Muscular strength measurements indicate bone mineral density loss in postmenopausal women

Figures & data

Table 1 Demographics, body composition, and strength measures by subject age group (N = 293)

Characteristic	All (n = 293)	Age, years
		≤50 (n = 56)	51–53 (n = 79)	54–56 (n = 81)	57–59 (n = 56)	≥60 (n = 21)
Subject age*	54.22 ± 3.85	48.64 ± 1.19	52.42 ± 0.82	55.23 ± 0.91	58.22 ± 0.86	61.39 ± 1.25
Postmenopausal years*	5.34 ± 3.53	2.33 ± 1.21	3.86 ± 2.39	5.74 ± 3.02	8.05 ± 3.39	10.12 ± 2.86
Height	157.19 ± 5.04	157.59 ± 5.12	156.13 ± 5.07	157.62 ± 5.03	157.20 ± 5.11	158.43 ± 4.26
Weight*	62.27 ± 7.68	63.97 ± 8.51	62.57 ± 7.52	61.85 ± 7.78	61.74 ± 6.56	59.64 ± 8.00
Body mass index, kg/m^2*	25.20 ± 2.91	25.76 ± 3.20	25.67 ± 2.88	24.88 ± 2.78	25.00 ± 2.56	23.75 ± 3.08
Total fat mass	22.08 ± 5.05	21.94 ± 5.67	22.64 ± 4.45	22.01 ± 5.21	21.94 ± 4.39	21.01 ± 6.47
Total lean mass*	36.85 ± 3.51	38.17 ± 3.35	36.41 ± 3.51	36.39 ± 3.45	36.91 ± 3.67	36.62 ± 3.01
BMD
Total body*	1.07 ± 0.09	1.14 ± 0.09	1.09 ± 0.08	1.05 ± 0.08	1.05 ± 0.08	1.01 ± 0.08
Lumbar 2–4*	1.10 ± 0.16	1.20 ± 0.16	1.11 ± 0.15	1.05 ± 0.14	1.08 ± 0.15	0.99 ± 0.11
Femoral*	0.93 ± 0.12	0.99 ± 0.15	0.94 ± 0.10	0.92 ± 0.12	0.90 ± 0.12	0.84 ± 0.08
Femoral neck*	0.87 ± 0.12	0.93 ± 0.14	0.89 ± 0.11	0.85 ± 0.11	0.83 ± 0.11	0.79 ± 0.07
Hip
Extend isometric, 90°	186.12 ± 46.0	184.57 ± 48.19	188.41 ± 52.77	189.85 ± 43.45	179.54 ± 35.51	184.81 ± 49.22
Flex isometric, 20°*	58.72 ± 15.75	60.95 ± 16.15	58.81 ± 14.84	61.81 ± 15.48	54.63 ± 15.58	51.38 ± 16.27
Flex, 120°/second*	45.25 ± 10.26	48.98 ± 10.92	44.51 ± 10.83	44.64 ± 9.59	44.30 ± 10.38	42.90 ± 5.96
Extend, 120°/second	107.18 ± 27.65	106.91 ± 30.34	110.25 ± 27.70	105.12 ± 26.50	105.32 ± 25.98	109.24 ± 30.09
Flex, 180°/second*	54.28 ± 14.23	58.41 ± 14.44	55.75 ± 13.82	53.54 ± 14.39	50.11 ± 14.47	51.76 ± 11.02
Extend, 180°/second	85.01 ± 29.89	85.20 ± 29.53	87.84 ± 30.20	81.62 ± 29.34	85.09 ± 28.88	86.81 ± 35.70
Back
Flex, 30°/second*	68.51 ± 21.24	77.89 ± 24.21	67.53 ± 21.54	66.22 ± 17.86	65.14 ± 21.70	64.90 ± 16.70
Extend, 30°/second*	136.55 ± 35.64	147.43 ± 37.15	140.33 ± 38.20	129.79 ± 28.75	138.04 ± 31.88	115.38 ± 43.67
Flex, 60°/second*	59.59 ± 20.06	65.84 ± 21.75	57.24 ± 19.88	59.59 ± 18.90	57.14 ± 20.89	58.33 ± 15.93
Extend, 60°/second*	117.28 ± 40.92	125.77 ± 45.70	121.22 ± 40.89	115.20 ± 40.50	111.96 ± 38.13	102.05 ± 32.08
Extend, 120°/second*	60.74 ± 24.41	67.07 ± 30.32	59.71 ± 24.78	58.89 ± 21.76	58.25 ± 21.76	61.48 ± 16.00
Flex, 120°/second*	84.95 ± 40.48	90.16 ± 40.23	91.53 ± 45.11	83.60 ± 38.26	82.41 ± 38.70	58.29 ± 22.49
Flex isometric, 20°*	197.39 ± 42.05	200.91 ± 40.90	199.91 ± 43.14	197.26 ± 35.99	197.89 ± 37.86	177.62 ± 66.11
Extend isometric, 20°*	65.02 ± 22.93	68.34 ± 18.36	62.16 ± 21.11	67.21 ± 29.10	65.09 ± 21.41	58.33 ± 15.19

