RESUMEN

Successful performance in grappling combat sports (GCS) can be influenced by the fighter's capacity to sustain high-intensity contractions of the handgrip muscles during combat. This study investigated the influence of GCS experience on the critical torque (CT), impulse above CT (W'), tolerance, and neuromuscular fatigue development during severe-intensity handgrip exercise by comparing fighters and untrained individuals. Eleven GCS fighters and twelve untrained individuals participated in three experimental sessions for handgrip muscles: (1) familiarization with the experimental procedures and strength assessment; (2) an all-out test to determine CT and W'; and (3) intermittent exercise performed in the severe-intensity domain (CT + 15%) until task failure. No significant differences were found in CT and neuromuscular fatigue between groups (p > 0.05). However, GCS fighters showed greater W' (GCS fighters 2238.8 ± 581.2 N·m·s vs. untrained 1670.4 ± 680.6 N·m·s, p < 0.05) and exercise tolerance (GCS fighters 8.38 ± 2.93 min vs. untrained 5.36 ± 1.42 min, p < 0.05) than untrained individuals. These results suggest that long-term GCS sports training can promote increased tolerance to severe-intensity handgrip exercise and improved W' without changes in CT or the magnitude of neuromuscular fatigue.

RESUMEN

The enigmatic benefits of acute limb ischemic preconditioning (IP) in enhancing muscle force and exercise performance have intrigued researchers. This study sought to unravel the underlying mechanisms, focusing on increased neural drive and the role of spinal excitability while excluding peripheral factors. Soleus Hoffmann (H)-reflex /M-wave recruitment curves and unpotentiated supramaximal responses were recorded before and after IP or a low-pressure control intervention. Subsequently, the twitch interpolation technique was applied during maximal voluntary contractions to assess conventional parameters of neural output. Following IP, there was an increase in both maximum normalized force and voluntary activation (VA) for the plantar flexor group, with negligible peripheral alterations. Greater benefits were observed in participants with lower VA levels. Despite greater H-reflex gains, soleus volitional (V)-wave and sEMG amplitudes remained unchanged. In conclusion, IP improves muscle force via enhanced neural drive to the muscles. This effect appears associated, at least in part, to reduced presynaptic inhibition and/or increased motoneuron excitability. Furthermore, the magnitude of the benefit is inversely proportional to the skeletal muscle's functional reserve, making it particularly noticeable in under-recruited muscles. These findings have implications for the strategic application of the IP procedure across diverse populations.

Asunto(s)

Precondicionamiento Isquémico , Músculo Esquelético , Masculino , Humanos , Electromiografía/métodos , Músculo Esquelético/fisiología , Contracción Muscular/fisiología , Neuronas Motoras/fisiología , Contracción Isométrica/fisiología , Reflejo H/fisiología , Estimulación Eléctrica

RESUMEN

The neural correlates of locomotion impairments observed in people with Parkinson's disease (PD) are not fully understood. We investigated whether people with PD present distinct brain electrocortical activity during usual walking and the approach phase of obstacle avoidance when compared to healthy individuals. Fifteen people with PD and fourteen older adults walked overground in two conditions: usual walking and obstacle crossing. Scalp electroencephalography (EEG) was recorded using a mobile 64-channel EEG system. Independent components were clustered using a k-means clustering algorithm. Outcome measures included absolute power in several frequency bands and alpha/beta ratio. During the usual walk, people with PD presented a greater alpha/beta ratio in the left sensorimotor cortex than healthy individuals. While approaching obstacles, both groups reduced alpha and beta power in the premotor and right sensorimotor cortices (balance demand) and increased gamma power in the primary visual cortex (visual demand). Only people with PD reduced alpha power and alpha/beta ratio in the left sensorimotor cortex when approaching obstacles. These findings suggest that PD affects the cortical control of usual walking, leading to a greater proportion of low-frequency (alpha) neuronal firing in the sensorimotor cortex. Moreover, the planning for obstacle avoidance changes the electrocortical dynamics associated with increased balance and visual demands. People with PD rely on increased sensorimotor integration to modulate locomotion.

