In master athletes the relationship between lactate threshold (LT) and endurance performance is unclear, possibly due to age-related decrease in VO2peak. To determine whether an absolute measure of LT was a significant predictor of 10km running performance in master athletes, 51 men master athletes (40-77 yrs) performed a treadmill graded exercise test with minute-by-minute venous blood samples for lactate analysis. Training status and recent 10 km performances were determined by questionnaire. VO2peak (r=-0.56, P<0.001) and the two absolute measures of LT, Power at LT (r=-0.44, P<0.001) and VO2 at LT (r=-0.39, P=0.002), were significantly correlated to 10 km performance, but relative LT (% of VO2peak) was not (r=0.10, P=0.48). VO2peak (R 2 =0.31, P<0.001) and Power at LT (∆R 2 =0.08, P=0.015) were significant predictors of 10 km performance. These findings suggest that absolute LT is predictive of endurance performance in master athletes. Furthermore, relative LT is not a useful evaluation of LT in master athletes, possibly because of the age-related decrease in VO2peak. (Biol.Sport 26:105-112, 2009)

Quadriceps strength and mass peak in the third decade of life, plateau, and then decline from the fifth decade on. To examine the influence of chronic endurance training and age on lean mass and leg strength, women runners (n = 62, age 43-69 years) and sedentary participants (n = 33, age 43-66 years) were divided into 40-, 50-, and 60-year age groups. Absolute isokinetic concentric torque did not differ between runners and sedentary women (97.9 +/- 19.5 and 104.6 +/- 22.7 N . m, respectively, p = .18) but was different between age groups independent of exercise status (107.6 +/- 18.4, 97.1 +/- 19.9, and 90.1 +/- 21.4 N . m, for 40s, 50s, and 60s, respectively, p < .05). Lean body mass also differed by age group (p < .05) but did not change differently among runners and sedentary women. These findings suggest that chronic endurance training might not influence the loss of muscle mass and muscle strength that occur with aging.

Physical activity is an important contributor to peak bone mass and bone maintenance in women. Previous research has indicated that participation in weight-bearing exercise and physical activities with high impact/ground reaction forces (GRFs) are critical to the development of peak bone mass. PURPOSE: To determine how physical activity patterns prior to and after menarche influence bone mineral density (BMD) in college-aged women. METHODS: The participants included 51 college-aged women (24.5 ± 0.4 years; 60.6 ±1.4 kg) currently participating in moderate to high levels of aerobic activity, both with and without participation in resistance exercise. BMD was measured at the hip, lumbar spine and whole body by DEXA (Hologic QDR 1500). Physical activity (pre-, post-menarche and current levels), menstrual history, bone health history, and calcium intake were assessed by questionnaire. Subjects were grouped by pre-menarche activity status (sedentary vs. active) and impact profiles of activities (based on GRFs) pre-menarche, post-menarche (menarche to age 20) and current. Activity group differences in BMD were determined by multiple analysis of covariance (MANCOVA) with tobacco use, alcohol use, lean body mass, age at menarche, age, and use of oral contraceptives (N=21) as the covariates. RESULTS: The sedentary (SED) vs. active (ACT) comparisons for participation in activity prior to menarche (Pre-Men) are presented below as X ± SD. *Significantly different from SED group at the P < 0.05 level.Table 1CONCLUSION: Women who participated in physical activity prior to menarche had higher BMD than women who were sedentary before menarche. Participation in physical activity prior to menarche appears important to the optimization of peak bone mass.

Understanding the etiology of factors influencing, bone mineral density (BMD) in Hispanic women for the prevention of osteoporosis was the aim of this investigation. Whole body BMD (WBBMD) of 39 Hispanic, premenopausal women aged 22-51 years was measured using dual-energy X-ray absorptiometry (DXA). Maximal aerobic capacity ((V) over dot O-2max) was determined by treadmill ergometry with direct measurement of oxygen consumption. Fat-free mass (FFM) and fat mass were estimated from two independent techniques, DXA and bioelectrical impedance analysis (BIA). A questionnaire was administered to determine weekly physical activity, age of menarche, oral contraceptive (OC) use, parity, and lactation. Factors with significant correlation to WBBMD were weight (r=0.74), body mass index (r = 0.66), fat mass (r = 0.68 - 0.69), FFM (r = 0.55 - 0.65), percent fat (r = 0.43 - 0.55), sagittal diameter (r = 0.58), waist circumference (r = 0.53), hip circumference (r = 0.66) and weekly activity (r = 0.40). Stepwise multiple linear regression revealed that 73% of the variance in WBBMD is attributed to fat mass (55%), FFM (10%), and (V) over dot O-2max (8%). When BIA was used instead of DXA in the regression, (V) over dot O-2max was no longer an independent predictor of WBBMD. Fat mass and FFM accounted for 43% and 20% of the variance in WBBMD, respectively, explaining a total of 63% of the variance. The addition of age, age of menarche, weekly physical activity, OC use, parity, and lactation did not make significant contributions to the variance. The findings of this study suggest that fat mass is a stronger predictor of bone mineral density than fat-free mass to BMD; aerobic capacity is another important predictor of BMD in Hispanic premenopausal women.

