Neuromuscular Changes During the Six-Minute Walk Test in Pediatric Sickle Cell Disease

Children/adolescents with sickle cell disease (SCD) experience muscle-related impairments and declines in physical function. These deficits result from chronic anemia and impaired oxygen delivery, limiting the development of safe and effective exercise-based interventions. To better understand the effects of SCD on sustained activity, this study aimed to compare the physical function of children/adolescents with SCD to normative values and evaluate changes in neuromuscular function and muscle oxygenation during the 6-min walk test (6MWT). Each child/adolescent underwent a standardized 6MWT while measuring vastus lateralis muscle activity and oxygenation using surface electromyography (EMG) and Near-infrared spectroscopy. Heart rate was also continuously monitored. Compared to age- and sex-matched norms (625.9 ± 55.1 m), children/adolescents with SCD had a higher resting heart rate (108.5 ± 11.7 vs. 90.3 ± 5.0 bpm; p = 0.023), covered less distance (482.7 ± 91.9 m; p = 0.002), but no difference in heart rate at the End of the 6MWT (p = 1.0). Heart rate rose steadily throughout the 6MWT, 121.3 ± 11.1 bpm at the Start (p = 0.17), 139.0 ± 20.3 bpm at Mid (p = 0.009), and 142.1 ± 24.2 bpm at the End (p = 0.009). EMG median frequency decreased significantly from pre-start (82.7 ± 11.7 Hz) to the Start of walking (68.5 ± 21.7 Hz; p = 0.028), and remained low at Mid (68.0 ± 22.4 Hz; p = 0.047) and End (65.7 ± 21.5 Hz; p = 0.047). Children/adolescents with SCD had reduced functional walking capacity, with an elevated resting heart rate and expected increases, sustained changes in neuromuscular activation during submaximal, sustained activities. This suggests that routine activities may place greater physiologic demands on children/adolescents with SCD, and that clinical assessments may require more than just walking distance.