Cardiovascular and nitric oxide response after maximal voluntary isometric contraction in adolescents with and without Down Syndrome

Este estudo teve como objetivo comparar as respostas cardiovasculares e de óxido nítrico (NO) à contração isométrica voluntária máxima (CIVM) com diferentes grupos musculares (leg press [LEP] e preensão manual isométrica [IHG]) de adolescentes com e sem síndrome de Down (SD). Alem de comparar a força IHG absoluta e relativa entre os grupos. Onze adolescentes com SD (14,1 ± 1,0 anos) e dez sem SD (13,7 ± 1,25 anos) realizaram duas sessões experimentais de exercícios LEP e IHG: 1) sessão de familiarização e 2) 3 tentativas x 5 segundos de contração na CIVM com 3- intervalo mínimo de descanso. A pressão arterial (PA), a frequência cardíaca (FC) e o NO foram coletados em repouso, imediatamente após a sessão de exercício e 10 minutos após o exercício. A dosagem de NO na saliva foi realizada pelo método colorimétrico de Griess. Não houve diferenças para respostas cardiovasculares e NO entre os grupos para CIVM. No entanto, o SD teve uma resposta cardiovascular menor, mas não significativamente, em repouso e após os testes de CIVM do que aqueles sem SD. O grupo SD apresentou maior concentração de NO em repouso, recuperação e após IHG quando comparado ao grupo não SD (P <0,05). Além disso, adolescentes com SD apresentaram menor nível de força de IHG absoluta e relativa quando comparados àqueles sem SD (P = 0,001). Indivíduos com SD apresentam menor resposta cardiovascular em repouso e após testes de CIVM e maior resposta de NO após o exercício quando comparados ao grupo sem SD.

Effects of Detraining on Muscle Strength and Hypertrophy Induced by Resistance Training: A Systematic Review

A detraining period after resistance training causes a significant decrease in trained-induced muscular adaptations. However, it is unclear how long muscle strength and hypertrophy gains last after different detraining periods. Thus, the present systematic review with meta-analysis aimed to evaluate the chronic effects of detraining on muscle strength and hypertrophy induced by resistance training. Searches were conducted on PubMed, Scopus, EBSCO, CINAHL, CENTRAL, and Web of Science. The difference in means and pooled standard deviations of outcomes were converted into Hedges’ g effect sizes (g). Twenty randomized and non-randomized trials (high and moderate risks of bias, respectively, and fair quality) were included for qualitative analysis of muscle strength and hypertrophy, while only two studies were included in the meta-analysis for maximum muscle strength. The resistance training group presented a significant increase in one-repetition maximum (1RM) chest press (g: 4.43 [3.65; 5.22], p < 0.001) and 1RM leg press strength (g: 4.47 [2.12; 6.82], p < 0.001) after training. The strength gains observed in the resistance training group were also maintained after 16–24 weeks of detraining (g: 1.99 [0.62; 3.36], p = 0.004; and g: 3.16 [0.82; 5.50], p = 0.008; respectively), when compared to the non-exercise control group. However, 1RM chest press and leg press strength level was similar between groups after 32 (g: 1.81 [−0.59; 4.21], p = 0.139; and g: 2.34 [−0.48; 5.16], p = 0.104; respectively) and 48 weeks of detraining (g: 1.01 [−0.76; 2.79], p = 0.263; and g: 1.16 [−1.09; 3.42], p = 0.311; respectively). There was not enough data to conduct a meta-analysis on muscular hypertrophy. In conclusion, the present systematic review and meta-analysis demonstrated that, when taking random error into account, there is no sufficient high-quality evidence to make any unbiased claim about how long changes in muscle strength induced by RT last after a DT period. Moreover, the effect of different DT periods on muscle hypertrophy induced by RT remains unknown since there was not enough data to conduct a meta-analysis with this variable.

