Farm youth often carry loads that are proportionally large and/or heavy, and field measurements have determined that these tasks are equivalent to industrial jobs with high injury risks. The purpose of this study was to determine the effects of age, load amount, and load symmetry on lower extremity joint moments during carrying tasks. Three age groups (8–10 years, 12–14 years, adults), three load amounts (0%, 10%, 20% BW), and three load symmetry levels (unilateral large bucket, unilateral small bucket, bilateral small buckets) were tested. Inverse dynamics was used to determine maximum ankle, knee, and hip joint moments. Ankle dorsiflexion, ankle inversion, ankle eversion, knee adduction, and hip extension moments were significantly higher in 8–10 and 12–14 year olds. Ankle plantar flexion, ankle inversion, knee extension, and hip extension moments were significantly increased at 10% and 20% BW loads. Knee and hip adduction moments were significantly increased at 10% and 20% BW loads when carrying a unilateral large bucket. Of particular concern are increased ankle inversion and eversion moments for children, along with increased knee and hip adduction moments for heavy, asymmetrical carrying tasks. Carrying loads bilaterally instead of unilaterally avoided increases in knee and hip adduction moments with increased load amount.
Jason C. Gillette (Corresponding Author) is with the Department of Kinesiology, Iowa State University, Ames, Iowa. Catherine A. Stevermer is with the Postprofessional DPT Program, Des Moines University, Des Moines, Iowa. Ross H. Miller is with the Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts. W. Brent Edwards is with the Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, Illinois. Charles V. Schwab is with the Agricultural and Biosystems Engineering Department, Iowa State University, Ames, Iowa.