Comparison of muscle morphology, electromyographic activity and force production between prepubertal boys and girls

The purpose of this research was to compare the maximal voluntary isometric force (MVIF), the electromyographic activity (EMG) and the muscle thickness between pre-pubertal boys and girls. The sample comprises 27children (12 boys and 15 girls) with 9.5W.52 years old. The M V F and the EMG signal were acquired when the subjects made a single exercise of arm curl and triceps press. To evaluate the MVIF was used a dynamometer (TSD121C from Biopac Systems Znc.). During the arm curl exercise, one surface electrode (TSD 150A from Biopac Systems Znc.) was attached in each biceps. During the triceps press, one surface electrode was attached to the vastus lateralis and other to the vastus medialis of the each triceps. Ground electrode was attached to the elbow. The EMG signals were amplified by a differential amplifier with 2MW, a gain of 1000 and a bandwidth between 15-450Hz. The EMG signals were full-wave rectified and smoothed, allowing to determinate the integral of the EMG signal (iEMG). The iEMG was relativized according to the duration of the contraction. The muscle thickness of the biceps and of the triceps of both arms were measured by B-mode ultrasonography, using real-time electronic scanner with 7.5MHz scanning head (Ecocamera Aloca SSD-500). For comparison of those variables between gender was used the ANOVA factorial and Scheffe as post-hoc test (p< 0.05). There was no significant differences on the MVIF between boys and girls doing the arm curl exercise F(1; 25)=4.128, p=0.0529] or the triceps press exercise F(1; 25)=0.003, p=0.9554]. In the same way, there were no significant differences according to gender on the thickness of the triceps of the left arm F(1; 25)= 0.075, p=0.7859] of the triceps of the right arm F(1;25)=0.925, p=0.3454] of the bicep sof the left arm F(1;25)=0.257, p=0.6166] and of the biceps of the right arm F(1; 25)= 0.016, p=0.8989]. The EMG parameters also didn't present significant differences according to gender for the vastus lateralis of both arms, for the vastus medialis of both arms and for the biceps of the right and of the left arm. Therefore, we might conclude that apparently there are no significant differences on the muscle morphology, electromyographic activity and force production between pre-pubertal boys and girls.info:eu-repo/semantics/publishedVersio

Habitual physical activity pattern of prepubescent boys and girls

The propose of this study is to identify the pattern physical activity of boys and girls during a week. The sample comprises 14 girls and 11 boys of 9.5 years of age. Physical activity was evaluated thought the computer science and applications (CSA - 7164) activity monitor, during 4 days - two-week days (Monday and Friday), and during the weekend (Saturday and Sunday). The activity monitor was worn in wrist of the non-dominant arm. After de data collection it was calculated the mean of activity per min in each day. The repeatedmeasuresMANOVAwasusedtoanalysedthechangesbetweenday's activity,and the gender differences. The results indicated a significant main effects of days, meaning that the pattern of activity change over days. The differences occurred between the Friday and Saturday, and between Saturday and Sunday. In the weekend it was registered less physical activity than in weekdays in booth boys and girls. There's no significant main effect for gender, meaning that the physical activity of boys and girls are similar. Also there's no interaction between gender and days, meaning that the changes in activity pattern was similar for booth boys and girls.info:eu-repo/semantics/publishedVersio