PURPOSE:It has been reported that maximal strength peaks at approximately 30 yr of age, plateaus, and remains relatively stable for the next 20 yr, with an age-related decline in strength becoming significant after age 50. Much of the research attributes this decrease in peak force to age-associated reductions in muscle mass, with a selective atrophy and reduction in Type II fiber area and number being the primary factors. The influence that chronic endurance training has upon age-associated changes in muscular strength and muscle morphology has been largely undetermined. The purpose of this investigation was to examine the influence of chronic endurance training and age on leg extensor strength, and muscle fiber size and type distribution. METHODS:Male master runners (N = 107, age range = 40-88 yr) were tested for maximal strength of the leg extensor muscles. A subgroup of 30 master athletes participated in muscle biopsy testing. The effects of age were addressed by subdividing the sample into five cohorts. RESULTS:Peak isokinetic concentric torque did not differ between age groups until after age 70 yr. Regression analysis revealed a significant (P < 0.05, r(2) = 0.1838) age-associated decrease in relative strength (N.m.kg(-1) lean body mass). Type I and Type II fiber area and distribution did not differ between age groups through the eighth decade. CONCLUSIONS:These data suggest that chronic endurance training can delay the age of significant decline in peak torque and changes in muscle morphology characteristics of the vastus lateralis.

Hispanics comprise one of the fastest-growing segments of the U.S. population. Mexican-American adults are more likely to be overweight, physically inactive, diabetic, and to have higher levels of hypertension than are white adults. However, studies addressing the relationship between physical fitness and coronary artery disease (CAD) risk factors among Mexican-Americans are much less conclusive. Therefore, understanding the etiology of factors influencing resting systolic (SBP) and diastolic blood pressure (DBP) in Hispanic women was the aim of this investigation. SBP, DBP, peak oxygen uptake (peak VO (2)), weekly physical activity, waist (WC) and hip circumference, blood glucose, and levels of plasma lipids (triglyceride, total cholesterol, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol) of 39 Hispanic women age 22 - 51 years were measured. Factors with significant correlation to SBP were age, WC, sagittal diameter, and weight. Similarly, significant correlations were observed between anthropometric indices, age, and DBP. Peak VO (2) ( r = - 0.53, p < 0.01) and heart rate at maximal effort ( r = - 0.34, p </= 0.05) were inversely associated to DBP. There was also a strong inverse correlation ( r = - 0.53, p < 0.01) between peak VO (2) and CAD risk profile (created from one or the combination of: hypertension, obesity, hyperglycemia, dyslipidemia, smoking). Stepwise multiple linear regression revealed that 33 % of the variance in SBP is attributed to age (25 %), and WC (8 %), while DBP is explained by WC alone (26 %). The addition of peak VO (2) did not make significant contributions to the variances in SBP or DBP. The findings of this study suggest that central adiposity is an important predictor of resting blood pressure in Hispanic women. The inverse association between aerobic fitness and diastolic blood pressure as well as CAD risk factors suggests that recommendations regarding prevention of hypertension in this population should be based on the interrelationships between physical fitness and obesity.

