**Variability of Muscular Recruitment in Hemiplegic Walking Assessed by EMG Analysis**

### **Francesco Di Nardo 1,\*, Susanna Spinsante 1, Chiara Pagliuca 1, Angelica Poli 1, Annachiara Strazza 1, Valentina Agostini 2, Marco Knaflitz 2 and Sandro Fioretti 1,\***


Received: 26 August 2020; Accepted: 23 September 2020; Published: 25 September 2020

**Abstract:** Adaptive variability during walking is typical of child motor development. It has been reported that neurological disorders could a ffect this physiological phenomenon. The present work is designed to assess the adaptive variability of muscular recruitment during hemiplegic walking and to detect possible changes compared to control populations. In the attempt of limiting the complexity of computational procedure, the easy-to-measure coe fficient of variation (CV) index is adopted to assess surface electromyography (sEMG) variability. The target population includes 34 Winters' type I and II hemiplegic children (H-group). Two further healthy populations, 34 age-matched children (C-group) and 34 young adults (A-group), are involved as controls. Results show a significant decrease (*p* < 0.05) of mean CV for gastrocnemius lateralis (GL) in H-group compared to both C-group (15% reduction) and A-group (35% reduction). Reductions of mean CV are detected also for tibialis anterior (TA) in H-group compared to C-group (7% reduction, *p* > 0.05) and A-group (15% reduction, *p* < 0.05). Lower CVs indicate a decreased intra-subject variability of ankle-muscle activity compared to controls. Novel contribution of the study is twofold: (1) To propose a CV-based approach for an easy-to-compute assessment of sEMG variability in hemiplegic children, useful in di fferent experimental environments and di fferent clinical purposes; (2) to provide a quantitative assessment of the reduction of intra-subject variability of ankle-muscle activity in mild-hemiplegic children compared to controls (children and adults), suggesting that hemiplegic children present a limited capability of adapting their muscle recruitment to the di fferent stimuli met during walking task. This finding could be very useful in deepening the knowledge of this neurological disorder.

**Keywords:** surface electromyography; cerebral palsy; hemiplegia; motor disorders; gait variability; coe fficient of variation
