Comparing Humeral Kinematic Variability During Farm Task Performance Between Laboratory and Field Agricultural...

Farmers experience high rates of shoulder injury, necessitating the need to better define the movement demands associated with farm work. Research is needed to determine whether simulating farm work in a laboratory environment will sufficiently capture the movement demands required in authentic agricultural environments. The purpose of this study was to compare variability in farm task performance between laboratory and field locations.

Inertial measurement units tracked humeral kinematics during four simulated farming work tasks (overhead drill, shovel, climb ladder, seed bag lift) and in three different locations; the laboratory, an agricultural tradeshow ("Ag in Motion"), and individual authentic grain/cattle farms. Ten participants per location were sex and age matched. Mean and peak humeral elevation, mean axial rotation, and peak internal and external rotation joint angles were evaluated for the primary "mover" arm during each of the tasks. Within and between participant variability, as well as differences in task performance across locations were evaluated.

The within variability for peak humeral internal rotation during the shovel task was significantly lower in the laboratory compared to Ag in Motion and the farms (F_2,27 = 5.59, p < .01, η² = 0.29). However, within variability was comparable across locations for all other outcomes. Between participant variability was lowest in the laboratory in 12/20 outcomes, lowest at Ag in Motion in 7/20 outcomes, and lowest on the farms in only one outcome, suggesting lower between participant variability in the more highly controlled environments. Finally, significant differences in performance were elicited across locations for the overhead drill, shovel, and climb seeder tasks. Generally, lower humeral elevation and axial rotation occurred in the laboratory environment compared to Ag in Motion or the farms.

Simulating an occupational task in the laboratory may not fully reflect the demands of the task when performed in real-world settings. While greater between participant variability may be unavoidable in-field due to differences in equipment and other environmental variables, the greater humeral elevation and axial rotation demands elicited in the field environments suggest in-field research is necessary to fully capture the complexity of occupational movements.