Strength training effects on pre-pubertal boys

There are some incongruent results in strength training effects on pre-pubertal boys. Vrijens (1979) shows that prepubescent boys were incapable of increasing strength or muscle cross-sectional area of the extremities following a program of resistance training. Various recent studies have shown that prepubescent boys are capable of making strength gains following an appropriate training program (Ramsay, et al., 1990). However the mechanisms underling strength gains following resistance strength training programs is not well clarified. There is some evidence that the gains are associated with neuromuscular adaptations with no muscle hypertrophy, but this later issue is an unresolved question. The purpose of this study is to investigate the resistance strength training effects on pre-pubertal boys, that is, the enhancement of strength and its correlates, namely the changes in muscular mass and neuro-muscular activity. The sample comprises 11 boys, aged 9,52±0,55 years, divided in an experimental group (EG) (n=6) and in a control group (CG) (n=5). All boys were in stage 1 according to Tanner’s scale of sexual maturation. The sample was evaluated in serum testosterone level, and all boys were above the level of 50 ng*dl-1,wich is considered to be within the normal range for pre-pubertal boys (Winter, 1978). The EG group was submitted to a training program with callisthenic exercises three sessions a week for 10 weeks. In each session the training comprised the following exercises: push-ups, modified pull-ups and the 2 exercises with elastics (elbows flexion and extension and extension of the arms above the head) until exhaustion. The training volume was being gradually adapted from 3 series between the 1st and 3rd week to 4 series between the 4th and 6th week and to 5 series between the 7th and 10th week. The sample was evaluated in pre and in post-test in maximal isometric voluntary force (MIVF), muscle mass, and in EMG. The MIVF was evaluated during the Shoulder Press (SP), the Arm Curl (AC) and the Triceps Press (TP). The MIVF was measured using a dynamometer (TST 121C from Biopac Systems Inc.). We also evaluated the maximal number of push ups (PU) and modified pull ups (MPU), and the distance in over arm throw with roller-skate hockey ball (THW). The EMG signals were acquired during the MIVF exercises (SP, AC, and TP). During the AC exercise, one surface electrode (TSD 150A from Biopac Systems Inc.) was attached to each biceps. During the SP and TP, one surface electrode was attached to the vastus medialis of each of the triceps. A ground electrode was attached to the elbow. The EMG signals were amplified through a differential amplifier with 2MW, a gain of 1000 and a bandwidth between 15-450Hz. The EMG signals were full-wave rectified and smoothed, allowing to determinate the integral (iEMG) and the amplitude (aEMG) of the EMG signal. The iEMG was standardised according to the duration of the contraction. Both aEMG and iEMG results of both arm in each exercise were summed. The muscle thickness of the biceps and of the triceps of both arms were measured by B-mode ultrasonography, using real-time electronic scanner with 7.5MHz scanning head (Ecocamera Aloca SSD-500). The data were analysed using the ANOVA repeated measures (group x training program). In THW the results indicate a significant interaction effect (F(1, 9) = 7,814; p = 0,021), with an increase of 22% in EG and a slight decrease in CG. In PU the results indicate a significant main effect (F(1, 9) = 15,537; p = 0,003), and a significant interaction effect (F(1, 9) = 16,61; p = 0,003), with an increase of 150% in EG and no changes in CG. In MPU the results indicate a significant main effect (F(1, ) = 8,006; p = 0,019), and a significant interaction effect (F(1, 9) = 17,667; p = 0,002), with an increase of 120,9% in EG and a slight decrease in CG. There were no significant changes in the three tests of MIVF and in iEMG, aEMG, or in the muscle mass. These results indicate that pre-pubertal boys could increase the resistance strength after a training program that include callisthenic exercises, but seems that the isometric strength could not be enhanced. The increase in resistance strength is not accompanied by an increase in muscle mass. Although in this study we only evaluated the neuro-muscular factors in MIVF, it seems that the factors underlying the enhanced strength might be neuro-muscular.info:eu-repo/semantics/publishedVersio

Effects of a 10 weeks training programs on prepubescent girls

The purpose of this study was to investigate effects of a training program on the development of the maximal isometric strengths, the push-ups, the pull-ups and the throw of the roller-skate hockey ball. The sample was composed by 16 girls, at the age of 9,5 years and in the maturation stage I according to Tanner's Scale. The sample was divided into two different groups, the experimental one (EG, n = 11) and the control one (CG, n = 5). The EG group was submit- ted to a training program with callisthenic exercises three times a week (90 min each session) during 10 weeks. The program comprised the training of push-ups, modified pull-ups and the 2 exercises with elastics (elbows flexion and extension and extension of the arms above the head) until exhaustion. The training volume has been gradually adapted from 3 series between the 1st and 3rd week to 4 series between the 4th and 6th week and to 5 series between 7th and 10th week. The maximal isometric voluntary force (MIVF) was evaluated during the Shoulder Press (SHPRES) exercise, the Arm Curl (ARMCURL) exercise and de Triceps Press (TRIPES) exercise. The MIVF was measured using a dynamometer (TST 121C from Biopac Systems Inc.). We also evaluated the maximal number of push ups and modified pull ups that each girl could do. Finally, we measured the distance made by the roller-skate hockey ball after being thrown (THRW). For the comparison between the two measurements (before and after the training program) was raised the "Paired Simple Test" in each group (p < 0.05). It compared the minimum values between the two moments on the e.g., the THRW (p = 0.006), the PULL (p=0.010), and the PUSH (p= 0.014), presented significant increases. However, the TRIPES (p = 0.096), the ARMCURL (p = 0.403), and the SHPRES (p = 0.066) didn't present significant differences. On the CG the only significant difference was found in the TRIPES (p = 0.003).info:eu-repo/semantics/publishedVersio

A produção de força e os seus factores condicionantes em crianças pré-pubertárias

A força á uma capacidade motora dependente de factores morfológicos (Brooks e Fahey, 1984; Enoka, 1988; Wilmore e Costill, 1994; B1imkie e Sale, 1998). A título ilustrativo, aumentos do tamanho do músculo, ou seja, da sua área de secção transversa aparentemente induzem ganhos de força. Na verdade, Enoka (1988) sugere a existência de uma correlação significativa entre a área de secção transversa e a produção de força muscular. Da mesma forma, adaptações neurais como sejam uma melhor coordenação intra e intermuscular, a sequência, a sincronização e a quantidade de unidades motoras recrutadas assim como, a frequência de disparo dos impulsos nervosos podem promover aumentos da força produzida (Enoka, 1988; B1irnkie et aI., 1989; Wilmore e costill, 1994). Assim, a força muscular é uma capacidade que depende quer de factores morfológicos, quer neurológicos.info:eu-repo/semantics/publishedVersio