Asunto(s)

Enfermedad de Parkinson , Corteza Sensoriomotora , Humanos , Anciano , Caminata , Locomoción , Algoritmos

RESUMEN

PURPOSE: The aim of this study was to identify a blood-flow-restriction (BFR) endurance exercise protocol that maximizes metabolic strain and minimizes muscle fatigue. METHODS: Twelve healthy participants accomplished 5 different interval cycling endurance exercises (2-min work, 1-min rest) in a randomized order: (1) control, low intensity with unrestricted blood flow (CON30); (2) low intensity with intermittent BFR (i-BFR30, ∼150 mm Hg); (3) low intensity with continuous BFR (c-BFR, ∼100 mm Hg); (4) unloaded cycling with i-BFR0 (∼150 mm Hg); and (5) high intensity (HI) with unrestricted blood flow. Force production, creatine kinase activity, antioxidant markers, blood pH, and potassium (K+) were measured in a range of 5 minutes before and after each cycling exercise protocol. RESULTS: HI showed the highest reduction (Δ = -0.26 [0.05], d = 5.6) on blood pH. Delta pH for c-BRF30 (Δ = -0.02 [0.03], d = 0.8) and Δ pH for i-BRF30 (Δ = -0.04 [0.03], d = 1.6) were different from each other, and both were higher compared with CON30 (Δ = 0.03 [0.03]). There was significant before-to-after force loss following HI (Δ = 55 [40] N·m-1, d = 1.5) and c-BFR30 (Δ = 27 [21] N·m-1, d = 0.7) protocols only, which were accompanied by significant increases in K+ (HI: Δ = 0.94 [0.65] mmol·L-1, d = 1.8; c-BFR30: Δ = 0.72 [0.85] mmol·L-1, d = 1.2). Moreover, all BFR conditions elicited slight increases in plasma creatine kinase, but not for HI and CON30. Glutathione changes from before to after were significant for all BFR conditions and HI, but not for CON30. CONCLUSIONS: The attenuation in fatigue-induced reductions in maximal force suggests that i-BFR exercise could be preferable to c-BFR in improving exercise capacity, with considerably less biologic stress elicited from HI exercises.

Asunto(s)

Fatiga Muscular , Entrenamiento de Fuerza , Creatina Quinasa/metabolismo , Humanos , Músculo Esquelético/fisiología , Flujo Sanguíneo Regional/fisiología , Entrenamiento de Fuerza/métodos

RESUMEN

BACKGROUND: Dopaminergic medication improves gait in people with Parkinson disease (PD). However, it remains unclear if dopaminergic medication modulates cortical activity while walking. OBJECTIVE: We investigated the effects of dopaminergic medication on cortical activity during unobstructed walking and obstacle avoidance in people with PD. METHODS: A total of 23 individuals with PD, in both off (PDOFF) and on (PDON) medication states, and 30 healthy older adults (control group [CG]) performed unobstructed walking and obstacle avoidance conditions. Cortical activity was acquired through a combined functional near-infrared spectroscopy electroencephalography (EEG) system, along with gait parameters, through an electronic carpet. Prefrontal cortex (PFC) oxygenated hemoglobin (HbO2) and EEG absolute power from FCz, Cz, and CPz channels were calculated. RESULTS: HbO2 concentration reduced for people with PDOFF during obstacle avoidance compared with unobstructed walking. In contrast, both people with PDON and the CG had increased HbO2 concentration when avoiding obstacles compared with unobstructed walking. Dopaminergic medication increased step length, step velocity, and ß and γ power in the CPz channel, regardless of walking condition. Moreover, dopaminergic-related changes (ie, on-off) in FCz/CPz γ power were associated with dopaminergic-related changes in step length for both walking conditions. CONCLUSIONS: PD compromises the activation of the PFC during obstacle avoidance, and dopaminergic medication facilitates its recruitment. In addition, PD medication increases sensorimotor integration during walking by increasing posterior parietal cortex (CPz) activity. Increased γ power in the CPz and FCz channels is correlated with step length improvements achieved with dopaminergic medication during unobstructed walking and obstacle avoidance in PD.

