Journal of Sports Science and Medicine

Table 1. Descriptive characteristics of participants

		Total sample^a		Females^a		Males^a
		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-gradient^1-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-gradient^5-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-gradient^15-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-gradient^30-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-gradient^60-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.