The Influence of Accelerometer Epoch Length on Associations of Physical Activity Intensity and Volume with Bone Outcomes

Supplementary Content 2. Associations of physical activity volume (average-acceleration) and intensity distribution (intensity-gradient) with bone outcomes in males (n = 96).

	1-s epoch				5-s epoch				15-s epoch				30-s epoch				60-s epoch
	Model 1		Model 2		Model 1		Model 2		Model 1		Model 2		Model 1		Model 2		Model 1		Model 2
	β(95% CI)	p	β(95% CI)	p	β(95% CI)	p	β(95% CI)	p	β(95% CI)	p	β(95% CI)	p	β(95% CI)	p	β(95% CI)	p	β(95% CI)	p	β(95% CI)	p
TBLH BMC (g)
Average-acceleration	92.17 (37.9 to 146.44)	0.001	78.11 (18.54 to 137.69)	0.01	92.17 (37.91 to 146.44)	0.001	78.31 (19.68 to 136.95)	0.009	92.17 (37.91 to 146.44)	0.001	80.82 (24.36 to 137.27)	0.006	92.17 (37.91 to 146.44)	0.001	79.96 (23.96 to 135.95)	0.006	92.17 (37.91 to 146.44)	0.001	71.77 (14.03 to 129.51)	0.02
Intensity-gradient	79.16 (12.0 to 146.34)	0.021	56.23 (-10.85 to 123.30)	0.10	76.94 (10.53 to 143.35)	0.02	49.80 (-19.00 to 118.59)	0.15	67.85 (1.42 to 134.28)	0.05	35.57 (-32.41 to 103.54)	0.30	69.02 (2.97 to 135.07)	0.04	37.39 (-29.82 to 104.60)	0.27	86.53 (17.33 to 155.74)	0.02	50.17 (-24.25 to 124.60)	0.18
Spine aBMD (g/cm²)
Average-acceleration	0.03 (0.02 to 0.05)	< 0.001	0.02 (0.01 to 0.04)	0.01	0.03 (0.02 to 0.05)	< 0.001	0.03 (0.01 to 0.04)	0.005	0.03 (0.02 to 0.05)	<0.001	0.03 (0.01 to 0.05)	0.003	0.03 (0.02 to 0.05)	<0.001	0.03 (0.01 to 0.04)	0.004	0.03 (0.02 to 0.05)	<0.001	0.02 (0.01 to 0.04)	0.009
Intensity-gradient	0.04 (0.02 to 0.06)	< 0.001	0.04 (0.01 to 0.06)	0.001	0.03 (0.01 to 0.06)	0.002	0.03 (0.00 to 0.05)	0.02	0.03 (0.01 to 0.05)	0.008	0.02 (-0.00 to 0.04)	0.09	0.03 (0.01 to 0.05)	0.004	0.02 (-0.00 to 0.04)	0.06	0.03 (0.01 to 0.05)	0.001	0.02 (-0.00 to 0.04)	0.06
Spine BMC (g)
Average-acceleration	3.69 (2.13 to 5.25)	< 0.001	2.91 (1.31 to 4.50)	0.001	3.69 (2.13 to 5.25)	< 0.001	2.89 (1.24 to 4.53)	0.001	3.69 (2.13 to 5.25)	<0.001	2.98 (1.36 to 4.60)	<0.001	3.69 (2.13 to 5.25)	<0.001	2.96 (1.34 to 4.58)	<0.001	3.69 (2.13 to 5.25)	<0.001	2.68 (1.00 to 4.35)	0.002
Intensity-gradient	3.99 (1.86 to 6.11)	< 0.001	3.13 (1.15 to 5.12)	0.002	3.88 (1.80 to 5.97)	< 0.001	2.88 (0.84 to 4.92)	0.006	3.41 (1.32 to 5.51)	0.002	2.22 (0.14 to 4.30)	0.04	3.40 (1.34 to 5.46)	0.002	2.23 (0.16 to 4.30)	0.04	3.85 (1.91 to 5.79)	<0.001	2.49 (0.38 to 4.61)	0.02
Total hip aBMD (g/cm²)
Average-acceleration	0.04 (0.01 to 0.07)	0.005	0.03 (-.00 to 0.06)	0.06	0.04 (0.01 to 0.07)	0.005	0.03 (0.00 to 0.06)	0.04	0.04 (0.01 to 0.07)	0.005	0.03 (0.01 to 0.06)	0.02	0.04 (0.01 to 0.07)	0.005	0.04 (0.01 to 0.06)	0.02	0.04 (0.01 to 0.07)	0.005	0.03 (0.00 to 0.06)	0.03
Intensity-gradient	0.05 (0.02 to 0.08)	0.002	0.04 (0.01 to 0.07)	0.02	0.04 (0.01 to 0.07)	0.02	0.03 (-0.01 to 0.06)	0.11	0.03 (-0.00 to 0.07)	0.076	0.02 (-0.02 to 0.05)	0.34	0.03 (-0.01 to 0.06)	0.11	0.01 (-0.02 to 0.05)	0.46	0.03 (-0.00 to 0.06)	0.05	0.01 (-0.02 to 0.05)	0.41
