S200 Published posters / Gait & Posture 24S (2006) S98–S289 PP-070 Can gait efﬁciency be fully normalized in healthy growing boys and girls? Patricia Van de Walle a,b,c,∗ , Rik Gosselink a , Kaat Desloovere a,b , Guy Molenaers b,d , Steven Truijen c , Kim Daniels a,b a Department of Rehabilitation Sciences, KuLeuven, Belgium b Clinical Motion Analysis Laboratory of the University Hospital Pellenberg, Belgium c Department of Health Sciences, Hogeschool Antwerpen, Antwerp, Belgium d Department of Paediatric Orthopedics, KuLeuven, Belgium 1. Summary/conclusions Age, size and sex inﬂuence parameters of energy efﬁ- ciency in growing children. Age and size inﬂuence can only partially be removed using normalization for mass but nor- malizing to non-dimensional gait variables and net oxygen consumption makes energy parameters largely independent to age and size. Differences between boys and girls, however, do not seem to be very sensitive to full normalization. 2. Introduction When children grow not only body dimensions changes but there is maturation of the neuromuscular system as well. During growth locomotor economy, expressed in oxygen uptake or oxygen cost also becomes more efﬁcient [1]. It is still not clear what changes of growth and maturation account for the increased efﬁciency and when mature gait efﬁciency is reached. More insight into age-related changes in normal pae- diatric gait is necessary to evaluate gait inefﬁciency caused by a pathological walking pattern in children, as aging and growth can be mistaken for improvement. The purpose of this study was to collect normative values on energy expenditure during walking at self-selected walk- ing speed in children aged between 3 and 12 years. We also aimed to evaluate the effect of body dimensions (mass, leg length) on energy efﬁciency during walking by normalizing gross oxygen consumption ﬁrst to body mass and second also to non-dimensional gait variables using net oxygen consump- tion as proposed by Schwartz et al. [2,3]. 3. Statement of clinical signiﬁcance When evaluating gait efﬁciency in growing children with gait pathology one should be careful not to mistake a gain in efﬁciency caused by growing or maturation as an improve- ment due to intervention. 4. Methods Twenty eight boys and thirty six girls between 3 and 12 years of age underwent a breath by breath oxygen con- sumption measurement (Cosmed K4b2) during walking on a normal surface. Energy measurement was performed using a standardized protocol of 5 min sitting (base line), 3 min standing and 8 min of walking on an eight shaped track. The mean and standard deviation of a steady state period of 2 min sitting and 3 min walking in the second half of each stage were calculated in both conditions for heart rate (HR) and oxygen rate. During walking, velocity and oxygen cost were also calculated. Gross oxygen rate and cost were ﬁrst normalized to mass and secondly to mass and length using net oxygen consumption (walking-baseline) by the formulas proposed by Schwarz et al. [2]. Comparison of boys and girls was done by a two tailed student t-test for anthropometric data and all parameters of energy measurement. The level of signiﬁcance was set at p < 0.05. For energy parameters, where no difference was found between boys and girls a linear regression was carried out on the total group. For parameters where boys and girls differed signiﬁcantly separate linear regression was done for both groups. 5. Results No differences between boys and girls were found for age, height, leg length or weight. Nor were there signiﬁcant differ- ences in mean between boys and girls for heart rate or veloc- ity and non-dimensional velocity (vNN) [2,3]. Oxygen rate at baseline was signiﬁcantly higher for boys (p = 0.02) and showed a similar trend during walking (p = 0.67). Net oxygen rate and oxygen rate after net non-dimensional (rateNN) nor- malization did not differ between boys and girls. Oxygen cost was signiﬁcant higher for boys (p = 0.008) when normalized to mass, but no longer after net non-dimensional normal- ization (p = 0.056). When comparing the youngest with the eldest children, the level of signiﬁcance became stronger for the older boys. By increasing age heart rate at base line (p = 0.008) and during walking (p =0.015) decreased signiﬁcantly. Walk- ing velocity increased signiﬁcantly with increasing age (p = 0.000) and by increasing leg length (p = 0.000) but when net normalized, the increase was no longer signiﬁcant. Oxy- gen rate at baseline decreased signiﬁcantly with increas- ing age for boys (p = 0.004) and girls (p = 0.003). For oxy- gen rate and rateNN during walking no signiﬁcant decrease with increasing could be found for either gender. Oxygen cost decreased signiﬁcantly with increasing age and increas- ing leg length for boys (p = 0.004 and 0.000) (Fig. 1) and girls (p = 0.008 and p = 0.000). When cost was net non- dimensional normalized (costNN) the decrease was no longer signiﬁcant for age or leg length in boys or girls.