Optimizing Backrest Geometry to Minimize Interfacial Pressure Concentrations in the Mid-To-Lumbar Region During Leg Press Resistance Training

The leg press is a resistance training (RT) exercise common to both weight- and powerlifting, where spine-related injuries remain prevalent. Here, the elevated loading has the potential to result in increased pressure on vertebral bodies and introduce the risk of spinal injury. This study therefore investigates back interfacial pressure under leg press loading conditions and offers design recommendations to minimize spatial pressure concentrations. A pressure mat was used to assess the back-backrest interfacial pressure distribution of 15 subjects executing RT leg-presses at 50% bodyweight, over 16 different back-support geometries. Real-time forces, knee angles, and pressures were captured. The resulting data show that more prominent (?2.1 cm) back-supports, positioned 19cm above the seat pan typically produced greater peak pressures (41.8±7.2 kPa). Conversely, less prominent supports (~0.7 cm) generally achieved lower peak pressures (with greater distribution). Our data suggest that the most prudent choice for fixed-shape backrests to best distribute interfacial pressure on leg-press devices is to incorporate shallow convex supports (~0.7 cm), and locate them away from P=19 cm. The result is surprising as this prominence location is a common ergonomic feature. If an adjustable backrest is considered, peak pressures may be reduced by up to 26±8% (9.7±3.1 kPa) compared to flat geometries.

Effect of Prior Information of the Number of Sets on Training Volume in Women

The induced adaptations from resistance training are dependent on the adequate manipulation of the variables involved in training, and volume is one of the most important. However, high volume training can be more stressful, thus prior information of the training volume to be performed may affect performance. The aim of this study is to verify the influence of prior knowledge of the number of sets to be performed on the training volume. For this, ten women (44 ± 2 years, 66 ± 9 kg, 165 ± 3 cm, 24 ± 2 kg / m2) with previous experience in resistance training (≥ 6 months) performed six sets in 45º leg press exercise in three conditions,: in the first (C1) the participants were informed that they would perform six sets and they completed them. In the second condition (C2), they were told they would perform three sets, however, after executing the third set, they were told to complete three more sets. In the third (C3), they did not receive information about how many sets they would complete, but they also did six sets. All sets were performed until the momentary concentric failure at 70% of the one repetition maximum. It was noted that there was no statistically significant difference among the conditions for the total number of repetitions (C1 = 119 ± 44; C2 = 123 ± 47; C3 = 121 ± 47; P = 0.98). Therefore, the results suggest that prior information on the number of sets to be performed in the session does not affect the volume of repetitions performed by middle-aged women.Keywords: Exercise. Physical Education and Training. Aging.ResumoAs adaptações induzidas pelo treinamento resistido são dependentes da adequada manipulação das variáveis envolvidas no treinamento, sendo o volume uma das de maior destaque. Porém, um treinamento com alto volume pode ser mais desgastante, logo, a informação prévia do volume de treino a ser realizado poderá afetar o desempenho. O objetivo deste estudo foi verificar a influência do conhecimento prévio do número de séries a serem executadas sobre o volume de treino. Para isso, 10 mulheres (44 ± 2 anos, 66 ± 9 kg, 165 ± 3 cm, 24 ± 2 kg/m2) com experiência prévia em treinamento resistido (≥ 6 meses) realizaram seis séries no exercício leg press 45º em três condições distintas, a saber: na primeira condição (C1) as participantes foram informadas que realizariam seis séries e as completaram. Na segunda condição (C2), foram comunicadas que fariam três séries, porém, após executar a terceira série, elas foram orientadas a completar mais três séries. Já na terceira condição (C3), não receberam informação sobre quantas séries cumpririam, mas também fizeram seis séries. Todas as séries foram realizadas até a falha momentânea concêntrica a 70% da força máxima, determinada mediante teste de uma repetição máxima. Notou-se que não houve diferença estatisticamente significante entre as condições para a quantidade total de repetições (C1 = 119 ± 44; C2 = 123 ± 47; C3 = 121 ± 47; P = 0,98). Portanto, os resultados sugerem que a informação prévia da quantidade de séries a serem executadas na sessão não afeta o volume de repetições praticadas por mulheres de meia idade.Palavras-chave: Exercício Físico. Educação Física e Treinamento. Envelhecimento.

Bayesian Estimation of the Variation in Strength and Aerobic Physical Performances in Young Eumenorrheic Female College Students during a Menstrual Cycle

