Introduction 2001 1988 2002 1995 1994 2007 1985 2 1987 1997 2003 1987 1991 2004 2004 1991 1993 1991 2006 1993 2005 Method Participants Recruitment Adolescents and young adults with MMC, aged between 16 and 30 years, were recruited from the university hospitals in Rotterdam, Leiden, Utrecht and Amsterdam and all rehabilitation centers in the Southwest of the Netherlands. Exclusion criteria were complete dependence on an electric wheelchair, presence of disorders other than MMC that affect daily physical activity (e.g. rheumatoid arthritis), and presence of disorders that contra-indicate a maximal exercise test (e.g. exercise-induced ischemia or arrhythmias, uncontrolled hypertension and exercise limitation due to chronic obstructive pulmonary disease). We invited 171 persons of whom 50 participated in the study (29%). Main reasons for non-participation were no interest, lack of time or duration of the measurements. No differences were found between participants and non-participants regarding age, gender, level of lesion and presence of hydrocephalus, as measured with an independent t-test or Chi square test (Buffart et al. in press). All participants and parents of adolescents aged less than 18 years gave written informed consent before participating in the study. The Medical Ethics Committee of the Erasmus MC Rotterdam and of all participating institutes approved the study. Characteristics 1 1973 2007 Table 1 n =  Gender (% male) 50 Age (mean ± SD in years) 21.2 ± 4.5 Height (mean ± SD in m) 1.57 ± 0.12 Body mass (mean ± SD in kg) 67.6 ± 15.6 Level of lesion (%)  Thoracic 2  Thoracolumbar 14  Lumbar 28  Lumbosacral 42  Sacral 14  Hydrocephalus (%) 82 a  Community ambulator 30  Household ambulator 14  Non (functional) ambulator 56 Educational level (%)  Low 37  Medium 39  High 24 a Aerobic capacity 1983 1992 n =  n =  2 2001 2 e 2 2 pet 2 2 e 2 2 pet 2 1979 1999 2  1982 1987 Muscle strength 1991 t Z 2000 1997 Z Z Z Flexibility As indicator of flexibility of lower extremity we assessed passive mobility of hip and knee joint while participants were lying supine and of the ankle joint while they were sitting. We considered mobility to be restricted when extension of hip and knee joint and ankle dorsal flexion did not reach neutral position. Since no differences were found in mobility restrictions between dominant and non-dominant side (tested with the Wilcoxon signed rank test) we used the results of the dominant side to calculate a sum score of joint mobility ranging from 0 (no mobility restrictions in any joint) to 3 (all three joints have mobility restrictions). Body composition 2001 Statistical analysis Results of health-related fitness components are presented as mean ± standard deviation (SD) for the total group and for subgroups regarding gender and ambulatory status. 2 2 Z 2 R 2 P  2 r P r  P 2004 Results 2 2 n 2 Z 2 Table 2 Descriptive results of health-related physical fitness components for the total group and for subgroups regarding gender and ambulatory status  n =  Gender Ambulatory status n =  n =  n =  n =  n =  Aerobic capacity (mean ± SD)  2 1.48 ± 0.52 1.78 ± 0.51 1.18 ± 0.30 1.85 ± 0.57 1.44 ± 0.45 1.29 ± 0.40 a 67 ± 15 71 ± 13 61 ± 18 68 ± 16 54 ± 2 – 2 22.6 ± 8.2 28.1 ±  7.0 17.0 ± 4.7 29.0 ± 7.7 22.3 ± 6.6 19.2 ± 6.8 Peak oxygen pulse (ml/bpm) 8.7 ± 3.0 10.1 ±  2.8 7.3 ± 2.4 10.7 ± 2.8 7.8 ± 2.4 7.8 ± 2.8 PeakRER 1.17 ± 0.22 1.17 ± 2.28 1.18 ± 0.20 1.15 ± 0.22 1.27 ± 0.16 1.16 ± 0.24 PeakW (W) 91 ± 42 113 ± 43 69 ± 28 123 ± 42 97 ± 35 73 ± 34 PeakHR (bpm) 174 ± 19 179 ± 16 169 ± 20 173 ± 21 183 ± 14 172 ± 18 PeakHR % of predicted maximum 90 ± 10 92 ± 8 89 ± 10 87 ± 10 95 ± 8 91 ± 10 VAT (l/min) 1.20 ± 0.43 1.39 ± 0.44 1.01 ± 0.32 1.55 ± 0.45 1.07 ± 0.29 1.05 ± 0.34 VAT% 82 ± 15 80 ± 14 86 ± 16 84 ± 10 77 ± 22 83 ± 16 Muscle strength (mean ± SD)  Z −2.1 ± 1.8 −2.3 ± 2.1 −1.9 ± 1.5 −2.7 ± 2.2 −2.0 ± 1.6 −1.8 ± 1.7 Z 61 58 64 79 57 54 Joint mobility (median [range])  Number of restricted joints  1 [0–3] 1 [0–3]  1 [0–3]  0 [0–2]  1 [0–2]  1.5 [0–3]  Impaired mobility in any joint (%) 61 54 67 29 57 82 Body composition (mean ± SD) Sum of four skin-folds (mm)  74.8 ± 38.8 51.2 ± 24.6 100.4 ± 35.1 59.1 ± 29.2 66.5 ± 34.7 86.0 ± 42.0 % of reference values 159 ± 77 146 ± 79 173 ± 73 121 ± 52 160 ± 101 181 ± 75 a n =  2 3 2 β P  β P  β P  2 Table 3 Regression models for aerobic capacity Independent variables 2 β  P R 2 Simple regression analysis  Personal characteristics     Gender 0.61 <0.001 0.36  Age −0.07  0.65 –  Lesion level −0.43 0.002 0.17  Hydrocephalus −0.18  0.22 –  Ambulatory status −0.48 <0.001 0.22  Educational level 0.13 0.39 – Multiple regression analysis a   Personal characteristics   0.50   Gender −0.55 <0.001    Ambulatory status −0.40 <0.001  b   Inter-relations    Z 0.22 0.04 0.55   Body composition (sum of four skin-folds in mm) 0.25 0.08 0.53   Joint mobility (number of restricted joints) 0.00 0.98 – Significant betas are presented in bold β R 2  Gender Lesion level Hydrocephalus Ambulatory status Educational level a b 2 3 2 β P  2 2 β P  Discussion Components of health-related physical fitness In the present study, several health-related components of physical fitness were studied simultaneously in a relatively large group of adolescents and young adults with MMC. In general, most participants had poor health-related physical fitness. 2 2 1978 2 1974 1975 1983 2 2 1975 2 2 2002 2 2001 2 r  P  2 1997 1986 1993 1999 2 2 1995 1987 1991 2004 2004 1987 1991 1993 1991 Relations between aerobic capacity and other components of health-related physical fitness 2 2006 1993 2005 2 1993 2 1986 2 2006 1987 Limitations of the study 2 1992 2 1978 2 1984 1997 1991 Z 2 Z 2004 2 2