A global view on how local muscular fatigue affects human performance.

There is a growing interest in scientific literature on identifying how and to what extent interventions applied to a specific body region influence the responses and functions of other seemingly unrelated body regions. To investigate such a construct, it is necessary to have a global multivariate model that considers the interaction among several variables that are involved in a specific task and how a local and acute impairment affects the behavior of the output of such a model. We developed an artificial neural network (ANN)-based multivariate model by using parameters of motor skills obtained from kinematic, postural control, joint torque, and proprioception variables to assess the local fatigue effects of the abductor hip muscles on the functional profile during a single-leg drop landing and a squatting task. Findings suggest that hip abductor muscles' local fatigue produces a significant effect on a general functional profile, built on different control systems. We propose that expanded and global approaches, such as the one used in this study, have great applicability and have the potential to serve as a tool that guarantees ecological validity of future investigations.

Structural Chirality of Polar Skyrmions Probed by Resonant Elastic X-Ray Scattering.

An escalating challenge in condensed-matter research is the characterization of emergent order-parameter nanostructures such as ferroelectric and ferromagnetic skyrmions. Their small length scales coupled with complex, three-dimensional polarization or spin structures makes them demanding to trace out fully. Resonant elastic x-ray scattering (REXS) has emerged as a technique to study chirality in spin textures such as skyrmions and domain walls. It has, however, been used to a considerably lesser extent to study analogous features in ferroelectrics. Here, we present a framework for modeling REXS from an arbitrary arrangement of charge quadrupole moments, which can be applied to nanostructures in materials such as ferroelectrics. With this, we demonstrate how extended reciprocal space scans using REXS with circularly polarized x rays can probe the three-dimensional structure and chirality of polar skyrmions. Measurements, bolstered by quantitative scattering calculations, show that polar skyrmions of mixed chirality coexist, and that REXS allows valuation of relative fractions of right- and left-handed skyrmions. Our quantitative analysis of the structure and chirality of polar skyrmions highlights the capability of REXS for establishing complex topological structures toward future application exploits.

The role of environment in the pathogenesis of keratoconus.

PURPOSE OF REVIEW: This study was conducted to demonstrate the importance of the environment in keratoconus (KC) genesis. RECENT FINDINGS: Genetic-related connective tissue disorders demonstrate the inconsistency of theories regarding KC pathogenesis since no corneal steepening was observed in the majority of these patients. Despite recent advances and decades of research into the genetics of KC, the identification of disease-causing KC genes has been frustrating. Variants found based on genome-wide and next-generation sequencing only seem to account for a small number of cases or play a limited role in KC pathogenesis. SUMMARY: The literature shows that mechanical manipulation may be the common underlying factor or the indispensable act precipitating the cascade of events leading to permanent corneal deformation. Hence, ophthalmologists have the opportunity to increase patient awareness about eye manipulation repercussions and treatment for ocular surface disorders. VIDEO ABSTRACT: http://links.lww.com/COOP/A42.

Hip, Knee, and Ankle Functional Demand During Habitual and Fast-Pace Walking in Younger and Older Women.

This study compared functional demand (FD) between older and younger women walking at habitual and fast speed and determined strength thresholds necessary to maintain FD below 80%. FD was calculated by expressing walking flexion and extension joint torques of the ankle, knee, and hip as a percentage of maximal strength. Young women had an average FD of 65% across joint actions and speeds, whereas older women had FD of 90%. In older women, the greatest FD occurred in the hip musculature. The hip, knee, and ankle extensor strengths required to maintain FD below 80% were 1.66, 1.86, and 0.57 Nm/kg, and flexor strengths were 1.24, 0.49, and 0.69 Nm/kg, respectively. Older women have limited functional reserve to increase gait speed and rely heavily on available hip strength during walking. This study identifies strength targets for the hip, knee, and ankle that will assist in maintaining FD of older women at a sustainable level.

Discriminatory Ability of Lower-Extremity Peak Torque and Rate of Torque Development in the Identification of Older Women With Slow Gait Speed.