Asunto(s)

Corteza Cerebral/fisiopatología , Dopaminérgicos/farmacología , Trastornos Neurológicos de la Marcha , Enfermedad de Parkinson , Desempeño Psicomotor , Caminata , Anciano , Corteza Cerebral/diagnóstico por imagen , Electroencefalografía , Femenino , Trastornos Neurológicos de la Marcha/diagnóstico por imagen , Trastornos Neurológicos de la Marcha/tratamiento farmacológico , Trastornos Neurológicos de la Marcha/etiología , Trastornos Neurológicos de la Marcha/fisiopatología , Humanos , Masculino , Persona de Mediana Edad , Enfermedad de Parkinson/complicaciones , Enfermedad de Parkinson/diagnóstico por imagen , Enfermedad de Parkinson/tratamiento farmacológico , Enfermedad de Parkinson/fisiopatología , Corteza Prefrontal/efectos de los fármacos , Corteza Prefrontal/fisiopatología , Desempeño Psicomotor/efectos de los fármacos , Desempeño Psicomotor/fisiología , Índice de Severidad de la Enfermedad , Espectroscopía Infrarroja Corta , Caminata/fisiología

RESUMEN

Parkinson's disease (PD) is often classified into tremor dominant (TD) and postural instability gait disorder (PIGD) subtypes. Degeneration of subcortical/cortical pathways is different between PD subtypes, which leads to differences in motor behavior. However, the influence of PD subtype on cortical activity during walking remains poorly understood. Therefore, we aimed to investigate the influence of PD motor subtypes on cortical activity during unobstructed walking and obstacle avoidance. Seventeen PIGD and 19 TD patients performed unobstructed walking and obstacle avoidance conditions. Brain activity was measured using a mobile functional near-infrared spectroscopy-electroencephalography (EEG) systems, and gait parameters were analyzed using an electronic carpet. Concentrations of oxygenated hemoglobin (HbO2) of the prefrontal cortex (PFC) and EEG absolute power from alpha, beta, and gamma bands in FCz, Cz, CPz, and Oz channels were calculated. These EEG channels correspond to supplementary motor area, primary motor cortex, posterior parietal cortex, and visual cortex, respectively. Postural instability gait disorder patients presented higher PFC activity than TD patients, regardless of the walking condition. Tremor dominant patients presented reduced beta power in the Cz channel during obstacle avoidance compared to unobstructed walking. Both TD and PIGD patients decreased alpha and beta power in the FCz and CPz channels. In conclusion, PIGD patients need to recruit additional cognitive resources from the PFC for walking. Both TD and PIGD patients presented changes in the activation of brain areas related to motor/sensorimotor areas in order to maintain balance control during obstacle avoidance, being that TD patients presented further changes in the motor area (Cz channel) to avoid obstacles.

Asunto(s)

Trastornos Neurológicos de la Marcha , Oxihemoglobinas/análisis , Enfermedad de Parkinson , Equilibrio Postural/fisiología , Corteza Prefrontal , Temblor , Anciano , Electroencefalografía/métodos , Neuroimagen Funcional/métodos , Análisis de la Marcha/métodos , Trastornos Neurológicos de la Marcha/metabolismo , Trastornos Neurológicos de la Marcha/fisiopatología , Humanos , Enfermedad de Parkinson/clasificación , Enfermedad de Parkinson/metabolismo , Enfermedad de Parkinson/fisiopatología , Corteza Prefrontal/metabolismo , Corteza Prefrontal/fisiopatología , Espectroscopía Infrarroja Corta/métodos , Temblor/metabolismo , Temblor/fisiopatología , Caminata/fisiología , Caminata/psicología

