The aim of this study was to evaluate the benefits and limitations of using three
dimensional (3D) musculoskeletal modelling (LifeModelerTM) in assessing the safety
and efficacy of exercising on an abdominal crunch resistance training machine.
Three anthropometric cases were studied, representing a 5th percentile female, 50th
percentile and 95th percentile male. Results indicated that the LifeModelerTM default
model was capable of solving the forward dynamics simulations without adjustments.
The modelling was able to indicate high risk for back injury when performing the
abdominal crunch exercise as a result of the unacceptable intervertebral joint loading
that occurs during the exercise. Individuals with small anthropometric dimensions
such as some females and children cannot be accommodated suitably on the
abdominal crunch machine which negatively impacts exercise posture and
technique. Hip flexor muscle contribution in the execution of the exercise for the 5th
percentile female was substantial thus reducing the efficacy of the exercise in
isolating the abdominal muscles.