TABLE III.

MEAN LEVELS OF FOUR OBJECTIVE MEASURES BY QUARTILE OF TOTAL PHYSICAL ACTIVITY EXPENDITURE AS DETERMINED FROM THE CARDIA PHYSICAL ACTIVITY HISTORY

Total Activity Exercise Units	Sum of Skinfolds (mm)			Caloric Intake (kcal)			Duration on Treadmill (seconds)			High density lipoprotein Cholesterol (mg/dl)
Total Activity Exercise Units	N	Mean	S.D.	N	Mean	S.D.	N	Mean	S.D.	N	Mean	S.D.
Females:
≤ 149 (Low)	687	64.9	33.0	689	2307	1097	671	432	117	686	53.6	12.4
150–284	691	62.2	31.6	693	2349	1106	670	471	121	689	55.1	12.9
285–467	689	57.7	27.7	688	2352	1162	675	501	124	679	55.6	12.5
≥ 468 (High)	687	54.2	27.7	690	2465	1262	662	564	144	684	58.4	13.5
Twice the S.D. of the difference^*		3.2			125			14			1.4
Correlation with total physical activity		−0.15			0.07			0.36			0.13
Males:
≥ 278 (Low)	575	47.6	26.1	574	3131	1390	555	647	137	573	49.1	13.4
279–468	577	44.8	23.0	575	3353	1492	568	686	131	577	49.7	13.2
469–699	569	41.7	20.5	565	3576	1451	557	721	133	565	49.7	12.6
≥ 700 (High)	572	40.7	20.6	552	4006	1779	566	742	140	567	52.3	12.4
Twice the S.D. of the difference^*		2.7			185			16			1.5
Correlation with total physical activity		−0.12			0.21			0.25			0.11

SD = Standard deviation.

Approximately 2 standard deviations of the difference in mean objective measure between any two quartiles. (The difference is computed as 2 × pooled SD × √ (2/n_min), where n_min is the minimum sample size among the four quartiles.) If the difference between 2 quartile means is greater than or equal to this number, the test of hypothesis that the two means are different carries P < 0.05.