Evaluation of habitual physical activity from a week's heart rate monitoring in French school children

Habitual physical activity (HPA) was studied in 30 boys and 34 girls aged 6-11 years. All the children performed a shuttle run test (SRT) to assess maximal heart frequency (f(cmaxSRT)) and to evaluate maximal oxygen uptake (VO2maxSRT) Heart rate (f(c)) was measured continuously from Monday to Sunday, using a heart rate counter. The time spent at f,greater than 140 beats . min(-1) (t(fc>140)) and at f(c) greater than 160 beats . min(-1) (t(fc>160)) permitted HPA to be evaluated. The daily heart rate (fed) and the percentage of heart rate reserve (%f(crd)) were calculated to evaluate the metabolic activity. In the boys and girls, f(cd) and %f(crd) varied little with age. The metabolic activity varied in a rhythmical way during the week and was higher during school days than during free days (P < 0.001). The children were more active during school days (d(s)) than during the free days (d(f)). This observation was particularly marked in the boys having t(fc>140) being twice as high during d(s) compared to d(f) [t(fc>140), d(s) 85 (SD 25), d(f) 40 (SD 26) min; t(fc>160), d(s) 36 (SD 19), d(f) 16 (SD 13) min]. During d(s) t(fc>160) was greater in the boys than in the girls (P < 0.01). The same held for t(fc>140) and %f(crd) from the age of 9 years (P < 0.001). It was during the recreation periods that the differences between the boys and the girls were observed (P < 0.01). There was no significant difference between the boys and the girls during lessons, in the evening and during d(f) (%f(crd) 26-28%, t(fc>140) 35-45 min, t(fc>160) 10-18 min). In contrast, the children who were physically active in a sports club, had less spontaneous physical activity and %f(crd), t(fc>140), t(fc>160) and VO2maxSRT were identical to those of the other children.