Factors Affecting Measurement of Salivary Cortisol and Secretory Immunoglobulin A in Field Studies of Athletes.

AIMS: Biological and lifestyle factors, such as daily rhythm, caffeine ingestion, recent infection, and antibiotic intake, have been shown to influence measurements of salivary cortisol (SC) and secretory immunoglobulin A (sIgA). Current methodology in unsynchronized, field-based biomarker studies does not take these effects into account. Moreover, very little is known about the combined effects of biological and lifestyle factors on SC and sIgA. This study supports development of a protocol for measuring biomarkers from saliva collected in field studies by examining the individual and combined effects of these factors on SC and sIgA. METHOD: At three time points (start of the pre-season; start of playing season; and end of playing season), saliva samples were collected from the entire squad of 45 male players of an elite Australian Football club (mean age 22.8 ± 3.5 years). At each time, point daily rhythm and lifestyle factors were determined via a questionnaire, and concentrations of both SC and sIgA via an enzyme linked immuno-sorbent (ELISA) assay of saliva samples. In addition, player times to produce 0.5 mL of saliva were recorded. RESULTS: Analysis of covariance of the data across the three time points showed that daily rhythm had a more consistent effect than the lifestyle factors of caffeine ingestion, recent infection, and antibiotic intake on SC, but not on sIgA. Data for sIgA and SC concentrations were then adjusted for the effects of daily rhythm and lifestyle factors, and correlational analysis of the pooled data was used to examine the relative effects of these two sources of influence on sIgA and SC. With the exception of time to produce saliva, the biological measures of stress were affected by players' daily rhythms. When daily rhythm was taken into account the group of lifestyle factors did not have an additional effect. DISCUSSION: It is recommended that future studies measuring SC and sIgA make additional adjustments for the daily rhythm, in particular time since first sight of daylight, as small measurement errors of biomarkers can confound discrimination among study participants.

The effect of motor control training on abdominal muscle contraction during simulated weight bearing in elite cricketers.

OBJECTIVES: To investigate whether motor control training alters automatic contraction of abdominal muscles in elite cricketers with low back pain (LBP) during performance of a simulated unilateral weight-bearing task. DESIGN: Clinical trial. METHODS: 26 male elite-cricketers attended a 13-week cricket training camp. Prior to the camp, participants were allocated to a LBP or asymptomatic group. Real-time ultrasound imaging was used to assess automatic abdominal muscle response to axial loading. During the camp, the LBP group performed a staged motor control training program. Following the camp, the automatic response of the abdominal muscles was re-assessed. RESULTS: At pre-camp assessment, when participants were axially loaded with 25% of their own bodyweight, the LBP group showed a 15.5% thicker internal oblique (IO) muscle compared to the asymptomatic group (p = 0.009). The post-camp assessment showed that participants in the LBP group demonstrated less contraction of the IO muscle in response to axial loading compared with the asymptomatic group. A trend was found in the automatic recruitment pattern of the transversus abdominis (p = 0.08). CONCLUSIONS: Motor control training normalized excessive contraction of abdominal muscles in response to a low load task. This may be a useful strategy for rehabilitation of cricketers with LBP.

Activation of the hip adductor muscles varies during a simulated weight-bearing task.

OBJECTIVE: To investigate the pattern of muscle activation of the individual hip adductor muscles using a standardised simulated unilateral weight-bearing task. DESIGN: A repeated measures design. SETTING: Laboratory. PARTICIPANTS: 20 healthy individuals (11 females, 9 males) participated in the study. Age ranged from 20 to 25 years. MAIN OUTCOME MEASUREMENTS: Surface electromyography recordings from adductor magnus and adductor longus muscles were taken at levels representing 10-50% of body weight during a simulated weight-bearing task. Electromyography (EMG) data were normalised to maximal voluntary isometric contraction. RESULTS: The adductor magnus was recruited at significantly higher levels than the adductor longus muscle during a simulated weight-bearing task performed across 10-50% of body weight (p < 0.01). CONCLUSIONS: Adductor magnus and adductor longus muscles are recruited to different extents during a simulated weight-bearing task. This information should be considered when selecting exercises for management and prevention of groin strains. Closed chain exercises with weight-bearing through the lower limb are more likely to recruit the adductor magnus muscle over the adductor longus muscle.

