Aging effects of haptic input on postural control under a dual-task paradigm.

Postural control relies on three principal sensory systems: vision, vestibular and proprioceptive; that are affected by aging. When performing a cognitive task concomitantly with a motor task, those sensory impairments lead to even greater deleterious effects on balance. We aimed to study the effects of a sensory aid (a light touch) on a dual task paradigm and sought to understand the different responses on balance due to aging. Fifty healthy and highly physical active women were divided in two groups: young (N = 25, 24.2 ± 4.0 years) and older adults (N = 25, 67.3 ± 4.2 years). In a random and balanced order, all participants performed five tasks: Stroop test while seated (Seated); Stroop test while standing quiet (ST); Standing quiet (BL); Standing quiet with a haptic input (LT); and Stroop test with a haptic input while standing quiet (SL). In the Stroop test, older women committed more errors (50 vs 11 errors, p < 0.001) and had higher reaction time (1.001 ± 0.191 vs 0.699 ± 0.081 s, p < 0.001). The haptic input (LT) reduced all body sway parameters, in both groups, regardless the condition. This means that postural control under a dual task paradigm (ST) deleterious effect can be mitigated by a haptic input.

Risk or benefit? Side effects of caffeine supplementation in sport: a systematic review.

PURPOSE: The aim of this study was to systematically review evidence on the prevalence and magnitude of side effects associated with caffeine supplementation in athletes. METHODS: Systematic searches through the PubMed, VHL, Scopus, and Web of Science databases were conducted according to the PRISMA guidelines. Peer-reviewed articles written in English that reported the prevalence/percentage or magnitude/effect size of side effects after caffeine supplementation in athletes in a sports context were included. Studies were grouped by the dose of caffeine administered as follows: low = ≤ 3.0 mg/kg; moderate = from 3.1 to 6.0 mg/kg; high = ≥ 6.1 mg/kg. The magnitude of the side effects was calculated with effect sizes. RESULTS: The search retrieved 25 studies that met the inclusion/exclusion criteria with a pooled sample of 421 participants. The supplementation with caffeine produced a higher prevalence or magnitude of all side effects under investigation when compared to placebo/control situations. The prevalence (magnitude) was between 6 and 34% (ES between 0.13 and 1.11) for low doses of caffeine, between 0 and 34% (ES between -0.13 and 1.20) for moderate doses of caffeine, and between 8 and 83% (ES between 0.04 and 1.52) with high doses of caffeine. The presence of tachycardia/heart palpitations and the negative effects on sleep onset had the highest prevalence and magnitude, in athletes using supplementation with caffeine. CONCLUSION: In summary, caffeine supplementation in the doses habitually used to enhance physical performance produces several side effects, both after exercise and at least 24 h after the ingestion. However, the prevalence and magnitude of side effects with high doses of caffeine were habitually higher than with low doses of caffeine. From a practical perspective, using ~3.0 mg/kg of caffeine may be the dose of choice to obtain the ergogenic benefits of caffeine with the lowest prevalence and magnitude of side effects.

Strength Training to Prevent Falls in Older Adults: A Systematic Review with Meta-Analysis of Randomized Controlled Trials.

We performed a systematic review with meta-analysis of randomized controlled trials (RCTs) to assess the effects of strength training (ST), as compared to alternative multimodal or unimodal exercise programs, on the number of falls in older adults (≥60 years). Ten databases were consulted (CINAHL, Cochrane Library, EBSCO, EMBASE, PEDro, PubMed, Scielo, Scopus, SPORTDiscus and Web of Science), without limitations on language or publication date. Eligibility criteria were as follows: RCTs with humans ≥60 years of age of any gender with one group performing supervised ST and a group performing another type of exercise training, reporting data pertaining falls. Certainty of evidence was assessed with Grading of Recommendations, Assessment, Development and Evaluation (GRADE). Meta-analysis used a random effects model to calculate the risk ratio (RR) for number of falls. Five RCTs with six trials were included (n = 543, 76% women). There was no difference between ST and alternative exercise interventions for falls (RR = 1.00, 95% CI 0.77-1.30, p = 0.99). The certainty of evidence was very low. No dose-response relationship could be established. In sum, ST showed comparable RR based on number of falls in older adults when compared to other multimodal or unimodal exercise modalities, but evidence is scarce and heterogeneous, and additional research is required for more robust conclusions. Registration: PROSPERO CRD42020222908.

Eccentric Strength Assessment of Hamstring Muscles with New Technologies: a Systematic Review of Current Methods and Clinical Implications.

