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 (fcmaxSRT) and to evaluate maximal oxygen uptake (VO2maxSRT). Heart rate (fc) was measured continuously from Monday to Sunday, using a heart rate counter. The time spent at fc greater than 140 beats. min-1 (tfc140) and at fc greater than 160 beats. min-1 (tfc160) permitted HPA to be evaluated. The daily heart rate (fcd) and the percentage of heart rate reserve (%fcrd) were calculated to evaluate the metabolic activity. In the boys and girls, fcd and % fcrd 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 (P0.001). The children were more active during school days (ds) than during the free days (df). This observation was particularly marked in the boys having tfc140 being twice as high during ds compared to df [tfc140, ds 85 (SD 25), df 40 (SD 26) min; tfc160, ds 36 (SD 19), df 16 (SD 13) min]. During ds tfc160 was greater in the boys than in the girls (P0.01). The same held for tfc140 and % fcrd from the age of 9 years (P0.001). It was during the recreation periods that the differences between the boys and the girls were observed (P0.01). There was no significant difference between the boys and the girls during lessons, in the evening and during df (% fcrd 26-28%, tfc140 35-45 min, tfc160 10-18 min). In contrast, the children who were physically active in a sports club, had less spontaneous physical activity and % fcrd, tfc140, tfc160 and VO2maxSRT were identical to those of the other children.