RESUMEN

This study examined whether short-term maximal resistance training employing fast-velocity eccentric knee extensor actions would induce improvements in maximal isometric torque and rate of force development (RFD) at early (<100 ms) and late phases (>100 ms) of rising torque. Twenty healthy men were assigned to two experimental groups: eccentric resistance training (TG) or control (CG). Participants on the TG trained three days a week for a total of eight weeks. Training consisted of maximal unilateral eccentric knee extensors actions performed at 180 °s-1. Maximal isometric knee extensor torque (MVC) and incremental RFD in successive 50 ms time-windows from the onset contraction were analysed in absolute terms (RFDINC) or when normalised relative to MVC (RFDREL). After eight weeks, TG demonstrated increases in MVC (28%), RFDINC (0-50 ms: 30%; 50-100 ms: 31%) and RFDREL (0-50 ms: 29%; 50-100 ms: 32%). Moreover, no changes in the late phase of incremental RFD were observed in TG. No changes were found in the CG. In summary, we have demonstrated, in active individuals, that a short period of resistance training performed with eccentric fast-velocity isokinetic muscle contractions is able to enhance RFDINC and RFDREL obtained at the early phase of rising joint torque.

Asunto(s)

Contracción Isométrica/fisiología , Fuerza Muscular/fisiología , Entrenamiento de Fuerza/métodos , Adulto , Humanos , Rodilla/fisiología , Masculino , Torque , Adulto Joven

RESUMEN

The aim of this study was to investigate the effect of unilateral balance training on the reactive recovery of balance for both trained and untrained limbs. Twenty-three subjects were randomly assigned to either a control group (CG) or a training group (TG). The latter performed six weeks of balance training for the right leg. The pre- and post-training measurements were based on single leg standing posture on a moveable force platform which moved 6 cm anteriorly. TG subjects were tested on the trained (TR) and untrained leg (UTR), whereas CG subjects were tested on the right leg (CTR). The center of pressure trajectory length (CPLEN) and average speed (CPSPD) as well as onsets of muscular activation and time to peak (EMGTP) from lower limb muscles were calculated and compared by a 2-way ANOVA (three legs×two training status). Muscular onsets were reduced after training for TR (∼19 ms, p<0.05) and UTR (∼17 ms, p<0.05) with no significant changes for CTR. No effects of training for CPLEN and medial-lateral CPSPD were found. Furthermore, the EMGTP of UTR was predominantly greater before training (∼17 ms, p<0.05). However, after training the EMGTP was similar among limbs. These results suggest that concomitant with improved balance recovery and neuromuscular reactions in TR, there is also a cross-education effect in UTR, which might be predominantly related to supraspinal adaptations shared between interconnected structures in the brain.

Asunto(s)

Adaptación Fisiológica/fisiología , Músculo Esquelético/fisiología , Modalidades de Fisioterapia , Equilibrio Postural/fisiología , Adulto , Electromiografía , Humanos , Pierna/fisiología , Masculino , Presión , Resultado del Tratamiento , Adulto Joven

RESUMEN

The aim of the study was to verify whether 8 weeks of resistance training employing maximal isokinetic eccentric (IERT) knee extensor actions would reduce the acute force loss observed after high-intensity treadmill running exercise. It was hypothesized that specific IERT would induce protective effects against muscle fatigue and ultrastructural damages, preventing or reducing the loss in mechanical muscle function after running. Subjects were tested before and after IERT protocol for maximal isometric, concentric and eccentric isokinetic knee extensor strength (60° and 180° s(-1)). In a second session, subjects performed treadmill running (~35 min) and the previously mentioned measurements were repeated immediately after running. Subsequently, subjects were randomized to training (n = 12) consisting of 24 sessions of maximal IERT knee extensors actions at 180° s(-1), or served as controls (n = 8). The effects of acute running-induced fatigue and training on isokinetic and isometric peak torque, and rate of force development (RFD) were investigated. Before IERT, running-induced eccentric torque loss at 180° s(-1) was -8 %, and RFD loss was -11 %. Longitudinal IERT led to reduced or absent acute running-induced losses in maximal IERT torque at 180° s(-1) (+2 %), being significantly reduced compared to before IERT (p < 0.05), however, RFD loss remained at -11 % (p > 0.05). In conclusion, IERT yields a reduced strength loss after high-intensity running workouts, which may suggest a protective effect against fatigue and/or morphological damages. However, IERT may not avoid reductions in explosive muscle actions. In turn, this may allow more intense training sessions to be performed, facilitating the adaptive response to running training.