BACKGROUND: Given the severe economic and performance implications of hamstring injuries, there are different attempts to identify their risk factors for subsequently developing injury prevention strategies to reduce the risk of these injuries. One of the strategies reported in the scientific literature is the application of interventions with eccentric exercises. To verify the effectiveness of these interventions, different eccentric strength measurements have been used with low-cost devices as alternatives to the widespread used isokinetic dynamometers and the technically limited handheld dynamometers. Therefore, the purpose of the present systematic review was to summarize the findings of the scientific literature related to the evaluation of eccentric strength of hamstring muscles with these new technologies. METHODS: Systematic searches through the PubMed, Scopus, and Web of Science databases, from inception up to April 2020, were conducted for peer reviewed articles written in English, reporting eccentric strength of hamstrings assessed by devices, different to isokinetic and handheld dynamometers, in athletes. RESULTS: Seventeen studies were finally included in the review with 4 different devices used and 18 parameters identified. The pooled sample consisted of 2893 participants (97% male and 3% female: 22 ± 4 years). The parameters most used were peak force (highest and average), peak torque (average and highest), and between-limb imbalance (left-to-right limb ratio). There is inconsistency regarding the association between eccentric hamstrings strength and both injury risk and athletic performance. There is no standardized definition or standardization of the calculation of the used parameters. CONCLUSIONS: The current evidence is insufficient to recommend a practical guide for sports professionals to use these new technologies in their daily routine, due to the need for standardized definitions and calculations. Furthermore, more studies with female athletes are warranted. Despite these limitations, the eccentric strength of hamstring muscles assessed by different devices may be recommended for monitoring the neuromuscular status of athletes.

Perception of impact is affected by stimulus intensity.

Perception of external loads may be a central topic to understand adjustments to the mechanical demands during movement. Nevertheless, the association between the perceived and the real load received is still controversial. This study aimed to correlate vertical ground reaction force (vGRF) to the perception of impact in different regimens of stimulus application. Ten physically active men performed drop jumps from four different heights (0.20, 0.40, 0.60 and 0.80 m). A force plate measured the vGRF, while perception of impact was evaluated through Borg's Ratings of Perceived Exertion. Higher values of maximum vGRF (Fy_max) and impulse of the first 50 ms (I_50), and reduced time to reach Fy_max indicate increased external forces as drop jump height raised. Perception of impact increased gradually with increasing jump height for I_50. Fy_max and I_50 showed moderate to strong correlations to perceived load for 70% and 90% of participants, respectively. Higher and different intensity of stimulus facilitated the perception of impact, presenting moderate to strong correlations to kinetic parameters related to external load during landing from drop jump. Perception of higher impacts could be used as a surrogate to monitor 'real' impacts and possibly also for managing impact-related injury risk.

Overall indexes of coordination in front crawl swimming.

The aim of this study was to propose a group of parameters able to quantify not only arm coordination but also inter limb coordination. These include the well know index of coordination with the relative duration of the stroke phases and two new parameters: the Index of synchronization (Ids) between arms and legs actions; and the Index of inter limb coordination (IdIC) calculated as the relative foot position during successive arm stroke phases. These parameters were compared between experts and amateur swimmers in a maximal front crawl sprint. The influence of arm stroke in leg kick parameters was also assessed, comparing the full stroke condition with a condition without arms actions. Sixty-five per cent of expert swimmers used synchronized limb actions while 95% of amateur swimmers used non-synchronized limb motions. These synchronized expert swimmers also converged towards a specific coordination pattern between foot position and arm stroke phases. In the condition without arms, both groups changed kick rate and amplitude. The present study reveals the interdependency of arms and legs actions and the importance of coordination and synchronization between limbs. Therefore, the proposed group of overall indexes of coordination provides a more complete marker for the analysis of swimming technique.

A High-Intensity Exercise Intervention Improves Older Women Lumbar Spine and Distal Tibia Bone Microstructure and Function: A 20-Week Randomized Controlled Trial.