Background: The purpose of the present investigation was to examine changes in strength and aerobic physical performances in young eumenorrheic female college students during the menstruation phase and different testing occasions within a menstrual cycle. Methods: A repeated measure experimental design used to investigate the variation in physical performance from different testing occasions compared to the menstruation phase. Twelve eumenorrhea female college students volunteered to participate in this study. The participants were 19.8 ± 0.8 (±SD) years old, with the body mass of 61.4 ± 11.6 kg, the height of 162.6 ± 5.1 cm, and BMI of 23.2 ± 3.8. All participants reported regular monthly menstrual cycles of 26–33 days, none of whom reported taking oral contraceptives in their entire life. None of the participants was an athlete, and their level of activity was limited to physical education classes and recreational activities. The menstrual cycles during the two cycles before testing had to be between 26 and 35 days to participate in this study. Second, there had to be no current or ongoing neuromuscular diseases or musculoskeletal injuries. Third, no one should be taking any dietary or performance-enhancing supplements that could have affected testing results during this study. The participants tested on one-repetition maximum (1RM) bench press, 1RM leg press, push-up to failure, leg press with 60% of 1RM to failure, and running 1600 m time trial. The participants were tested on four occasions based on the classical model of the menstrual cycle (i.e., 28 days; early follicular phase (menstruation phase) on day 2 (T1), late follicular phase on day 8 (T2), ovulation phase on day 14 (T3), and mid-luteal phase on day 21 (T4)). Data were analyzed using the Bayesian hierarchical model (Bayesian Estimation) with Markov Chain Monte Carlo simulation using the decision-theoretic properties of the high-density interval (HDI) + ROPE decision rule. Results: The Bayesian estimated difference from the four testing occasions neither showed that the most credible parameter values (95% HDI) were sufficiently away from the null value nor showed that the most credible parameter values are close to the null value (Rope odds ratio among all tests were spread in 12.7% < 0 < 87.3% with an effect size ranging between d = −0.01 and 0.44). Hence, no decision can be made as to whether strength and aerobic physical performances change during the menstruation phase compared to the other testing occasions within a menstrual cycle. Conclusions: It was noticed that different studies concluded different results, which make the research in menstrual cycle difficult. However, the results from this study and published studies suggest that future research should investigate and profile motivation and autonomic nervous system activity during the menstruation phase and examine the interaction effect of the three on performance compared to other testing occasions within a menstrual cycle.

The Analysis of Effectiveness of Elastic Training (Resistant) Bands Application to Develop Explosive Strength

ned: 1) the smallest increase in the standing long jump was observed in the group in which there were trainings with elastic training bands – 4,3 cm; in the group where isometric exercises were used, the increase in standing long jump was 10,9 cm; in the group in which students trained with weights, the increase in the standing long jump was 14 cm; 2) the increase of the leg press index at an angle of 45° in the group that used elastic training bands as a means of weighting was the lowest, i.e. 14 kg; in the group performing isometric exercises it was the highest – 19,5 kg; in the group that used weights – 18 kg. Purpose: to research the effectiveness of elastic training bands (resistance bands) application to develope explosive strength in a comparative aspect. Material and methods: theoretical material for the article has been taken from the research of Ukrainian and foreign scholars and experts. The basis for the study was a research laboratory of functional diagnostics and physical rehabilitation. The study involved 60 18-19-year-old students (40 girls and 20 boys), young people with excellent, very good or good health status. The main methods used for the experiment and the article were comparison, questionnaires, final tests, statistical analysis (parametric and nonparametric analysis, systematization, creation of varieties (arrays), determination of Student’s t-test and Pearson’s χ2 test). Results: the questionnaire of students on the expected effectiveness of various ways of explosive strength training revealed that the lowest result was expected from isometric exercises (5%), the average one was found out from the use of weights (61,67%), and the highest result was shown from the application of elastic training (resistant) bands (65%). According to the results of the experiment the following data has been obtained: 1) the smallest increase in the standing long jump was observed in the group in which there were trainings with elastic training bands – 4,3 cm; in the group where isometric exercises were applied, the increase in standing long jump was 10,9 cm; in the group in which students trained with weights, the gain in the standing long jump was 14 cm; 2) the increase of the leg press index at an angle of 45° in the group that used elastic training bands as a means of weighting was the lowest, i.e. 14 kg; in the group performing isometric exercises it turned out to be the highest – 19,5 kg; in the group that used weights – 18 kg. Conclusion: our experiment involved comparing the impact on the explosive strength development of different means of weighting: elastic training bands, isometric exercises and weighting objects. Despite the expectations of the respondents it was demonstrated that the application of the elastic training bands does not have a significant advantage over other means of weighting. The resistance bands application show lower results compared to the training with the isometric weighting and weighting of objects. The application of exercises in the isometric mode of weighting showed a significant gain in explosive strength, although the expected results were not met. The application of objects’ weighting showed the expected high results. Therefore, the prediction of the high efficiency of elastic training bands as a means of weighting turned out to be spurious