Notes: Data are expressed as mean values ± standard deviation. Statistical significance is represented by *P < 0.05.

Abbreviation: BMD, bone mineral density.

Table 2 Correlations between subject age, total lean mass, muscle strength, and bone density (N = 293)

Pearson correlation	Subject’s age	Total lean mass	BMD
			Total body	BMD L2–4	Femoral neck	Femoral
Subject’s age	1.00**	0.11	0.42**	0.36**	0.35**	0.33**
Total lean mass	0.10	1.00	0.45**	0.22**	0.33**	0.29**
Hip
Extend isometric, 90°	0.02	0.40**	0.42**	0.41**	0.34**	0.34**
Flex isometric, 20°	0.13*	0.34**	0.23**	0.20**	0.20**	0.14*
Flex, 120°/second	0.16**	0.44**	0.45**	0.37**	0.32**	0.31**
Extend, 120°/second	0.02	0.38**	0.43**	0.34**	0.34**	0.33**
Flex, 180°/second	0.17**	0.30**	0.27**	0.25**	0.14*	0.17**
Extend, 180°/second	0.01	0.25**	0.17**	0.16**	0.09	0.11*
Back
Flex, 30°/second	0.18**	0.33**	0.36**	0.38**	0.37**	0.33**
Extend, 30°/second	0.20**	0.32**	0.48**	0.46**	0.38**	0.39**
Flex, 60°/second	0.12*	0.35**	0.31**	0.28**	0.28**	0.23**
Extend, 60°/second	0.17**	0.20**	0.32**	0.28**	0.26**	0.26**
Extend, 120°/second	0.10	0.08	0.09	0.11*	0.06	0.05
Flex, 120°/second	0.17**	0.09	0.17**	0.20**	0.13*	0.15**
Flex isometric, 20°	0.08	0.30**	0.28**	0.21**	0.22**	0.21**
Extend isometric, 20°	0.05	0.21**	0.14*	0.14*	0.12*	0.08

Note: Statistical significance is represented by **P < 0.01

* P < 0.05.

Abbreviation: BMD, bone mineral density.

Table 3 Partial correlations between total lean mass, muscle strength, and bone density measures after controlling for subject age (N = 293)

Controlling age	Total lean mass	BMD
		Total body	L2–4	Femoral neck	Femoral
Total lean mass	1.00	0.46**	0.20**	0.32**	0.27**
Hip
Extend isometric at 90°	0.40**	0.45**	0.43**	0.36**	0.35**
Flex isometric at 20°	0.33**	0.19**	0.16**	0.16**	0.11
Flex at 120°/second	0.42**	0.43**	0.34**	0.28**	0.28**
Extend at 120°/second	0.38**	0.47**	0.36**	0.36**	0.35**
Flex at 180°/second	0.28**	0.22**	0.21**	0.09	0.12*
Extend at 180°/second	0.24**	0.19**	0.17**	0.10	0.12*
Back
Flex at 30°/second	0.32**	0.32**	0.35**	0.34**	0.29**
Extend at 30°/second	0.31**	0.45**	0.43**	0.34**	0.35**
Flex at 60°/second	0.34**	0.29**	0.26**	0.25**	0.20**
Extend at 60°/second	0.18**	0.27**	0.24**	0.21**	0.22**
Extend at 120°/second	0.07	0.05	0.08	0.02	0.02
Flex at 120°/second	0.07	0.11	0.15**	0.08	0.10
Flex isometric at 20°	0.29**	0.27**	0.19**	0.21**	0.20**
Extend isometric at 20°	0.21**	0.13*	0.13*	0.11	0.06