Introduction: The effects of ageing on bone can be mitigated with different types of physical training, such as power training. However, stimuli that combine increasing external and internal loads concomitantly may improve bone quality. The goal of this study was to assess the efficacy of a combined power and plyometric training on lumbar spine and distal tibia microstructure and function. Methods: 38 sedentary elderly women between 60 and 70 years were randomly allocated in experimental (N = 21) and control group (N = 17). The effects of the 20-week protocol on lumbar spine microstructure and tibia microstructure and function were assessed by trabecular bone score (TBS), high resolution peripheral quantitative computed tomography (HR-pQCT) and microfinite element analysis. Results: when compared to the effects found in the control group, the experimental group showed significant improvements in lumbar spine TBS (Hedges' g = 0.77); and in distal tibia trabecular thickness (g = 0.82) and trabecular bone mineral density (g=0.63). Conclusion: our findings underscore the effectiveness of the proposed intervention, suggesting it as a new strategy to slow down and even reverse the structural and functional losses in the skeletal system due to ageing.

Back Squat vs. Hip Thrust Resistance-training Programs in Well-trained Women.

The study compared the effects of back squat (BS) and hip thrust (HT) exercises on muscle strength and hypertrophy in well-trained women. Twenty-two participants were divided in two groups: BS group (n=12, 26.4±1.32 years, 171.8±3.79 cm, and 69.5±4.9 kg) performed the BS exercise and HT group (n=10, 27.5±1.42 years, 170.8±4.4 cm, 67.5±4.7 kg) performed the HT exercise. Training was performed for 12 weeks. Before and after the training period, participants were assessed for quadriceps femoris and gluteus maximus muscle thickness (MT) and 1 repetition maximum (1RM) test on the BS and HT. Both groups significantly increased hip extensors MT and HT 1RM; however, the improvements in BS group were higher than in HT group on quadriceps femoris (12.2% for BS and 2% for HT, P<0.001) and gluteus maximus MT (9.4% for BS and 3.7% for HT, P=0.001) and BS 1 RM (35.9% for BS and 4.3% for HT, P<0.001). BS was more efficient than HT, since it resulted in greater muscle hypertrophy of the quadriceps femoris and gluteus maximus, increases in BS 1RM and similar increases in HT.

Sleep quality monitoring in individual sports athletes: parameters and definitions by systematic review.

In the present review, we identify which instruments and parameters are used for sleep quality monitoring in individual sport athletes and which definitions were used for sleep quality parameters in this literature field. Systematic searches for articles reporting the qualitative markers related to sleep in team sport athletes were conducted in PubMed, Scopus and Web of Science online databases. The systematic review followed the Preferred Reporting Items for Systematic Reviews. The initial search returned 3316 articles. After the removal of duplicate articles, eligibility assessment, 75 studies were included in this systematic review. Our main findings were that the most widely used measurement instruments were Actigraphy (25%), Rating Likert Scales (16%) and Sleep Diary (13%). On sleep quality parameters (Sleep duration = 14%; Wake after sleep onset = 14%; Sleep Quality = 12%; Sleep Effciency = 11% and Sleep Latency = 9%), the main point is that there are different definitions for the same parameters in many cases reported in the literature. We conclude that the most widely used instruments for monitoring sleep quality were Actigraphy, Likert scales and Sleep diary. Moreover, the definitions of sleep parameters are inconsistent in the literature, hindering the understanding of the sleep-sport performance relationship.

Muscle stretching changes neuromuscular function involved in ankle stability.

It has been postulated that the mechanical and neurophysiological effects induced by stretching decrease maximal muscle strength and power. Additionally, the reduction in neural input and muscle stiffness can affect the joint stabilization process. However, there is no evidence available to support this hypothesis. Thus, the aim of this study is to analyze the influence of static stretching on dynamic joint stability. Twenty physically active female university students (22.8 ± 5.3 years; 58 ± 8.8 kg; 1.62 ± 0.07 m) performed a series of static-passive stretching exercises for the peroneus longus and brevis muscles (four repetitions of 30 s). Before and after the stretches, electromyography was performed on both muscles during simulated ankle sprain. Mathematical algorithms calculate the latency and the electromyography activity (RMS). After stretching, the latency increased from 66ms to 73 ms (p = 0.003) for the peroneus brevis muscle and from 70 ms to 79 ms (p = 0.001) for the peroneus longus muscle. The RMS, calculated 100 ms after the simulation, decreased in the peroneus brevis muscle, from 25.05 to 18.16 (p = 0.001), and in the peroneus longus muscle, from 22.84 to 15.61 (p = 0.001). Muscle stretching changed the motor responses of both muscles. The increase in latency and the decrease in RMS indicate that static stretching influences the neuromuscular function involved in the joint stabilization process.

Current Approaches to the Use of Artificial Intelligence for Injury Risk Assessment and Performance Prediction in Team Sports: a Systematic Review.

