Table 1. Descriptive characteristics of participants
|
Total samplea |
Femalesa |
Malesa |
| Mean |
SD |
Mean |
SD |
Mean |
SD |
| Age at DXA scan at wave 9 (years) |
23.4 |
0.5 |
23.4 |
0.5 |
23.4 |
0.6 |
| Years from peak height velocity at wave 9 |
10.7 |
1.3 |
11.5* |
0.8 |
9.7* |
1.0 |
| Body weight at wave 9 (kg) |
81.5 |
22.6 |
74.0* |
20.0 |
91.3* |
22.2 |
| Stature at wave 9 (cm) |
171.9 |
9.8 |
166.0* |
7.0 |
179.5* |
7.5 |
| Bone measures at wave 9 |
| TBLH BMC (g) |
2100 |
481 |
1826* |
311 |
2454* |
428 |
| Spine aBMD (g/cm2) |
1.085 |
0.120 |
1.069* |
0.127 |
1.105* |
0.108 |
| Total hip aBMD (g/cm2) |
1.080 |
0.151 |
1.031* |
0.128 |
1.143* |
0.157 |
| Femoral neck cross-sectional area (cm2) |
3.63 |
0.77 |
3.26* |
0.58 |
4.11* |
0.72 |
| Femoral neck section modulus (cm3) |
1.80 |
0.53 |
1.49* |
0.35 |
2.20* |
0.46 |
| Physical Activity from mean of available waves |
| Mean age of physical activity measurements (years) |
21.3 |
1.5 |
21.2 |
1.5 |
21.3 |
1.5 |
| Proportion of 24-hour wear |
0.87 |
0.08 |
0.87 |
0.08 |
0.86 |
0.07 |
| Average-acceleration |
15.30 |
3.95 |
14.96 |
3.92 |
15.74 |
3.96 |
| 1-s epoch |
Intensity-gradient1-S |
-2.91 |
0.20 |
-2.92 |
0.21 |
-2.90 |
0.19 |
| R2 for linear fit |
0.90 |
0.04 |
0.89* |
0.04 |
0.91* |
0.03 |
| 5-s epoch |
Intensity-gradient5-S |
-2.62 |
0.21 |
-2.62 |
0.22 |
-2.62 |
0.19 |
| R2 for linear fit |
0.89 |
0.04 |
0.89 |
0.05 |
0.90 |
0.04 |
| 15-s epoch |
Intensity-gradient15-S |
-2.41 |
0.22 |
-2.42 |
0.23 |
-2.40 |
0.20 |
| R2 for linear fit |
0.90 |
0.04 |
0.90 |
0.05 |
0.90 |
0.04 |
| 30-s epoch |
Intensity-gradient30-S |
-2.33 |
0.24 |
-2.35 |
0.25 |
-2.32 |
0.22 |
| R2 for linear fit |
0.91 |
0.04 |
0.91 |
0.05 |
0.91 |
0.03 |
| 60-s epoch |
Intensity-gradient60-S |
-2.27 |
0.25 |
-2.28 |
0.27 |
-2.24 |
0.23 |
| R2 for linear fit |
0.91 |
0.04 |
0.92 |
0.04 |
0.91 |
0.04 |
a For anthropometric variables, maturation, and bone measures, n = 220 (females = 124, males =96). For physical activity data, n = 217 (females = 121, males = 96).* indicates sex difference with p < 0.05 from independent samples t-tests. Intensity-gradient was calculated from accelerometer data averaged over a 1-s epoch (intensity-gradient
1-S), a 5-s epoch (intensity-gradient
5-S), a 15-s epoch (intensity-gradient
15-S), a 30-s epoch (intensity-gradient
30-S), and a 60-s epoch (intensity-gradient
60-S). SD, standard deviation; DXA, dual-energy X-ray absorptiometry; TBLH, total body less head; BMC, bone mineral content; aBMD, areal bone mineral density.
