Sickle cell anemia is a chronic disease that can severely affect the ability to process information quickly. The aim of this study was to evaluate the reaction time in children with sickle cell anemia using simple reaction time and choice reaction time tests. A cross-sectional study was performed at the Children's Hospital of Brasilia, with patients from the hematology outpatient clinic. The experimental group was composed of 24 sickle cell children and the control group of 22 children not affected by sickle cell anemia. The simple reaction time and choice reaction time were evaluated using equipment developed for this purpose. The results showed a significant deficit in the choice reaction time of children with sickle cell anemia (p= 0.000161). In simple reaction time, the experimental group showed less attention, committing a higher proportion of errors by omission when compared to the control group (p= 0.00678). The lower rate of success in simple reaction time and choice reaction time tests in children with sickle cell anemia may be related to the high incidence of silent cerebral infarction in this population. Another fact that may be associated with high reaction time in patients with sickle cell anemia is the lack of experience and opportunities for motor activities throughout childhood due to the pathology. KEYWORDS: chronic disease; hemoglobin, sickle; child development; psychomotor performance; brain injuries.

The combination of aging with reduced muscle mass and muscle strength results in a higher risk of falls, hospitalizations, dependence, poorer quality of life, and all-cause mortality. Our hypothesis, in the present study, is that the elderly who present higher values in gait speed, as well as lower values in the Time Up and Go test, will have higher values of lower limb muscle strength. PURPOSE: To correlate functional capacity of walking and time up and go tests with the maximal isometric lower limb strength test in community-dwelling elderly. METHODS: Thirty-two elderly (2 men; age: 72 ± 9,2 yrs; body mass: 66 ± 10,6 kg; height: 152,27 ± 7,79 cm) who attended the Centro de Convivência do Idoso located in Paranoá, Brasília, DF participated. The tests were performed in an integrated and dynamic circuit format, where each station had a single evaluator. The maximal isometric muscle strength of lower limbs used the mid tight pull position where a traction dynamometer (E-lastic) was fixed to the ground by a metal chain and at its other end a hand strap. The elderly were instructed to perform their maximal concentric movement strength with semi-flexed knees and extended arms for 3-5 seconds with verbal encouragement. The muscle strength was measured in kilograms (kg). In the Walking Test (TC), the elderly should walk through the distance of 10m as fast as possible. Gait speed (m/s) was calculated. In the Time Up and Go (TUG) test, the elderly should get up from a chair without the aid of their arms and walk at a comfortable pace at a distance of three meters, get around an obstacle, return and sit again while time to end the task was measured. A Pearson correlation coefficient was determined between the maximum isometric strength test and the walking and time up and go tests. The statistical package adopted was SPSS (IBM, version 23). RESULTS: The findings revealed a significant and moderate correlation for gait speed and lower limb muscle strength (r = 0.391; p = 0.033) as well as the functional test and lower limb muscle strength level (r = -0.376; p = 0.041). CONCLUSION: Elderly who had higher lower limb strength values obtained the shortest times in the time up and go test and the highest gait speed in the walking test.

RESUMO Buscou-se investigar os parâmetros eletromiográficos da fadiga muscular durante exercício dinâmico realizado com resistência variável (elástica) e resistência fixa (polia). Dez homens treinados participaram voluntariamente do estudo. Foram realizadas duas contrações voluntárias isométricas máximas (CVIM) de flexão do cotovelo com 5 segundos de duração cada e 2 minutos de intervalo entre as mesmas. Em seguida, os voluntários realizaram a flexão unilateral do cotovelo até a exaustão, utilizando resistência fixa e elástica com ritmo pré-estabelecido de 2 segundos para cada fase do movimento. A resistência constante foi realizada na polia a 30% da CVIM. Para a resistência elástica, o controle de carga era baseado na percepção subjetiva de esforço do participante. A ordem do exercício foi randomizada, e o sinal de eletromiografia do músculo bíceps braquial foi registrado durante as contrações. A partir do sinal eletromiográfico referente a cada execução de movimento, foram traçadas retas de regressão linear para as variáveis RMS e frequência de potência mediana (FPM). As inclinações das retas normalizadas pelo coeficiente linear das equações de regressão foram comparadas por meio do teste t pareado. Não foram observadas diferenças significativas entre os tipos de resistência (elástica e polia). Os parâmetros eletromiográficos de fadiga não foram diferentes durante o exercício de flexão do cotovelo realizado com resistência elástica e polia. A percepção de esforço durante o exercício com implemento elástico não influencia no padrão do sinal eletromiográfico (RMS e FPM).