Total hip BMC (g)
Average-acceleration	2.54 (0.93 to 4.14)	0.002	2.19 (0.47 to 3.91)	0.013	2.54 (0.93 to 4.14)	0.002	2.34 (0.66 to 4.02)	0.007	2.54 (0.93 to 4.14)	0.002	2.42 (0.79 to 4.05)	0.004	2.54 (0.93 to 4.14)	0.002	2.36 (0.69 to 4.02)	0.006	2.54 (0.93 to 4.14)	0.002	2.19 (0.47 to 3.92)	0.013
Intensity-gradient	2.05 (0.32 to 3.78)	0.02	1.41 (-0.28 to 3.10)	0.10	1.52 (-0.36 to 3.41)	0.11	0.71 (-1.18 to 2.60)	0.46	1.33 (-0.47 to 3.14)	0.15	0.36 (-1.39 to 2.12)	0.68	1.49 (-0.30 to 3.27)	0.10	0.55 (-1.20 to 2.31)	0.53	1.96 (0.21 to 3.70)	0.03	0.85 (-1.01 to 2.70)	0.37
Femoral neck cross-sectional area (cm²)
Average-acceleration	0.15 (0.04 to 0.27)	0.008	0.12 (-0.01 to 0.25)	0.06	0.15 (0.04 to 0.27)	0.008	0.12 (-0.00 to 0.25)	0.06	0.15 (0.04 to 0.27)	0.008	0.12 (0.00 to 0.25)	0.05	0.15 (0.04 to 0.27)	0.008	0.12 (-0.01 to 0.24)	0.06	0.15 (0.04 to 0.27)	0.008	0.10 (-0.03 to 0.22)	0.13
Intensity-gradient	0.17 (0.04 to 0.29)	0.01	0.13 (-0.00 to 0.27)	0.06	0.15 (0.02 to 0.28)	0.02	0.11 (-0.03 to 0.25)	0.13	0.14 (0.02 to 0.27)	0.02	0.09 (-0.04 to 0.23)	0.17	0.16 (0.04 to 0.28)	0.01	0.11 (-0.02 to 0.24)	0.09	0.19 (0.07 to 0.31)	0.002	0.14 (0.01 to 0.28)	0.04
Femoral neck section modulus (cm³)
Average-acceleration	0.09 (0.01 to 0.16)	0.03	0.06 (-0.02 to 0.14)	0.11	0.09 (0.01 to 0.16)	0.03	0.07 (-0.01 to 0.14)	0.10	0.09 (0.01 to 0.16)	0.03	0.07 (-0.01 to 0.15)	0.09	0.09 (0.01 to 0.16)	0.03	0.07 (-0.01 to 0.14)	0.09	0.09 (0.01 to 0.16)	0.03	0.05 (-0.03 to 0.13)	0.21
Intensity-gradient	0.11 (0.03 to 0.19)	0.01	0.09 (0.01 to 0.17)	0.03	0.10 (0.01 to 0.18)	0.02	0.07 (-0.01 to 0.16)	0.09	0.08 (0.01 to 0.16)	0.03	0.06 (-0.02 to 0.13)	0.14	0.09 (0.01 to 0.16)	0.02	0.06 (-0.02 to 0.13)	0.12	0.11 (0.04 to 0.19)	0.004	0.09 (0.01 to 0.17)	0.03

Values are regression coefficients (ß), their 95% confidence intervals (CI), and p values from linear regression models. Activity metrics were standardised before entry into analysis, so values represent the change in the outcome associated with a 1 standard deviation change in the activity metric.

^aAverage-acceleration (average of waves 6 to 9) is the mean acceleration across wear-time.

^bIntensity-gradient (average of waves 6 to 9) calculated, with imputing zeros for non-wear during the night, as the regression line from log-log plot of intensity (x) and time accumulated (y).

Model 1 includes the activity variable (average-acceleration or intensity-gradient) adjusted for age at wave 9, stature at wave 9, mass at wave 9, years from peak height velocity at wave 9, the proportion of the 24-hour cycle the accelerometer was worn, and the mean age for physical activity measures. Model 2 includes both activity variables in the same model (average-acceleration and intensity-gradient).

Bold emphasis indicates statistical significance at p < 0.05.

TBLH, total body less head; BMC, bone mineral content; aBMD, areal bone mineral density.