The influence of sex and strength capacity on normalized low-back exposure during lifting: Insights from a joint power analysis

Quantifying how functional and structural personal factors influence biomechanical exposures in paramedic lifting tasks

It is unknown how structural (sex, stature, body mass) and functional (strength, flexibility) personal factors influence lifting strategy in paramedic work. We explored whether variance in peak low back forces and kinematic coordination patterns could be explained by structural and functional personal factors in paramedic lifting tasks. Seventy-two participants performed backboard and stretcher lifts. Peak low back forces normalised to body mass, as well as kinematic coordination patterns, were calculated as dependent variables. Being female, stronger, shorter, having higher body mass, and/or having greater lower body range of motion (ROM) were all independently associated with lower normalised low back forces across backboard and stretcher lifting. Females and stronger individuals seemed to define a movement objective to consistently minimise compressive forces, while individuals with greater hip ROM consistently minimised anteroposterior shear forces. The efficacy of improving strength and hip ROM to reduce low back forces in paramedic lifting should be investigated.Practitioner summary: Females, stronger individuals, and individuals with greater hip range of motion consistently exhibited lower normalised low back forces in paramedic lifting. Improving strength and hip range of motion via training is a potential proactive ergonomics approach to reduce peak low back forces in paramedic lifting tasks.

Sensitivity of principal component analysis outcomes to data pre-processing conditions when quantifying trial-to-trial variability in whole-body kinematics

This study investigated whether modes of variance in trial-to-trial whole-body kinematic variability identified by principal component analysis (PCA) were consistent across data pre-processing conditions generated from a common dataset. Comparisons made included 1) when trajectory data was expressed in a global vs. local reference frame; 2) when the number of landmarks used to represent whole-body motion differed, and; 3) whether input trajectory data were normalized to participant stature. Varying data pre-processing conditions prior to PCA does not bias the total variance identified. However, it can influence how modes of variance are dispersed across PCs, which in turn, can influence interpretation.

Differential effects of sex on upper body kinematics and kinetics during fatiguing, Asymmetric lifting

This study quantified sex-specific biomechanical adaptations to fatigue in asymmetric lifting. Twenty-one females and fifteen males performed a prolonged asymmetric lifting protocol while upper body, trunk and pelvis kinematics were collected. Features of movement identified with principal component analysis, and peak joint angular velocities and moments were calculated. Sex-specific kinematic adaptations to fatigue included females adopting a 'stoop-like' lifting strategy to a greater extent than males. Additionally, females exhibited higher vertical elbow positions during load rotation, moved their body toward the destination for load deposit, and did not reduce peak right shoulder flexion velocities, in contrast to male participants. Females also had greater low back and shoulder peak normalized joint moments. When fatigued, females adopted an asymmetric lifting strategy that minimized metabolic demand as supported by smaller decreases in maximum voluntary contractions. However, females' fatigue-related adaptations increased biomechanical exposures associated with injury risk.

Factors influencing the likelihood of females passing the Ottawa paramedic physical ability test

The Ottawa Paramedic Physical Ability Test (OPPAT) was launched in Ontario as a physical employment standard for front-line paramedics. When considering pass rates based on sex, males had a higher likelihood of passing than females. To help understand how to improve pass rates among females we aimed to understand if factors such as participant demographics, college type, employment status and/or peak heart rate (a surrogate of fitness level) were related to OPPAT pass rates. Females who were employed, who were educated in a public paramedic college, and who had higher body mass were more likely to successfully complete the OPPAT. Those educated in a public paramedic college were more than twice as likely to pass relative to those educated in a private college program. This may underscore a need to further explore different modes of paramedic education to understand why public college program trained students are more likely to pass.