Objective To explore measures of peripheral muscular oxygenation, coupled to gait characteristics, between preterm and full-term children during a 6-minute walking test (6MWT). Study design Prepubescent children performed a 6MWT. During the test, changes in muscular oxyhemoglobin, deoxyhemoglobin, and total hemoglobin were measured with Near-infrared spectroscopy technology, positioned on subjects’ calves. Gait variables were monitored with the OptoGait system. Results Forty-five children (33 full-term children and 12 preterm children, mean age, 4.9 0.7 and 4.6 0.9 years, respectively) participated in this study. Statistical analysis highlighted a decreased walking performance for preterm children, with significantly lower walking distance (P < .05) than children born full-term (405.1 91.8 m vs 461.0 73.3 m respectively; 9%). A concomitant increase of oxygen extraction (over the time course of Variation of desoxyhemoglobin) was observed from the third minute of the test (P < .05). No statistically significant difference was found for other near-infrared spectroscopy measures. Finally, the analysis of gait variables highlighted a group effect for walking speed (P < .05) and stride length (P < .01). Conclusions Premature children showed decreased walking performance and greater change in peripheral muscular oxygen extraction, associated with slower walking speed and stride length. This may point to a muscular maladjustment and reduced functional capacities for children born preterm. These phenomena could be responsible for greater muscular fatigue. (J Pediatr 2020;227:142-8).