The aim was to compare torque and rate of torque development of lower limb muscles between older women with functional and slow gait speeds to determine which muscle group is the best predictor of functional gait speed, and to establish strength thresholds needed for functional walking speed. Torque and rate of torque development of hip, knee, and ankle muscles were measured in older women who were divided in 2 groups according to gait speed: slow gait speed (<1.22 m·s-1) and functional gait speed (≥1.22 m·s-1). For each muscle group, 3 maximal isometric contractions were performed, and peak torque and rate of torque development were recorded. Older women with slow gait speed had lower peak torque than older women with functional gait speed for hip extension (28%), knee flexion (15%), knee extension (14%), and plantar flexion (16%) (all Ps < .05). Older women with slow gait speed had lower peak rate of torque development for hip flexion (29%), hip extension (37%), knee flexion (34%), knee extension (33%), and plantar flexion (19%) (all Ps < .05). Knee extension peak rate of torque development and hip extension peak torque were the better predictors of functional gait speed with thresholds of 2.96 N·m·s-1·kg-1 and 1.26 N·m·kg-1, respectively.

Applying different mathematical variability methods to identify older fallers and non-fallers using gait variability data.

BACKGROUND: The clinical assessment of gait variability may be a particularly powerful tool in the screening of older adults at risk of falling. Measurement of gait variability is important in the assessment of fall risk, but the variability metrics used to evaluate gait timing have not yet been adequately studied. OBJECTIVES: The aims of this study were (1) to identify the best mathematical method of gait variability analysis to discriminate older fallers and non-fallers and (2) to identify the best temporal, kinematic parameter of gait to discriminate between older fallers and non-fallers. METHODS: Thirty-five physically active volunteers participated in this study including 16 older women fallers (69.6 ± 8.1 years) and 19 older women non-fallers (66.1 ± 6.2 years). Volunteers were instructed to walk for 3 min on the treadmill to record the temporal kinematic gait parameters including stance time, swing time and stride time by four footswitches sensors placed under the volunteers' feet. Data analysis used 40 consecutive gait cycles. Six statistical methods were used to determine the variability of the stance time, swing time and stride time. These included: (1) standard deviation of all the time intervals; (2) standard deviation of the means of these intervals taken every five strides; (3) mean of the standard deviations of the intervals determined every five strides; (4) root-mean-square of the differences between intervals; (5) coefficient of variation calculated as the standard deviation of the intervals divided by the mean of the intervals; and (6) a geometric method calculated based on the construction of a histogram of the intervals. RESULTS: The standard deviation of 40 consecutive gait cycles was the most sensitive (100 %) and specificity (100 %) parameter to discriminate older fallers and non-fallers. CONCLUSION: The standard deviation of stance time is the kinematic gait variability parameter that demonstrated the best ability to discriminate older fallers from non-fallers. PROTOCOL NUMBER OF BRAZILIAN REGISTRY OF CLINICAL TRIALS: RBR-6rytw2.

Neuromuscular performance in the hip joint of elderly fallers and non-fallers.

BACKGROUNDS: Low strength and neuromuscular activation of the lower limbs have been associated with falls making it an important predictor of functional status in the elderly. AIM: To compare the rate of neuromuscular activation, rate of torque development, peak torque and reaction time between young and elderly fallers and non-fallers for hip flexion and extension. METHODS: We evaluated 44 elderly people who were divided into two groups: elderly fallers (n = 20) and elderly non-fallers (n = 24); and 18 young people. The subjects performed three isometric hip flexion and extension contractions. Electromyography data were collected for the rectus femoris, gluteus maximus and biceps femoris muscles. RESULTS: The elderly had 49 % lower peak torque and 68 % lower rate of torque development for hip extension, 28 % lower rate of neuromuscular activation for gluteus maximus and 38 % lower rate of neuromuscular activation for biceps femoris than the young (p < 0.05). Furthermore, the elderly had 42 % lower peak torque and 62 % lower rate of torque development for hip flexion and 48 % lower rate of neuromuscular for rectus femoris than the young (p < 0.05). The elderly fallers showed consistent trend toward a lower rate of torque development than elderly non-fallers for hip extension at 50 ms (29 %, p = 0.298, d = 0.76) and 100 ms (26 %, p = 0.452, d = 0.68).The motor time was 30 % slower for gluteus maximus, 42 % slower for rectus femoris and 50 % slower for biceps femoris in the elderly than in the young. DISCUSSION: Impaired capacity of the elderly, especially fallers, may be explained by neural and morphological aspects of the muscles. CONCLUSION: The process of senescence affects the muscle function of the hip flexion and extension, and falls may be related to lower rate of torque development and slower motor time of biceps femoris.