Asunto(s)

Fatiga Muscular/fisiología , Músculo Esquelético/fisiología , Entrenamiento de Fuerza , Carrera/fisiología , Adulto , Fenómenos Biomecánicos , Ejercicio Físico/fisiología , Humanos , Rodilla/fisiología , Articulación de la Rodilla/fisiología , Masculino , Contracción Muscular/fisiología , Fuerza Muscular/fisiología , Torque , Adulto Joven

RESUMEN

UNLABELLED: With the universal hearing screening we can prevent auditory disorders in children. AIM: To characterize the program of neonatal auditory screening into a population of neonates. MATERIALS AND METHODS: longitudinal cohort study. We surveyed the clinic's database on neonatal auditory screening in the city of Porto Velho, Rondônia. RESULTS: Among the 6,889 newborns in the database, 5,700 (82.7%) passed and 1,189 (17.3%) failed the first screening. Of the group which failed 900 (75.7 %) returned for retesting. Among these, 15 (0.22 %) newborns had hearing loss confirmed. The most prevalent was neural hearing loss with 46.7% confirmed cases; they had hyperbilirubinemia as the most prevalent risk factor. CONCLUSION: hyperbilirubinemia was the most prevalent risk factor found in the group of hearing impaired children. The prevalence of hearing loss was of 2 in 1,000 newborns. It is important to highlight the relevant association between neural hearing loss caused by hyperbilirubinemia and sensorineural hearing loss of unknown causes.

Asunto(s)

Pérdida Auditiva/epidemiología , Hiperbilirrubinemia Neonatal/epidemiología , Tamizaje Neonatal , Brasil/epidemiología , Femenino , Pérdida Auditiva/etiología , Pruebas Auditivas/métodos , Pruebas Auditivas/estadística & datos numéricos , Humanos , Hiperbilirrubinemia Neonatal/complicaciones , Recién Nacido , Masculino , Emisiones Otoacústicas Espontáneas , Prevalencia , Estudios Retrospectivos , Factores de Riesgo

RESUMEN

Triagem auditiva neonatal de rotina é capaz de detectar precocemente alterações auditivas que poderão interferir na vida do indivíduo. OBJETIVO: Caracterizar o programa de triagem auditiva neonatal em uma população de neonatos. MATERIAL E MÉTODO: Estudo de coorte histórico longitudinal. Levantamento no banco de dados da clínica responsável pela triagem auditiva neonatal na cidade Porto Velho-RO do período de fevereiro de 2004 a outubro de 2006. RESULTADOS: Dos 6889 recém-nascidos cadastrados, 5700 (82,7 por cento) passaram e 1189 (17,3 por cento) falharam na primeira etapa da triagem. Dos que falharam 900 (75,7 por cento) compareceram para o reteste. Dentre estes, 15 (0,22 por cento) recémnascidos tiveram deficiência auditiva confirmada. A deficiência auditiva mais prevalente foi à perda auditiva neural com 46,7 por cento dos casos confirmados, tendo como indicador de risco mais prevalente a hiperbilirrubinemia. CONCLUSÃO: A hiperbilirrubinemia apresentou maior prevalência dentre os indicadores de risco encontrados nos recém-nascidos com deficiência auditiva confirmada. A prevalência de perda auditiva observada é de dois recém-nascidos para cada 1000 nascidos. Observa-se ainda uma correlação estatisticamente significante entre a perda auditiva neural com o indicador de risco hiperbilirrubinemia e perda auditiva neurossensorial com a etiologia desconhecida.

