Table 4.

Mean, standard deviation and p-value of backpack and total load expressing in kilograms and normalizing for body mass by gender, physical education participation, BMI, afternoon with classes and lunch spot

	Backpack				Total load
	5th grade		9th grade		5th grade		9th grade
	load (kg)	load·BW−1	load (kg)	load·BW−1	load (kg)	load·BW−1	load (kg)	load·BW−1
Sex
M	4.87 (1.42)	0.129 (0.046)	3.75 (1.25)	0.064 (0.022)	5.27 (1.57)	0.139 (0.050)	4.08 (1.47)	0.072 (0.027)
F	5.13 (1.42)	0.131 (0.042)	4.29 (1.13)	0.087 (0.026)	5.56 (1.48)	0.141 (0.046)	4.64 (1.39)	0.095 (0.032)
p	0.064	0.546	< 0.001	< 0.001	0.040	0.513	< 0.001	< 0.001
BMI
Normal	5.05 (1.28)		4.09 (1.14)		5.45 (1.37)		4.46 (1.43)
Overw.	5.19 (1.50)		4.48 (1.25)		5.66 (1.67)		4.86 (1.43)
p	0.730		0.027		0.467		0.044
Physical Education day
Yes	4.63 (1.12)	0.123 (0.037)	4.00 (1.25)	0.080 (0.026)	5.64 (1.42)	0.148 (0.047)	4.83 (1.64)	0.097 (0.035)
No	5.20 (1.55)	0.134 (0.048)	4.10 (1.19)	0.076 (0.028)	5.26 (1.59)	0.136 (0.049)	4.14 (1.23)	0.077 (0.028)
p	0.003	0.057	0.651	0.163	0.018	0.061	< 0.001	< 0.001
Afternoon with classes
Yes	5.39 (1.49)	0.132 (0.046)	4.13 (1.24)	0.080 (0.028)	5.87 (1.50)	0.153 (0.049)	4.56 (1.49)	0.089 (0.034)
No	4.33 (1.02)	0.114 (0.036)	3.80 (1.07)	0.069 (0.021)	4.64 (1.26)	0.120 (0.040)	3.82 (1.07)	0.069 (0.021)
p	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001
Lunch
Home	4.31 (1.03)	0.112 (0.035)	3.60 (1.04)	0.065 (0.019)	4.63 (1.23)	0.120 (0.040)	3.70 (1.04)	0.068 (0.020)
School	5.25 (1.48)	0.137 (0.046)	4.38 (1.22)	0.084 (0.028)	5.69 (1.55)	0.149 (0.050)	4.90 (1.48)	0.094 (0.034)
p	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001