Personalization of military load carriage simulations affects muscle and joint contact forces.

Personalized muscle strength scaling produced greater joint contact impulses at the lumbar, hip, and knee compared to non-personalized models.

• Personalized muscle strength scaling had greater joint contact impulses at the lumbar (42%), hip (25%), and knee (8%) compared to not personalized (p < .001)
• Smaller impulses were found at the ankle (-4%) with personalized muscle strength scaling (p = .048)
• Results were similar for peak joint contact forces
• Muscle strengths were scaled from eight maximum voluntary isometric contractions measured using an instrumented dynamometer including the lumbar, hip, knee, and ankle

Personalized mass-distribution scaling produced greater lumbar joint contact impulses during walking compared to non-personalized models.

• Personalized mass-distribution scaling had 6% greater lumbar joint contact impulses in walking compared to not personalized (p = .006)
• Modeled segment masses were scaled using measured regional masses from dual-energy x-ray absorptiometry (DXA)
• This effect was observed across walking conditions including no-pack and pack conditions

The study collected biomechanical data from 16 active-duty military participants under two load carriage conditions.

• 16 active-duty participants were included in the study
• Two walking conditions were evaluated: 1) no-pack and 2) pack (posteriorly added load, total 46 kg)
• Full-body kinematics, ground reaction forces, and electromyography were collected
• These data drove and validated musculoskeletal simulations of models with different types of personalization

Modeled muscle strength from average adults is likely underestimated for trained active-duty military personnel, which can influence internal load calculations.

• The authors note that modeled muscle strength from average adults is likely underestimated for trained, active-duty military personnel
• Low muscle strength is identified as a modifiable injury risk factor for military overuse injuries
• Military overuse injuries are associated with greater internal loads during load carriage and cause decreased readiness and increased costs

Model personalization is beneficial for quantifying internal loading and evaluating training interventions in military populations.

• Both muscle strength and segment mass distribution personalization significantly affected joint contact impulses and peak forces
• Personalization is particularly relevant for individuals with unique muscle strengths and body segment mass distributions
• The authors conclude that model personalization is beneficial to quantify internal loading and evaluate training interventions