Segmental fibre type composition of the rat iliopsoas muscle.

The iliopsoas of the rat is composed of two muscles - the psoas major muscle and the iliacus muscle. The psoas major muscle arises from all the lumbar vertebrae and the iliacus muscle from the fifth and sixth lumbar vertebrae and ilium. Their common insertion point is the lesser trochanter of the femur, and their common action is the lateral rotation of the femur and flexion of the hip joint. Unlike humans, the rat is a quadruped and only occasionally rises up on its hind legs. Therefore, it is expected that the fibre type composition of the rat iliopsoas muscle will be different than that of humans. The iliopsoas muscle of the rat is generally considered to be a fast muscle. However, previous studies of the fibre type composition of the rat psoas muscle showed different results. Moreover, very little is known about the composition of the rat iliacus muscle. The aim of our study was to examine the fibre type composition of the rat iliopsoas muscle in order to better understand the complex function of the listed muscle. The psoas major muscle was examined segmentally at four different levels of its origin. Type I, IIA, IIB and IIX muscle fibres were typed using monoclonal antibodies for myosin heavy chain identification. The percentage of muscle fibre types and muscle fibre cross-sectional areas were calculated. In our study we showed that in the rat iliopsoas muscle both the iliacus and the psoas major muscles had a predominance of fast muscle fibre types, with the highest percentage of the fastest IIB muscle fibres. Also, the IIB muscle fibres showed the largest cross-sectional area (CSA) in both muscles. As well, the psoas major muscle showed segmental differences of fibre type composition. Our results showed changes in percentages, as well as the CSAs of muscle fibre types in cranio-caudal direction. The most significant changes were visible in type IIB muscle fibres, where there was a decrease of percentages and the CSAs from the cranial towards the caudal part of the muscle. From our results it is evident that the rat iliopsoas muscle has a heterogeneous composition and is composed of all four muscle fibre types. Primarily, it is a fast, dynamic muscle with a predominance of fast type IIB muscle fibres with the largest CSAs. The composition of the rat psoas major muscles changes in a cranio-caudal direction, thus pointing to a more postural role of the caudal part of the muscle.

MRI features of the psoas major muscle in patients with low back pain.

PURPOSE: The purpose was to investigate the changes of the psoas major muscles (PM) cross-sectional area (CSA) and fat infiltration in the PM and to investigate the association between the morphology of the PM and expression of the degenerative changes of lumbar spine in patients with low back pain (LBP). METHODS: T2-weighted scans for measurements of the CSA and analysis of fat infiltration were performed on 42 patients and 49 controls using a 1.5 Tesla MR system. For a quantitative analysis of fat tissue infiltration a 4-grade visual scale was used. RESULTS: Patients had bigger CSA of the PM than controls at the levels of L3/L4 and L4/L5 intervertebral disc (P < 0.05). Patients with apparent degenerative changes of the lumbar spine had smaller CSA of the PM compared to the patients without apparent changes at the levels of L3/L4 and L4/L5 (P < 0.05). At the levels of L4/L5 and L5/S1 patients with present Modic changes in the lumbar vertebral bodies showed smaller CSA of the PM compared to the patients without Modic changes (P < 0.05). However, CSA of the PM in the patients with degenerative changes of lumbar spine and Modic changes was still bigger than the one of the controls. At all analyzed levels correlation between CSAs of the PM and fat infiltration of the lumbar paraspinal muscles was negative. CONCLUSION: Results suggest increased activity of the PM in LBP patients but PM also remains active regardless of the presence of degenerative and Modic changes of the lumbar spine.

Segmental composition of the porcine iliopsoas muscle and influence of the body size and posture on the composition of the iliopsoas muscle.

