COMPARISON OF 9TH GRADE STUDENTS’ PHYSICAL ACTIVITY LEVELS DURING RECESS AND REGULAR CLASS PERIODS USING OBJECTIVE MEASUREMENT

Purpose: to assess and compare secondary school students’ physical activity levels during recess and regular class periods using objective measurement. Material: The study sample consisted of 26 9th grade school students (M = 15.28 years, SD = 0.47) of a German secondary school. They wore the Actiheart the whole school day for one week. All students followed the same school schedule and participated in the same classes. 9th grade school students’ physical activity levels during recess and regular class periods were assessed using the physical activity monitoring device Actiheart, which validly and objectively measures physical activity. Results: total recess time physical activity levels accounted for M = 2.38 METs, whereas total class period time physical activity levels only reached M = 1.58 METs. This difference could be proven statistically significant. Conclusions: Total recess time accounts for significantly higher physical activity levels compared to total class period time and the overall time students spend in school, respectively.

The Actiheart device was attached to participants' chest using two ECG electrodes (Figure 1).The Actihearts setting was adjusted to record heart rate in short-term recording mode continuously over 30-seconds epochs.

Results
The following diagram (Figure 2) has been randomly selected among participants to make it easier to refer to corresponding recess times and gives a first indication that students are at least a little more physically active in breaks than in lesson times.An average MET value of 2.4 is roughly equivalent to carrying 7 kg or walking from house to car or bus [19] and indicates that students are definitely more physically active during recess than during mere class period times.To look closer at the actual physical activity levels of the students during recess, it makes sense to compare the METs according to the grouping variable of type of timeframe (i.e.comparing values from recess time to values from class period or school time).Though the variable is normally distributed, its variances are not.Thus, a Mann-Whitney U test has been conducted (see Table 2).The Mann-Whitney U test shows that there is a highly significant difference (recess vs. total class period time: p < 0.001, and recess vs. total school time: p < 0.001) in both cases.This means that descriptive analysis and the related suggestion of Table 2 indicate that students show statistically significantly higher levels of physical activity during recess time as compared to mere class period time.
To see whether the same holds for amounts of energy expenditure, active energy expenditure (AEE) has been calculated for single hours, giving the results of Table 3 (inferential statistical analysis).AEE is the amount of calories a person burns over a certain period of time that accounts for physical activity during periods of non-rest [20].AEE was chosen for display in Table 3 to highlight the realistic MET values for recess, total class period time, and total school time due to physical activity only.Total school time is the accumulated time students spend at school on a given school day.Again, a Mann-Whitney U test has been conducted to find out about the statistical significance that can be assumed from the obvious descriptive differences that can be seen in Table 4.As the result of the Mann-Whitney U test shows, the amount of physical activity (AEE) show statistically highly significant differences between recess time and total class period time (p < 0.001), and respectively total school time (p < 0.001), too.Conclusively, students show higher amounts and levels of physical activity during recess as compared to accumulated mere class period time physical activity levels.
All together, the sample's schedule included 10 major breaks that made up 3 hours and 20 minutes.It could be shown that the students use recess times to be physically active to a higher degree than during class periods and overall school time.The statistically highly significant difference between intensities and energy expenditures per average hour, verify that students show higher amounts and levels of physical activity during recess time as compared to mere class period times.

Discussion
Investigating physical activity behavior of students during recess time can be interesting regarding to find out about the influence school-related physical activity has on overall amounts of physical activity, as well as for legitimization of recess time per se.
The results of this study show that school and recess is an ideal area to promote physical activity in children and adolescents.Unfortunately, efforts by policy makers, and national and regional programs to cut recess and breaks in schools can be seen in various countries, however, with the intention to maximize learning time.To combat these trends, Comprehensive School Physical Activity Programs that center around 1) quality physical education, 2) physical activity before and after school, 3) physical activity during school (both recess and classroom activity), 4) staff involvement, and 5) family and community engagement should be strengthened [21].
In line with developing school (physical activity and health) programs that explicitly cover recess, specific interventions can be developed and applied that may be particularly tackling age ranges and gender appropriateness.For instance, female students seem to be less engaged in physical activity during recess in the school settings compared to male students [22].
The Actiheart device has proven a feasible research method to assess physical activity levels in the target population of school-aged adolescents.The Actiheart can therefore be applied to any school setting.However, the costs per device may exceed ordinary funding options in most cases.In addition, the proper set-up and attachment to study participants need properly trained personnel and additional clearance to use on students.Nevertheless, in regard to validity and objectivity standards, the Actiheart appears to be the device most accurate to be used in field studies and real-world settings in school.

Conclusions
Total recess time accounts for significantly higher physical activity levels compared to total class period time.Moreover physical activity levels during recess by itself are also higher than the accumulated physical activity levels for the time students spend in school (school time).
The results indicate that even unaltered "natural" recess provides high amounts of physical activity.Its potential to significantly and evidently add to school students' overall physical activity legitimized its own existence, defying any effort to cut school recess times short.
Future research may focus on developing and applying interventions to promote and increase physical activity during recess.Particular emphasis may be put on school-aged children and adolescents' socioeconomic status, race, gender, and/or age [23,24].

Figure 2 .
Figure 2.An average forenoon's physical activity-diagram of an adolescent 9th grade student Recess breaks were regularly scheduled from 9.10 to 9.30 am and from 11.00 to 11.20 am.Before, after and in between the two breaks, students attended regular school subject classes.Table 1 descriptively shows that recess time has higher means for METs than other school times.Table 1.Comparison of physical activity's intensity between recess time (breaks) and other significant periods N Minimum Maximum Mean SD Total recess time 26 1.88 3.44 2.38 0.36 Total class period time 26 1.25 1.91 1.58 0.17 Total school time 26 1.30 2.14 1.68 0.20 Note.Minimum, maximum, and mean values' unit is MET.

Table 1
descriptively shows that recess time has higher means for METs than other school times.

Table 1 .
Comparison of physical activity's intensity between recess time (breaks) and other significant periods

Table 2 .
Relationship physical activity level of recess and total class period time/school time (Mann-Whitney U test) Recess

Table 3 .
Comparison of physical activity amounts between recess time (breaks) and other significant periods

Table 4 .
Relationship between AEE of recess and total class period time/total school time (Mann-Whitney U test) Recess