Cardiorespiratory and metabolic responses during forward and backward walking

Level and incline backward treadmill walking techniques are used in the rehabilitation of certain lower extremity injuries (eg., anterior cruciate ligament reconstruction). Of interest to clinicians is the maintenance of cardiorespiratory fitness resulting from these activities. The purpose of the present study was to determine the cardiorespiratory and metabolic stress of backward walking compared with forward walking. The metabolic cost of backward incline walking above a 1% grade has previously not been reported. Seventeen volunteers (11 males and six females, age = 25 +/- 2 years) underwent a forward maximal running test and four random-ordered 6-minute submaximal walking bouts at 93.8 m/min (3.5 mph). The bouts consisted of forward walking at 0% and 5% elevation and backward walking at 0% and 5% elevation. Measurements taken for each exercise session were oxygen uptake, expired ventilation, heart rate, and ratings of perceived exertion. Statistical analysis of these dependent variables indicates that: 1) at a given elevation, backward walking elicited greater cardiorespiratory, metabolic, and perceptual responses than forward walking and 2) backward walking at 5% elevation could provide a sufficient stimulus to maintain cardiorespiratory fitness.