Physical activity, academic and developmental measures in older primary school-children: A principal components analysis

Figures & data

Table 1. Summary of variables examined in the principal component analysis

Measure	Procedure
Read NAPLAN	National measure of reading ability
Writing NAPLAN	National measure of writing ability
Numeracy NAPLAN	National measure of numeracy
Parent education (SES)	Parental education level
Rod and frame test	Measures the ability to accurately predict the direction of vertical when confronted by a visual task distorting your spatial perception (qualitative measure)
Semi-tandem DPS	Balance for 30 s on a balance board rocking in the frontal plane only in a semi-tandem posture (qualitative measure)
Eye–hand coordination	Number of successful ball throw and catches (qualitative measure)
Jump height	Jump height recorded (qualitative measure)
PA	Pedometer estimate of PA levels. Every child wore a pedometer for approx. 7 days (quantitative measure)
CRF	20 metre shuttle run. Number of runs competed (quantitative measure)
core endurance	timed abdominal hold posture (quantitative measure)
Height	height in cm
Weight	weight in kg
Puberty score (tanner)	tanner self-estimate of pubescent maturity
Per cent fat (dexa)	regional body composition is measured using dual energy x-ray absorptiometry

Notes: Socio-Economic Status (SES), Physical Activity (PA), Cardio-Respiratory Fitness (CRF), Dynamic Postural Stability (DPS).

Figure 1. Semi-tandem frontal plane dynamic postural stability testing platform. A child in the semi-tandem stance on the unstable platform, balancing. The rocking movements in the frontal plane.

Table 2. Descriptive statistics

Variables	Mean	Standard deviation
Read NAPLAN	517.5	75.8
Writing NAPLAN	500.4	68.3
Numeracy NAPLAN	505.2	70.8
Rod and frame test	2.9	1.7
Parent education (SES)	2.6	0.67
Semi-tandem DPS	0.3	0.22
Height	153.6	7.34
Weight	45.9	9.2
Puberty score (Tanner)	5.3	1.7
Percent fat (DEXA)	25.8	6.5
PA	95.9	12
CRF	6.2	1.9
Jump	33.6	5.99
Core	73.8	46
Ball catch and throw	34.1	6.7

Notes: Measurements fully repeated in 261 participants. Semi-tandem dynamic postural stability (DPS), physical activity (PA) and cardio-respiratory fitness (CRF).

Table 3. Component variance and eigenvalues

Sub type	Initial Eigenvalues			Extraction sums of squared loadings			Rotation sums of squared loadings
	Total	% of variance	Cum %	Total	% of variance	Cum %	Total	% of variance	Cum %
1	3.34	22.24	22.24	3.34	22.242	22.24	2.49	16.6	16.6
2	2.45	16.33	38.58	2.45	16.334	38.58	2.22	14.81	31.41
3	1.96	13.04	51.62	1.96	13.041	51.62	2.2	14.66	46.07
4	1.14	7.57	59.18	1.14	7.566	59.18	1.97	13.11	59.18

Table 4. Rotated component matrix

Loading matrix exhibiting the amount of correlation between the individual measures of child development producing 4 principal components
Characteristic	Principal component 1 = academic cognitive	Principal component 2 = pubescent development	Principal component 3 = fitness strength and body mass	Principal component 4 = PA and motor coordination
Read NAPLAN	0.84^†			−0.18
Writing NAPLAN	0.77^†
Numeracy NAPLAN	0.84^†
Rod and frame test	−0.44			−0.2
Parent education (SES)	0.44
Semi-Tandem DPS	−0.25	0.22		−0.35
Height		0.87^†
Weight		0.78^†	−0.53
Puberty score (Tanner)		0.76^†	0.12	−0.15
Percent fat (DEXA)		0.18	−0.91^†
PA				0.76^†
Cardio-respiratory Fitness			0.55	0.63
Jump height		0.25	0.74	0.24
Core endurance		−0.34	0.41	0.41
Ball catch and throw			0.16	0.73^†

Notes: Loading components below ≥ 0.1 or ≤ −0.1 suppressed.

Component loading above ≥ 0.25 or ≤ −0.25 in bold and considered meaningful to interpretation.

^† Variables that contribute most strongly to each sub-type provide the naming of the principal component.

Table 5. Gender independent t-test using Z scores to for grand variables

Principal component variable	t	df	Sig (p)
Academic cognitive	−0.311	259	0.756
Pubescent development	1.812	259	0.071
Fitness and strength	−4.082	259	0.001
PA and motor coordination	−5.129	259	0.001