BACKGROUND: The application of artificial intelligence (AI) opens an interesting perspective for predicting injury risk and performance in team sports. A better understanding of the techniques of AI employed and of the sports that are using AI is clearly warranted. The purpose of this study is to identify which AI approaches have been applied to investigate sport performance and injury risk and to find out which AI techniques each sport has been using. METHODS: Systematic searches through the PubMed, Scopus, and Web of Science online databases were conducted for articles reporting AI techniques or methods applied to team sports athletes. RESULTS: Fifty-eight studies were included in the review with 11 AI techniques or methods being applied in 12 team sports. Pooled sample consisted of 6456 participants (97% male, 25 ± 8 years old; 3% female, 21 ± 10 years old) with 76% of them being professional athletes. The AI techniques or methods most frequently used were artificial neural networks, decision tree classifier, support vector machine, and Markov process with good performance metrics for all of them. Soccer, basketball, handball, and volleyball were the team sports with more applications of AI. CONCLUSIONS: The results of this review suggest a prevalent application of AI methods in team sports based on the number of published studies. The current state of development in the area proposes a promising future with regard to AI use in team sports. Further evaluation research based on prospective methods is warranted to establish the predictive performance of specific AI techniques and methods.

Immediate effects of a distal gait modification during stair descent in individuals with patellofemoral pain.

Background: Knee pain during stair managing is a common complaint among individuals with PFP and can negatively affect their activities of daily living. Gait modification programs can be used to decrease patellofemoral pain. Immediate effects of a stair descent distal gait modification session that intended to emphasize forefoot landing during stair descent are described in this study. Objectives: To analyze the immediate effects of a distal gait modification session on lower extremity movements and intensity of pain in women with patellofemoral pain during stair descent. Method: Nonrandomized controlled trial. Sixteen women with patellofemoral pain were allocated into two groups: (1) Gait Modification Group (n = 8); and 2) Control Group (n = 8). The intensity of pain (visual analog scale) and kinematics of knee, ankle, and forefoot (multi-segmental foot model) during stair descent were assessed before and after the intervention. Results: After the gait modification session, there was an increase of forefoot eversion and ankle plantarflexion as well as a decrease of knee flexion. An immediate decrease in patellofemoral pain intensity during stair descent was also observed. Conclusion: The distal gait modification session changed the lower extremity kinetic chain strategy of movement, increasing foot and ankle movement contribution and decreasing knee contribution to the task. An immediate decrease in patellofemoral pain intensity during stair descent was also observed. To emphasize forefoot landing may be a useful intervention to immediately relieve pain in patients with patellofemoral pain during stair descent. Clinical studies are needed to verify the gait modification session effects in medium and long terms.

Interpretation of propulsive force in tethered swimming through principal component analysis / Interpretação da força propulsora no nado estacionário através da análise do componente principal / Interpretación de la fuerza propulsora en el nado estacionario a través del análisis del componente principal

ABSTRACT Introduction: Propulsive force in swimming, represented through impulse, is related to performance. However, since the as different biomechanical parameters contribute to impulse generation, coaches have a difficult task when seeking for performance improvement. Objective: Identify the main components involved in impulse generation in the front crawl stroke. Methods: Fourteen swimmers underwent a 10-second all-out fully tethered swimming test. The following parameters were obtained from the force-time curve: minimum force, peak force, mean force, time to peak force, rate of force development and stroke duration. This stage was followed by a principal component analysis. Results: The principal component analysis showed that component 1, predominantly kinetic, was composed of peak force, mean force and rate of force development, and accounted for 49.25% of total impulse variation, while component 2, predominantly temporal, composed of minimum force, stroke duration, and time to peak force, represented 26.43%. Conclusion: Kinetic parameters (peak force, mean force, and rate of force development) are more closely associated with impulse augmentation and, hypothetically, with non-tethered swimming performance. Level of Evidence II; Diagnostic studies - Investigating a diagnostic test.