The relationship between the piriformis muscle, low back pain, lower limb injuries and motor control training among elite football players.

OBJECTIVES: Australian Football League (AFL) players have a high incidence of back injuries. Motor control training to increase lumbopelvic neuromuscular control has been effective in reducing low back pain (LBP) and lower limb injuries in elite athletes. Control of pelvic and femoral alignment during functional activity involves the piriformis muscle. This study investigated (a) the effect of motor control training on piriformis muscle size in AFL players, with and without LBP, during the playing season, and (b) whether there is a relationship between lower limb injury and piriformis muscle size. DESIGN: Stepped-wedge intervention. METHODS: 46 AFL players participated in a motor control training programme consisting of two 30min sessions per week over 7-8 weeks, delivered across the season as a randomised 3 group single-blinded stepped-wedge design. Assessment of piriformis muscle cross-sectional area (CSA) involved magnetic resonance imaging (MRI) at 3 time points during the season. Assessment of LBP consisted of player interview and physical examination. Injury data were obtained from club records. RESULTS: An interaction effect for Time, Intervention Group and LBP group (F=3.7, p=0.03) was found. Piriformis muscle CSA showed significant increases between Times 1 and 2 (F=4.24, p=0.046), and Times 2 and 3 (F=8.59, p=0.006). Players with a smaller increase in piriformis muscle CSA across the season had higher odds of sustaining an injury (OR=1.08). CONCLUSIONS: Piriformis muscle size increases across the season in elite AFL players and is affected by the presence of LBP and lower limb injury. Motor control training positively affects piriformis muscle size in players with LBP.

Repeated-sprint ability and team selection in Australian football league players.

PURPOSE: To investigate the relationship between selected physical capacities and repeated-sprint performance of Australian Football League (AFL) players and to determine which physical capacities contributed to being selected for the first competition game. METHODS: Sum of skinfolds, 40-m sprint (with 10-, 20-, 30-, and 40-m splits), repeated-sprint ability (6 × 30-m sprints), and 3-km-run time were measured during the preseason in 20 AFL players. The physical qualities of players selected to play the first match of the season and those not selected were compared. Pearson correlation coefficients were used to determine the relationship among variables, and a regression analysis identified variables significantly related to repeated-sprint performance. RESULTS: In the regression analysis, maximum velocity was the best predictor of repeated-sprint time, with 3-km-run time also contributing significantly to the predictive model. Sum of skinfolds was significantly correlated with 10-m (r = .61, P < .01) and 30-m (r = .53, P < .05) sprint times. A 2.6% ± 2.1% difference in repeated-sprint time (P < .05, ES = 0.88 ± 0.72) was observed between those selected (25.26 ± 0.55 s) and not selected (25.82 ± 0.80 s) for the first game of the season. CONCLUSIONS: The findings indicate that maximum-velocity training using intervals of 30-40 m may contribute more to improving repeated-sprint performance in AFL players than short 10- to 20-m intervals from standing starts. Further research is warranted to establish the relative importance of endurance training for improving repeated-sprint performance in AFL football.

Can motor control training lower the risk of injury for professional football players?

PURPOSE: Among injuries reported by the Australian Football League (AFL), lower limb injuries have shown the highest incidence and prevalence rates. Deficits in the muscles of the lumbopelvic region, such as a smaller size of multifidus (MF) muscle, have been related to the occurrence of lower limb injuries in the preseason in AFL players. Motor control training programs have been effective in restoring the size and control of the MF muscle, but the relationship between motor control training and occurrence of injuries has not been extensively examined. METHODS: This pre- and postintervention trial was delivered during the playing season as a panel design with three groups. The motor control program involved voluntary contractions of the MF, transversus abdominis, and pelvic floor muscles while receiving feedback from ultrasound imaging and progressed into a functional rehabilitation program. Assessments of muscle size and function were performed using magnetic resonance imaging and included the measurement of cross-sectional areas of MF, psoas, and quadratus lumborum muscles and the change in trunk cross-sectional area due to voluntarily contracting the transversus abdominis muscle. Injury data were obtained from club records. Informed consent was obtained from all study participants. RESULTS: A smaller size of the MF muscle (odds ratio [OR] = 2.38) or quadratus lumborum muscle (OR = 2.17) was predictive of lower limb injury in the playing season. At the time point when one group of players had not received the intervention (n = 14), comparisons were made with the combined groups who had received the intervention (n = 32). The risk of sustaining a severe injury was lower for those players who received the motor control intervention (OR = 0.09). CONCLUSION: Although there are many factors associated with injuries in AFL, motor control training may provide a useful addition to strategies aimed at reducing lower limb injuries.

