Table 2.

Distribution of upper- and lower-body muscle strength deciles and age-, sex-, and race-specific aBMD and BMC Z-scores.

Characteristic	Total	n	Female	n	Male	n
Muscle strength
Upper-body reference decile (%)
1	32.8	38	32.7	16	32.8	22
2	24.1	28	26.5	13	22.4	15
3	12.1	14	12.2	6	11.9	8
4	6.0	7	6.1	3	6.0	4
5	5.2	6	6.1	3	4.5	3
6	7.8	9	8.2	4	7.5	5
7	6.9	8	4.2	2	8.9	6
8	2.6	3	2.0	1	3.0	2
9	1.6	2	0	0	3.0	2
10	0.9	1	2.0	1	0	0
Lower-body reference decile (%)
1	40.9	47	40.8	20	40.9	27
2	19.1	22	22.5	11	16.7	11
3	9.6	11	6.1	3	12.1	8
4	12.2	14	18.4	9	7.6	5
5	7.0	8	6.2	3	7.6	5
6	5.2	6	2.0	1	7.6	5
7	2.6	3	2.0	1	3.0	2
8	0.9	1	0	0	1.5	1
9	1.7	2	0	0	3.0	2
10	0.9	1	2.0	1	0	0
aBMD Z-score
Total body (less head)	–0.2 ± 1.4	116	–0.2 ± 1.2	49	–0.2 ± 1.5	67
Total hip	0.1 ± 1.3	115	0.2 ± 1.2	48	0.1 ± 1.3	67
Femoral neck	–0.2 ± 1.4	115	0.1 ± 1.5	48	–0.4 ± 1.3	67
Lumbar spine	–0.1 ± 1.3	116	–0.1 ± 1.2	49	–0.1 ± 1.5	67
BMC Z-score
Total body (less head)	–0.5 ± 1.3	116	–0.5 ± 1.1	49	–0.5 ± 1.4	67
Total hip	0.4 ± 1.4	115	0.3 ± 1.2	48	0.5 ± 1.6	67
Femoral neck	–1.3 ± 1.5	115	–1.4 ± 1.5	48	–1.2 ± 1.5	67
Lumbar spine	–0.5 ± 1.3	116	–0.4 ± 1.1	49	–0.5 ± 1.4	67

Notes: Data are presented as mean ± SD or as percentage (%), as indicated. Upper- and lower-body muscle strength reference deciles are shown using FitBack reference values. Age-, sex-, and race-specific aBMD and BMC Z-scores at each site are presented using international reference data from the Bone Mineral Density in Childhood Study. Percentage may not add to 100% due to rounding.

Abbreviations: aBMD = areal bone mineral density; BMC = bone mineral content.