Francisco J Vera-Garcia

Universidad Miguel Hernández de Elche, Elche, Valencia, Spain

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Publications (21)27.38 Total impact

  • [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;
  • Janice M Moreside, David Barbado, Casto Juan-Recio, Francisco J Vera-Garcia
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    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.
    Manual therapy 06/2013; · 2.32 Impact Factor
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    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; · 2.15 Impact Factor
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    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. · 2.00 Impact Factor
  • Francisco J Vera-Garcia, Janice M Moreside, Stuart M McGill
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    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. · 2.00 Impact Factor
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    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.
    Fisioterapia 01/2010; 32(1):4-10.
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    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.
    Fisioterapia 01/2010; 32(4):165-171.
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    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. · 2.18 Impact Factor
  • Francisco J Vera-Garcia, Janice M Moreside, Stuart M McGill
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    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. · 2.00 Impact Factor
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    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 01/2009; 32(3):232-44. · 1.06 Impact Factor
  • Janice M Moreside, Francisco J Vera-Garcia, Stuart M McGill
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    ABSTRACT: Previous studies analyzing neuromuscular independence of the abdominal wall have involved a participant population with no specific training in separating individual muscle segments. We chose to study nine women trained in the art of middle-eastern dance, anticipating they may have unique skills in motor control. Specifically, we were searching for evidence of separation of upper rectus abdominis (URA) from lower rectus abdominis (LRA), as well as understanding what role the oblique muscles play in abdominal wall synergies. EMG analysis was done on eight trunk muscles bilaterally as the dancers participated in 30 dance, planar, and curl-up activities. The filtered data were then cross-correlated to determine the time lag between pairs of signals. Only three dance movements demonstrated consistent evidence of an ability to separate URA/LRA activation timing. The external and internal oblique muscles tend to align themselves temporally with the LRA. However, these findings were only evident in these three specific "belly-roll" conditions, all with low levels of muscle activation, and no external torque. Evidence of significantly different activation levels (% MVC) between URA/LRA was demonstrated in eight conditions, all of which required various pelvis movements with minimal thorax motion.
    Journal of Electromyography and Kinesiology 09/2008; 18(4):527-37. · 1.64 Impact Factor
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    ABSTRACT: Although exercise speed is an acute variable to prescribe abdominal strengthening programs, current literature lacks studies analyzing the influence of speed on muscular activation in abdominal exercises. The aim of this work was to determine the influence of trunk curl-up speed on the amplitude of muscular activation and the way in which the trunk muscles were coactivated. Twenty recreationally trained volunteers (16 women and 4 men; age, 23.7 +/- 4.3 years; height, 166.2 +/- 6.3 cm; mass, 61.0 +/- 8.2 kg) participated in this study. Surface electromyographic data were collected from the rectus abdominis, external oblique, internal oblique, and erector spinae during 4 different curl-up cadences [1 repetition per 4 seconds (C4), 1 repetition per 2 seconds (C2), 1 repetition per 1.5 seconds (C1.5), 1 repetition per 1 second (C1)], and during maximum speed curl-ups (Cmax). The electromyographic amplitude was averaged and normalized using maximum voluntary isometric contractions (MVICs). Statistical analyses were performed using repeated-analyses of variance. Normalized electromyographic mean amplitudes of trunk muscles increased with curl-up speed. Although the rectus abdominis (ranged from 23.3% of MVICs at C4 to 49.6% of MVICs at Cmax) and internal oblique (ranged from 19.2% of MVICs at C4 to 48.5% of MVICs at Cmax) were the most active analyzed muscles at each speed, contribution of the external oblique increased appreciably with velocity (ranged from 5.3% of MVICs at C4 to 33.3% of MVICs at Cmax). Increasing trunk curl-up speed supposed greater trunk muscular coactivation, probably required for a faster performance and to ensure dynamic spine stability. On the basis of our findings, curl-up speed had an important effect on trunk muscular recruitment and must be taken into account when prescribing exercise programs for abdominal conditioning.
