[Show abstract][Hide abstract] ABSTRACT: In this work we present a scientific literature review on core stability with the aim of clarifying the meaning of this concept and its relation with sport performance and injury. The results of this review show that the use of the term core stability is ambiguous, as there is a great terminological confusion in both scientific literature and professional fields. Several biomechanical and epidemiological studies suggest that the neuromuscular control deficit of core stability is related to low back pain and lower limb injuries. Nevertheless, despite the fact that core stability exercises are key elements in sport training programs, there is not enough evidence to establish a clear relation between the practice of these exercises and the improvement in sport performance.
Revista Andaluza de Medicina del Deporte 06/2015; 36(2). DOI:10.1016/j.ramd.2014.02.004
[Show abstract][Hide abstract] ABSTRACT: Trunk exercise speed has significant effects on neuro-mechanical demands; however, the influence of a variety of exercise speeds on motor control of the trunk displacement remains unknown. The aim of this study was to assess the effect of performance speed on trunk motion control during the curl-up exercise by analyzing the kinematic variance about the sagittal trajectory. Seventeen subjects volunteered to perform curl-ups at different cadences controlled by a metronome. Standard deviation (SD) and range (RG) of shoulder girdle medial-lateral displacement (SGML) and detrended fluctuation analysis (DFA) of SGML were calculated to examine linear variability and long range autocorrelation of medial-lateral upper trunk displacements, respectively. In addition, SD, RG and DFA of centre of pressure medial-lateral displacement (COPML) were performed to analyze the behavior of the motor system while controlling trunk displacement. Although SD and RG of COPML increased as speed increased, the curl-up cadence did not have significant effects on SD and RG of SGML. These results suggest that although high speed curl-ups challenged participants' ability to carry out medial-lateral adjustments, an increase of performance speed did not modify the linear variability about the sagittal trajectory. Regarding DFA, the scaling exponent α of SGML and COPML was higher for the fastest movements, mainly in long term fluctuations. Therefore, to maintain the target trajectory, participants used different strategies depending on performance speed. This is to say, there were less trajectory changes when participants performed the fastest exercises.
Journal of Human Kinetics 06/2015; 46(1):29-37. DOI:10.1515/hukin-2015-0031 · 0.70 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Despite core exercise programs are broadly used to increase muscle function and to promote low back health, there is a lack of scientific evidence on some of the most important characteristics of trunk exercise programs, as for example training frequency. This study aimed to compare the short-term effect of training frequencies of 1, 2 and 3 days per week (d/wk) on abdominal muscle endurance in untrained adolescents. One hundred and eighteen high-school students (59 men and 59 women) with no previous experience in structured abdominal exercise programs were assigned randomly to groups that trained 1 d/wk (G1; N.=21), 2 d/wk (G2; N.=27), 3 d/wk (G3; N.=23), or to a control group (CG; N.=47) that did not train. The training groups performed crunch and cross-crunch exercises 1, 2 or 3 d/wk during six weeks. Before and after the training period, the bench trunk-curl test (BTC test) was carried out to assess abdominal muscle endurance. Men obtained higher BTC test scores than women before and after training. Training frequencies of 1, 2 and 3 d/wk provided a significant increase in BTC test scores; however, no significant differences between the three groups' scores were found after training. Therefore, a small dose of crunch exercise training (1 d/wk) may be sufficient stimulus to increase abdominal endurance in untrained male and female adolescents, at least during the first weeks of an abdominal exercise program, which seems a very relevant finding in terms of time-cost efficiency.
The Journal of sports medicine and physical fitness 04/2015; 55(4):280-9. · 0.76 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A glenohumeral internal rotation deficit of the dominant shoulder relative to the non-dominant shoulder (GIRD) is considered a risk factor for shoulder injury in overhead athletes. The aim of this study was to investigate whether professional tennis players with a history of self-reported shoulder pain show differences in rotation range of motion (ROM) of the dominant and non-dominant shoulder compared to asymptomatic controls. Forty-seven professional tennis players belonging to the Association of Tennis Professionals World Tour took part in the study: 19 with shoulder pain history and 28 without. Passive shoulder ROM was measured using a process of photography and software calculation of angles. The dominant shoulder had reduced internal rotation (IR) ROM and total rotation ROM, and increased external rotation (ER) ROM compared to the non-dominant side. These differences did not correlate significantly with years of tennis practice, years of professional play, nor the players' age. However, glenohumeral rotation ROMs correlated negatively with the duration of tennis practice and players' age. Although tennis players with shoulder pain history showed less IR ROM in both shoulders compared with the no-pain group, no significant differences between groups were found for ER ROM, side-to-side ROM asymmetries, years of tennis practice or years of professional play. In professional tennis players, limited IR ROM rather than a GIRD, seems to be associated with shoulder pain history, duration of tennis practice and the players' age, when compared to a similar cohort with no history of shoulder pain.
