Introduction:
Physical fitness is a resultant of the efficiency of adaptive mechanisms for physical effort. People with intellectual disabilities may exhibit limited adaptive capacities, not only regarding their mental development, but also physiological, social and emotional development. Dysfunctions of the central nervous system observed in individuals with intellectual disabilities cause difficulties in gaining movement experience as well as problems with coordination and kinesthetic sense. Thus, intellectual disability might cause low physical activity and, consequently, low physical fitness.

Objective:
The aim of the present investigations was to evaluate aerobic capacity of intellectually disabled adults and determine its potential relationships with the degree of intellectual disability, somatic parameters, age and gender.

Material and Methods:
The study group consisted of 85 intellectually disabled adults aged 20 to 40 years. The investigations were based on direct observation of the participants. The following somatic parameters were measured: body height and weight, waist and hip circumference, body fat percentage, body mass index and waist-to-hip ratio. Physical fitness was evaluated based on PWC170; VO2max was also calculated. Qualitative assessment of physical fitness level was carried out using Astrand’s classification (with respect to age and gender).

Results:
30% of women and 46.3% of men had very low level of aerobic capacity. Absolute values of PWC170 and VO2max were significantly higher in men. However, relative values expressed in millilitres of oxygen per kilogram of body weight did not reveal statistically significant inter-gender differences. Age and degree of intellectual disability did not significantly influence the level of physical fitness. Multiple regression analysis to estimate VO2max/kg revealed a negative correlation with %FAT and WHR.

Conclusions:
1. A large sample of the study population (30% female, 46,3% male) showed very low levels of aerobic capacity. 2. Our investigations did not demonstrate a relationship between physical fitness and age or the degree of intellectual disability. Gender turned out to be a differentiating factor but only for the absolute PWC170 and VO2max. 3. The level of physical fitness was significantly related to somatic parameters including body mass, waist and hips circumference, percentage of body fat, BMI and WHR.