1823 Chronic pharmacologic anabolic-androgenic steroid (AAS) treatment using testosterone propionate (TP) has previously been shown to improve the force generating capabilities of the diaphragm muscle of gonadally intact adult male rats without altering cross-sectional area. PURPOSE: The purpose of this study is to determine the effect of AAS treatment on satellite cell activation in the diaphragm muscle. METHODS: Adult male rats (250–275 g initial body weight) were housed in the USC vivarium with food and water supplied ad libium. Serum testosterone levels were elevated to approximately 10x physiologic levels for up to 28 days through the use of subcutaneously implanted Silastic™ capsules filled with crystalline TP. Animals were deeply anesthetized and killed by transcardial saline perfusion followed by 4% paraformaldehyde in situ. The right and left costal diaphragm muscle (DIAm) were harvested and prepared for immunohistochemistry. Immunohistochemical analysis was performed on 10 μm-thick sections utilizing standard protocols. Goat anti-Mcadherin, Santa Cruz, CA (satellite cells), rabbit anti-Laminin, DAKO, Denmark (basal lamina), rabbit anti-MyoD, Santa Cruz, CA, (myogenic regulatory factor) were used to visualize to identify quiescent and activated satellite cells. Nuclei were labeled with DAPI (Molecular Probes, OR). One-way ANOVA with Bonferroni correction was used to determine differences between groups. RESULTS: Significant increases in DIAm quiescent satellite cell number, relative to controls, were observed after 7-days of TP treatment, (39.3 and 16.0, respectively; F = 4.97, p = 0.01). Interestingly, quiescent DIAm satellite cell numbers appear to return to control values after 14 and 28 days of TP treatment. Cross-sectional area (μm2) and number of myonuclei per fiber were not affected by TP treatment (F = 0.45, p = NS, and F = 0.59, p = NS, respectively). CONCLUSIONS: These data suggest that pharmacologic TP treatment transiently increases quiescent satellite cell number. These observations suggest that TP treatment of sedentary adult male rats transiently increases the capability of this muscle to rapidly adapt to physiologic stresses by increasing the number of cells capable of myogenic differentiation. (Research funded by NHLBI: HL-59904 to CEB).

Prescription of exercise intensity is generally based upon relations between VO2, Heart Rate (HR), and HR reserve (HRR) expressed as a percent of maximum. Recent evidence suggests that these relations may be altered by aging. However, it remains unclear how chronic exercise may influence the effect of aging on the relations between %VO2, %HR and %HRR. PURPOSE To determine in Master Athlete's (MA) the efficacy of using the ACSM guidelines as an appropriate method of prescribing exercise intensity. METHODS A total of 157 (mean age 52.3±8 yrs, range 40–77 yrs.) subjects participated in the study (96 males, 61 females). Subjects were considered MA's as evident by their meeting our criteria of 1) Running for a period of > 5 years, 2) Running ≥ 10 mile/week, 3) Older than 40 years of age. Subjects performed a maximal VO2 treadmill examination. Heart rates were assessed during testing by a 12-lead ECG. VO2, and HR were measured at one-minute intervals during the VO2max test and HRR were calculated. One-Sample T-Test's were performed to compare the values obtained to the standards created by ACSM. RESULTS See table (* significantly greater from corresponding ACSM values p < .001)Table: No Caption AvailableCONCLUSION % HRR in MA's is similar to ACSM guidelines however, at increased intensities %HRR is greater than the reported guidelines. % HRmax was not an accurate measure of exercise intensity at any given level of VO2. Modified guidelines for Master athletes need to be established in order to accurately prescribe exercise intensities during exercise.

While chronic exercise is known to have a positive influence on lipids in older individuals, numerous research studies have shown that many health and fitness measures decline with aging. PURPOSE To determine the changes of cardiovascular risk factors and aerobic capacity decrement between age and gender in master athletes. Two hundred forty-eight masters athletes (male=155, 59.53 ± 9.45, female=93, 55.38 ± 9.06) participated in the study as subjects. METHODS Coronary risk factors were determined from the resting blood samples taken during the pre-exercise physical examination. VO2max was determined using a continuous, incremental protocol on a motorized treadmill. Blood samples were drawn from the in-dwelling catheter at the end of each minute of exercise. Activity history was determined by questionnaire. Data were analyzed by t-test, with significance determined at p < 0.05. Data is presented as mean ± standard deviation. RESULTS There were significant differences between groups in age (t = −3.403), weight (t = −16.718), and VO2max (t = −3.069). However, TRIG and CHOL were not different between males and females, despite differences in HDL-C (t = 6.137). The best fit equation for triglyceride in males was using a 2nd degree polynomimal fit (y = −0.0489x2 + 5.9225x − 90.329; r2 = 0.0275), the same was true for females (y = −0.0392x2 + 5.1937x − 90.241; r2 = 0.0583). Cholesterol versus age was best described using a linear fit for males (y = 0.2276x + 184.56; r2 = 0.0038) and females (y = 1.8184x + 107.52; r2 = 0.1485). HDL cholesterol was best described with a 2nd degree polynomial fit in males (y = −0.0002x2 + 0.0599x + 60.399; r2 = 0.0006) and females (y = −0.0372x2 + 3.8433x − 17.606; r2 = 0.0539). CONCLUSION We conclude that, using cross-sectional methods, the kinetics of the age related changes in blood lipids are similar between males and females.