RESUMO Introdução: A força propulsora na natação, representada através do impulso, está relacionada ao desempenho. Entretanto, já que diferentes parâmetros biomecânicos contribuem para a geração do impulso, os treinadores têm uma difícil tarefa ao buscarem a melhora do desempenho. Objetivos: Identificar os principais componentes envolvidos na geração do impulso na braçada do nado crawl. Métodos: Catorze nadadores foram submetidos ao teste de nado estacionário, totalmente all-out, com duração de 10 segundos. Os parâmetros de força mínima, força máxima, força média, tempo para força máxima, taxa de desenvolvimento da força e a duração da braçada foram obtidos a partir da curva força-tempo e, depois, foi realizada uma análise do componente principal. Resultados: A análise do componente principal revelou que o componente 1, predominantemente cinético, era composto pelos parâmetros de força máxima, força média e taxa de desenvolvimento da força e contava com 49,25% da variação total do impulso, enquanto que o componente 2, predominantemente temporal, composto pelos parâmetros de força mínima, duração da braçada e tempo para força máxima, representava 26,43%. Conclusão: Os parâmetros cinéticos (força máxima, força média e taxa de desenvolvimento de força) estão mais associados ao aumento do impulso e, hipoteticamente, ao desempenho no nado não estacionário. Nível de Evidência II; Estudos diagnósticos - Investigação de um exame para diagnóstico.

RESUMEN Introducción: La fuerza propulsora en la natación, representada a través del impulso, está relacionada al desempeño. Entretanto, ya que diferentes parámetros biomecánicos contribuyen para la generación del impulso, los entrenadores tienen una difícil tarea al buscar la mejora del desempeño. Objetivos: Identificar los principales componentes involucrados en la generación del impulso en la brazada del nado crawl. Métodos: Catorce nadadores fueron sometidos al test de nado estacionario, totalmente all-out, con duración de 10 segundos. Los parámetros de fuerza mínima, fuerza máxima, fuerza promedio, tiempo para fuerza máxima, tasa de desarrollo de la fuerza y la duración de la brazada fueron obtenidos a partir de la curva fuerza-tiempo y, después, fue realizado un análisis del componente principal. Resultados: El análisis del componente principal reveló que el componente 1, predominantemente cinético, era compuesto por los parámetros de fuerza máxima, fuerza promedio y tasa de desarrollo de la fuerza y contaba con 49,25% de la variación total del impulso, mientras que el componente 2, predominantemente temporal, compuesto por los parámetros de fuerza mínima, duración de la brazada y tiempo para fuerza máxima, representaba 26,43%. Conclusión: Los parámetros cinéticos (fuerza máxima, fuerza promedio y tasa de desarrollo de fuerza) están más asociados al aumento del impulso e, hipotéticamente, al desempeño en el nado no estacionario. Nivel de Evidencia II; Estudios diagnósticos - Investigación de un examen para diagnóstico.

Moderate intensity is a better stimulus to induce quadripecs femoris power in elderly adults / Intensidade moderada é o estímulo mais adequado para induzir potência de quadriceps em idosos / Intensidad moderada es el más adecuado para inducir potencia de quadriceps en ancianos

ABSTRACT Introduction: The best strategy for improving knee extensor power, a major functional capacity indicator in older adults, is power training. Nonetheless, the training intensity required to induce optimal gains is yet to be found. Objective: Our purpose was to compare knee extensor peak power responses between low, moderate, and high intensity load conditions (30%, 50% and 70% of 1RM). Methods: Thirteen sedentary elderly women performed six knee extensions in each load condition, calculating knee extensor mechanical work/power output and knee extension peak angular velocity. Results: No difference in peak power was found between the high (207.0 ± 68.1 W) and moderate (206.1 ± 71.6 W) load conditions (p = 0.994), and both had higher values (p ≤0.004) than the low intensity condition (135.6 ± 56.3 W). Conclusion: Moderate load at 50% of 1RM appears to be the preferred strategy for inducing knee extensor power output because in contrast with the high intensity condition, the moderate load yielded higher angular peak velocity, which is also a functional indicator. Level of Evidence ll; Therapeutic studies - Investigating treatment results.

RESUMO Introdução: A melhor estratégia para melhorar a potência dos extensores do joelho, principal indicador da capacidade funcional em idosos, é o treinamento de força. No entanto, a intensidade do treinamento exigida para induzir a maiores benefícios ainda não é conhecida. Objetivo: Nosso objetivo consistiu em comparar as respostas de potência máxima dos extensores do joelho entre as condições de carga baixa, moderada e de alta intensidade (30%, 50% e 70% de uma repetição máxima). Métodos: Treze mulheres idosas sedentárias realizaram seis extensões de joelho em cada condição de carga, sendo calculado o trabalho mecânico/débito de força e a velocidade angular máxima (ou pico) dos extensores do joelho. Resultados: Não houve diferença significativa na potência máxima entre as condições de carga alta ((207,0 ± 68,1 W) e moderada (206,1 ± 71,6 W) (p = 0,994), e ambas apresentaram valores maiores (p ≤ 0,004) do que a condição de baixa intensidade (135,6 ± 56,3 W). Conclusão: A carga moderada a 50% de 1RM parece ser a estratégia preferida para induzir o débito de força dos extensores do joelho, uma vez que quando comparada com a condição de alta intensidade, a carga moderada apresentou um pico de velocidade angular maior, o que também é um indicador funcional. Nível de Evidência II; Estudos terapêuticos - Investigação dos resultados do tratamento.