[Show abstract][Hide abstract] ABSTRACT: It is theorized that the development of the ability to stabilize the trunk may improve the performance of a judoka because it improves body balance control and optimizes force transmission from the lower extremities to the upper limbs. However, there is a lack of scientific evidence to establish a clear relationship between trunk stability and performance in judo.Aim: The purpose of this study was to determine whether the quantification of trunk stability and muscular strength and endurance allowed differentiation between national level (n = 7) and international level judoka (n = 6). In addition, the relationship between trunk stability and muscular strength and endurance of the muscles involved in trunk stability control was analyzed.Method: To assess trunk stability, trunk responses to sudden loads applied by a pneumatic mechanism were analyzed, as well as trunk postural control through an unstable sitting paradigm. Muscular strength and endurance were assessed via a flexion and extension trunk test using an isokinetic dynamometer.Results/Conclusions: International level judokas showed lower CoP displacement in the most complex task in unstable seat (7.00 ± 1.19 vs 8.93 ± 1.45 mm, T = .025) and higher absolute and relative peak torque in extensor muscles (7.05 ± 0.87 vs 5.74 ± 0.72 Nm, T = .013) than national level judoka. According to these results, core stability and trunk muscular condition are important qualities in the physical training of elite judoka. Correlational analysis found no relation between the analyzed variables, thus muscular strength and endurance appear to have a non-significant effect on performance in the trunk stability tests.
[Show abstract][Hide abstract] ABSTRACT: Abstract The influence of speed on trunk exercise technique is poorly understood. The aim of this study was to analyse the effect of movement speed on the kinematics and kinetics of curl-up, sit-up and leg raising/lowering exercises. Seventeen healthy, recreationally trained individuals (13 females and 4 males) volunteered to participate in this study. Four different exercise cadences were analysed: 1 repetition/4 s, 1 repetition/2 s, 1 repetition/1.5 s and 1 repetition/1 s. The exercises were executed on a force plate and recorded by three cameras to conduct a 3D photogrammetric analysis. The cephalo-caudal displacement of the centre of pressure and range of motion (ROM) of six joints describing the trunk and hip movements were measured. As sit-up and curl-up speed increased, hip and knee ROM increased. Dorsal-lumbar and upper trunk ROM increased with speed in the curl-up. Faster cadence in the sit-up exercise had minimal effect on trunk ROM: only the upper trunk ROM decreased significantly. In the leg raising/lowering exercise there was a decrease in the pelvic tilt and hip ROM, and increased knee flexion ROM. During higher speed exercises, participants modified their technique to maintain the cadence. Thus, professionals would do well to monitor and control participants' technique during high-speed exercises to maintain performance specificity. Results also suggest division of speed into two cadence categories, to be used as a reference for prescribing exercise speed based on preferred outcome goals.
European Journal of Sport Science 11/2013; DOI:10.1080/17461391.2013.860483 · 1.31 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Active range of motion trials are frequently used as a baseline for normalizing other data. However, previous research has not focused on methods utilized to achieve maximum active range of motion.
Twenty-seven males (age 20-38 years) participated in this study. Active hip extension in upright standing was compared to active lumbar extension with regards to degrees of total hip and spine extension obtained. Similarly, active spine rotation whereby participants attempted to constrain associated pelvis and hip rotation was compared to rotation trials in which the pelvis and hips were free to rotate concurrently. An infra-red motion capture system and associated software were used to capture movement and determine joint angles.
Results indicate that average degrees of hip extension did not differ between the two methods (p = 0.138), nor did either method result more frequently in the highest measurement. Spine extension values were significantly greater in the active spine extension manoeuvre compared to the associated back extension that occurred when participants were asked to actively extend their hip (p < 0.001). Average degrees of spine rotation were greater in the unconstrained trials: when concurrent hip and pelvis rotation were allowed to take place (p < 0.001). Of the 27 participants, 23 obtained maximum rotation during the unconstrained trials.
To obtain maximum active hip joint extension, both hip and back extension trials should be collected. Maximum spine rotation is more likely to occur when the pelvis and hips are unconstrained.