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With the universal hearing screening we can prevent auditory disorders in children. AIM: To characterize the program of neonatal auditory screening into a population of neonates. MATERIALS AND METHODS: longitudinal cohort study. We surveyed the clinic's database on neonatal auditory screening in the city of Porto Velho, Rondônia. RESULTS: Among the 6,889 newborns in the database, 5,700 (82.7 percent) passed and 1,189 (17.3 percent) failed the first screening. Of the group which failed 900 (75.7 percent) returned for retesting. Among these, 15 (0.22 percent) newborns had hearing loss confirmed. The most prevalent was neural hearing loss with 46.7 percent confirmed cases; they had hyperbilirubinemia as the most prevalent risk factor. CONCLUSION: hyperbilirubinemia was the most prevalent risk factor found in the group of hearing impaired children. The prevalence of hearing loss was of 2 in 1,000 newborns. It is important to highlight the relevant association between neural hearing loss caused by hyperbilirubinemia and sensorineural hearing loss of unknown causes.

Asunto(s)

Femenino , Humanos , Recién Nacido , Masculino , Pérdida Auditiva/epidemiología , Hiperbilirrubinemia Neonatal/epidemiología , Tamizaje Neonatal , Brasil/epidemiología , Pérdida Auditiva/etiología , Pruebas Auditivas/métodos , Pruebas Auditivas/estadística & datos numéricos , Hiperbilirrubinemia Neonatal/complicaciones , Emisiones Otoacústicas Espontáneas , Prevalencia , Estudios Retrospectivos , Factores de Riesgo

RESUMEN

Single training session (STS) may increase the power output (i.e., maximal torque) in different contraction types; however, little is known about the neuromuscular adaptations to reach this enhancement. In this way, the present study examined the differences between knee extensors EMG, kinematics, and dynamometry at 60 and 180° s(-1) before (PRE) and after (POST) a STS. Seventeen healthy males completed three different tasks: (1) 5-maximal isokinetic knee extensions, without previous habituation (PRE) at 60 and 180° s(-1); (2) in the same day and after a proper rest, two bouts of 5-maximal isokinetic contractions (STS) at 60 and 180° s(-1); and (3) in a new visit, POST consisted in new 5-maximal isokinetic contractions at 60 and 180° s(-1). The main parameters examined were: knee extensors peak torque (PT), total work (TW), EMG (prior to the movement onset, agonist and antagonist activation), rate of force (RFD), and velocity development (RVD). There was significant increase in PT [12% (60° s(-1)) and 8.7% (180° s(-1))] and TW [13.5% (60° s(-1)) and 10.7% (180° s(-1))] from PRE to POST sessions. Increases in RFD were found for both velocities (p < 0.05); however, RVD and vastus lateralis EMG prior to the movement onset were significantly higher for POST only at 60° s(-1). The RFD percentage of change (%change) was significantly correlated to %change for PT at 60° s(-1) (r(2) = 0.53) and 180° s(-1) (r(2) = 0.45). In conclusion, STS improves neural strategies to contract muscles stronger and faster at the slowest velocity, while higher velocities present different adaptations and might need more practice to further adaptations.

Asunto(s)

Adaptación Fisiológica/fisiología , Neuronas Motoras/fisiología , Movimiento/fisiología , Educación y Entrenamiento Físico/métodos , Adulto , Fenómenos Biomecánicos , Electromiografía , Humanos , Masculino , Contracción Muscular/fisiología , Fuerza Muscular/fisiología , Músculo Esquelético/fisiología , Músculo Cuádriceps/fisiología , Rango del Movimiento Articular/fisiología , Torque , Adulto Joven