    The Journal of Strength and Conditioning Research 06/2008; 22(3):684-90. · 1.80 Impact Factor
  • Juan Carlos Santana, Francisco J Vera-Garcia, Stuart M McGill
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    ABSTRACT: This study compared the standing cable press (SCP) and the traditional bench press (BP) to better understand the biomechanical limitations of pushing from a standing position together with the activation amplitudes of trunk and shoulder muscles. A static biomechanical model (4D Watbak) was used to assess the forces that can be pushed with 2 arms in a standing position. Then, 14 recreationally trained men performed 1 repetition maximum (1RM) BP and 1RM single-arm SP exercises while superficial electromyography (EMG) of various shoulder and torso muscles was measured. The 1RM BP performance resulted in an average load (74.2 +/- 17.6 kg) significantly higher than 1RM single-arm SP (26.0 +/- 4.4 kg). In addition, the model predicted that pushing forces from a standing position under ideal mechanical conditions are limited to 40.8% of the subject's body weight. For the 1RM BP, anterior deltoid and pectoralis major were more activated than most of the trunk muscles. In contrast, for the 1RM single-arm SP, the left internal oblique and left latissimus dorsi activities were similar to those of the anterior deltoid and pectoralis major. The EMG amplitudes of pectoralis major and the erector muscles were larger for 1RM BP. Conversely, the activation levels of left abdominal muscles and left latissimus dorsi were higher for 1RM right-arm SP. The BP emphasizes the activation of the shoulder and chest muscles and challenges the capability to develop great shoulder torques. The SCP performance also relies on the strength of shoulder and chest musculature; however, it is whole-body stability and equilibrium together with joint stability that present the major limitation in force generation. Our EMG findings show that SCP performance is limited by the activation and neuromuscular coordination of torso muscles, not maximal muscle activation of the chest and shoulder muscles. This has implications for the utility of these exercise approaches to achieve different training goals.
    The Journal of Strength and Conditioning Research 12/2007; 21(4):1271-7. · 1.80 Impact Factor
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    ABSTRACT: Much discussion exists about which is the most effective technique to improve spine stability. The purpose of this study was to evaluate the effectiveness of abdominal bracing and abdominal hollowing maneuvers to control spine motion and stability against rapid perturbations. Eleven healthy males were posteriorly loaded in different experimental conditions: resting with no knowledge of the perturbation timing; performing each of the stabilization maneuvers at 10%, 15% and 20% of internal oblique maximum voluntary contraction with no knowledge of the perturbation timing; and naturally coactivating the trunk muscles when perturbation timing was known. An EMG biofeedback system was used to control the pattern and intensity of abdominal coactivation. The muscular preactivation of seven trunk muscles (bilaterally registered), the applied force, and the torso muscular and kinematic responses to loading were measured; and the spine stability and compression were modeled. The hollowing maneuver was not effective for reducing the kinematic response to sudden perturbation. On the contrary, the bracing maneuver fostered torso cocontraction, reduced lumbar displacement, and increased trunk stability, but at the cost of increasing spinal compression. When the timing of the perturbation was known, the participants were able to stabilize the trunk while imposing smaller spine compressive loads.
    Journal of Electromyography and Kinesiology 11/2007; 17(5):556-67. · 1.64 Impact Factor
  • Janice M Moreside, Francisco J Vera-Garcia, Stuart M McGill
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    ABSTRACT: The objective of this study was to analyze the trunk muscle activation patterns, spine kinematics, and lumbar compressive forces that occur when using the Bodyblade, a popular tool in physical medicine clinics. The participants were 14 male subjects who were healthy and who were recruited from a university population. With data collected from surface electromyography of selected trunk and shoulder muscles, video analysis, and a 3-dimensional lumbar spine position sensor, modeling methods were used to quantify L4-5 compressive forces and spine stability. Large-amplitude oscillation of a vertically oriented Bodyblade resulted in the greatest activation levels of the internal oblique and external oblique muscles (average amplitude=48% and 26% of maximal voluntary isometric contraction, respectively), which were associated with L4-5 compressive forces as high as 4,328 N. Instantaneous stability increased with well-coordinated effort, muscle activation, and compression, but decreased when subjects had poor technique. The way the Bodyblade is used may either enhance or compromise spine stability. Associated lumbar compressive forces may be inappropriate for some people with compression-intolerant lumbar spine pathology.
    Physical Therapy 03/2007; 87(2):153-63. · 2.78 Impact Factor
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    Revista de la Facultad de Ciencias Sociales y Jurídicas de la Universidad Miguel Hernández, ISSN 1886-6611, Nº. 2, 2007 (Ejemplar dedicado a: Las Nuevas Tecnologías), pags. 156-183. 01/2007;
  • Stephen H M Brown, Francisco J Vera-Garcia, Stuart M McGill
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    ABSTRACT: A repeated measures biomechanical analysis of the effects of abdominal bracing in preparation for a quick release of the loaded trunk. To quantify the ability of individuals to abdominally brace the externally loaded trunk, and assess their success in achieving and enhancing appropriate spine stability. Spine stability requires trunk muscle coactivation, which demands motor control skill that differs across people and situations. The quick release protocol may offer insight into the motor control scheme and subsequent effect on spine stability. There were 10 individuals who sat, torso upright, in an apparatus designed to foster a neutral spine position. They were instructed to support a posteriorly directed load to the trunk in either their naturally chosen manner, or by activating the abdominal muscles to 10%, 20%, or 30% of maximum ability. The externally applied load was then quickly released, thereby unloading the participant. Muscle pre-activation patterns, spine stability, and kinematic measures of trunk stiffness were quantified. Participants were able to stabilize their spine effectively by supporting the load in a naturally selected manner. Conscious, voluntary overdriving of this natural pattern often resulted in unbalanced muscular activation schemes and corresponding decreases in stability levels. Individuals in an externally loaded state appear to select a natural muscular activation pattern appropriate to maintain spine stability sufficiently. Conscious adjustments in individual muscles around this natural level may actually decrease the stability margin of safety.