Utility of electromyographic fatigue threshold during treadmill running.

INTRODUCTION: We investigated 2 different methods for determining muscle fatigue threshold by electromyography (EMG). METHODS: Thirteen subjects completed an incremental treadmill running protocol for EMG fatigue threshold (EMGFT ) determination based on the critical power concept (EMGFT 1) and the breakpoint in the linear relationship between EMG amplitude and exercise intensity (EMGFT 2). Then, both the EMGFT 1 and EMGFT 2 were tested in a continuous treadmill running protocol. EMG was recorded from the rectus femoris (RF), vastus lateralis (VL), biceps femoris (BF), and lateral gastrocnemius (LG) muscles. RESULTS: For BF, EMGFT 2 was higher than EMGFT 1, and EMGFT 1 for BF was lower than EMGFT 1 for LG. EMG of RF was higher at EMGFT 2 than at EMGFT 1, and LG EMG was lower at EMGFT 2. CONCLUSIONS: EMGFT can be determined during a single treadmill running test, and EMGFT 1 may be the most appropriate method to estimate the muscle fatigue threshold during running.

Isokinetic eccentric resistance training prevents loss in mechanical muscle function after running.

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.

Electromyographic Activation and Co-contraction of the Thigh Muscles During Pilates Exercises on the Wunda Chair.

Objective: The aim of the present study was to investigate whether Pilates exercises on the Wunda chair (Going Up Front and Mountain Climb) activate the muscles rectus femoris (RF) and biceps femoris (BF) in 2 situations (foot on the pedal and foot on the seat). Methods: Sixteen young female Pilates practitioners (18-35 years old) participated in this study. The muscles of their right leg were then submitted to electromyography analysis during the exercises. Results: Significant differences were found for the RF muscle (maximal voluntary isometric contraction [%MVIC]), which was assessed and compared between the 2 exercises (Going Up Front and Mountain Climb: F = 9.83; P = .03; np2 = 0.14); 2 conditions (foot on the pedal and foot on the seat: F = 40.02; P < .001; np2 = 0.90) and interactions (F = 14.49; P < .001; np2 = 0.20) and for BF muscle (%MVIC) in the comparisons between the 2 conditions (foot on the pedal and foot on the seat: F = 27.5; P < .001; np2 = 0.82) and interactions (F = 12.57; P < .001; np2 = 0.17). The percentage of cocontraction presented the significant difference in the comparisons between the 2 conditions (foot on the pedal and foot on the seat: F = 24.07; P < .001; np2 = 0.286). Conclusion: Both Pilates exercises activated the thigh core muscles in the moderate and high categories. The highest percentage of cocontraction levels were presented when the foot was resting on the pedal.

Chiral structures of electric polarization vectors quantified by X-ray resonant scattering.

Resonant elastic X-ray scattering (REXS) offers a unique tool to investigate solid-state systems providing spatial knowledge from diffraction combined with electronic information through the enhanced absorption process, allowing the probing of magnetic, charge, spin, and orbital degrees of spatial order together with electronic structure. A new promising application of REXS is to elucidate the chiral structure of electrical polarization emergent in a ferroelectric oxide superlattice in which the polarization vectors in the REXS amplitude are implicitly described through an anisotropic tensor corresponding to the quadrupole moment. Here, we present a detailed theoretical framework and analysis to quantitatively analyze the experimental results of Ti L-edge REXS of a polar vortex array formed in a PbTiO3/SrTiO3 superlattice. Based on this theoretical framework, REXS for polar chiral structures can become a useful tool similar to x-ray resonant magnetic scattering (XRMS), enabling a comprehensive study of both electric and magnetic REXS on the chiral structures.

Improvements in metabolic and neuromuscular fitness after 12-week bodypump® training.

