The relationship between dynamic, isokinetic and isometric strength and bone mineral density in a population of 45 to 65 year old women.
This study investigated the relationship between age, lumbar spine bone mineral density (LS BMD) and muscular strength of peri and postmenopausal women between 45 and 65 years either taking or not taking hormone replacement therapy (HRT). Ninety six women were tested for LS BMD (L2-L4), one repetition maximum (1RM) bench press and squat, maximal voluntary isometric contraction (MVC) of the knee extensors and peak torque of back extensor muscles at a speed of 30 degrees s(-1). Bone and strength data were analysed to evaluate the relationships in incrementing five year age groups and based on groups either taking or not taking HRT. ANOVA revealed significant differences in LS BMD between the 45-49 and 55-59 (F[3,92]=2.6411, p<0.05; -8%) age groups amounting to an annual bone loss of 0.8% for this Australian based population. Non significant LS BMD results were evident after controlling for the influence of age and menopausal status on the groups either taking or not taking HRT. Significant differences between the 45-49 and 60-64 (F[3,92]=2.7463, p<0.05) age groups for 1RM bench press and the 45-49 and 60-64, 50-54 and 60-64, and, 55-59 and 60-64 (F[3,92]=4.2816, p<0.05) age groups for 1RM squat amounting to an 18.8% and 37.5% loss of dynamic upper and lower body strength, respectively. Group correlation coefficients ranged between (r=-0.20 and -0.34, p<0.05) for LS BMD, strength and age. The conclusions demonstrate a concomitant decline in maximal muscle strength and bone density between women 45 and 65 years irrespective of HRT. These results also demonstrate a 50% greater decline in lower body strength compared to upper body strength between women 45 and 65 years.
Humphries
B
B
The School of Health and Human Performance, Central Queensland University, Rockhampton, Australia.
Triplett-McBride
T
T
Newton
R U
RU
Marshall
S
S
Bronks
R
R
McBride
J
J
Häkkinen
K
K
Kraemer
W J
WJ
D015502:Absorptiometry, Photon; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D001315:Australia; D015519:Bone Density / Q000502:physiology*; D003430:Cross-Sectional Studies; D005080:Exercise Test; D005260:Female; D020249:Hormone Replacement Therapy; D006801:Humans; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D013131:Spine / Q000502:physiology