Table 3. The mutually adjusted associations of physical activity volume (average-acceleration) and intensity distribution (intensity-gradient) with bone outcomes in females (n = 121).
|
1-s epoch |
5-s epoch |
15-s epoch |
30-s epoch |
60-s epoch |
| β (95% CI) |
β (95% CI) |
β (95% CI) |
β (95% CI) |
β (95% CI) |
| TBLH BMC (g) |
| aAverage-acceleration |
2.54 (-36.46 to 41.53) |
8.39 (-29.33 to 46.11) |
5.71 (-35.88 to 47.29) |
4.44 (-41.06 to 49.95) |
3.54 (-48.14 to 55.23) |
| bIntensity-gradient |
46.47** (18.4 to 74.55) |
32.43* (0.2 to 64.66) |
33.6 (-2.33 to 69.53) |
31.5 (-8.54 to 71.54) |
28.45 (-16.01 to 72.91) |
| Spine aBMD (g/cm2) |
| aAverage-acceleration |
0.00 (-0.02 to 0.03) |
0.00 (-0.02 to 0.03) |
0.00 (-0.02 to 0.03) |
0.00 (-0.02 to 0.03) |
0.01 (-0.03 to 0.04) |
| bIntensity-gradient |
0.01 (-0.01 to 0.03) |
0.01 (-0.01 to 0.03) |
0.01 (-0.01 to 0.04) |
0.01 (-0.02 to 0.04) |
0.01 (-0.03 to 0.04) |
| Total hip aBMD (g/cm2) |
| aAverage-acceleration |
0.01 (-0.01 to 0.03) |
0.01 (-0.01 to 0.03) |
0.01 (-0.02 to 0.03) |
0.01 (-0.02 to 0.04) |
0.01 (-0.03 to 0.04) |
| bIntensity-gradient |
0.02* (0.00 to 0.04) |
0.02 (0.00 to 0.04) |
0.02 (0.00 to 0.04) |
0.02 (-0.01 to 0.05) |
0.02 (-0.01 to 0.05) |
| Femoral neck cross-sectional area (cm2) |
| aAverage-acceleration |
0.02 (-0.06 to 0.09) |
0.02 (-0.06 to 0.1) |
0.01 (-0.07 to 0.09) |
0.02 (-0.07 to 0.11) |
0.02 (-0.08 to 0.13) |
| bIntensity-gradient |
0.06* (0.01 to 0.12) |
0.06 (0.00 to 0.12) |
0.06 (-0.01 to 0.13) |
0.05 (-0.03 to 0.13) |
0.03 (-0.06 to 0.13) |
| Femoral neck section modulus (cm3) |
| aAverage-acceleration |
0.03 (-0.02 to 0.07) |
0.03 (-0.02 to 0.08) |
0.02 (-0.03 to 0.08) |
0.03 (-0.03 to 0.09) |
0.02 (-0.04 to 0.09) |
| bIntensity-gradient |
0.02 (-0.03 to 0.06) |
0.00 (-0.04 to 0.05) |
0.02 (-0.03 to 0.06) |
0.00 (-0.05 to 0.06) |
0.02 (-0.04 to 0.07) |
Values are regression coefficients (β) and their 95% confidence intervals (CI) from linear regression models. Regression coefficients are 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, the mean age for physical activity measures, and the alternate activity metric (intensity-gradient or average-acceleration). 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).* p < 0.05.** p < 0.01.TBLH, total body less head; BMC, bone mineral content; aBMD, areal bone mineral density.
