Effect of back belt on maximum displacement and center of pressure velocity in different lifting styles

Purpose: Mechanical loading is said to be an important factor in the development of low back pain [LBP]. One of the main concerns in manual material handling [MMH] tasks is lifting loads, as this activity is present in most jobs. Despite the controversy about their effectiveness, belts are used in industry as either protective or assistive devices in manual load handling. The present investigation aimed to determine whether a commonly used back belt could improve maximum center of pressure displacement [COPMD] and center of pressure velocity [COPV] as the balance parameters during each of three common styles of lifting [squat, semi-squat, stoop]

Methods: Twenty healthy female subjects participated in this study who were selected by non-probability convenience sampling. The participants stood barefoot on the force plate. They lifted a box, weighting 4.53 kg [10 pound]. The subjects were instructed to bend their knees [squat] or their lumbar [stoop] or both their knees and lumbar [semi-squat], to grasp the box handles, and to lift the load to the level of greater trochanter height. Half of the subjects performed the 3 trials with wearing belt at first try and the other half performed the trials without wearing the belt at first try

Results: The mean of maximum displacement and velocity showed that there was a trend of increase in these variables in all 3 styles of lifting [squat, semi-squat and stoop] after wearing belt. One-way ANOVA with repeated measures results for COPMD and COPV showed that 'Belt condition' significantly affected the dependent variables

Conclusion: Wearing belt may decrease stability caused by increased COPMD and COPV

[Latency and recruitment order of the shoulder muscles in dynamic complex movement in patients with shoulder impingement syndrome]

Shoulder muscle timing is very important, however, study on the shoulder muscle timing and recruitment patterns is limited. Thus, the aim of the study was to determine and compare the timing and recruitment order of the shoulder muscles in subjects with and without Shoulder Impingement Syndrome [SIS]. In this case-control study, 9 female subjects with shoulder impingement syndrome and 13 matched healthy female volunteer subjects selected by simple-non random sampling participated. Surface electromyography of serratus anterior, pectoralis major, upper trapezium, lower trapezium, posterior deltoid, and anterior deltoid muscles of dominant side were recorded during D1flex movement. Muscle latency time, relative muscle latency time and recruitment order were processed and compared in subjects with and without SIS. Non parametric test [2 independent samples [Mann-Whitney U]] was used for data analysis In patient group some muscles showed a greater latency time than healthy group but this increase wasn't statistically significant. Also, in patient group recruitment order of shoulder muscles was changed. Altered recruitment patterns of one or more muscles in the patient group as compared to healthy group indicate neuromuscular control has changed. Thus rehabilitation programs should be designed to restore and optimize the activation sequences and motor control of these muscles