Effects of Load Carriage on Postural Control and Spatiotemporal Gait Parameters during Level and Uphill Walking.

Load carriage and uphill walking are conditions that either individually or in combination can compromise postural control and gait eliciting several musculoskeletal low back and lower limb injuries. The objectives of this study were to investigate postural control responses and spatiotemporal parameters of gait during level and uphill unloaded (UL), back-loaded (BL), and front-loaded (FL) walking. Postural control was assessed in 30 asymptomatic individuals by simultaneously recording (i) EMG activity of neck, thoracic and lumbar erector spinae, and rectus abdominis, (ii) projected 95% ellipse area as well as the anteroposterior and mediolateral trunk displacement, and (iii) spatiotemporal gait parameters (stride/step length and cadence). Measurements were performed during level (0%) and uphill (5, 10, and 15%) walking at a speed of 5 km h-1 without and with a suspended front pack or a backpack weighing 15% of each participant's body weight. The results of our study showed that postural control, as indicated by increased erector spinae EMG activity and changes in spatiotemporal parameters of gait that manifested with decreased stride/step length and increased cadence, is compromised particularly during level and uphill FL walking as opposed to BL or UL walking, potentially increasing the risk of musculoskeletal and fall-related injuries.

A comprehensive method for assessing postural control during dynamic balance testing.

Postural control, despite its complexity, has been investigated based on single or multiple domain parameters, mainly under static conditions. The purpose of this study was to investigate whether semi-squatting in one leg, in contrast to simply standing in one leg, can challenge the postural control in a more dynamic manner similar to those encountered during sporting activities, using posturographic-based parameters coupled with EMG data of the ankle musculature. Our findings revealed that the decreased stability induced with single-leg semi-squatting (SLSQ) required primarily the contribution of the tibialis anterior and the peroneus brevis, as opposed to the medial gastrocnemius and lateral gastrocnemius who were the main controllers of body posture during single-leg standing (SLST) with open eyes. The lower variability found in the CoP-based parameters and the EMG activity of the muscle under investigation suggests that postural control can be more accurately assessed under dynamic conditions such as with SLSQ compared to the more static SLST test. Multi-factorial analysis of postural control combining posturographic and EMG data, particularly under dynamic conditions, can provide useful information in the diagnosis and rehabilitation of clinical cases where the assessment of muscle dysfunction is required to design a rehabilitation program and monitor patient progress. •Simultaneous recordings of posturographic-based parameters and the EMG activity of the ankle/foot musculature suggest that postural control is challenged more during SLSQ.•Postural control with SLSQ is mainly controlled by the tibialis anterior and peroneus brevis in response to a greater anteroposterior- compared to mediolateral-directed sway of the body.•The limited body sway elicited with the traditional SLST test is mainly controlled by the gastrocnemius muscle.•Postural control may be assessed more accurately under dynamic conditions such as with SLSQ as opposed to the standard SLST test.

Ankle muscles activation and postural stability with Star Excursion Balance Test in healthy individuals.

INTRODUCTION: The ankle joint, a part of the kinetic chain of the lower limb, plays a significant role in the maintenance of postural stability during bipedal and unipedal balancing activities. This study aimed to evaluate the neuromuscular control of the ankle joint and the postural stability while executing the Star Excursion Balance Test (SEBT), by recording the EMG activity of the extrinsic ankle musculature and the displacement of the center of pressure (CoP). METHODS: The EMG activity of the tibialis anterior (TA), the peroneus brevis (PB) and the medial and lateral gastrocnemius (GM, GL), along with the anteroposterior and mediolateral displacements (APd and MLd) of CoP as well as the plantar pressure distribution of the supportive lower limb were recorded during reaching to the eight directions of SEBT in 29 healthy, physically active college students (15 males and 14 females; mean ± SD of age 25.6 ± 4.5 yrs.; height: 172.5 ± 8.2 cm; body weight: 67.7 ± 13.6 kg; and BMI: 22.6 ± 2.9 kg/m2). RESULTS: The tibialis anterior muscle demonstrated the greatest EMG activity during SEBT, followed by the PB, GL and GM muscles. The increased EMG activity of TA and PB during the execution of all posterior-oriented and lateral directions coincided with a decreased APd of CoP and increased reaching distances. The opposite occurred during the execution of all the anterior-oriented and medial directions. The differences among the directions of SEBT regarding the EMG activity of GL, GM and the mediolateral displacement of CoP were, in general, not significant. CONCLUSIONS: The neuromuscular control of the ankle joint and the associated postural stability during SEBT was highly depended upon the activation level of TA and PB, which should be considered by clinicians and sports specialists when using this test for screening and/or rehabilitation purposes.

