The role of physical activity in the prevention of non-insulin-dependent diabetes mellitus (NIDDM) is of utmost importance. The aim of the present study was to evaluate the metabolic effects of aerobic endurance exercise and circuit-type resistance training in subjects with impaired glucose tolerance (IGT). Twenty-two individuals participated in the study. Fourteen subjects were enrolled in the aerobic endurance exercise part of the study; seven exercised regularly for six months, while seven served as controls. Maximal aerobic capacity (VO2max) was measured and insulin sensitivity and insulin secretion were assessed by a frequently sampled intravenous glucose tolerance test (FSIVGTT). Eight subjects participated in a circuit-type resistance training program for three months. Insulin sensitivity and substrate oxidation were then assessed using the euglycemic insulin clamp technique combined with indirect calorimetry. The aerobic endurance exercise program caused in increase in VO2max (21.6 +/- 1.9 to 25.4 +/- 2.4 ml/kg.min; p < 0.05) and HDL-cholesterol (1.14 +/- 0.06 to 1.23 +/- 0.08 mmol/l; p < 0.05), but no change in insulin sensitivity nor insulin secretion occurred. However, comparing the changes between the intervention and control group, the differences disappeared. Circuit-type resistance training increased insulin sensitivity (glucose disposal) by 23% (p < 0.05), primarily due to a 27% increase in non-oxidative glucose metabolism. Both circuit-type resistance training and aerobic endurance exercise seem to have beneficial effects in subjects with impaired glucose tolerance. However, by improving insulin sensitivity, circuit-type resistance training may postpone the manifestations of NIDDM in these high-risk individuals and should therefore be included in an exercise program for IGT subjects.

Maximal oxygen uptake (VO2 max) was measured in 180 children during exhaustive work on a bicycle ergometer. The material comprised 12 blind boys and 11 blind girls (8-14 years) as well as 82 normal boys and 75 normal girls (8-17 years). VO2 max increased linearly with age in all four groups. In normal girls mature values were reached at the age of 14 years. Normal boys had significantly higher values than normal girls and their VO2 max increased faster with age. No sex differences in VO2 max were found in blind children. Normal children had significantly higher values than the blind. VO2 max/kg was uninfluenced by age in three of the groups: 55, 45 and 37 ml/min/kg in normal boys, blind boys and blind girls, respectively. In normal girls VO2 max/kg decreased with age from 51 to 42 ml/min/kg. Significant sex differences were found in both normal and blind children. VO2 max/kg in blind boys was 82% of that of normal boys, while blind girls had significantly lower values than normal girls. Most of these differences were established already at the age of 8 years. It is concluded that the differences in maximal oxygen uptake between normal and blind children are to a high degree due to different levels of physical activity during early childhood.

The purpose of this study was to examine the relationship between VO2max and acute resistance exercise performance and the acute metabolic effects of exercise sequencing. Seventeen resistance-trained men were tested for VO2max and 1 repetition maximum (1RM) strength. Subjects were randomly assigned to either a group that performed the squat first in sequence followed by the bench press (S; n = 8) or a group that performed the bench press first followed by the squat (BP; n = 9). Each group performed 3 protocols (using 1-, 2-, or 3-minute rest intervals [RIs] between sets in random order) consisting of 5 sets of each exercise with 75% of their 1RM for up to 10 repetitions while oxygen consumption was measured. Total repetitions completed were highest with 3-minute RI and lowest with 1-minute RI. Mean VO2 was significantly highest with 1-minute RI and lowest using 3-minute RI. Analysis of each exercise revealed a tendency (p = 0.07) for mean bench press VO2 to be higher when it was performed after the squat using 1- and 2-minute RIs. VO2max was significantly negatively correlated to 1RM bench press and squat (r = -0.79 and -0.60, respectively) and was significantly correlated to squat repetitions (r = 0.43-0.57) but did not correlate to bench press performance. It seems that VO2max is related to lower-body resistance exercise performance when short RIs are used, and the metabolic response to the bench press is augmented when it follows the squat in sequence using short RIs.

Resting ECG was recorded in 59 endurance trained athletic and 81 non-athletic boys aged 10-17 years and the findings were correlated with heart volume and cardiorespiratory fitness. The two groups were physically similar, but the athletes had significantly higher maximal oxygen uptake and the 15-17-year-old athletes had larger heart volumes. ECG findings were rather similar in both groups, the major differences being a lower heart rate in the athletes than in the controls (71 vs 82 beats/min) and a longer PQ interval (0.151 vs. 0.140 s) and a greater sum of SV2 and RV4 (59 vs. 50 mm) in the 15-17-year-old athletes. In the controls no correlation existed between precordial voltage criteria for ventricular hypertrophy and heart volume or between heart volume and cardiorespiratory fitness. Contrary to this, in the athletes both SV2 + RV5 and SV2 + RV4 correlated significantly (r about 0.40) with relative heart volume, and relative heart volume with both maximal oxygen uptake per kg (r = 0.41) and calculated work at heart rate 170 beats/min expressed per kg (r = 0.61). Our findings seem to indicate that as a consequence of endurance training the high level of cardiorespiratory fitness becomes related to a large heart volume. It is obvious that ECG changes due to relative vagal dominance develop earlier in the adolescent athletes than those attributable to anatomical changes.

Thirty-four male elite endurance runners aged 12-16 years and 56 ordinary boys of the same age were studied in cross-sectional age groups. At the age of 12-14 years, there were only a few differences between the runners and the controls: the runners weighted less, were leaner and had higher VO2 max/kg body weight. The runners' good competitive performance could not be explained by a superior aerobic power at that age. In the age group of 16-year-olds, additional major differences were found: significantly higher VO2 max (4.05 1/min, 66 ml/min/kg), W170 (214 W, 3.5 W/kg), vital capacity (5.31 l), maximal expiratory volume (153 1/min), lower resting heart rate (62 beats/min) and larger heart volume (792 ml and 453 ml/m2 BSA) in the runners. In this respect our runners resembled adult endurance athletes. No differences could be observed in any age group as to height, hemoglobin concentration, blood pressure and maximal heart rate. The differences at the age of 16 years are either training effects or due to a selection of certain "endurance runner types".