African Higher Education: Researching Absences, Equalities and Aspirations

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Hábitos de consumo de suplementos de creatina em ginásios da cidade de Bragança

A suplementação de creatina hoje em dia é uma prática muito comum, adotada por atletas e frequentadores de ginásios para um melhor desempenho físico. Com o número de pessoas que frequentam ginásios a aumentar, consequentemente aumentam também os mitos e a desinformação, o que pode levar a sérios problemas de saúde pelo uso indevido da suplementação de creatina Objetivo: Avaliar hábitos de consumo de suplementos de creatina em pessoas que frequentam ginásios. Metodologia: O estudo caracteriza-se como transversal e observacional de carácter quantitativo. Foi aplicado a frequentadores dos ginásios da cidade de Bragança durante o mês de setembro, onde foi divulgado um Qr code de um inquérito eletrónico. Participaram 158 pessoas, dos quais 95 eram consumidores de suplementos de creatina (15,19% homens; 24,68% mulheres). A análise estatística foi conduzida para a descrição amostral e análise comparativa entre os grupos por sexo, sendo aplicado o teste de qui-quadrado de duas proporções simples. Resultados: Constatou-se que 8,47% dos homens e 22,22% das mulheres sentem que não têm informação suficiente sobre este suplemento e 20,34% dos homens e 30,56% das mulheres não conhece os efeitos adversos. A maioria consome estes suplementos para aumentar a força (72,88% dos homens; 72,22% das mulheres) e aumentar a energia (55,93% dos homens; 69,44% das mulheres). O modelo de regressão logística apresentou uma boa capacidade preditiva do uso excessivo de creatina considerando as variáveis sexo, IMC, ser fumador, quantidade de creatina ingerida por dia, nível de informação e conhecimento dos efeitos colaterais. Conclusão: O grupo que tem menos conhecimento sobre a suplementação tem um maior uso da creatina. A informação científica sobre a suplementação de creatina tem de ser divulgada a mais pessoas para que estas possam usar a suplementação de forma mais segura.info:eu-repo/semantics/publishedVersio

Reproduction of the blue jack mackerel, Trachurus picturatus, in western Portugal: microscopic gonad analysis reveals indeterminate fecundity and skipped spawning patterns

Blue jack mackerel, Trachurus picturatus, is the fifth most landed fish species in mainland Portugal, but information on its reproductive biology is scarce. From September 2018 to August 2019, 626 specimens were collected from commercial vessels to clarify the reproductive strategy of the T. picturatus population off the west coast of Portugal. The proportion and length range of males and females were similar. Only three of the specimens collected were categorized as immature, indicating that the fish caught in the fishery are primarily mature. The spawning season lasted from late January until the end of March, with gonadosomatic indices being similar for males and females. Fecundity was indeterminate, and estimated batch fecundity ranged between 6,798 (at 25.4 cm TL) and 302,358 oocytes (at 33.8 cm TL). The low number of females showing direct evidence of imminent or recent spawning suggests a low number of spawning events. In addition, 12.7% of females were considered non-reproductive due to ovary abnormalities including parasitic infection by Kudoa species, atretic structures and skipped spawning events. This study highlights the importance of accounting for skipped spawning events and ovary abnormalities in the management of species fisheries.info:eu-repo/semantics/publishedVersio

The influence of abdominal adiposity and physical fitness on obesity status of portuguese adolescents

The aim of this study was to verify the relationship between abdominal adiposity and physical fitness in the obesity status of Portuguese adolescents. BMI, abdominal adiposity, and physical fitness tests from the FITescola® were evaluated in a total of 654 Portuguese adolescents, aged 10-19 years old—male: n = 334 (51%), female: n = 320 (49%). For the final model, BMI was positively related with age (β = 0.25), abdominal adiposity (β = 0.313), horizontal jump (β = −0.100), 40 m maximal velocity (β = 0.274), and aerobic fitness (β = −0.250, R2 = 0.75, F = 382.2, and p = 0.0001). We conclude that higher age and abdominal adiposity are positively related with a higher adolescent BMI. Furthermore, lower horizontal jump distances and worse times on the 40 m maximal velocity were inversely related with a higher adolescent BMI, and lower aerobic fitness was inversely related with a higher adolescent BMI.This research was funded by the National Funds through FCT—Portuguese Foundation for Science and Technology (UIDB/DTP/04045/2020) and the Higher Institute of Educational Sciences of the Douro (grant number NIDEF.21-22).info:eu-repo/semantics/publishedVersio