[Show abstract][Hide abstract] ABSTRACT: Brotons-Gil, E, García-Vaquero, MP, Peco-González, N, and Vera-Garcia, FJ. Flexion-rotation trunk test to assess abdominal muscle endurance: Reliability, learning effect, and sex differences. J Strength Cond Res 27(6): 1602–1608, 2013—Trunk endurance tests are generally performed in sagittal or frontal plane. However, trunk field tests that measure the endurance of the rotator muscles are lacking. In view of this situation, we developed a flexion-rotation trunk test (FRT test) to assess the oblique abdominal muscle endurance. This new field test consists mainly in performing the maximum number of upper trunk flexion and rotation movements (reps) possible in 90 seconds. The objectives of this study were to analyze the FRT test reliability and to examine the effect of both the repetition and sex on test results. Fifty-one recreationally trained men (n = 35) and women (n = 16) completed 4 trials of the FRT test (T1, T2, T3, and T4), separated by 7 days each. The scores increased significantly between T1 and T3 (p < 0.001), showing a clear learning effect, but the increase between T3 and T4 was only 4.25% (p = 0.108). The intraclass correlation coefficients (ICCs) between trials were ≥0.83 and the standard errors of measurement (SEMs) ≤7.54 reps. The ICCs between trials increased, and SEMs decreased with test repetition, reaching an ICC of 0.94 and an SEM of 6.46 reps between T3 and T4. The comparison between sexes showed a higher abdominal endurance in men when compared with that in women (p = 0.003), and also a higher learning effect in men, especially at the beginning of the study. These findings suggest that, the FRT test is a reliable field protocol that differentiates between the abdominal endurance of men and women. However, it is necessary to perform an extensive familiarization period before testing (at least 3 trials of practice) to make learning effect negligible.
The Journal of Strength and Conditioning Research 06/2013; 27(6):1602-1608. DOI:10.1519/JSC.0b013e31827124d9 · 1.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Studies about the relationship between complexity and performance in upright standing balance have yielded mixed results and interpretations. The aim of the present study was to assess how the increasing difficulty in standing balance task affects performance and the complexity of postural sway and neuromuscular activation. Thirty-two young healthy participants were asked to stand still on a stability platform with visual feedback in three levels of difficulty. EMG signals from gastrocnemius medialis, tibialis anterior, rectus femoris and biceps femoris were measured with surface electromyography. As task difficulty increased, the amplitude of postural sway also increased. In the antero-posterior axis, Fuzzy Entropy (complexity) of postural sway decreased from the stable condition to the medium instability condition, and increased again at the highest instability condition. Fuzzy Entropy in the medio-lateral axis was higher in the stable condition; however, no differences were observed between the two instability conditions. Lower values of Fuzzy Entropy in postural sway during stable condition correlated with greater percent increases in postural sway in medio-lateral and antero-posterior axis from the standing still condition to the highest instability condition. In addition, mean and coefficient of variation of EMG increased and Fuzzy Entropy of EMG decreased when the difficulty in standing balance tasks increased. These results suggest that the higher postural sway complexity in stable condition, the greater capacity of the postural control system to adapt to the platform instability increases. In addition, changes in the complexity of EMG modulated by task difficulty do not necessarily reflect similar changes on postural sway.
Human movement science 06/2012; 31(5). DOI:10.1016/j.humov.2012.01.002 · 2.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to analyze trunk muscle activity during bridge style stabilization exercises, when combined with single and double leg support strategies. Twenty-nine healthy volunteers performed bridge exercises in 3 different positions (back, front and side bridges), with and without an elevated leg, and a quadruped exercise with contralateral arm and leg raise ("bird-dog"). Surface EMG was bilaterally recorded from rectus abdominis (RA), external and internal oblique (EO, IO), and erector spinae (ES). Back, front and side bridges primarily activated the ES (approximately 17% MVC), RA (approximately 30% MVC) and muscles required to support the lateral moment (mostly obliques), respectively. Compared with conventional bridge exercises, single leg support produced higher levels of trunk activation, predominantly in the oblique muscles. The bird-dog exercise produced greatest activity in IO on the side of the elevated arm and in the contralateral ES. In conclusion, during a common bridge with double leg support, the antigravity muscles were the most active. When performed with an elevated leg, however, rotation torques increased the activation of the trunk rotators, especially IO. This information may be useful for clinicians and rehabilitation specialists in determining appropriate exercise progression for the trunk stabilizers.
Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 03/2012; 22(3):398-406. DOI:10.1016/j.jelekin.2012.02.017 · 1.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to compare trunk muscular recruitment and lumbar spine kinematics when motion was constrained to either the thorax or the pelvis. Nine healthy women performed four upright standing planar movements (rotations, anterior-posterior translations, medial-lateral translations, and horizontal circles) while constraining pelvis motion and moving the thorax or moving the pelvis while minimizing thorax motion, and four isometric trunk exercises (conventional curl-up, reverse curl-up, cross curl-up, and reverse cross curl-up). Surface EMG (upper and lower rectus abdominis, lateral and medial aspects of external oblique, internal oblique, and latissimus dorsi) and 3D lumbar displacements were recorded. Pelvis movements produced higher EMG amplitudes of the oblique abdominals than thorax motions in most trials, and larger lumbar displacements in the medial-lateral translations and horizontal circles. Conversely, thorax movements produced larger rotational lumbar displacement than pelvis motions during rotations and higher EMG amplitudes for latissimus dorsi during rotations and anterior-posterior translations and for lower rectus abdominis during the crossed curl-ups. Thus, different neuromuscular compartments appear when the objective changes from pelvis to thorax motion. This would suggest that both movement patterns should be considered when planning spine stabilization programs, to optimize exercises for the movement and muscle activations desired.
Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 09/2011; 21(6):893-903. DOI:10.1016/j.jelekin.2011.08.003 · 1.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objective
To determine the effects of repeated hamstring stretching on the muscle activation pattern of the erector spinae during trunk flexion and extension movements.
[Show abstract][Hide abstract] ABSTRACT: The aims were to describe the behavior of the subtalar joint and foot in the race walk, and seek for correlations between them and the footprint. 12 race walkers participated in the study. The arch index was calculated on their footprints. Plantar pressures were measured and 3D photogrammetry used on a single support while they race walked at their own competitive speed. Maximum pressures were calculated in each region of the foot and also the maximum and minimum values of the three angles that describe the subtalar joint. The maximum pronation was higher than that described in the walking gait and similar to that of the running gait (-13.6 ± 3.90). In the beginning of the support the subtalar joint was between the walking and the running gaits. This suggests that the cushioning mechanism of this joint is adjusted according to the type of locomotion. The region of the foot that registered higher pressures was the external rearfoot (21.02 kPa/kg) followed by the internal forefoot (13.12 kPa/kg), showing a different behaviour to that of the running gait, in which both present similar maximum pressures. The subjects with lower arches tended to support with the internal face of the foot (r=-0.713) and with the leg inclined medially (r=0.874). Likewise, the racewalkers with higher arches registered higher pressures in the external part of the rearfoot, whereas the lowest ones did it in the internal part of the midfoot. Key Words: Biomechanics, race walk, footprint, subtalar joint, plantar pressure. Los objetivos fueron describir el comportamiento de la articulación subastragalina y el pie en la marcha atlética y buscar correlaciones entre estos y la huella plantar. Participaron 12 marchadores. Se calculó el índice del arco sobre sus huellas plantares. Se registraron presiones plantares y se aplicó fotogrametría 3D durante un apoyo mientras marchaban a velocidad individual de competición. Se calcularon las presiones máximas en cada región del pie y los valores máximos y mínimos de los tres ángulos que describen la articulación subastragalina. La máxima pronación ha mostrado ser mayor que la descrita en la marcha común y similar a la de la carrera (-13.6±3.90). Al inicio del apoyo, la articulación subastragalina se encuentra entre la marcha y la carrera, sugiriendo un ajuste en su mecanismo amortiguador según el tipo de locomoción. La zona que registra mayores presiones es el retropié externo (21.02 kPa/kg) yseguida lu ego del antepié interno (13.12 kPa/kg), a diferencia de la carrera, que presenta presiones máximas similares. Los sujetos con pies más planos tienden a apoyar con la cara interna del pie (r=-0.713) y con la pierna inclinada medialmente (r=0.874). Asimismo, los marchadores con pies más cavos registran mayores presiones en la parte externa del retropié y, mientras que los más planos lo hacen en la parte interna del mediopié.Palabras Clave: Biomecánica, marcha atlética, huella plantar, articulación subastragalina, presiones plantares.
[Show abstract][Hide abstract] ABSTRACT: Objective
To analyze the immediate effect of the application of Kinesio Tape (KT) on reflex response of biceps femoris and gastrocnemius lateralis subject to a sudden and unexpected perturbation applied to the knee by means of a technique known as quick release.
[Show abstract][Hide abstract] ABSTRACT: To compare trunk muscle activation patterns and trunk kinematics when using an oscillating blade in standing and unsupported sitting postures, and with different orientations of the blade.
A cross-sectional survey of trunk muscle activities and lumbar motion.
