Fractional order human arm dynamics with variability analyses

• The human arm can be modelled using fractional derivatives.
• Fractional models have fewer parameters than integer models from the literature.
• They are better adjusted to experimental data and parameter uncertainty is lower.
• This agrees with literature on the fractional order of muscle viscoelastic behaviour.

This paper uses experimental data to model the human arm at the elbow joint, using both third order integer dynamic models, commonly found in the literature, and fractional order models (involving derivatives of fractional order, between 1.2 and 1.4). The latter models prove to be superior, as they provide a better adjustment, with less parameters, with lower parameter uncertainty, and without instability problems. These novel results for modelling the human arm are in line with published literature suggesting that muscles may be profitably modelled with fractional derivatives.