Figure 3.

Gross metabolic cost of transport and preferred walking velocity. (a) PWA using the bionic prosthesis (blue diamonds) had nearly the same average metabolic cost of transport (COT) as non-amputees (green squares) (p > 0.50 for 0.75–1.50 m s⁻¹; p = 0.17 for 1.75 m s⁻¹). Cost of transport is the metabolic energy needed to transport unit weight a unit distance, equal to (metabolic demand)/(body weight × distance travelled). PWA using a passive-elastic prosthesis (red circles) had 11–25% greater cost of transport (p < 0.05) at 1.00–1.75 m s⁻¹ compared with non-amputees. (b) Average preferred walking velocities of PWA using the bionic prosthesis (blue bar) and non-amputees (green bar) were equivalent (p = 0.97). PWA using a passive-elastic prosthesis (red bar) preferred to walk significantly slower (p = 0.008). Values within bars indicate averages (s.e.m.). Asterisks (*) indicate significant differences between PWA using the bionic prosthesis compared with using a passive-elastic prosthesis. Error bars indicate s.e.m. Second-order polynomial curve equations in (a) are, non-amputee: COT = 0.303v² – 0.846v + 0.934, r² = 0.49; bionic prothesis: COT = 0.308v² – 0.808v + 0.895, r² = 0.39; and passive-elastic prosthesis: COT = 0.295v² – 0.750v + 0.295, r² = 0.52. COT is calculated in Joules per Newton body weight per metre. v is velocity in metres per second.