Biomechanics research laboratory.
Healthy men (N=13).
An oscillating blade was held with 2 hands and oscillated with vertical and horizontal orientations of blade. These exercises were performed both in an erect standing position and in an erect sitting position.
Surface electromyography from 14 trunk and 2 shoulder muscles, together with lumbar angular displacement in the 3 planes of motion, were measured while subjects used an oscillating blade at different performance variations. Electromyographic signals were normalized to isometric maximal voluntary contraction (MVC) amplitudes.
With the exception of internal oblique and anterior deltoid for the horizontal condition, and erector spinae at L5 level for the vertical condition, the subject's posture had no effect on trunk muscular recruitment when using the oscillating blade. The vertical blade orientation resulted in higher amplitudes of spine rotation on the horizontal plane and produced the greatest activation levels of the internal oblique (47% MVC), pectoralis major (33% MVC), and external oblique (23% MVC). On the other hand, the horizontal orientation resulted in the greatest activation levels of erector spinae at T9 level (28% MVC), latissimus dorsi (26% MVC), and rectus abdominis (17% MVC).
Muscle activation and spine motion from using an oscillating blade were not affected by the standing or sitting posture of the subject. The choice of blade orientation was more important, because it defined the main group of muscles recruited during the exercise.
Archives of physical medicine and rehabilitation 07/2009; 90(6):1055-60. DOI:10.1016/j.apmr.2008.12.015 · 2.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Normalization of the surface electromyogram (EMG) addresses some of the inherent inter-subject and inter-muscular variability of this signal to enable comparison between muscles and people. The aim of this study was to evaluate the effectiveness of several maximal voluntary isometric contraction (MVC) strategies, and identify maximum electromyographic reference values used for normalizing trunk muscle activity. Eight healthy women performed 11 MVC techniques, including trials in which thorax motion was resisted, trials in which pelvis motion was resisted, shoulder rotation and adduction, and un-resisted MVC maneuvers (maximal abdominal hollowing and maximal abdominal bracing). EMG signals were bilaterally collected from upper and lower rectus abdominis, lateral and medial aspects of external oblique, internal oblique, latissimus dorsi, and erector spinae at T9 and L5. A 0.5s moving average window was used to calculate the maximum EMG amplitude of each muscle for each MVC technique. A great inter-subject variability between participants was observed as to which MVC strategy elicited the greatest muscular activity, especially for the oblique abdominals and latissimus dorsi. Since no single test was superior for obtaining maximum electrical activity, it appears that several upper and lower trunk MVC techniques should be performed for EMG normalization in healthy women.
Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 05/2009; 20(1):10-6. DOI:10.1016/j.jelekin.2009.03.010 · 1.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this article is to synthesize the literature on studies that investigate electromyographic activity of abdominal muscles during abdominal exercises performance.
MEDLINE and Sportdiscus databases were searched, as well as the Web pages of electronic journals access, ScienceDirect, and Swetswise, from 1950 to 2008. The terms used to search the literature were abdominal muscle and the specific names for the abdominal muscles and their combination with electromyography, and/or strengthening, and/or exercise, and/or spine stability, and/or low back pain. The related topics included the influence of the different exercises, modification of exercise positions, involvement of different joints, the position with supported or unsupported segments, plane variation to modify loads, and the use of equipment. Studies related to abdominal conditioning exercises and core stabilization were also reviewed.
Eighty-seven studies were identified as relevant for this literature synthesis. Overall, the studies retrieved lacked consistency, which made it impossible to extract aggregate estimates and did not allow for a rigorous meta-analysis. The most important factors for the selection of abdominal strengthening exercises are (a) spine flexion and rotation without hip flexion, (b) arm support, (c) lower body segments involvement controlling the correct performance, (d) inclined planes or additional loads to increase the contraction intensity significantly, and (e) when the goal is to challenge spine stability, exercises such as abdominal bracing or abdominal hollowing are preferable depending on the participants' objectives and characteristics. Pertaining to safety criteria, the most important factors are (a) avoid active hip flexion and fixed feet, (b) do not pull with the hands behind the head, and (c) a position of knees and hips flexion during upper body exercises.
Further replicable studies are needed to address and clarify the methodological doubts expressed in this article and to provide more consistent and reliable results that might help us build a body of knowledge on this topic. Future electromyographic studies should consider addressing the limitations described in this review.
Journal of manipulative and physiological therapeutics 03/2009; 32(3):232-44. DOI:10.1016/j.jmpt.2009.02.007 · 1.25 Impact Factor