RESUMEN

Testes incrementais em esteira rolante são muito utilizados para prescrição de treinamentos, havendo alterações fisiológicas e cinemáticas devido à natureza de incremento da intensidade do exercício. Contudo, a antropometria é um fator que não apresenta consenso na literatura. Neste sentido, os objetivos do presente estudo foram verificar o efeito de exercício incremental na concentração de lactato sanguíneo ([LAC]), e glicose ([GLI]), como também na frequência (FP) e amplitude de passadas (AP). Além disso, correlacionar valores de dados antropométricos (massa, altura, por cento de gordura) com as alterações existentes das [LAC] e [GLI]. Treze voluntários saudáveis realizaram teste incremental em esteira rolante (início a 8km/h, com incrementos de 1km/h a cada 3min até a exaustão). Antes e 3min após a realização do teste incremental foram registrados os valores de [LAC] e [GLI]. Durante cada intensidade do teste incremental foram realizadas avaliações da AP e FP por meio de filmagens no plano sagital. Como resultados, verificou-se que a [LAC] e [GLI] antes do teste incremental (1,94 ± 0,4mmol/L e 94,3 ± 7mg/dL, respectivamente) foram significantemente menores que os valores encontrados após o teste incremental (9,51 ± 2,7mmol/L e 126 ± 16mg/dL, respectivamente). Além disso, verificou-se aumento significante e gradativo da AP e FP ao longo do teste incremental. Correlações inversas e significantes (p < 0,05) foram encontradas entre a [LAC] e altura, massa corporal e o nível de treinamento dos voluntários. Conclui-se que a execução do teste incremental altera parâmetros cinemáticos (pela necessidade de deslocamento mais rápido) e fisiológicos (processo de fadiga muscular, em decorrência do aumento da velocidade). Além disso, voluntários menores e mais leves podem apresentar maiores concentrações de metabólitos.

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Incremental treadmill tests are widely used for prescription of aerobic and anaerobic training. Physiological and kinematics parameters are changed by the progressive nature of this activity. However, there is no consensus on how anthropometric characteristics may affect the incremental test performance. Therefore, the aims of this study were (1) to verify the effects of the incremental treadmill test on the blood lactate concentration ([LAC]), glucose concentration ([GLU]), step frequency (SF) and step length (SL), and (2) to correlate anthropometric data (body mass, height, percentbody fat) to changes in [LAC] and [GLU]. Thirteen healthy males volunteered to this study and performed an incremental running test on a treadmill (start: 8 km/h, with progressive increases [1 km/h] at each three minute until exhaustion). [LAC] and [GLU] were registered before and 3 min after the incremental test performance. SF and SL were registered for each running speed by digital images at the sagital plane. As results, we verified that [LAC] and [GLU] before the incremental test (1.94 ± 0.4 mmol/L and 94.3 ± 7 mg/dL, respectively) were significantly lower (p < 0.05) than after the incremental test (9.51 ± 2.7 mmol/L and 126 ± 16. mg/dL, respectively). In addition, SF and SL presented significant increase (p < 0.05) throughout the incremental test. [LAC] presented inverse and significant correlations (p < 0.05) to height and body mass. Thus, an incremental treadmill running test affects kinematic (SF and SL) and physiological conditions (muscular fatigue, as consequence of the speed increase). Besides this, shorter and lighter subjects may present higher metabolite concentrations after this type of test.

Asunto(s)

Humanos , Masculino , Ácido Láctico/análisis , Ácido Láctico/sangre , Índice de Masa Corporal , Prueba de Esfuerzo , Glucosa/análisis , Esfuerzo Físico

RESUMEN

The main objective of this study was to compare electromyography (EMG), heart rate (HR), and perceived exertion (PE) during different elbow flexion exercises in standing position (biceps curl [BC] and adapted BC [ABC]) and seated position (preacher BC [PBC]). Twenty healthy subjects performed the dynamic 1-repetition maximum (1RM) test. The following week (1 exercise per day), these exercises were performed at 25, 30, 35, and 40% 1RM at 1 minute for each one (20 repetitions). Biceps brachii and brachioradialis root mean square (RMS), HR, and PE were recorded in the 5th (R5), 10th (R10), 15th (R15), and 20th (R20) repetitions. Effects of exercise type (BC x ABC x PBC), load level (25% 1RM x 30% 1RM x 35% 1RM x 40% 1RM), and exercise duration (R5 x R10 x R15 x R20) were analyzed. The RMS of the elbow flexors in the PBC R20 was significantly lower than BC and ABC at 40% 1RM, and, in the same way, for all load levels, HR and PE were significantly lower in PBC R20 at 40% 1RM compared with BC and ABC. For all exercises, RMS, HR, and PE at 25% 1RM were significantly lower than at 40% 1RM. The execution of the exercises caused significant increases in the RMS, HR, and PE mainly between R5 compared with R15 and R20. In conclusion, different positions demand different neuromuscular (EMG), cardiovascular (HR), and sensorial (PE) responses. A decreased effort sensation in PBC at the same relative load level can contribute to better execution when standing and seated exercises are compared.

