How accurately can elbow flexion force be estimated?

@article{Bohannon1989HowAC,
  title={How accurately can elbow flexion force be estimated?},
  author={Richard W. Bohannon and N Endemann},
  journal={Perceptual and motor skills},
  year={1989},
  volume={68 3 Pt 2},
  pages={1159-62}
}