Scapular muscles' activity in female volleyball players with scapular asymmetry in the resting position.

BACKGROUND/AIM: Resting scapular asymmetry with a more protracted and depressed position of the scapula in the dominant throwing side relative to the scapula of the contralateral side is commonly detected in overhead athletes with both healthy and disabled shoulders. It has been proposed that possible alterations in the EMG activity of periscapular muscles due to asymmetric position of the scapula may alter its kinematics leading to shoulder pathology. The aim of the current study was to identify possible alterations in the activation of periscapular muscles of healthy female volleyball players with scapular asymmetry in the resting position. METHODS: Resting position of the scapula was determined in 37 healthy professional female volleyball players. Twenty-two players, with the scapula of the dominant side in a more protracted and depressed position compared to the non-dominant side, were classified as the asymmetry group. Fifteen players with almost symmetrical position of both scapulae comprised the control group. All participants performed an upper extremity closed chain exercise (knee push-ups) on a stable (floor) and an unstable surface (BOSU platform), while the EMG activity of serratus anterior (SA), upper trapezius (UT) and middle trapezius (MT) was recorded bilaterally. RESULTS: No significant group (asymmetry vs. control) by side (dominant vs. non-dominant) by surface condition (floor vs. BOSU platform) interaction was detected with regard to the EMG activity of SA, UT and MT. Although not statistically significant the asymmetry group demonstrated a tendency for reduced EMG activity of the SA on the dominant compared to the contra-lateral side and compared to the dominant side of the control group. CONCLUSIONS: The EMG activity of periscapular muscles (SA, UT and MT) was not affected during execution of a close chain exercise in healthy female volleyball players with the scapula of the dominant side in a more protracted and depressed resting position.

Systemic levels of human ß-defensin 1 are elevated in patients with cirrhosis.

BACKGROUND: Bacterial translocation (BT) commonly occurs in cirrhosis. Reliable biomarkers for BT are currently lacking. Human beta defensin-1 (hBD-1) is a member of the family of natural antimicrobial peptides produced by epithelial cells and participates in the mucosal defensive mechanisms that prevent BT. The aim of the present study was to examine the local and systemic expression of hBD-1 in patients with cirrhosis. METHODS: Plasma concentrations of hBD-1 and of soluble CD14 (sCD14) proteins were measured by ELISA in patients with chronic viral hepatitis, cirrhosis, and healthy controls. Relative mRNA expression of various natural antimicrobial peptides was determined by real-time PCR in biopsies from the terminal ileum and colon. RESULTS: We found significant upregulation of hBD-1 and sCD14 in the peripheral blood of patients with cirrhosis compared to patients with chronic viral hepatitis and healthy controls. The etiology of cirrhosis did not affect the concentration of either protein. The levels of hBD-1 protein correlated significantly with the levels of sCD14 in blood collected from hepatic veins of cirrhotic patients. In contrast, no significant differences were observed in the intestinal mucosal mRNA expression of the Paneth cell specific defensin A5 or hBD-1 between patients with cirrhosis and healthy controls. CONCLUSIONS: hBD-1 is upregulated in patients with cirrhosis and highly correlates with the lipopolysaccharide-induced protein sCD14. hBD-1 may serve as a biomarker of BT in patients with cirrhosis.