Asunto(s)

Codo/fisiología , Electromiografía , Frecuencia Cardíaca/fisiología , Contracción Muscular/fisiología , Músculo Esquelético/fisiología , Esfuerzo Físico/fisiología , Postura/fisiología , Entrenamiento de Fuerza/métodos , Análisis de Varianza , Antropometría , Humanos , Masculino , Fatiga Muscular/fisiología , Adulto Joven

RESUMEN

The main purposes of this study were 1) to describe and to compare blood lactate ([La]), heart rate (HR), and electromyographic (EMG) parameters during high-repetition training sessions (HRTSs), 2) to analyze the influence of physical fitness levels in these parameters, and, 3) to analyze the relationship between metabolic ([La]) and neuromuscular (EMG) responses during the HRTS. Fifteen healthy untrained women (21.7 +/- 2.1 years) performed an HRTS called Bodypump for 1 hour, which incorporated the use of variable free weights and high repetitions in a group setting. This session involved 10 music selections (M1-M10) containing resistive exercises for different muscle groups. After music selections 2 (M2), 4 (M4), 6 (M6), 7 (M7), and 9 (M9), [La], HR, and EMG (vastus medialis [VM], vastus lateralis [VL], iliocostalis lumborum [IC], and longissimus thoracis <) were determined. The [La] (M2, 4.00 +/- 1.45 mM; M7, 5.02 +/- 1.73 mM) and HR (M2, 153.64 +/- 18.89 bpm; M7, 16.14 +/- 20.14 bpm) obtained at M2 and M7 were similar but were significantly higher than the other moments of the session. However, EMG (root mean square [RMS]) at M2 (VL, VM, and LT) was lower than at M7. There was no significant correlation of strength and aerobic physical fitness with [La], RMS. In the same way, there was no significant correlation of [La] with RMS at M2 and M7. On the basis of our data, we can conclude that metabolic, cardiovascular, and EMG variables present different and independent behavior during an HRTS. Accordingly, for neuromuscular conditions during HRTS, it seems to be enough to induce improvement in the muscular strength of inferior limbs in untrained subjects.

Asunto(s)

Electromiografía , Músculo Esquelético/fisiología , Entrenamiento de Fuerza , Adulto , Umbral Anaerobio , Femenino , Frecuencia Cardíaca , Humanos , Contracción Isométrica , Ácido Láctico/sangre , Aptitud Física , Adulto Joven

RESUMEN

The aim of this study was to determine the time to restore the biceps brachii (BB) electromyographic (EMG) activity after the biceps curl (BC) exercise, at different intensities. Ten males performed initially maximal voluntary isometric contractions (MVC) of the elbow flexors, followed by one isometric submaximal contraction at 50% MVC (reference contraction). After this, four bouts of the BC at 25%, 30%, 35%, and 40% 1 RM during 1 minute (randomly assigned, with 10 minutes rest between them) were performed. During the rest intervals at preestablished moments (15 seconds, 1, 3, 5, and 10 min), isometric 50% MVC were performed. The EMG variables (root mean square [RMS], zero crossings [ZC], median frequency, [MF] and peak power [PP]) at rest were compared with reference values. Immediately after the exercise, RMS and PP increased, while ZC and MF decreased, indicating fatigue. After 1 minute most of the variables were similar to the reference. Different load levels did not affect the EMG recovery. In conclusion, the EMG variables recovered after 1 minute rest, indicating the optimal muscular condition for subsequent bouts.

Asunto(s)

Contracción Isométrica/fisiología , Fatiga Muscular/fisiología , Músculo Esquelético/fisiología , Recuperación de la Función/fisiología , Entrenamiento de Fuerza , Brazo , Electromiografía , Humanos , Masculino , Descanso/fisiología , Factores de Tiempo , Adulto Joven