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 (tfc > 140) and at fc greater than 160 beats. min-1 (tfc > 160) 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 (P < 0.001). The children were more active during school days (ds) than during the free days (df). This observation was particularly marked in the boys having tfc > 140 being twice as high during ds compared to df [tfc > 140, ds 85 (SD 25), df 40 (SD 26) min; tfc > 160, ds 36 (SD 19), df 16 (SD 13) min]. During ds tfc > 160 was greater in the boys than in the girls (P < 0.01). The same held for tfc > 140 and % fcrd 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 df (% fcrd 26-28%, tfc > 140 35-45 min, tfc > 160 10-18 min). In contrast, the children who were physically active in a sports club, had less spontaneous physical activity and % fcrd, tfc > 140, tfc > 160 and VO2maxSRT were identical to those of the other children.