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

Abstract

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 (VO_2maxSRT). Heart rate (f _c) was measured continuously from Monday to Sunday, using a heart rate counter. The time spent at f _c 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 (f _cd) 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>160was greater in the boys than in the girls (P < 0.01) . The same held for t _fc>140and % 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>14035–45 min, t _fc>16010–18 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>160and VO_2maxSRT were identical to those of the other children.