We know that the results were hindered by water -- so those who sweat may have disabled the device or changed the result. 11 Were the relevant outcome measures ignored?

There was no analysis of the results of sexual maturity on BMI or exercise. Since all three groups could be aggregated for this portion of the study, the results might have been interesting and suggestive.

12 Are the statistical methods described?

Yes and no. We need to have an indication of the n. For each compliant subgroup, not just the total group.

13 Did untoward events occur during the study?

Yes, and the non-compliance should have been explained. Also, moving from the target of 7 days to 3 days smacks of a failed study -- either the measurement technique was too fussy, or the girls didn't want to comply. That implies even more selection bias than with the initial selection by brochure.

14 Was the basic data adequately described?

No. If there were additional data points, such as sexual maturity, they should have been presented.

15 Did the analysis allow for the passage of time?

No. 7 days establishes a point in time. It would be more interesting to understand the longer-term changes in exercise levels and BMI. The fact that there was only a 6% difference between those who exercised and those who didn't wasn't helpful.

16 Do The numbers add up?

The comparison between the "actigraph" and heart rate, oxygen uptake and heart rate are all too low. Although they mention the r, or correlation, they should use r2, which would look even worse. That is, the oxygen uptake, which has aan r=.73, is actually an r2 of about 0.50, which is way below the level needed for statistical significance.

17 Was the statistsical significance assessed?

"p"...

See above note on correlation with the actigraph and the amount of exercise actually done...very poor correlation.
18 What do the main findings mean?

Not much. We don't have a correlation between the movement and the amount of calories burned, such that we could create a graph showing the relationship between the two. A 6% difference between the "more active" and "less active" groups in BMI doesn't seem to meet statistical significance, even cumulated, with only ~80 total compliant subjects.

19 How are the null findings interpreted?

They are not interpreted

20 Are important effects overlooked?

Yes, the effects of puberty on BMI and on exercise levels.

21 What else might influence the observed outcomes?

We have a 7-day snapshot which was then reduced to 3 days within the 7-day window (in order not to lose all the data). We don't know if this corresponds to the amount of activity that girls are experiencing more broadly. If, for example, a girl was having her period during the 7-day period, it could be that she is less active.

How do results compare to other reports?

It is clear from the study/literature review that there is a correlation between BMI and exercise. It is also clear that Hispanics and African-Americans exercise less and have higher BMI. Therefore, there were no surprises and no new questions raised by the study.

23 What are the implications of the study?

The most interesting new work would have been on the impact of puberty on exercise levels. Although the data was taken, it wasn't revealed or explored.

Relationship between Physical Activity and Body Mass Index in Adolescents.