Skeletal integrity is related to the balance between bone formation and bone resorption, which is mediated by factors including genetics, hormones, loading, and calcium supply. The extent to which these determinants of bone environment influence markers of bone turnover remains unclear. PURPOSE This investigation was conducted to evaluate the importance of 17β-HSD1 genotype, estradiol (E2), androstenedione (AD), testosterone (T), insulin-like growth factor-I (IGF-I), physical activity, and calcium intake to concentrations of markers of bone formation (osteocalcin, OC) and resorption (cross-laps, LAPS) in college-aged young women. METHODS Fasting serum was obtained from 32 women aged 21.6 ± 3.4 years (X ±SD) for the determination of OC, E2, AD, T, and IGF-I on day 11 ± of an ovulatory menstrual cycle. OC and IGF-I concentrations were determined by immunoradiometric assay, while E2, AD, and T were determined by radio-immuno assay. 17β-HSD1 genotype was determined by PCR as A/A, A/G, or G/G. LAPS were determined from urine by enzyme-linked immunosorbent assay. Physical activity and dietary calcium intake were derived from questionnaires. Stepwise linear regression analysis determined the proportion of the variance in OC and LAPS accounted for by the variables. Significance was set at p < 0.05. RESULTS For osteocalcin, E2 accounted for 18.8% of the variance (p = 0.012), with physical activity accounting for an additional 16.3% (p = 0.011). The variance in LAPS was explained by IGF-I concentrations (11.4%, p = 0.044) and calcium intake (11.1%, p = 0.039). None of the other variables were significant predictors of either marker. CONCLUSION It is evident from the results that diverse factors are important in determining rates of bone formation and resorption in young women. These results underscore the complex roles of estrogen, physical activity, IGF-I and calcium in the maintenance of skeletal integrity. Supported by USC James H. Zumberge Faculty Research and Innovation Fund, USC MFWA Research Fund, and BCRP 1KB-0060

PURPOSEThe lack of relationship between lactate threshold (LT) and running performance in older runners, and the increase in LT with age, has not been previously studied in a longitudinal design. We evaluated the cross-sectional and longitudinal changes in LT with age and compared the changes in LT with changes in performance variables.METHODSFifty-one male and 23 female runners (39-77 yr) performed two graded treadmill exercise tests with minute-by-minute venous blood lactate analysis, separated by 5.8 +/- 1.6 yr (mean +/- SD). Body composition was determined by hydrodensitometry and training history by questionnaire.RESULTSThere was no change in LBM over time, but significant decreases in [OV0312]O(2max) and training volume irrespective of age and gender (P < 0.05). LT as a percent of [OV0312]O(2max) increased with age (P < 0.05), demonstrated poor stability over time (r = 0.29, P = 0.01) compared with other parameters measured, and changes in LT were not related to changes in fitness or performance.CONCLUSIONBased upon these findings, we conclude that the LT may be less precise than [OV0312]O(2max) or performance in the prescription of exercise intensities or as an evaluation tool in older individuals.

Previous reports from our laboratory suggest that bone mineral density (BMD) differs by 17β- hydroxysteriod dehydrogenase 1 (17β-HSD1) genotype. PURPOSE This investigation was conducted to test the hypothesis that 17β-HSD1 genotype would account for significant portions of the variance in BMD in college-aged young women. METHODS Forty-nine young women aged 21.2 ± 3.2 years (X ± SD) participated in this investigation. 17β-HSD1 genotype was determined by PCR as A/A, A/G, or G/G. BMD was assessed at the spine (SP), proximal femur (total hip (TH)), and whole body (WB) by dual energy x-ray absorptiometry (DXA). Lean mass was also determined by WB DXA scanning. In the subjects who ovulated, fasting serum estradiol (E2) was determined by radio-immuno assay (RIA) on samples obtained on day 22 of the menstrual cycle. Weekly physical activity patterns during the year prior to testing were based on data derived from questionnaires. The proportion of the variance in BMD accounted for by 17β-HSD1 genotype was determined by stepwise linear regression techniques, with ethnicity, lean body mass, gynecologic age, calcium intake and minutes of physical activity included in the equation. RESULTS The only significant predictor of BMD of the SP and WB was lean mass (r2 = 0.197, p = 0.001 and r2 = 0.540, p < 0.001, respectively). In contrast, at the TH, while lean mass accounted for 34.6% of the variance, 17β-HSD1 genotype explained an additional 9.4% of the variance in BMD. The addition of luteal phase estradiol concentrations, calcium intake, ethnicity, gynecologic age, and physical activity to the equation failed to add significantly to the explanation of the variance in BMD at the reported sites. CONCLUSION The above results provide further evidence of the importance of 17β-HSD1 genotype in the determination of TH BMD in college-aged young women. Supported by USC James H. Zumberge Faculty Research and Innovation Fund, USC MFWA Research Fund, and BCRP 1KB-0060

