Background and aim:The knee joint is one of the most important joints of human body, witch tolerates many forces while the subject is standing up or walking especially during close chain and squat positions.

Muscle fatigue may causes some modifications on effects of forces and accordingly some changes on strategy of movement, therefore the concentration in thigh muscles impression on continuous movements is a guidance that makes the investigation on these changes so important.

Materials and Methods: Fifteen healthy women in the range of 20-30 years were contributed in this study. Muscle fatigue were applied in separate sessions by maximal voluntary contraction (MVC) in both open and close chains.

Subjects were done five dynamic repetitions of flexion / extension motion of knee before and after fatigue tests. Surface electromyography (sEMG) recorded from vastus medialis (VM), rectus femoris (RF) and vastus lateralis (VL) muscles during all conditions of tests. Normalized electromyography (NEMG) of muscles activities in two conditions of concentric (Con) and eccentric (Ecc), also median frequency (MF) were calculated for fatigue index. Muscle timing or recruitment pattern indicated by onset of muscle activities for both dynamics chains.

Results:  There are significant different of fatigue indexes between before and after fatigue tests (p<0.05).  After fatigue muscle timing delayed in open chain (p<0.05) and recruitment patterns changed from VL- VM- RF to VL-RF-VM. Fatigue test in close chain caused increment of muscle timing (p<0.05), but it did not change recruitment patterns.

Conclusion: After fatigue tests MF reduced little than NEMG. Significant difference occurred in muscle timing. These variations were increase and delay of timing with change of recruitment in open chain. These findings suggest that motor control strategy is will change at different condirions of with and without load situations.

Background and Aim : Chronic non-specific low back pain is one of the important health problem in military and different factors have been reported in its emergence. The aim of this study is to determine the association between low back pain and education level, Body Mass Index (BMI), exercise, smoking status ,work status and bad postures in military men.

Materials and Methods : In this non-experimental case-control study, 92 subjects (mean age= 29.16 year, SD= 8.55 year) with chronic non-specific low back pain and 93 subjects (mean age= 26.80 year, SD=9.22 year) without low back pain were selected by simple non-probability method from military centers in Tehran. Evaluation tools of this study included a self-administrated questionnaire, weighting scale and metal tape measure.

Results : According to the results of bivariate logistic regression, risk factors of exercise (P= 0.003), smoking status (P= 0.042), grade of BMI (P= 0.034), bad posture grades including heavy objects lifting movements (P= 0.007), bending movements (P= 0.003), rotating movements from the lumbar (P= 0.011), carrying bulky objects (P= 0.034), carrying heavy objects (P= 0.05) and working in squatting position (P= 0.005) had a significant association with low back pain. Job status (P= 0.999), education level (P= 0.056) and bad postures grades movements like wringing clothes (P= 0.958) had not a significant association with low back pain.

Conclusion : Doing regular exercise and having normal BMI decrease the risk of suffering from low back pain in the military while smoking and doing injurious physical activities during work (lifting heavy objects, bending movements and rotating from the lumbar, carrying bulky and heavy objects, and working in squatting position for a long time) increase the risk of suffering from low back pain.

Key Words : Chronic non-specific low back pain, Military forces, Biomechanical risk factors, Exercise

Background and Aim: One of the main causes of chronic non-specific low back pain is inappropriate working conditions, high repetition of one activity or work heaviness. An appropriate, accurate, inexpensive and easy assessment tools is necessary for measuring intensity of exposure to injurious  work activities, Identify individuals at risk and using appropriate treatment. The aim of this study is to compare the single-item Borg scale with JRPD scale to identify individuals at risk of exposure to injurious work activities in chronic non-specific LBP.

Materials and Methods: In this cross-sectional survey study, 92 subjects with non-specific low back pain by mean age of 29.16 (SD= ± 8.55) years and 93 healthy subjects by mean age of 26.80 (SD= ± 9.17) years and matched of work time, age and type of service with subjects with non-specific low back pain were selected by simple non-probability method. Single-item Borg scale and JRPD scale were used to assess the intensity of injurious work activities.

Results: Considering JRPD scale as a criterion scale, the sensitivity rate of 82% and specificity rate of 28% was obtained for single-item Borg scale at the moderate threshold. While the severe threshold for this scale, sensitivity and specificity rate were 25% and 85%, respectively. Also, the results showed that both single-item Borg scale and JRPD scale has significant ability to classify subjects with non-specific low back pain which are exposed or not exposed to injurious work ability (P<0.001). 

Conclusion: The single-item Borg scale has high sensitivity and low specificity at the moderate threshold and above and high specificity and low sensitivity at severe threshold to identify individuals Exposed to injurious work activities in military with chronic non-specific LBP.

Keywords: Injurious work activities, Non-specific LBP, Single-item Borg scale, JRPD scale

Background and Aim: An suitable prosthesis may have contributed effectively to amputee’s ability to accomplish activities. According to the search field and empirical evidence Dynamic-Response feet and SACH feet are common prosthetic components used. Consequently, the purpose of the present review was to compare the biomechanical studies of running with SACH and Dynamic-Response according to main parameters in running analysis.

Materials and Methods: An  electronical  search  was  done  in  PubMed,  Ovid and  Science Direct without time limitation. The abstract and title of papers were reviewed based on selected Criteria. The quality of the papers was evaluated based on Downs and Black tool. Key words include “Amputee”, “Dynamic-Response”, “energy-storing”, “SACH”, and “Running” were selected for the search.

Results: Based on the search keywords, 722 articles were found. Regarding the selection criteria, 4 articles were chosen. Amount of biomechanical studies have been found is not  too enough to distinguish preference between SACH feet and Dynamic-Response feet.

Conclusion: The biomechanical preference among SACH feet and Dynamic-Response during running feet is not cleared. In addition, various dependent variables among studies has made harder a comprehensive conclusion. So further studies with similar topics, measurement tools and outcome measures are recommended.

Keywords: Transtibial amputee, SACH feet, Dynamic-Response feet, Biomechanical, Running