Note: Statistical significance is represented by **P < 0.01

* P < 0.05.

Abbreviation: BMD, bone mineral density.

Table 4 Unstandardized coefficient, standard error, partial correlation, and adjusted R² of stepwise multiple regression analysis on bone density

Predictor variables	B	SE	P-value*	r	Adjusted R^2
Total body BMD
Step 1					0.19
Intercept	1.481	0.0840	0.0001
Postmenopausal years	−0.004	0.0020	0.026	−0.12
Subject age	−0.007	0.0020	0.0001	−0.23
Step 2					0.26
Hip extend at 120°/second	0.001	0.0001	0.0001	0.20
Back extend at 30°/second	0.001	0.0001	0.0001	0.23
Hip flex at 120°/second	0.001	0.0001	0.009	0.12
BMD L2–4
Step 1					0.14
Intercept	1.692	0.1520	0.0001
Postmenopausal years	−0.007	0.0030	0.027	−0.12
Subject age	−0.01	0.0030	0.001	−0.18
Back extend at 30°/second	0.001	0.0001	0.0001	0.30
Step 2					0.19
Hip extend at 120°/second	0.001	0.0001	0.0001	0.19
BMD of femoral
Step 1					0.12
Intercept	1.339	0.1230	0.0001
Postmenopausal years	−0.006	0.0030	0.027	−0.12
Subject age	−0.007	0.0020	0.005	−0.16
Back extend at 30°/second	0.001	0.0001	0.0001	0.23
Step 2					0.15
Hip extend at 120°/second	0.001	0.0001	0.0001	0.22
BMD of femoral neck
Step 1					0.15
Intercept	1.245	0.1170	0.0001
Postmenopausal years	−0.008	0.0030	0.002	−0.17
Subject age	−0.006	0.0020	0.008	−0.14
Hip extend at 120°/second	0.001	0.0001	0.0001	0.23
Step 2					0.15
Back extend at 30°/second	0.001	0.0001	0.0001	0.21

Note:

* All regression models were statistically significant (P < 0.05).

Abbreviations:B, unstandardized coefficient; SE, standard error; r, partial correlation; BMD, bone mineral density.

Table 5 Unstandardized coefficient, standard error, partial correlation, and adjusted R² of stepwise multiple regression on total bone density, stratified by age group

Age group in years and predictor variables	B	SE	P-value*	r	Adjusted R^2‡
≤50					0.30
Hip flex at 120°/second	0.003	0.001	0.018	0.27
Back extend at 30°/second	0.001	0.0001	0.02	0.27
51–53					0.28
Back extend at 30°/second	0.001	0.0001	0.024	0.22
Hip extend at 120°/second	0.001	0.0001	0.0001	0.36
54–56					0.35
Hip flex at 120°/second	0.002	0.001	0.028	0.19
Back extend at 30°/second	0.001	0.0001	0.001	0.29
Hip extend at 120°/second	0.001	0.0001	0.025	0.19
57–59					0.25
Hip flex at 120°/second	0.004	0.001	0.0001	0.52
≥60					0.31
Hip flex at 120°/second	0.009	0.002	0.002	0.61

Notes:

* All regression models were statistically significant (P < 0.05)

‡ variance accounted for by variables retained at the last step of regression, adjusted for postmenopausal years.

Abbreviations:B, unstandardized coefficient; SE, standard error; r, partial correlation.