RESUMEN Introducción: La mejor estrategia para mejorar la potencia de los extensores de la rodilla, principal indicador de la capacidad funcional en personas de la tercera edad, es el entrenamiento de fuerza. Sin embargo, la intensidad del entrenamiento exigida para inducir a mayores beneficios aún no es conocida. Objetivo: Nuestro objetivo consistió en comparar las respuestas de potencia máxima de los extensores de la rodilla entre las condiciones de carga baja, moderada y de alta intensidad (30%, 50% y 70% de una repetición máxima). Métodos: Trece mujeres de la tercera edad sedentarias realizaron seis extensiones de rodilla en cada condición de carga, siendo calculado el trabajo mecánico/débito de fuerza y la velocidad angular máxima (o pico) de los extensores de la rodilla. Resultados: No hubo diferencia significativa en la potencia máxima entre las condiciones de carga alta ((207,0 ± 68,1 W) y moderada (206,1 ± 71,6 W) (p = 0,994), y ambas presentaron valores mayores (p ≤ 0,004) que la condición de baja intensidad (135,6 ± 56,3 W). Conclusión: La carga moderada a 50% de 1RM parece ser la estrategia preferida para inducir el débito de fuerza de los extensores de la rodilla, dado que cuando comparada con la condición de alta intensidad, la carga moderada presentó un pico de velocidad angular mayor, lo que también es un indicador funcional. Nivel de Evidencia II; Estudios terapéuticos - Investigación de los resultados del tratamiento.

CrossFit Overview: Systematic Review and Meta-analysis.

BACKGROUND: CrossFit is recognized as one of the fastest growing high-intensity functional training modes in the world. However, scientific data regarding the practice of CrossFit is sparse. Therefore, the objective of this study is to analyze the findings of scientific literature related to CrossFit via systematic review and meta-analysis. METHODS: Systematic searches of the PubMed, Web of Science, Scopus, Bireme/MedLine, and SciELO online databases were conducted for articles reporting the effects of CrossFit training. The systematic review followed the PRISMA guidelines. The Oxford Levels of Evidence was used for all included articles, and only studies that investigated the effects of CrossFit as a training program were included in the meta-analysis. For the meta-analysis, effect sizes (ESs) with 95% confidence interval (CI) were calculated and heterogeneity was assessed using a random-effects model. RESULTS: Thirty-one articles were included in the systematic review and four were included in the meta-analysis. However, only two studies had a high level of evidence at low risk of bias. Scientific literature related to CrossFit has reported on body composition, psycho-physiological parameters, musculoskeletal injury risk, life and health aspects, and psycho-social behavior. In the meta-analysis, significant results were not found for any variables. CONCLUSIONS: The current scientific literature related to CrossFit has few studies with high level of evidence at low risk of bias. However, preliminary data has suggested that CrossFit practice is associated with higher levels of sense of community, satisfaction, and motivation.

Correction: 16 Weeks of Progressive Barefoot Running Training Changes Impact Force and Muscle Activation in Habitual Shod Runners.

[This corrects the article DOI: 10.1371/journal.pone.0167234.].

Determination of a quantitative parameter to evaluate swimming technique based on the maximal tethered swimming test.

The aim of this study was to propose a new force parameter, associated with swimmers' technique and performance. Twelve swimmers performed five repetitions of 25 m sprint crawl and a tethered swimming test with maximal effort. The parameters calculated were: the mean swimming velocity for crawl sprint, the mean propulsive force of the tethered swimming test as well as an oscillation parameter calculated from force fluctuation. The oscillation parameter evaluates the force variation around the mean force during the tethered test as a measure of swimming technique. Two parameters showed significant correlations with swimming velocity: the mean force during the tethered swimming (r = 0.85) and the product of the mean force square root and the oscillation (r = 0.86). However, the intercept coefficient was significantly different from zero only for the mean force, suggesting that although the correlation coefficient of the parameters was similar, part of the mean velocity magnitude that was not associated with the mean force was associated with the product of the mean force square root and the oscillation. Thus, force fluctuation during tethered swimming can be used as a quantitative index of swimmers' technique.

