Total body potassium fat free weight and maximal aerobic power in children with anorexia nervosa.

Body composition and aerobic work performance have been studied in 5 boys and 10 girls suffering from anorexia nervosa. The average ages of the two groups of children were 15.4 (boys) and 15.2 (girls) years respectively. Measurements of body composition included height, weight (W), body potassium (40K), skinfold thickness (SFT) at triceps and subscapularis, blood volume (BV) and femoral condylar and radioulnar breadths. From these measurements estimates of fat free weight (FFW), skeletal weight (S) and lean body mass (LBM) were made. Work performance was assessed by measurement of the maximal aerobic power (VO2 max). The patients had lost on average 26% of their former body weight. The boys had on average greater than 7% of their body weight as fat compared with greater than 9% in the girls. However, the loss of weight was not solely due to loss of body fat, but could also be ascribed to a decrease in soft fatfree tissue. LBM or FFW could be estimated as well from SFT as from 40k. vo2 max averaged 1.43 1/min (35.1 ml/kg/min) in the anorexic boys and 1.24 l/min (33.2 ml/kg/min) in the girls and was associated with FFW and LBM. However, VO2 max was lower in relation to LBM than in healthy children of the same age. Thus it was suggested that the emaciation in anorexia is directly attributable to loss of both fat and muscle and accounts in part for the reduction of aerobic power observed. However, an important factor may be the debilitating effect of starvation on the patient, particularly in its advanced and later stages, which reduces his/her level of habitual physical activity.

Effect of strength training on enzyme activities and fibre characteristics in human skeletal muscle.

Progressive strength training was performed 3 times a week for 8 weeks by 14 male students (19-31 yrs.). The training program consisted mainly of dynamic exercises for the leg extensors with maximal or close to maximal loads. The training caused significant improvements in dynamic and isometric strength. One repetition maximum in squats increased with 67%, Sargent jump with 22%, and maximal voluntary isometric contraction (MVC) with 13%, respectively. Body weight and leg muscle circumferences remained unchanged after training, whereas total body potassium, lean body mass and calculated total muscle mass increased, suggesting a change in body composition with training. Muscle biopsies were obtained from vastus lateralis for fibre analyses and determination of enzyme activities. There were no changes in muscle fibre composition or fibre area with training. The activities of Mg2+ stimulated ATPase, creatine phosphokinase and phosphofructokinase remained unchanged, whereas myokinase activity was increased after training from (1.41 to 1.52 moles x 10(-4) x g-1 x min-1, p less than 0.05). After training significant correlations (p less than 0.01) were demonstrated between Mg2+ stimulated ATPase activity and % fast twitch fibres (% FT) (r = 0.67), as well as between myokinase activity and % FT (r = 0.86).