Acute Effects of Intermittent Foot Cooling on 1 RM Leg Press Strength in Resistance-Trained Men: A Pilot Study

Inter-set peripheral cooling can improve high-intensity resistance exercise performance. However, whether foot cooling (FC) would increase 1 repetition maximum (RM) lower-limb strength is unclear. This study investigated the effect of intermittent FC on 1 RM leg press strength. Ten recreational male lifters performed three attempts of 1 RM leg press with FC or non-cooling (NC) in a repeated-measures crossover design separated by 5 days. FC was applied by foot immersion in 10 °C water for 2.5 min before each attempt. During the 1 RM test, various physiological measures were recorded. The results showed that FC elicited higher 1 RM leg press strength (Δ [95% CI]; Cohen’s d effect size [ES]; 13.6 [7.6–19.5] kg; ES = 1.631) and electromyography values in vastus lateralis (57.7 [8.1–107.4] μV; ES = 0.831) and gastrocnemius (15.1 [−3.1–33.2] μV; ES = 0.593) than in NC. Higher arousal levels (felt arousal scale) were found in FC (0.6 [0.1–1.2]; ES = 0.457) than in NC. In conclusion, the preliminary findings, although limited, suggest intermittent FC has a potential ergogenic role for recreational athletes to enhance maximal lower-limb strength and may partly benefit strength-based competition events.

Exploring the acute affective responses to resistance training: A comparison of the predetermined and the estimated repetitions to failure approaches

Background In resistance-training (RT), the number of repetitions is traditionally prescribed using a predetermined approach (e.g., three sets of 10 repetitions). An emerging alternative is the estimated repetitions to failure (ERF) approach (e.g., terminating sets two repetitions from failure). Despite the importance of affective responses experienced during RT, a comparison between the two approaches on such outcomes is lacking. Methods Twenty women (age range: 23–45 years) without RT experience completed estimated one repetition maximum (RM) tests in four exercises. In the next two counterbalanced sessions, participants performed the exercises using 70%1RM. Participants completed ten repetitions in all three sets (predetermined condition) or terminated the sets when perceived to be two repetitions away from task-failure (ERF condition). Primary outcomes were affective-valence, enjoyment, and approach-preference and secondary outcomes were repetition-numbers completed in each exercise. Results We observed trivial differences in the subjective measures and an approximately even approach-preference split. Under the ERF condition, we observed greater variability in repetition-numbers between participants and across exercises. Specifically, the mean number of repetitions was slightly lower in the chest-press, knee-extension, and lat-pulldown (~1 repetition) but considerably higher in the leg-press (17 vs. 10, p<0.01). Conclusions Both approaches led to comparable affective responses and to an approximately even approach preference. Hence, prior to prescribing either approach, coaches should consider trainee’s preferences. Moreover, under the ERF condition participants completed a dissimilar number of repetitions across exercises while presumably reaching a similar proximity to task-failure. This finding suggests that ERF allows for better effort regulation between exercises.

Reference data on anthropometrics, aerobic fitness and muscle strength in young Norwegian men and women

Purpose Anthropometrics, aerobic fitness and muscle strength are measured in one-third of all 18-year-old Norwegian men and women during yearly selection for compulsory military service. The large sample size and geographical representativity make these data valuable for reference. The main purpose of this study was to present reference data for anthropometrics and physical fitness in young Norwegian men and women. Methods All 154,659 subjects (66% men and 34% women, 17–21 years old) who completed physical examinations at conscript selection from 2011 to 2019 were included in the study. Body mass index (BMI) was calculated from height and weight measurements. Peak oxygen uptake (VO2peak) was estimated from performance on a maximal treadmill test. Muscle strength was measured by isometric chest and leg press, or seated medicine ball throw, standing long jump and pull-ups. Results Mean BMI (SD) was 23.1 (3.4) and 22.9 (3.3) kg·m−2 in men and women, respectively (P < 0.001), and 24% of men and 21% of women had a BMI ≥ 25 kg·m−2. Estimated VO2peak was 52.9 (4.6) and 42.7 (3.9) mL·kg−1·min−1 in men and women, respectively (P < 0.001). Men performed significantly better than women on all muscle strength tests, with corresponding effect sizes varying from 1.14 for isometric leg press to 2.96 for seated medicine ball throw. Conclusion The presented reference data on physical fitness in young Norwegian men and women can be used to evaluate population health, serve as reference material for future studies and describes sex differences in several physical fitness parameters.