132 The Open Rehabilitation Journal, 2010, 3, 132-135 1874-9437/10 2010 Bentham Open Open Access Physiological Electromyographic Activations Patterns of Lower Limb Muscle in Children Maria Grazia Benedetti *,1 , Valentina Agostini 2 , Giulia D’Apote 1 and Marco Knaflitz 2 1 Movement Analysis Laboratory, Istituto Ortopedico Rizzoli, Bologna Italy 2 Dipartimento di Elettronica, Politecnico di Torino, Torino, Italy Abstract: Kinesiological electromyography (KEMG) is an essential part of gait analysis as it supports clinicians with the objective assessment of muscular function during walking. During the gait cycle muscles are active with definite actions aimed at controlling joints in order to accomplish requirements of gait such as stability, loading acceptance, and progression. The knowledge of the development of normal EMG activity is of relevance in interpreting gait analysis data. While there is a wide literature on normative kinematics and kinetics data in children, only a few studies reported reference KEMG dataset on a paediatric population and on the maturation of gait in children. The available literature reported that the surface KEMG in children has a significant amount of variability, which should be taken into consideration when performing clinical interpretations. The KEMG timing and duration in normal children can vary with age, body height, body weight, gait velocity and stride length. Moreover, there is evidence that within session EMG variability in children aged 6-8 years is twice than that of adults. Although children in this age range can be considered to have a mature walk, variability about the mean performance continues to develop for many years and stable locomotion may be achieved despite significant variability in the muscle recruitment patterns. Further studies using accurate techniques of signal detection and analysis are required to improve our knowledge on physiological and pathological patterns of muscular activation in children. Keywords: Muscle, surface electromyography, lower limbs, children, gait. INTRODUCTION Kinesiological electromyography (KEMG) is an essential part of gait analysis as it supports clinicians with the objective assessment of muscular function during walking. Especially when associated with dynamic of gait, it provides insight on biomechanics of walking and on neural control during walking [1, 2]. There is wide evidence on its role in clinical diagnosis making in Cerebral Palsy [3] as well as in stroke patients [4]. While there is a wide literature on normative KEMG data in adults [5-7] only a few studies reported reference KEMG datasets on a paediatric population [8-10], and particularly on changes depending on the maturation of gait in children [11, 12]. In paediatrics, in fact, there is a significant change in body size and neurological function during development that could affect the KEMG activity [8]. Actually, in most cases, data provided by Perry [5] in adults are still the only reference most clinicians take into account for children. A few works are devoted to the analysis of KEMG pattern changes induced by speed of progression [9, 10, 13]. As most disabled children walk with reduced speed, it is very important to differentiate EMG modifications induced by speed of progression from those due to pathology [10]. *Address correspondence to this author at the Movement Analysis Laboratory, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy; Tel: +390516366529; Fax: +390516366561; E-mail: benedetti@ior.it During the gait cycle, muscles are active with definite actions (Fig. 1) aimed at controlling joints in order to accomplish requirements of gait such as stability, loading acceptance, and progression on support foot and, as overall function, energy conservation [5]. The biomechanics of normal gait has been extensively treated in fundamental books [5, 6, 14] to which we refer the readers for further insight in this topic. The aim of this work is to review literature on the effects of age and speed of progression on the EMG signal. EMG PATTERN AND AGE The knowledge of the development of normal EMG activity in children is of relevance in interpreting abnormal changes seen in the diagnostic gait analysis laboratory. One of the early works reporting age related surface EMG timing of activation in children was that one of Sutherland [11]. With increasing age, Sutherland found that the Gluteus Maximus showed a slight trend toward shortening of the activation time during stance phase as well as the Vastus Medialis which showed a reduction in the time of activity during both stance phase and swing phase, while the Tibialis Anterior showed a gradual reduction in the time of activation during stance phase. Both the Medial and Lateral Hamstrings of children showed prolonged stance-phase activity compared with adults, but the activity gradually decreased with increasing age. No change with age was observed in Gluteus Medius activity. In particular, Sutherland evidenced that the Gastrocnemius–Soleus complex showed a pattern of activity age related. While a normal adult phasic activity was present from two up to seven years old children (mature