The iliopsoas muscle (IPM) of the pig consists of the iliacus muscle (IM) and the psoas major muscle (PMM). Due to the differences in posture and size between animal species, the musculoskeletal system is subjected to different functional demands, which affects the morphological characteristics of the musculoskeletal system. The aim of this study was to determine the muscle fiber type composition in pigs IPM, as pigs are large quadrupeds that differ in body size and posture from humans and small mammals, and to determine the influence of body size and posture on the composition of IPM. Muscle samples were collected from the Pietrain Landrace pigs, a sample from IM and a samples at four segments of the PMM. Samples were analyzed with monoclonal antibodies specific for different isoforms of the myosin heavy chain. The percentages and cross-sectional area (CSA) of type I, IIA, and IIX/IIB muscle fibers were calculated. Our studies revealed that in pigs IPM, type IIX/IIB muscle fibers were predominant with the largest CSA. A decrease in the proportion of type IIX/IIB muscle fibers, an increase in type I and IIA muscle fibers, and a decrease in the CSA of all muscle fiber types from the cranial to the caudal part of the PMM were observed. The pig IPM has primarily a dynamic function. The function of the PMM in the cranio-caudal direction changes from a dynamic to a static role. Body size and posture influence the composition of the IPM.

Exploring the Association between Alcohol Drinking and Physical Activity in Adolescence; Two-Year Prospective Study in Younger Adolescents from Bosnia and Herzegovina.

Insufficient physical activity and alcohol consumption (AC) are important health-threatening behaviors in adolescence, but there are controversial findings regarding the association that may exist between AC and physical activity levels (PALs) at this age. This study aimed to prospectively examine the relationship that may exist between AC and PAL in younger adolescence, considering the potential confounding effect of sports participation. The participants (n = 669, 337 females) were adolescents from Bosnia and Herzegovina who were tested on two occasions, at baseline (14 years of age) and again at follow-up (16 years of age). The variables included AC (as indicated by the AUDIT questionnaire), sports participation, age, gender (predictors), and PAL (obtained by the PAQ-A questionnaire) criterion. The results indicated that PAL at baseline was higher in those adolescents (boys) with a higher AUDIT score, but this association was partially confounded by sports participation. Multinomial regression indicated a higher risk of a decline in PAL over the study course in adolescents with a higher AUDIT score at baseline (OR = 1.32, 95%CI: 1.11-1.54 for being in the high-risk group for a decline in PAL). The most probable explanation is likely found in the high drop-out from sports in the studied period and earlier initiation of AC in adolescents involved in sports. Public health and sports authorities should urgently act preventively and develop educational programs against alcohol drinking in youth athletes.

Does Participation in Sports Influence the Prevalence of and Initiation into Multiple Substance Misuse in Adolescence? A Two-Year Prospective Analysis.

Concurrent smoking and harmful drinking (CSHD) in adolescence is an important public health and social problem, while participation in sports is considered as being protective against CSHD. This study aimed to prospectively evaluate the influence of various facets of sports participation on the prevalence of and initiation into CSHD of adolescents. Participants were adolescents from southern Croatia (n = 711, 43.6% females, 16 years of age at study baseline), who were tested at baseline and at follow-up (two years later). Variables included gender, age, sports factors (participation in individual and team sports, sport experience, competitive success, intensity of involvement in sports), and CSHD. The CSHD prevalence did not increase significantly over the course of the study (from 5.6% to 7.5%, p > 0.05). Binomial logistic regression with age and gender as covariates suggested that team sports participation correlated to CSHD prevalence at baseline, and follow-up, with higher risk for CSHD among those adolescents who quit team sports (OR = 9.18 and 2.68, 95%CI = 2.04-22.26 and 1.05-6.83 for baseline and follow-up, respectively), and those never involved in team sports (OR = 9.00 and 3.70, 95%CI = 2.07-39.16 and 1.57-8.72 for baseline and follow-up, respectively). A higher risk of CSHD at baseline was seen among those adolescents who were involved in sports for longer (OR = 1.66, 95%CI = 1.16-2.38). The results are discussed in the context of the fact that the study included adolescents at the age of rigid sports selection (the transition from youth to professional-level sports). Since the majority of participants began CSHD at an earlier age, further studies in subjects of a younger age range are warranted.