Small Multifidus Muscle Size Predicts Football Injuries.

BACKGROUND: In Australian football, lower limb injuries have had the highest incidence and prevalence rates. Previous studies have shown that football players with relatively more severe preseason and playing season hip, groin, and thigh injuries had a significantly smaller multifidus muscle compared with players with no lower limb injuries. Rehabilitation of the multifidus muscle, with restoration of its size and function, has been associated with decreased recurrence rates of episodic low back pain and decreased numbers of lower limb injuries in football players. Assessment of multifidus muscle size and function could potentially be incorporated into a model that could be used to predict injuries in football players. PURPOSE: To examine the robustness of multifidus muscle measurements as a predictor of lower limb injuries incurred by professional football players. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Ultrasound examinations were carried out on 259 male elite football players at the start of the preseason and 261 players at the start of the playing season. Injury data were obtained from records collected by the Australian Football League (AFL) club staff during the preseason and the playing season. RESULTS: Decreased size of the multifidus muscle at L5 consistently predicted injury in the preseason and playing season. Asymmetry of the multifidus muscle and low back pain were significantly related to lower limb injuries in the preseason, and having no preferred kicking leg was related to season injuries. Seasonal change in the size of the multifidus muscle indicating a decrease in muscle mass was linked to injury. Sensitivity and specificity of the model were 60.6% and 84.9% for the preseason and 91.8% and 45.8% for the playing season, respectively. CONCLUSION: A model was developed for prediction of lower limb injuries in football players with potential utility for club medical staff. Of particular note is the finding that changes in muscle size from the preseason to the playing season predicted injury. CLINICAL RELEVANCE: As size of the multifidus muscle has been shown to be modifiable with training and has been associated with reduced pain and occurrence of injuries, this information could be incorporated in current programs of injury prevention.

Muscle imbalance among elite Australian rules football players: a longitudinal study of changes in trunk muscle size.

CONTEXT: Trunk muscles, such as the transversus abdominis (TrA) and multifidus, play a key role in lumbopelvic stability, which is important in athletic performance. Asymmetry or imbalance in these and other trunk muscles could result from the specific requirements of the game of Australian rules football. OBJECTIVE: To determine whether seasonal variations in the sizes of key trunk muscles associated with lumbopelvic stability occur in Australian Football League players. DESIGN: Cross-sectional study. SETTING: Hospital. PATIENTS OR OTHER PARTICIPANTS: The number of players eligible to participate at each of the 4 time points was 36 at the start of preseason 1 (T1), 31 at end of season 1 (T2), 43 at the end of preseason 2 (T3), and 41 at the start of preseason 3 (T4). The group with data at all 4 time points (n = 20) was used in the analyses and was shown to be representative of the total sample. INTERVENTION(S): Magnetic resonance imaging was used to determine the cross-sectional areas (CSAs) of the multifidus (vertebral levels L2 to L5) and lumbar erector spinae (LES) muscles (L3), as well as the thickness of the TrA and internal oblique (IO) muscles at L3. MAIN OUTCOME MEASURE(S): Cross-sectional areas of the multifidus and LES muscles and thickness of the TrA and IO muscles. RESULTS: By the end of the playing season, results showed 11.1% atrophy for multifidus CSA at L3 and 21% atrophy for TrA thickness at rest. In comparison, the CSA of the LES muscles increased by 3.6%, and the thickness of the IO muscle increased by 11.8% compared with the start of the preseason. CONCLUSIONS: The results indicated an imbalance of the key muscles associated with lumbopelvic stability.

Multifidus muscle size and symmetry among elite weightlifters.

