Asthmatic patients experience an increase in airway resistance that overburdens both respiratory and non-respiratory muscles. The objective of the present study was to determine whether children with persistent asthma present muscle shortening and postural changes. The 60 boys evaluated, aged 7-12 (pubertal ages up to Tanner stage G2) were divided into three age- and BMI-matched groups of equal number: CON (no history of asthma or allergy); MPA (mild persistent asthma); SPA (severe persistent asthma). Pulmonary function, muscle shortening and static posture were evaluated. The SPA group presented higher protraction of the head and shoulder compared with the CON group [9.5 (6.0-12.0) degrees vs 5.5 (0.0-12.0) degrees, P < 0.05; 0.89 (0.80-0.94) anterior/posterior ratio vs 0.94 (0.87-1.1) anterior/posterior ratio, P < 0.01)]. Severe asthmatic patients also presented shortening of arm flexor and posterior muscle of the thigh compared with the CON group [18.0 (10.0-24.0) degrees vs 12.0 (6.0-16.0) degrees, P < 0.05; and 16.5 (10.0-38.5) cm vs 8.0 (0.0-21.0) cm, respectively, P < 0.05]. Chest expansion at axillar and xiphoid levels were limited in SPA subjects compared with CON subjects [3.7 (1.5-6.5) cm vs 5.5 (2.0-8.0) cm and 4.7 (1.5-6.5) vs 6.0 (3.5-8.0) cm, respectively, P < 0.01]. SPA subjects also presented a higher incidence of lumbar spine straightening compared with CON and MPA subjects. Moderate asthmatic subjects presented intermediate values compared with severe and control subjects in five out nine evaluated outcomes. Our data suggest that severe asthmatic children present postural adaptations and muscle shortening that seem to be related to disease severity.