The effect of limited hip mobility on the lumbar spine in a young adult population

Limited hip mobility is known to affect the lumbar spine. Much of the previous research has utilized a participant population whose hip mobility is compromised due to arthritic or neurological dysfunctions. Such aetiologies may confound the outcomes, as their effects may not be limited to the hip. The purpose of this thesis was to recruit a healthy young adult population with limited hip mobility to further investigate its effect on the lumbar spine, as well as the role of exercise intervention. Several cascading studies were conducted that were unified around a central theme of links between hip and spine function: Study # 1 investigated the normal distribution of passive hip extension and rotation in a group of 77 males (age 19-30). Data was collected using an infra-red motion capture system and compared to goniometric measurements. The resulting angles represent the 5th – 95th percentiles, including the averages and standard deviations. Study # 2 compared movement patterns between groups of males with limited and excessive hip mobility. Participants were required to perform simple functional activities (lunging, twisting, walking, etc) as well as use the elliptical trainer. Resulting hip and spine angles demonstrated that the men with limited hip mobility stood with a more anteriorly tilted pelvis, and assumed a posture with more lumbar and hip flexion on the elliptical trainer, compared to those with greater mobility. This, in turn, resulted in a greater lumbar compression load due to increased back muscle activity. Study #3 involved recruitment of 24 young adult males with limited hip mobility. Their movement patterns were assessed (as in study #2), then they were assigned to one of four intervention groups: hip stretching, spine stabilizing, hip stretching combined with spine stabilization, and control. Participants in the 3 exercise groups attended supervised exercise sessions once/week for 6 weeks, but were expected to exercise a minimum of 4 times/week on their own. At the end of the 6 weeks, intake parameters were re-assessed, and movement pattern assessment repeated. Despite significant increases in available hip flexibility and/or large increases in trunk muscle endurance and trunk motor control, there were few indications that participants were any more adept at decreasing lumbar motion, or utilizing their newfound hip flexibility during functional activities. Study #4 compared those in the 10th and 90th percentiles of available hip rotation, using a frictionless apparatus to investigate passive stiffness properties of the hip. Participants adopted a posture of upright standing, with one leg supported on a turntable apparatus, and upper body and pelvis secured. A an applied rotational moment resulted in passive hip internal and external rotation. Outcomes demonstrate that those with limited hip mobility stand with the leg more externally rotated and require a larger moment to initiate motion. Passive stiffness curves indicate greater stiffness properties in those with limited hip mobility, and more resistance to an external rotation moment than internal rotation. Study #5 investigated passive hip stiffness in the sagittal plane, comparing those with limited and excessive hip extension. Using a frictionless jig, with the participants lying on their left side, the left hip was pulled into extension with knee position varying. Those with limited hip mobility demonstrated increased passive stiffness compared to the more mobile group, and stiffness was greater when the knee was in extension. The group with limited mobility also showed a trend of increased back extension compared to the more mobile group, when the hip and lumbar spine were both free to react to the applied extension moment. Study #6 summarizes the spine/hip kinematics and muscle activation levels produced when using the elliptical trainer, as well as lumbar compressive and shear forces. It differs significantly from walking in that it produces more lumbar motion in flexion/extension and lumbar twist, but less lateral bend. Participants also tended to adopt a greater mean lumbar flexion angle on the elliptical, which in turn resulted in greater muscle activity in the back extensors. Varying hand position, velocity and stride length were all found to significantly affect the amount of lumbar motion. Highly phasic muscle activity is seen, with the gluteal muscles and internal obliques demonstrating the greatest activation levels

Comparison of shoulder rotation range of motion in professional tennis players with and without history of shoulder pain

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

Activació dels músculs del tronc durant situacions que requereixen l’estabilització del raquis. Estudi de cas únic

L’objectiu d’aquest estudi va ser analitzar la intensitat de la contracció i la coordinació de 14 músculs del tronc i del muscle d’un subjecte durant la recepció i el llançament d’una pilota medicinal (acció pliomètrica), una acció d’embranzida en posició dempeus (pressió de pit horitzontal amb politja) i l’ús del Bodyblade® (barra flexible l'oscil·lació de la qual sotmet el cos a vibracions i desequilibris continus). Igualment, amb l'objecte de facilitar la discussió en relació amb l'estabilització activa del raquis, es va registrar la resposta dels músculs esmentats durant l'aplicació controlada sobre el tronc de càrregues i descàrregues desequilibrants. Els nostres resultats indiquen que l'activació dels músculs del tronc és important, tant per a estabilitzar el raquis davant pertorbacions i desequilibris sobtats, com per a l'execució d'accions on els membres superiors manegen objectes. En aquest sentit, la coactivació dels músculs del tronc va ser necessària per estabilitzar el raquis davant les oscil·lacions del Bodyblade® i davant les forces de reacció produïdes en empènyer una càrrega pesada en posició erecta. De la mateixa manera, la recepció i el llançament immediat de la pilota medicinal és una activitat relativament complexa que requereix l'acció coordinada dels músculs del tronc i de les extremitats