OBJECTIVES: To examine muscle cross-sectional areas (CSA) and symmetry of lumbar multifidus (LM) muscles in elite weightlifters. DESIGN: Cross-sectional observational study SETTING: Neuromuscular and Pain Research Unit. PARTICIPANTS: Thirty-one elite weightlifters (15 males) participated in the study, representing the population of Thai weightlifters eligible for national selection. MAIN OUTCOME MEASURES: Resting CSA of the LM muscle were assessed bilaterally at 4 lumbar vertebral levels using ultrasound imaging. The between side differences (relative to the side of the preferred hand) were used to determine the asymmetry. RESULTS: The between side differences (relative to the preferred hand) of the LM muscle CSA were less than 3% for all vertebral levels and suggested symmetry between sides (p > .05). No difference was found between weightlifters with unilateral or bilateral pain symptoms. CONCLUSION: This study provides new information on resting CSA for the LM muscle in elite weightlifters. Future studies could investigate other aspects of neuromotor control of the LM muscle to determine if there are impairments which could be addressed in an attempt to decrease the high prevalence of LBP in this population.

Abdominal muscle response to a simulated weight-bearing task by elite Australian Rules football players.

The aim of this study was to examine the automatic recruitment of the deep abdominal muscles during a unilateral simulated weight-bearing task by elite Australian Rules football (AFL) players with and without low back pain (LBP). An observational cross-sectional study was conducted using ultrasound imaging to measure the thickness of the internal oblique (IO) and transversus abdominis (TrA) muscles. Thirty-seven elite male AFL players participated. Repeated measures factors included 'force level' (rest, 25% and 45% of body weight), 'leg' (dominant or non-dominant kicking leg) and 'side' (ultrasound side ipsilateral or contralateral to the leg used for the weight-bearing task). The dependent variables were thickness of the IO and TrA muscles. The results of this study showed that thickness of the IO (p<.0001) and TrA (p<.0001) muscles increased in response to 'force level'. During the task, the thickness of the IO muscle on the contralateral side of the trunk relative to the leg being tested, increased more in participants with current LBP (p=.034). This pattern was more distinct on the non-dominant kicking leg. Altered abdominal muscle recruitment in elite athletes with low back pain may be an attempt by the central nervous system (CNS) to compensate for inadequate lumbo-pelvic stability.

Effect of motor control training on muscle size and football games missed from injury.

PURPOSE: This panel-randomized intervention trial was designed to examine the effect of a motor control training program for elite Australian Football League players with and without low back pain (LBP). METHODS: The outcome measures included cross-sectional area (CSA) and symmetry of multifidus, quadratus lumborum, and psoas muscles and the change in CSA of the trunk in response to an abdominal drawing-in task. These measures of muscle size and function were performed using magnetic resonance imaging. Availability of players for competition games was used to assess the effect of the intervention on the occurrence of injuries. The motor control program involved performance of voluntary contractions of the multifidus and transversus abdominis muscles while receiving feedback from ultrasound imaging. Because all players were to receive the intervention, the trial was delivered as a stepped-wedge design with three treatment arms (a 15-wk intervention, a 8-wk intervention, and a waitlist control who received a 7-wk intervention toward the end of the playing season). Players participated in a Pilates program when they were not receiving the intervention. RESULTS: The intervention program was associated with an increase in multifidus muscle size relative to results in the control group. The program was also associated with an improved ability to draw-in the abdominal wall. Intervention was commensurate with an increase in availability for games and a high level of perceived benefit. CONCLUSIONS: The motor control program delivered to elite footballers was effective, with demonstrated changes in the size and control of the targeted muscles. In this study, footballers who received the intervention early in the season missed fewer games because of injury than those who received it late in the playing season.

Screening the lumbopelvic muscles for a relationship to injury of the quadriceps, hamstrings, and adductor muscles among elite Australian Football League players.