Investigations have demonstrated that exercise-induced muscle damage can inhibit muscle performance post-exercise. However, to overcome the non-stationary condition and low sensitivity to muscle fatigue of the traditional parameters, some new techniques have been proposed to monitor muscle fatigue more accurately. PURPOSE: To correlate the traditional and stationary wavelet transform parameters which can explain peak torque output during maximal isometric contractions before and after exercise-induced muscle damage. METHODS: Thirteen resistance trained males (age: 23.9 ±5.2 years; body mass: 79.2 ±9.9 kg; height: 176.1 ±6.3 cm) volunteered to take part in this study. Subjects performed 4 sets of 10 unilateral maximal elbow flexion concentric/eccentric reciprocal actions with their dominant arm. They were seated in a chair with their arms draped over a “preacher curl bench.” All exercise was performed on a Biodex System 3 isokinetic dynamometer at 120°s-1 with one minute rest between sets. Maximal voluntary isometric contraction of the elbow flexors was measured at 90° of flexion for 3 seconds. Isometric peak torque (PT) and the surface electromyography (sEMG) of the biceps brachii were collected at baseline and immediately post exercise. Traditional parameters of amplitude (RMS) and frequency (MdF) of the sEMG signal were calculated with a specific routine written in Matlab (v 6.5, Mathworks, Natick, MA). The signal was also decomposed into five detail coefficients (D1 to D5) using the discrete wavelet transform (mother wavelet Daubechies 5). A Pearson correlation was used to associate the decrease in PT (ΔPT) with variations in RMS, MdF and energy of the wavelets details. RESULTS: Pearson’s r values were positive correlated between PT and all sEMG parameters. However, there was only a strong relationship between ΔPT and D3 (r=0.79). CONCLUSION: The energy of D3 from discrete wavelet transform used in the present study was more sensitive in assessing changes in muscle performance following exercise-induced muscle damage.

METHODS: Surface EMG of the vastus medialis (VM), vastus lateralis (VL), semitendinosus (ST) and biceps (BF) and rectus femoris (RF) were recorded at 4800Hz in 16 female, DI soccer players (19.7 ± 1.1 yrs), during an agility test. Subjects completed 4 trials of the test, alternating sides. Rest between trials ensured non-FAT. Subjects then ran trials starting every 30s, alternating sides, until a 5% decrement in their non-FAT times occurred on 2 successive runs. Two trials from each side were then run and recorded as the FAT trials. For each muscle, the EMG data were band pass filtered. The MF of a 107 ms moving window was calculated using a time-frequency analysis based on power spectra estimation (short-time Fourier transform) for each muscle, for each trial. The mean MF for the trial was determined using the obtained MFs. The mean PA for each muscle was determined by dividing the trial into 107 ms windows obtaining the PA of the window and then obtaining the mean of the individual PAs. The average MFs and PAs for each trial were grouped into 3 trial periods: the first 4 non-FAT, 4 middle and the last 4 FAT trials. Linear mixed models, with trial period as a repeated factor, were used to test for differences in average MF and PA between trial periods. RESULTS: For all 5 muscles for both legs, there was a significant difference in average MF and PA across trial periods (p <0.001). Pairwise comparisons showed a significant decrease for both the MF and PA from the non-FAT trials to the middle trials on all muscles for both legs (p <0.001). Significant decreases from middle trials to FAT trials were noted for all muscles for both legs for PA (p <0.05) except the left BF, while for MF, significant differences were noted for the right RF and VL, and the left VM, RF, and VL (p-<0.01). Across all muscles MF decreased 7.6% from the non-FAT to middle trials and decreased another 3.1% from middle to FAT trials. Similarly, across all muscles PA decreased 17.5% from the non-FAT to middle trials and further decreased 16.9% from middle to FAT trials. CONCLUSIONS: In the current testing paradigm, during a dynamic task in which performance decreases overtime, a decrease in the average MF and PA are potential indicators of muscle fatigue.