Can the structure of motor variability predict learning rate?

Recent studies show that motor variability is actively regulated as an exploration tool to promote learning in reward-based tasks. However, its role in learning processes during error-based tasks, when a reduction of the motor variability is required to achieve good performance, is still unclear. In this study, we hypothesized that error-based learning not only depends on exploration but also on the individuals’ ability to measure and predict the motor error. Previous studies identified a less auto-correlated motor variability as a higher ability to perform motion adjustments. Two experiments investigated the relationship between motor learning and variability, analyzing the long-range autocorrelation of the center of pressure fluctuations through the score of a Detrended Fluctuation Analysis in balance tasks. In Experiment 1, we assessed the relationship between variability and learning rate using a standing balance task. Based on the results of this experiment, and to maximize learning, we performed a second experiment with a more difficult sitting balance task and increased practice. The learning rate of the 2 groups with similar balance performances but different scores was compared. Individuals with a lower score showed a higher learning rate. Because the scores reveal how the motor output changes over time, instead of the magnitude of those changes, the higher learning rate is mainly linked to the higher error sensitivity rather than the exploration strategies. The results of this study highlight the relevance of the structure of output motor variability as a predictor of learning rate in error-based tasks

Large Asymmetric Hypertrophy of Rectus Abdominis Muscle in Professional Tennis Players

Purpose: To determine the volume and degree of asymmetry of the musculus rectus abdominis (RA) in professional tennis players. Methods: The volume of the RA was determined using magnetic resonance imaging (MRI) in 8 professional male tennis players and 6 non-active male control subjects. Results: Tennis players had 58 % greater RA volume than controls (P = 0.01), due to hypertrophy of both the dominant (34% greater volume, P = 0.02) and non-dominant (82 % greater volume, P = 0.01) sides, after accounting for age, the length of the RA muscle and body mass index (BMI) as covariates. In tennis players, there was a marked asymmetry in the development of the RA, which volume was 35 % greater in the non-dominant compared to the dominant side (P,0.001). In contrast, no sideto-side difference in RA volume was observed in the controls (P = 0.75). The degree of side-to-side asymmetry increased linearly from the first lumbar disc to the pubic symphysis (r = 0.97, P,0.001). Conclusions: Professional tennis is associated with marked hypertrophy of the musculus rectus abdominis, which achieves a volume that is 58 % greater than in non-active controls. Rectus abdominis hypertrophy is more marked in the non-dominant than in the dominant side, particularly in the more distal regions. Our study supports the concept that humans can differentially recruit both rectus abdominis but also the upper and lower regions of each muscle. It remains to b

The relevance of stretch intensity and position-a systematic review

Stretching exercises to increase the range of motion (ROM) of joints have been used by sports coaches and medical professionals for improving performance and rehabilitation. The ability of connective and muscular tissues to change their architecture in response to stretching is important for their proper function, repair, and performance. Given the dearth of relevant data in the literature, this review examined two key elements of stretching: stretch intensity and stretch position; and their significance to ROM, delayed onset muscle soreness (DOMS), and inflammation in different populations. A search of three databases, Pub-Med, Google Scholar, and Cochrane Reviews, identified 152 articles, which were subsequently categorized into four groups: athletes (24), clinical (29), elderly (12), and general population (87). The use of different populations facilitated a wider examination of the stretching components and their effects. All 152 articles incorporated information regarding duration, frequency and stretch position, whereas only 79 referred to the intensity of stretching and 22 of these 79 studies were deemed high quality. It appears that the intensity of stretching is relatively under-researched, and the importance of body position and its influence on stretch intensity, is largely unknown. In conclusion, this review has highlighted areas for future research, including stretch intensity and position and their effect on musculo-tendinous tissue, in relation to the sensation of pain, delayed onset muscle soreness, inflammation, as well as muscle health and performance