The countermovement jump to monitor neuromuscular status: A meta-analysis.

OBJECTIVES: The primary objective of this meta-analysis was to compare countermovement jump (CMJ) performance in studies that reported the highest value as opposed to average value for the purposes of monitoring neuromuscular status (i.e., fatigue and supercompensation). The secondary aim was to determine the sensitivity of the dependent variables. DESIGN: Systematic review with meta-analysis. METHODS: The meta-analysis was conducted on the highest or average of a number of CMJ variables. Multiple literature searches were undertaken in Pubmed, Scopus, and Web of Science to identify articles utilizing CMJ to monitor training status. Effect sizes (ES) with 95% confidence interval (95% CI) were calculated using the mean and standard deviation of the pre- and post-testing data. The coefficient of variation (CV) with 95% CI was also calculated to assess the level of instability of each variable. Heterogeneity was assessed using a random-effects model. RESULTS: 151 articles were included providing a total of 531 ESs for the meta-analyses; 85.4% of articles used highest CMJ height, 13.2% used average and 1.3% used both when reporting changes in CMJ performance. Based on the meta-analysis, average CMJ height was more sensitive than highest CMJ height in detecting CMJ fatigue and supercompensation. Furthermore, other CMJ variables such as peak power, mean power, peak velocity, peak force, mean impulse, and power were sensitive in tracking the supercompensation effects of training. CONCLUSIONS: The average CMJ height was more sensitive than highest CMJ height in monitoring neuromuscular status; however, further investigation is needed to determine the sensitivity of other CMJ performance variables.

16 Weeks of Progressive Barefoot Running Training Changes Impact Force and Muscle Activation in Habitual Shod Runners.

Short-term effects of barefoot and simulated barefoot running have been widely discussed in recent years. Consequences of adopting barefoot running for a long period, including as a training approach, still remain unknown. The present study evaluated the influence of 16 weeks of progressive barefoot running training on impact force and muscle activation in habitual shod runners. Six habitual shod runners (3 men and 3 women, 29.5 ± 7.3 years) were tested barefoot (BF) and shod (SH), before and after 16 weeks of progressive barefoot running training. Tests consisted of running on instrumented treadmill at 9 km/h, for 10 minutes in each experimental condition. Nine data acquisitions (10 s) of vertical ground reaction force (VGRF) and electromyographic (EMG) signal were conducted in each experimental condition for each test. BF training was effective to alter VGRF and EMG parameters of running in habitual shod runners, regardless of footwear condition (SH or BF). The magnitude of first peak of VGRF (Fy1) and the impulse of the first 50 ms decreased after training for BF and SH (p<0.01). The activation reduced from PRE to POST training for four muscles in BF running (p<0.001), whereas only muscle gastrocnemius lateralis decreased significantly its activation (p<0.01) in SH running. A 16-week progressive barefoot running training seems to be an effective training strategy to reduce impact force, improve shock attenuation and to decrease muscle activation intensity, not only in BF running, but also in SH running, although BF condition seems to be more influenced by BF training.

KINESIO TAPING NÃO ALTERA A RELAÇÃO EMG ENTRE VASTO LATERAL E VASTO MEDIAL DURANTE MEIO-AGACHAMENTO / KINESIO TAPING DON'T CHANGE EMG RELATION BETWEEN VASTUS LATERALIS - MEDIALIS IN HALF SQUAT / KINESIO TAPING NO ALTERA LA RELACIÓN EMG ENTRE VASTO LATERAL Y VASTO MEDIAL DURANTE MEDIO AGACHAMIENTO