Greco, CC, Oliveira, AS, Pereira, MP, Figueira, TR, Ruas, VD, Gonçalves, M, and Denadai, BS. Improvements in metabolic and neuromuscular fitness after 12-week Bodypump® training. J Strength Cond Res 25(12): 3422-3431, 2011-The purpose of this study was to evaluate the effects of a 12-week group fitness training program (Bodypump®) on anthropometry, muscle strength, and aerobic fitness. Nineteen women (21.4 ± 2.0 years old) were randomly assigned to a training group (n = 9) and to a control group (n = 10). We show that this training program improved the 1 repetition maximum squats by 33.1% (p < 0.001) and the maximal isometric voluntary contraction (MVC) by 13.6% (p < 0.05). Additionally, decreases in knee extensor electromyographic activity during the MVC (30%, p < 0.01) and during the squats (15%, p < 0.05) and lunges of a simulated Bodypump® session were observed after the training. Concomitantly, blood lactate and heart rate after squats of a simulated Bodypump® session were decreased by 33 and 7% (p < 0.05), respectively. Body mass, body fat, and the running velocity at the onset of blood lactate accumulation did not change significantly in response to this training program. We conclude that Bodypump® training improves muscular strength and decreases metabolic stress during lower limb exercises. However, no significant improvements in running aerobic fitness nor in body mass and body fat were observed. Practitioners of Bodypump® training may benefit from the increased muscular strength and the decreased muscular fatigability during exercise tasks whose motor patterns are related to those involved in this training program. However, these functional gains do not seem to be transferable into running aerobic fitness.

Are isokinetic leg torques and kick velocity reliable predictors of competitive level in taekwondo athletes?

The aim of this study is to analyze how isokinetic knee and hip peak torques and roundhouse kick velocities are related to expertise level (elite vs. sub-elite) in taekwondo athletes. Seven elite and seven sub-elite athletes were tested for kick-specific variables (KSV, composed of kinematic variables and power of impact) and for concentric isokinetic peak torque (PT) at 60°/s and 240°/s. First, KSVs and PTs were compared between groups, then PTs were correlated with KSVs. Parametric variables with larger effect sizes (Cohen's d) were entered in a stepwise linear discriminant analysis (LDA), generating an equation to estimate competitive level. Between-group differences were found in hip flexors (p = 0.04, d = 0.92) and extensors (p = 0.04, d = 0.96) with PT at 240°/s. Hip flexion PT at 60°/s and 240°/s correlated negatively with kick time (R = -0.46, p = 0.0499 and R = -0.62, p = 0.01 respectively). Hip flexion torque at 60°/s correlated positively (R = 0.52, p = 0.03) with peak linear velocity of the foot (LVF) and power of impact (R = 0.51, p = 0.03). Peak torque of hip extension at 60°/s and hip abduction at 240°/s also correlated with LVF (R = 0.56, p = 0.02 and R = 0.46, p = 0.0499). Hip extension at 60°/s correlated positively with peak linear velocity of the knee (R = 0.48, p = 0.04). The LDA showed an accuracy of 85.7% (p = 0.003) in predicting expertise level based on hip flexion and extension torques at 240°/s and on knee extension velocity during the kick. The study demonstrates that hip muscle strength is probably the dominant muscular factor for determining kick performance. Knee angular velocity combined with hip torques is the best discriminator for competitive level in taekwondo athletes.

Core muscle activation during Pilates exercises on the Wunda chair.

OBJETIVES: The Pilates method, developed by Joseph Pilates (1886-1967), has been widely used to improve trunk stability, muscle flexibility and strength, physical fitness, and body awareness. To measure the electromyography of four trunk muscles during three Pilates exercises carried out of the wunda chair. DESING: cross-section study. METHODS: Sixteen women participated in this study with a height and body weight of 1.64 ± 0.04 m and 58.7 ± 7.4 kg, respectively, and a mean age of 27.6 ± 3.7 years. Rectus abdominis (RA), internal oblique (IO), longissimus (LO), and multifidus (MU) muscles was evaluated by electromyographic (EMG) tests activity during three Pilates exercises: going up front (GF), mountain climb (MC), and swan (SW). EMG was normalized and expressed in the time domain, by the RMS. RESULTS: The highest EMG values concerning the four muscles were observed for the MC exercise, followed by GF and SW (ANOVA: p = 0.0001, p = 0.04, p = 0.0002, and p = 0.0013, respectively). Our results show that the three Pilates exercises could recruit all the muscles, with a moderate activity intensity. The ANOVA; p < 0.05 showed significant difference between the muscles, concerning SW (p = 0.0002). CONCLUSION: Our results show that the three Pilates exercises could recruit all the muscles, with a moderate activity intensity.

