Background: Firefighters are required to carry self-contained breathing apparatus (SCBA), which increases the risk of musculoskeletal disorders. This study assessed the newly recruited firefighters’ internal forces and potential musculoskeletal disorders when carrying SCBA. The effects of SCBA strap lengths were also evaluated. Methods: Kinematic parameters of twelve male subjects running in a control condition with no SCBA equipped and three varying-strapped SCBAs were measured using 3D inertial motion capture. Subsequently, motion data and predicted ground reaction force were inputted for subject-specific musculoskeletal modeling to estimate joint and muscle forces. Results: The knee was exposed to the highest internal force when carrying SCBA, followed by the rectus femoris and hip, while the shoulder had the lowest force compared to the no-SCBA condition. Our model also revealed that adjusting SCBA straps length was an efficient strategy to influence the force that occurred at the lumbar spine, hip, and knee regions. Grey relation analysis indicated that the deviation of the center of mass, step length, and knee flexion-extension angle could be used as the predictor of musculoskeletal disorders. Conclusion The finding suggested that the training of the newly recruits focuses on the coordinated movement of muscle and joints in the lower limb. The strap lengths around 98-105 cm were also recommended. The findings are expected to provide injury interventions to enhance the occupational health and safety of the newly recruited firefighters.

OBJECTIVETo study the incidence rate and risk factors of HIV infection among sero-negative spouses of people living with HIV/AIDS (HIV/AIDS) in Dehong prefecture, Yunnan province.

METHODSA prospective cohort study was conducted from February 2009 to December 2014 in Dehong prefecture, Yunnan province. Questionnaire survey and HIV related tests were carried out once a year.

RESULTSBy the end of December 2014, 2 091 sero-negative spouses had been recruited, of whom 1 692 were followed-up for at least one time. RESULTS showed that 34 new HIV infections were identified within 5 494.52 person years of follow-up, for an overall incidence of 0.62 per 100 person years. HIV incidence rates appeared as 0.79 per 100 person years, 0.62 per 100 person years, 0.47 per 100 person years in 2009-2010, 2011-2012, 2013-2014, respectively. Data from the Cox proportional hazard regression model indicated that risk factors of HIV infection among sero-negative spouses of HIV/AIDS were: non-consistent condom use (HR=4.64, 95%CI: 1.89-11.40,P= 0.001), HIV/AIDS delayed antiviral retrovirus therapy (ART) for more than one year (HR=3.70, 95% CI: 1.44-9.49,P=0.007) after the HIV negative spouses were initially recruited, HIV/AIDS did not receive any ART (HR=3.62, 95% CI: 1.14-11.51,P=0.029).

CONCLUSIONSThe incidence of HIV infection among sero-negative spouses in Dehong prefecture was relatively low. Publicity on consistent condom use program should be emphasized among sero-negative spouses of HIV/AIDS, together with the timely provision of ART to those HIV/AIDS.

Adolescent ; Adult ; China ; epidemiology ; Female ; HIV Infections ; epidemiology ; transmission ; HIV Seronegativity ; Humans ; Incidence ; Male ; Mass Screening ; Middle Aged ; Prospective Studies ; Risk Factors ; Sexual Behavior ; Spouses ; Surveys and Questionnaires ; Young Adult