RESUMO Introdução: Kinesio Taping é uma técnica realizada com aplicação de fitas elásticas sobre a pele, que se propõe a produzir determinados efeitos com fins de prevenção e tratamento das lesões musculoesqueléticas. No entanto, os meios pelos quais tais efeitos ocorrem continuam sendo investigados e discutidos, principalmente no que diz respeito à utilização no campo da reabilitação e do esporte. Objetivo: Analisar a relação da atividade eletromiográfica encontrada nos músculos vasto lateral (VL) e vasto medial (VM) em duas condições: sem aplicação de Kinesio Taping (GnKT) e com aplicação de Kinesio Taping (GKT) em uma população saudável, com experiência em treinamento de força. Métodos: Dezoito sujeitos do sexo masculino (idade: 28,1 ± 6,9 anos; massa corporal: 85,5 ± 8,3 kg; estatura: 179,5 ± 6,9 cm; comprimento de membro inferior: 97,0 ± 4,2 cm) realizaram o exercício de meio-agachamento livre, com velocidade controlada, sem e com aplicação de Kinesio Taping. A relação foi verificada pela proporção de magnitude de ativação (VM/VL), utilizando-se os valores de root mean square (RMS). A sequência para realização dos exercícios nas condições mencionadas foi randomizada e balanceada. Resultados: Os valores encontrados para a razão VM/VL na situação GnKT foram de 83,96 ± 5,79% para VM e 84,13 ± 7,16% para VL. Já na situação GKT, 84,55 ± 16,97% para VM e 80,53 ± 9,20% para VL. Não foram observadas diferenças significativas nos valores de RMS para a relação VM/VL submetidos a aplicação de Kinesio Taping. Conclusão: A aplicação de Kinesio Taping não demonstrou influenciar a relação da atividade eletromiográfica entre os músculos vasto lateral e vasto medial durante a execução do exercício de meio-agachamento.

ABSTRACT Introduction: Kinesio Taping is a technique carried out with application of elastic tapes on the skin, which is intended to produce certain effects on prevention and treatment of musculoskeletal injuries. However, the means by which these effects occur are still being investigated and discussed, particularly with regard to rehabilitation and sport. Objective: To analyze the relationship of the electromyographic activity found in the vastus lateralis (VL) and vastus medialis (VM) muscles on two conditions: without the application of Kinesio Taping (GnKT) and with the application of Kinesio Taping (GKT) in a healthy population with experience in strength training. Methods: Eighteen male subjects (age: 28.1 ± 6.9 years, body mass: 85.5 ± 8.3 kg, height: 179.5 ± 6.9 cm, length of lower limb: 97.0 ± 4.2 cm) performed the exercise of free half-squat with controlled speed with and without applying Kinesio Taping. The relationship was verified by the ratio of activation magnitude (VM/VL) using the root mean square (RMS). The sequence for the exercises under such conditions was randomized and balanced. Results: The values for the ratio VM/VL in the GnKT situation were 83.96 ± 5.79% for VM and 84.13 ± 7.16% for VL. In the GKT situation, 84.55 ± 16.97% for VM and 80.53 ± 9.20% for VL. No significant differences were observed in RMS values for the VM/VL ratio when the Kinesio Taping was applied. Conclusion: The application of Kinesio Taping did not affect the electromyographic ratio between the vastus lateralis and vastus medialis muscles during the half-squat exercise.

RESUMEN Introducción: Kinesio Taping es una técnica realizada con aplicación de cintas elásticas sobre la piel, que se propone producir determinados efectos con fines de prevención y tratamiento de las lesiones musculoesqueléticas. Sin embargo, los medios por los que tales efectos ocurren continúan siendo investigados e discutidos, principalmente en lo que refiere al uso en el campo de la rehabilitación y del deporte. Objetivo: Analizar la relación de la actividad electromiográfica encontrada en los músculos vasto lateral (VL) y vasto medial (VM) en dos condiciones: sin aplicación de Kinesio Taping (GnKT) y con aplicación de Kinesio Taping (GKT) en una población saludable, con experiencia en entrenamiento de fuerza. Métodos: Dieciocho sujetos del sexo masculino (edad: 28,1 ± 6,9 años; masa corporal: 85,5 ± 8,3 kg; estatura: 179,5 ± 6,9 cm; longitud de miembro inferior: 97,0 ± 4,2 cm) realizaron el ejercicio de medio agachamiento libre, con velocidad controlada, sin y con aplicación de Kinesio Taping. La relación fue verificada por la proporción de magnitud de activación (VM/VL), utilizándose los valores de root mean square (RMS). La secuencia para realización de los ejercicios en las condiciones mencionadas fue aleatorizada y balanceada. Resultados: Los valores encontrados para la razón VM/VL en la situación GnKT fueron de 83,96 ± 5,79% para VM y 84,13 ± 7,16% para VL. Ya en la situación GKT, 84,55 ± 16,97% para VM y 80,53 ± 9,20% para VL. No fueron observadas diferencias significativas en los valores de RMS para la relación VM/VL sometidos a la aplicación de Kinesio Taping. Conclusión: La aplicación de Kinesio Taping no demostró influenciar la relación de la actividad electromiográfica entre los músculos vasto lateral y vasto medial durante la ejecución del ejercicio de medio agachamiento.