Energy demands of walking in persons with postpoliomyelitis syndrome: Relationship with muscle strength and reproducibility

Objectives: To describe the energy demands of walking in subjects with postpoliomyelitis syndrome (PPS) in comparison with the demands in healthy subjects, and to assess the reproducibility of walking energy measurements. Design: Four repeated measurements with a 1-week interval between each measurement. Setting: Outpatient clinic of a university hospital. Participants: Fourteen subjects with PPS and 14 age- and sex-matched healthy subjects. Interventions: Not applicable. Main Outcome Measures: Walking speed and energy cost of walking. The correlation parameter was lower-extremity muscle strength sum (MSS). The reproducibility parameters were standard error (SE) of measurement and smallest detectable difference (SDD). Results: Walking speed in subjects with PPS (61.8m/min) was significantly lower (-28%) and energy cost (4.8J center dot kg(-1)center dot m(-1)) was significantly higher (40%) than in healthy subjects. MSS correlated strongly with energy cost (r=-.84, P=.000), explaining 71% of the variance. The SE of measurement of energy cost measurements ranged between 1.7% and 3.4% for PPS subjects and between 1.2% and 2.4% for healthy subjects. The SDD ranged between 4.6% and 9.4% for PPS subjects and between 3.3% and 6.6% for healthy subjects, depending on the number of repeated measurements that were considered. Conclusions: Energy cost of walking in subjects with PP is strongly related to the extent of muscle weakness in the lower extremities. Although variability was greater for PPS subjects than for healthy subjects, reproducibility of energy cost measurements was high. Therefore, metabolic assessment of energy cost of walking is a sensitive tool that can reveal clinically relevant changes even in the condition of a person with PPS.