STUDY DESIGN: Longitudinal observational study. OBJECTIVES: To examine the relationship between severity of preseason hip, groin, and thigh (HGT) muscle injuries, and lumbopelvic muscle size, asymmetry, and function at the start and end of the preseason. BACKGROUND: In Australian Rules Football, HGT muscle injuries have the highest prevalence and incidence. Deficits within the lumbopelvic region, such as impaired muscle function and muscle asymmetry, could contribute to injuries in the preseason, and injury could, in turn, affect muscle size and function. METHODS: MRI examinations were performed on 47 male elite Australian Rules Football players at the start and at the end of the football preseason. The cross-sectional area (CSA) of multifidus, psoas major, and quadratus lumborum muscles was measured, as well as change in trunk CSA due to the function of voluntarily contracting the transversus abdominis muscle. Injuries occurring during each preseason training session were routinely recorded by the club's performance staff. RESULTS: Analysis of variance indicated that players with more severe preseason HGT injuries (more training sessions missed) had significantly smaller multifidus muscle CSA compared to players with no HGT injury (P = .006). No relationship was found for size or asymmetry of the quadratus lumborum or psoas major muscles, or ability to contract the transversus abdominis muscle through drawing in of the abdominal wall (P>.05). Small multifidus muscle size at L5 predicted 5 of 6 players who incurred a more severe HGT injury. CONCLUSIONS: An association between multifidus muscle size (relative to age, height, and weight) and preseason injury suggests a way to identify players at risk of severe HGT injuries. This result needs to be replicated in a larger sample before resources are committed to intervention efforts.

The relationship of transversus abdominis and lumbar multifidus clinical muscle tests in patients with chronic low back pain.

INTRODUCTION: Previous research of transversus abdominis (TrA) and multifidus muscle function in the presence of chronic low back pain (LBP) has investigated these muscles in isolation. In clinical practice, it is assumed that a relationship exists between these muscles and so they are often assessed and rehabilitated together. However, no studies have tested or documented this association. This study aimed to examine the relationships between clinical muscle testing and other measures taken in the course of a clinical assessment at a back clinic. METHODS: This retrospective chart audit examined the files of 82 patients (40 Males, 42 Females) for results of clinical tests of TrA and multifidus muscle contraction, multifidus muscle size measurements and other clinical measures such as distribution of pain and pain on manual examination. RESULTS: The ability to contract multifidus was related to the ability to contract TrA with the odds of a good contraction of multifidus being 4.5 times higher for patients who had a good contraction of TrA. A poor ability to contract multifidus was related to poor TrA contraction. Patients with unilateral LBP had more multifidus muscle asymmetry (11.6%) than those with bilateral/central pain (0.01%) and had a poor multifidus contraction on the affected side (p < 0.01). No other significant relationships were found. DISCUSSION & CONCLUSION: Current clinical practice of assessment and rehabilitation of both TrA and multifidus muscles in patients with chronic LBP is supported by the findings of this study. Future studies may investigate if a neurophysiological relationship exists between these muscles.

The effects of rehabilitation on the muscles of the trunk following prolonged bed rest.

Microgravity and inactivity due to prolonged bed rest have been shown to result in atrophy of spinal extensor muscles such as the multifidus, and either no atrophy or hypertrophy of flexor muscles such as the abdominal group and psoas muscle. These effects are long-lasting after bed rest and the potential effects of rehabilitation are unknown. This two-group intervention study aimed to investigate the effects of two rehabilitation programs on the recovery of lumbo-pelvic musculature following prolonged bed rest. 24 subjects underwent 60 days of head down tilt bed rest as part of the 2nd Berlin BedRest Study (BBR2-2). After bed rest, they underwent one of two exercise programs, trunk flexor and general strength (TFS) training or specific motor control (SMC) training. Magnetic resonance imaging of the lumbo-pelvic region was conducted at the start and end of bed rest and during the recovery period (14 and 90 days after re-ambulation). Cross-sectional areas (CSAs) of the multifidus, psoas, lumbar erector spinae and quadratus lumborum muscles were measured from L1 to L5. Morphological changes including disc volume, spinal length, lordosis angle and disc height were also measured. Both exercise programs restored the multifidus muscle to pre-bed-rest size, but further increases in psoas muscle size were seen in the TFS group up to 14 days after bed rest. There was no significant difference in the number of low back pain reports for the two rehabilitation groups (p=.59). The TFS program resulted in greater decreases in disc volume and anterior disc height. The SMC training program may be preferable to TFS training after bed rest as it restored the CSA of the multifidus muscle without generating potentially harmful compressive forces through the spine.