Constant resistance is the most common method to enhance strength. Constant resistance load is always the same across the full range of movement. However, pulleys can generate forces in different directions (x and y axis) while free-weights only generate force in one direction (y axis). PURPOSE: To investigate torque and muscle activation between elbow flexion exercise performed with free-weights and pulleys. METHODS: Five resistance trained males (body mass: 73.43±17.32 kg; height: 176.03 ±12.73 cm) and two females (body mass: 53.9±6.79 kg; height: 163.75 ±8.84 cm) participated. Maximal voluntary isometric contraction of the elbow flexors was measured at 90° of flexion for 5 seconds. Subjects performed 10 unilateral elbow flexions using free-weights and pulleys with 40% of their maximal isometric contraction load. Exercises were performed in a randomized order and at a pre-established rhythm of 2 seconds for each dynamic action controlled by a metronome. Ten minutes of rest between protocols was given. Surface electromyography of the biceps brachii was collected at 2400 Hz and synchronized with two-dimensional sagittal plane video at 60 Hz. Anatomical markers on the upper-limb and an electrogoniometer were used. During the pulley exercise, a load cell was used to record force. Five repetitions were analyzed. Root mean square (RMS) and mean sum of torques (MST) were calculated with a specific routine written in Matlab. Paired t-tests were used to determine significant (p≤0.05) differences between exercises. RESULTS: For the load used, there was no significant difference between pulley and free-weight. Similarly, there was no significant difference between pulley and free-weight for RMS (free-weight: 0.025 ± 0.006 mV; pulley: 0.026 ± 0.005 mV). However, MST was significantly greater for pulley (3,942.9 ± 1,013.7 N.m) than for free-weight (2,604.3 ± 705.6 N.m). CONCLUSION: The use of a pulley during elbow flexion exercise produced greater torque when compared with free-weight. However, biceps brachii activation was not different. More studies are necessary to investigate muscle activation in other muscles performed with different types of constant resistance.

Investigations have demonstrated that the use of different types of resistance can enhance strength of athletes and those in rehabilitation programs. Furthermore, perception of effort during variable resistance exercise is usually used to determine exercise load. However, studies regarding the pattern of fatigue in exercise with different types of resistance are lacking. PURPOSE: To investigate the electromyography pattern of fatigue during dynamic exercise performed with two different types of resistance. METHODS: Eleven resistance trained males (age: 27±6 ys; body mass: 79.48±5.41 kg; height: 175.62±4.70 cm) volunteered to take part in this study. They performed 2 maximal isometric unilateral elbow flexion repetitions at 90° of flexion for five seconds with 2 minutes rest between repetitions. Following that, subjects performed maximal unilateral elbow flexions to exhaustion at a pre-established rhythm of 2 seconds for each action controlled by a metronome. Constant load was performed with a pulley exercise at 30% of maximal isometric torque while the elastic resistance load was based on each subject’s perception of the same intensity. Exercise order was randomized. Surface electromyography (sEMG) of the biceps brachii was collected and traditional parameters of amplitude (RMS) and frequency (MdF) were calculated with a specific routine written in Matlab. From RMS and MdF data, slopes of the linear regression were obtained and normalized using the linear coefficients of the regression equations. Comparisons between types of resistance were performed with paired t-tests for each electromyography parameter. RESULTS: For RMS linear regression slopes, there was no significant difference between resistance types (elastic resistance: 0.03±0.02; pulley: 0.02±0.03). For MdF linear regression slopes, there was no significant difference between elastic resistance (-0.02 ±0.01) and constant resistance (-0.03±0.02). CONCLUSION: Electromyographic fatigue patterns during elbow flexion exercise performed with constant resistance was not different from elastic resistance. These results indicate that perception of effort during elastic resistance exercise does not influence the electromyographical pattern.