Energy costs of walking in lower-extremity plaster casts.

The energy cost of walking with axillary crutches and each of three types of plaster casts (long, short, and cylinder) on the lower extremity was measured in twenty normal adult men. The knee and ankle joints were immobilized unilaterally in the neutral positions. Oxygen uptake was measured using a modified Douglas-bag technique. Heart rate, respiratory rate, and step frequency were telemetered from transducers that were attached to the subjects. When walking and bearing full weight on a cast without the use of crutches, the average rates of energy expenditure for subjects wearing the three varieties of casts did not significantly differ from the value for normal walking. Velocity, however, was reduced depending on the extent of immobilization. The average velocity of the subjects was fifty-six meters per minute in a long cast, sixty-four meters per minute in in a cylinder cast, and seventy meters per minute in a short cast, compared with seventy-eight meters per minute without immobilization of the limb. The subjects' average oxygen cost per meter was 0.24 milliliter per kilogram in a long cast, 0.20 milliliter per kilogram in a cylinder cast, and 0.19 milliliter per kilogram in a short cast, compared with 0.15 milliliter per kilogram for normal walking. Using a unilateral non-weight-bearing swing-through gait, the average rate of oxygen uptake for subjects wearing the three types of casts did not differ from the mean value without a cast (21.2 milliliters per kilogram per minute). All values were at least 60 per cent higher than the average for normal level walking.