Effects of a single habituation session on neuromuscular isokinetic profile at different movement velocities.

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.

Effect of load level on the emg spectra of longissimus thoracis muscle during isometric fatiguing contractions.

The present study analyzed the effect of different magnitudes of isometric contraction of longissimus thoracis muscle until fatigue by means power spectra analysis. Eight healthy male subjects volunteered for this study The electromyography signals were sampled at 1 kHz using surface electrodes placed bilaterally over the longissimus thoracis muscle at the level L1. The isometric contraction was made at 30% and 60% of isometric maximal voluntary contraction (MVC) randomly in the MA ISOSTATION 2001 with the trunk at 45 degrees of flexion. A gain of 1000, a high pass filter at 20 Hz and low pass filter at 500 Hz was used. The endurance time with the load of 30% was longer than the load of 60%. It was found a significant drop in the median frequency and in the mean power frequency for both loads in both sides with progression of time. Also, analyzing the load effect, it was found significant differences in the total power and peak power for the longissimus thoracis in the interval of 0-100%, with lower values to 30%. The present study allows verifying the longissimus thoracis muscular fatigue by means the electromiographics parameters. It was showed that the total power and the peak power variables are sensible due changes in the load, once there are low values for the low loads.

Co-contraction of the core muscles during Pilates exercise on the Wunda Chair.

BACKGROUND: The co-contraction of the core muscles has been reported as the key mechanism towards spinal stability. Classic Pilates exercises aimed at these muscles are known to improve the stability and strength of the trunk without damaging the deep structures of the spine. OBJECTIVE: To evaluate the co-contraction of the mobilizing (rectus abdominis; longissimus) and stabilizing (multifidus; internal oblique) trunk muscles during Pilates exercises - going up front, mountain climber, and swan. METHODS: Sixteen women, all Pilates practitioners, participated in the study. The stabilizing and mobilizing muscles of the trunk (right side) were submitted to electromyography to calculate the percentage of co-contraction during the exercises. One-way repeated measures analysis of variance (ANOVA) was used to verify the difference in %COCON between stabilizers and mobilizers among the three exercises. The post-hoc Bonferroni test (P< 0.01) was applied when necessary. The paired t-test (P< 0.01) was used to verify the difference in %COCON between stabilizers and mobilizers separately for each exercise. RESULTS: The co-contraction values of the stabilizers were higher than those of the mobilizers for all exercises. The going up front (stabilizers) and the swan (mobilizers) exercises showed the highest %COCON values. CONCLUSIONS: The Pilates method is effective for either rehabilitating pathologies or training the trunk muscles in healthy individuals and athletes.

Positioning during resistance elbow flexor exercise affects electromyographic activity, heart rate, and perceived exertion.

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.

Physiological and neuromuscular profile during a bodypump session: acute responses during a high-resistance training session.

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.

Electromyographic evaluation of trunk core muscles during Pilates exercise on different supporting bases.

OBJECTIVE: To evaluate the electromyographic (EMG) activity of the rectus abdominis (RA) and internal oblique (IO) muscles during Pilates exercise on different trunk supporting bases. METHODS: Sixteen female Pilates practitioners participated in the study. EMG of the RA and OI muscles was evaluated during the double leg stretch (DLS) exercise on three different supporting bases - mat, long box, and short box. Trunk stability varies according to the size and type of the base. To normalize the data, the RMS value (EMG) obtained during the DLS exercise was divided by the RMS value from the torque test - the maximal voluntary isometric contraction (MVIC) - and multiplied by 100 (%MVIC). One-way repeated-measured analysis of variance (ANOVA) and Bonferroni tests were used to compare data concerning the supporting bases and Student t-test regarding the muscles (p < 0.05). RESULTS: The comparison among the bases involving each muscle - RA or IO (p < 0.05) - showed significant difference (%MVIC) between the mat and the short box. No significant difference was observed between the muscles concerning the exercise on the mat (p = 0.9266), on the long box (p = 0.5113) and on the short box (p = 0.2972). CONCLUSION: The short box increased the activity of the rectus abdominis and internal oblique muscles during exercise. The DLS exercise was able to challenge the stability of the trunk and thus recruit its stabilizer and mobilizer muscles at the same intensity.