Brentano, MA, Cadore, EL, Da Silva, EM, Ambrosini, AB, Coertjens, M, Petkowicz, R, Viero, I, Kruel, LFM. Physiological adaptations to strength and circuit training in postmenopausal women with bone loss. J Strength Cond Res 22(6): 1816-1825, 2008-Strength training (ST; high intensity/low volume/long rest) has been used in several populations, including children, young adults, and older adults. However, there is no information about circuit weight training (CWT; low intensity/high volume/short rest) in apparently healthy postmenopausal women. The purpose of the present study was to analyze the effects of high-intensity ST and circuit training on isometric strength (IS), upper limb dynamic strength (ULS) and lower limb dynamic strength (LLS), muscle activation of quadriceps (EMGquad), maximal oxygen uptake (V̇o2max), time to exhaustion (TE), and bone mineral density (BMD). Twenty-eight postmenopausal women were divided into 3 groups: 1) ST group (STG, n = 9, 45-80% 1 repetition maximum (1RM), 2-4 sets, 20-6 reps), 2) circuit training group (CTG, n = 10, 45-60% 1RM, 2-3 sets, 20-10 reps), and 3) a control group (CON, n = 9, no exercise). Significance level was defined as p ≤ 0.05 for all analyses. After 24 weeks of training, increases were observed in STG and CTG. However, whereas in the STG, the IS (32.7%), ULS (28.7%), LLS (39.4%), EMGquad (50.7%), V̇o2max (22%), and TE (19.3%) increased, CTG showed changes only in IS (17.7%), ULS (26.4%), LLS (42.2%), V̇o2max (18.6%), and TE (16.8%). BMD did not change in any experimental group. In the CON, there were no changes in the variables analyzed. Our results suggest that ST and circuit training positively affect postmenopausal women's muscular strength, muscular activation, and cardiorespiratory fitness, with no changes in BMD.