    Spine 07/2006; 31(13):E387-93. · 2.16 Impact Factor
  • Francisco J Vera-Garcia, Stephen H M Brown, John R Gray, Stuart M McGill
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    ABSTRACT: Studies examining rapid spine loading have documented the influence of steady-state trunk preloads, and the resulting levels of trunk muscle preactivation, on the control of spine stability. However, the effects of different levels of muscle coactivation, and resulting spine loads, on the response to a perturbation of the externally unloaded trunk are unclear. Fourteen male subjects coactivated the abdominal muscles at four different levels (approximately 0%, 10%, 20% and 30% of the maximal voluntary contraction) monitored by an electromyography biofeedback system while semi-seated in a neutral lumbar spine position. They were loaded posteriorly in two directions (0 degrees and 30 degrees from the sagittal plane) and with two different loads (6.80 and 9.07 kg). Force perturbation, spine displacement and electromyography activity were measured, and torso compression and stability were modeled. Abdominal coactivation significantly increased spine stability and reduced the movement of the lumbar spine after perturbation, but at the cost of increasing spinal compression. Preactivation also reduced the frequency and magnitude, and delayed the onset of muscle reactions, mainly for the back muscles and the internal oblique. The higher magnitude load and the load applied in an oblique direction both showed more potentially hazardous effects on the trunk. Torso coactivation increases spinal stiffness and stability and reduces the necessity for sophisticated muscle responses to perturbation. Although further investigation is needed, it appears there is an asymptotic function between coactivation and both stiffness and stability. There also appears to be more hazard when buttressing twisting components of a sudden load compared to sagittal components. Patients with trunk instability and intolerance to spine compression may benefit from low to moderate levels of coactivation.
    Clinical Biomechanics 07/2006; 21(5):443-55. · 1.87 Impact Factor
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    ABSTRACT: The purpose of this paper was to determine the effect of the race walking exercise on the structures of the foot, so much in the immediate responses to the practice as in the long term training adaptations. Footprints were recorded tree times using the photopodogram methodology on a sample of 17 young race walkers. The first one and second footprints were carried out in both feet at the middle of the season, in rest and after 30 min race walking respectively. The third was taken in rest on the dominant foot 3 months later, at the end of the season. The results indicate that there are not differences among the right and left foot, neither before nor after the exercise. However, the responses showed different behaviour. While the right foot showed significant increments in the width of the forefoot and midfoot (P < 0.05), the left foot showed an increment in the length of the foot. This different behaviour can be due to the characteristics of the circuit on which the race walk was carried out, circular with turn to the left. This takes us to suggest that, to avoid overloads and muscular unbalances the race walkers should train in circuits balanced in curves to either sides, or if in circular circuits frequently change the turning sense. The adaptations followed a similar pattern to that of the responses of the right foot. There were significant increments in the width of the forefoot, although the length of the foot also increased significantly. Anyway, we believe that the last could be due to the intrinsic characteristic of the athletes, since many of them were in age of growing. El propósito de este trabajo fue determinar el efecto que tiene la práctica de la marcha atlética sobre las estructuras del pie, tanto en las respuestas inmediatas a la práctica como en las adaptaciones a largo plazo por el entrenamiento. Para ello se realizaron tres tomas de la huella plantar por el método el fotopodograma a una muestra de 17 marchadores jóvenes. La primera y segunda toma se realizaron en ambos pies a mediados de temporada, en reposo y tras 30 min de marcha respectivamente. La tercera toma también en reposo sobre el pie dominante 3 meses después, al final de la temporada. Los resultados indican que no hay diferencias entre el pie derecho e izquierdo, ni antes ni después del ejercicio. Sin embargo al analizar el efecto en las respuestas se encontraron comportamientos distintos. Mientras que el pie derecho mostró incrementos significativos en el ancho del antepié y mediopié (P < 0.05), en el pie izquierdo se manifestó un incremento en la longitud del pie. Este comportamiento distinto puede deberse a las características del circuito sobre el que se realizó la marcha, circular con giro a la izquierda. Esto nos lleva a sugerir que, para evitar posibles sobrecargas y descompensaciones los entrenamientos se desarrollen en circuitos equilibrados en curvas a ambos lados, o en caso de realizarse en circuito cerrado, que se cambie con frecuencia el sentido de giro. En cuanto a las adaptaciones, siguen un patrón similar al de las respuestas del pie derecho, se encontraron incrementos significativos en el ancho del antepié, aunque también se incrementó significativamente la longitud del pie, si bien creemos que esto último puede haberse debido al desarrollo propio de los atletas, ya que muchos se encontraban en edad de crecimiento.
    Cultura, Ciencia y Deporte
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    Francisco J Vera-Garcia, Stuart M McGill, Miguel Hernandez