Magnetic resonance imaging assessment of regional abdominal muscle function in elite AFL players with and without low back pain.

Changes in the motor control of trunk muscles have been identified in people with low back pain (LBP) including elite football players. Previous research has found functional differences in the anatomical regions of abdominal muscles; however, this has not been examined in football players with LBP. The aim of this study was to investigate if the ability to draw-in the abdominal wall is altered among football players with LBP, and to determine if there are functional differences between the middle and lower abdominal regions in participants with and without LBP. Forty-three elite Australian Football League players were imaged using magnetic resonance imaging (MRI) as they drew in their abdominal walls, and the trunk cross-sectional area (CSA) was measured in relaxed and contracted states. At the lower region, participants with LBP (1.1%) reduced their trunk CSA to a lesser extent than those without LBP (3.2%) (P = 0.018). The results also showed that the draw-in of the abdominal wall was smaller in Region 1 (8.8%) compared to Region 2 (16.0%) and Region 3 (19.7%) (P < 0.001). This study provides evidence of regional differences in motor control and altered control of the lower region in participants with LBP. This may direct physiotherapists, especially those treating athletes, to focus on the lower abdominal region in those with LBP.

Validity of real-time ultrasound imaging to measure anterior hip muscle size: a comparison with magnetic resonance imaging.

STUDY DESIGN: Clinical measurement, criterion standard. OBJECTIVES: To investigate the validity of real-time ultrasound imaging (USI) to measure individual anterior hip muscle cross-sectional area. BACKGROUND: The hip flexor muscles are important for hip joint function and could be affected by joint pathology or injury. Objectively documenting individual anterior hip muscle size can be useful in identifying muscle size asymmetry and monitoring treatment efficacy for patients with hip problems. USI offers a novel method of measuring individual muscle size in the clinic, but its validity in measuring the anterior hip muscles has not been investigated. METHODS: Nine healthy participants (5 males, 4 females) underwent imaging of their iliopsoas, sartorius, and rectus femoris muscles with USI and magnetic resonance imaging. Bilateral muscle cross-sectional areas were measured on images from both modalities. RESULTS: There was no significant difference (P>.05) in mean cross-sectional area measurements from USI and magnetic resonance imaging for each muscle. Agreement between measurements was high for the iliopsoas (left: intraclass correlation coefficient [ICC3,1] = 0.86; 95% confidence interval [CI]: 0.51, 0.97; right: ICC3,1 = 0.88; 95% CI: 0.57, 0.97), sartorius (left: ICC3,1 = 0.82; 95% CI: 0.41, 0.96; right: ICC3,1 = 0.81; 95% CI: 0.39, 0.95), and rectus femoris (left: ICC3,1 = 0.85; 95% CI: 0.49, 0.96; right: ICC3,1 = 0.89; 95% CI: 0.61, 0.97). Reliability of measuring each muscle with USI was high between 2 trials (ICCs3,1 = 0.84 to 0.94). CONCLUSION: USI is a valid measure of iliopsoas, sartorius, and rectus femoris muscle size in healthy people, as long as a strict measurement protocol is followed.

A magnetic resonance imaging investigation of the transversus abdominis muscle during drawing-in of the abdominal wall in elite Australian Football League players with and without low back pain.

STUDY DESIGN: Single-blinded quasi-experimental study. OBJECTIVE: To investigate the ability of elite football players with and without low back pain (LBP) to voluntarily draw-in the abdominal wall. BACKGROUND: While there has been considerable debate regarding the contribution of the transversus abdominis (TrA) muscle to control the lumbar spine and pelvis, there is evidence that retraining motor control of the deep trunk muscles is commensurate with decreases in LBP. Magnetic resonance imaging (MRI) has been used to assess the TrA muscle during the draw-in maneuver, with the contraction of the TrA muscle reducing the circumference of the trunk. Impairments in performance of the draw-in maneuver have been shown in people with LBP. METHODS: Forty-three elite players from a team in the Australian Football League were allocated to 3 groups: those with "no LBP," "a history of LBP but no current LBP," or "current LBP." MRI was used to image the cross-sectional area (CSA) of the trunk at the level of the L3-4 disc at the start and end of the draw-in maneuver. RESULTS: There was a significant decrease in the CSA of the trunk with the performance of the draw-in maneuver (P<.001). Subjects in the "no LBP" group were better able to "draw-in" the abdominal wall than subjects with current LBP (P = .015). CONCLUSIONS: This study provides evidence of an altered ability to draw-in the abdominal wall in footballers with current LBP. Retraining contraction of the TrA muscle may constitute one part of an exercise-therapy approach for athletes with current LBP.

