Low compliance of orthosis locomotion : selection criteria based on energy expenditure

Oxygen consumption (V̇O2), heart rate (HR) and cost of locomotion (C, energy required to cover 1 m per unit of transported mass) were measured in 14 paraplegics (age 19-59 yrs, BW 48-100 Kg, injury level C7-T11), during both wheelchair (Whch) and orthosis-assisted locomotion at 2-4 speeds, up to exhaustion (peak value, p). Subjects were divided into three groups; the HIP Guidance Orthosis Orlau Parawalker (PW, n=4), the Reciprocating Gait Orthosis (RGO, n=6) and the RGO with functional neuromuscular stimulation (RGO+FNS, n=4). Alms of the study were: a) to find out indicators of the poor long-term compliance (all but 2 RGO withdrawals in 5 yrs) on the basis of cost of locomotion and physical fitness; b) to assess selection criteria for the assignment of the different type of orthoses; c) to estimate whether electrical stimulation improves locomotion reducing fatigue. In RGO+FNS walking the slope difference of HR/V̇O2 curves between Whch and orthosis (ΔslHR/V̇O2) is significantly lower than in the other groups (=0 beats-l-1 for RGO+FNS vs 39 and 61 beats-I-1, for RGO and PW, respectively). Neither C, nor V̇O2P or ΔslHR/V̇O2 correlates with ortnosis length of use. C was higher (p<0.05) in RGO+FNS at low speeds (0.4-0.7 Km/h), but for medium to high speeds (0.7-1 Km/h) C was similar for the 3 orthoses, averaging 0.9*0.1 mlO2·m-1·Kg-1. It appears that: a) the poor long-term compliance for orthosis use depends on mechanisms (presumably psychological) apparently not related to fitness level; b) only those subjects who can deambulate at higher speeds might be suitable for electrical-stimulated types of orthosis. Hypothesis is made that adequate psychological and specific muscular training may improve compliance.