes in walk pattern, but information about heart transplant patients is lacking. Alterations of the gait pattern are related to interaction changes between the metabolism, neurological system and the mechanical demands of the locomotor task. The aim of this study was to investigate the electromyographic cost, coactivation and cost of transport of walking of chronic heart failure and heart transplant patients. Design This research was of an exploratory, cross-sectional design. Methods Twelve chronic heart failure patients, twelve healthy controls and five heart transplant patients participated in the study. Electromyographic data and oxygen uptake were collected simultaneously at five walking speeds. Results In the experimental groups, the electromyographic cost, percentage of coactivation in the leg and cost of transport were higher than in controls. The electromyographic cost was in line with the cost of transport. The minimum electromyographic cost matched with the self-selected walking speed in controls, while in chronic heart failure and heart transplant patients, it was reached at speeds higher than the self-selected walking speed. Conclusion The largest postural isometric activation and antagonist activation resulted in the highest metabolic demand. These findings are of great clinical relevance because they support the concept that interventions in order to improve the muscle performance in these patients can increase the self-selected walking speed and therefore the metabolic economy of walking.

Swimming Training Assessment: The Critical Velocity and the 400-m Test for Age-group Swimmers

Abstract Zacca, R, Fernandes, RJP, Pyne, DB, and Castro, FAdS. Swimming training assessment: the critical velocity and the 400-m test for age-group swimmers. J Strength Cond Res 30(5): 1365–1372, 2016—To verify the metabolic responses of oxygen consumption (V[Combining Dot Above]O2), heart rate (HR), blood lactate concentrations [La], and rate of perceived exertion (RPE) when swimming at an intensity corresponding to the critical velocity (CV) assessed by a 4-parameter model (CV4par), and to check the reliability when using only a single 400-m maximal front crawl bout (T400) for CV4par assessment in age-group swimmers. Ten age-group swimmers (14–16 years old) performed 50-, 100-, 200-, 400- (T400), 800-, and 1,500-m maximal front crawl bouts to calculate CV4par. V[Combining Dot Above]O2, HR, [La], and RPE were measured immediately after bouts. Swimmers then performed 3 × 10-minute front crawl (45 seconds rest) at CV4par. V[Combining Dot Above]O2, HR, [La], and RPE were measured after 10 minutes of rest (Rest), warm-up (Pre), each 10-minute repetition, and at the end of the test (Post). CV4par was 1.33 ± 0.08 m·s−1. V[Combining Dot Above]O2, HR, [La], and RPE were similar between first 10-minute and Post time points in the 3 × 10-minute protocol. CV4par was equivalent to 92 ± 2% of the mean swimming speed of T400 (v400) for these swimmers. CV4par calculated through a single T400 (92%v400) showed excellent agreement (r = 0.30; 95% CI: −0.04 to 0.05 m·s−1, p = 0.39), low coefficient of variation (2%), and root mean square error of 0.02 ± 0.01 m·s−1 when plotted against CV4par assessed through a 4-parameter model. These results generated the equation CV4par = 0.92 × v400. A single T400 can be used reliably to estimate the CV4par typically derived with 6 efforts in age-group swimmers.

Position of arm and forearm, and elbow flexion during performance of the sculling technique: Technical recommendation versus actual performance

Sculling motion is a swimming technique executed in a vertical position with the head above the waters surface and, based on the technical recommendation, should be performed maintaining an elbow flexion angle of 90°, arms kept stationary while the forearms move. In order to verify if this recommendation is indeed realistic, the aim of this study was to describe the elbow flexion angle ant its angular velocity, linear speed and range of motion of the shoulder, elbow and wrist during the sculling motion. Data were calculated using three-dimensional kinematic process from underwater video images of ten athletes of synchronized swimming. The results indicate that the arm is relatively stationary and the forearm moves, which agrees with the technical recommendation. However, the elbow flexes and extends, which contradicts the technical recommendation. These findings should be considered when this action is practiced, especially in synchronized swimming, in which sculling motion is a fundamental technique.

Critical stroke rate as a parameter for evaluation in swimming

El objetivo de este estudio fue investigar la frecuencia critica de brazadas (FCB) en comparacion con la frecuencia de brazadas (FB) al nadar a la velocidad critica (VC) y diferentes porcentajes de la VC en estilo crol. Diez nadadores realizaron repeticiones maximas a distancias de 200 y 400 m para obtener la VC y la FCB. Posteriormente, los sujetos realizaron cinco repeticiones a 200 m para 90, 95, 100, 103 y 105% de la VC, de forma aleatoria. LaFCB fue significativamente mayor que la FC obtenida a 90 % y menor que la FC obtenida a 105 % de la VC. La longitud de la brazada (LB) a 103 % y 105 % de la VC fue menor en comparacion con las repeticiones al 90, 95 y 100 % de la VC. La combinacion de los conceptos de VC y FCB puede ser util para aumentar tanto la capacidad / potencia aerobio y la tecnica destinada a reducir la FB (y aumentar LB) al nadar en el ritmo de la VC o aumentar la velocidad de nado con la FCB.El objetivo de este estudio fue investigar la frecuencia critica de brazadas (FCB) en comparacion con la frecuencia de brazadas (FB) al nadar a la velocidad critica (VC) y diferentes porcentajes de la VC en estilo crol. Diez nadadores realizaron repeticiones maximas a distancias de 200 y 400 m para obtener la VC y la FCB. Posteriormente, los sujetos realizaron cinco repeticiones a 200 m para 90, 95, 100, 103 y 105% de la VC, de forma aleatoria. LaFCB fue significativamente mayor que la FC obtenida a 90 % y menor que la FC obtenida a 105 % de la VC. La longitud de la brazada (LB) a 103 % y 105 % de la VC fue menor en comparacion con las repeticiones al 90, 95 y 100 % de la VC. La combinacion de los conceptos de VC y FCB puede ser util para aumentar tanto la capacidad / potencia aerobio y la tecnica destinada a reducir la FB (y aumentar LB) al nadar en el ritmo de la VC o aumentar la velocidad de nado con la FCB.

Esforço percebido e cinemática em percentuais da velocidade crítica na natação

The aim of the present study was to investigate the effects of different percentages of critical speed (CS) in the heart rate (HR), the mean stroke rate (SR), the mean stroke length (SL), and perceived exertion (PE) in front crawl. Fifteen swimmers of both genders performed five repetitions of 200 m at different percentages of CS (90, 95, 100, 103, and 105%), in random order. HR, PE and SR showed a significant positive correlation with the percentage of CS (rho = 0.585, p 0.05). The results from percentages of CS may help coaches to understand the impact of responses related to the internal load during training program.