Effect of prolonged bed rest on the anterior hip muscles.

Prolonged bed rest and inactivity is known to cause muscular atrophy with previous research indicating that muscles involved in joint stabilisation are more susceptible. The anterior hip muscles are important for hip joint function and stability but little is known about the effects of prolonged inactivity on their function. This study investigated the effect of prolonged bed rest on the size of the anterior hip muscles and their pattern of recovery. The effect of resistive vibration exercise (RVE) as a countermeasure to muscle atrophy was also investigated. 12 male participants, randomly assigned to either a control or an exercise group, underwent 8 weeks of bed rest with 6 months follow-up. Changes in muscle cross-sectional area (CSA) of the iliacus, psoas, iliopsoas, sartorius and rectus femoris muscles were measured by magnetic resonance imaging at regular intervals during bed rest and recovery phases. CSAs of iliopsoas and sartorius decreased at the hip joint (p<0.05) during bed rest but iliacus, psoas, and rectus femoris CSAs were unchanged (p>0.05). No significant difference was found between the two groups for all muscles (all p>0.1), suggesting inefficacy of the countermeasure in this sample. These findings suggest that prolonged bed rest can result in the atrophy of specific muscles across the hip joint which may affect its stability and function.

The association between degenerative hip joint pathology and size of the gluteus medius, gluteus minimus and piriformis muscles.

This study aimed to investigate changes in the deep abductor muscles, gluteus medius (GMED), piriformis (PIRI), and gluteus minimus (GMIN), occurring in association with differing stages of unilateral degenerative hip joint pathology (mild: n=6, and advanced: n=6). Muscle volume assessed via magnetic resonance imaging was compared for each muscle between sides, and between groups (mild, advanced, control (n=12)). GMED and PIRI muscle volume was smaller around the affected hip in subjects with advanced pathology (p<0.01, p<0.05) while no significant asymmetry was present in the mild and control groups. GMIN showed a trend towards asymmetry in the advanced group (p=0.1) and the control group (p=0.076) which appears to have been associated with leg dominance. Between group differences revealed a significant difference for the GMED muscle reflecting larger muscle volumes on the affected side in subjects with mild pathology, compared to matched control hips. This information suggests that while GMED appears to atrophy in subjects with advanced hip joint pathology, it may be predisposed to hypertrophy in early stages of pathology. Assessment and exercise prescription methods should consider that the response of muscles of the abductor synergy to joint pathology is not homogenous between muscles or across stages of pathology.

The effect of chronic low back pain on size and contraction of the lumbar multifidus muscle.

Decreases in the size of the multifidus muscle have been consistently documented in people with low back pain. Recently, ultrasound imaging techniques have been used to measure contraction size of the multifidus muscle, via comparison of the thickness of the muscle at rest and on contraction. The aim of this study was to compare both the size (cross-sectional area, CSA) and the ability to voluntarily perform an isometric contraction of the multifidus muscle at four vertebral levels in 34 subjects with and without chronic low back pain (CLBP). Ultrasound imaging was used for assessments, conducted by independent examiners. Results showed a significantly smaller CSA of the multifidus muscle for the subjects in the CLBP group compared with subjects from the healthy group at the L5 vertebral level (F=29.1, p=0.001) and a significantly smaller percent thickness contraction for subjects of the CLBP group at the same vertebral level (F=6.6, p=0.02). This result was not present at other vertebral levels (p>0.05). The results of this study support previous findings that the pattern of multifidus muscle atrophy in CLBP patients is localized rather than generalized but also provided evidence of a corresponding reduced ability to voluntarily contract the atrophied muscle.