Lipodystrophy with central fat accumulation occurs in 30–50% of persons infected with HIV. It is unknown whether diet modification or exercise can positively affect abdominal obesity in this population. PURPOSE We sought to assess the effects of diet restriction, a structured aerobic exercise protocol, or the combination on body compositional changes after 8 weeks. METHODS 22 HIV+ individuals < 60 years old with abdominal obesity defined as waist/hip circumference ratio 0.95 (men) and 0.85 (women) were enrolled for this study. Subjects were randomized to one of three groups: a calorie restricted diet (D); aerobic exercise (E); or calorie restriction plus exercise (D+E). Caloric restriction (0.20) was calculated from the estimated total daily caloric expenditure determined by indirect calorimetry and nitrogen excretion. Aerobic exercise (3 times/week for 30 minutes) consisted of treadmill exercise at 65% of maximal heart rate range (MHRR) initially, with biweekly incremental increases of 5%, until week 7–8, where MHRR was 85%. RESULTS 11 subjects completed the study: D (n=4), E (n=3), and D+E (n=4). By combining groups D & D+E (n=8), significant reductions in: total body weight (1.54Kg, p = 0.045); total fat (605g, p = 0.02); and trunk fat (476g, p = 0.02) occurred. For the combined D and D+E groups there were greater reductions in trunk fat compared to E, −4.9%, +5.9%, respectively, p = 0.02. Pooled data for E & D+E groups (n=7) demonstrated significant increases in absolute and relative VO2max, (0.25L/min, p = 0.03 and 3.19ml/kg/min, p = 0.02, respectively. CONCLUSION Caloric restriction with or without exercise appears to decrease central fat in HIV+ individuals in as little as 8 weeks. Moreover, positive training effects can be achieved with structured aerobic exercise in this population although the dropout rate may be high.

Purpose: Prior research has suggested that chronic running may not prevent age-related bone loss in women and may inhibit the influence of hormone replacement therapy (HRT) on bone. The purpose of this study was to longitudinally determine the effect of chronic running exercise alone, and in conjunction with HRT, on bone mineral density (BMD) in premenopausal and postmenopausal women. Methods: Forty-one women runners were tested an average of 4.8 yr apart, and separated into four groups according to their menstrual and HRT status at both test 1 and test 2. Measurements included BMD, body composition, and VO2max, as well as training, menstrual, and nutritional histories. Factorial and one-way ANOVA were used for analysis. Results: Group differences existed for body mass and body composition but did not change over time. Fitness and training variables were not different by group or time. Calcium intake did not differ between groups, but increased over time (829 +/- 310 vs 1058 +/- 468 mg(.)d(-1)). BMD of the hip, spine, and whole body were different between groups but did not change significantly over time. Regression analysis revealed age as the only significant predictor of change in bone mass. Conclusion: These data demonstrate no significant loss of bone mass over a 5-yr period in these chronic runners with relatively high calcium intakes regardless of menstrual or HRT status. Further, chronic running did not inhibit nor enhance the effect of HRT on bone in these women.

INTRODUCTION/PURPOSE Research addressing the role of biology and behavior on bone development during times of peak bone acquisition in adolescence is limited. The present investigation was conducted to address the influence of body composition (lean body mass, fat mass), menarche, leisure physical activity, sports team participation, smoking, and second-hand smoke on skeletal mass of a unique sample of Asian adolescents in China. METHODS A total of 166 girls and 300 boys (ages 12-16 yr) participated in this study. Bone mineral density (BMD) and content (bone mineral content (BMC)) of the forearm and the os calcis were measured using dual energy x-ray absorptiometry (DXA); lean body mass (LBM) and fat mass were estimated by bioelectrical impedance analysis (BIA); grip strength was measured by isometric dynamometry. Menarche, leisure physical activity, sports team participation, and active and passive smoking were determined using questionnaire. RESULTS In girls, a total of 44% of the variance in forearm BMC was attributed to a model which included LBM (32%), time since menarche (10%), and age (2%); heel BMC was best predicted by LBM alone (42%), with no significant contribution by other variables. In boys, a total of 39% of the variance in forearm BMC was attributed to a model which included LBM (28%), age (5%), sports team participation (4%), height (1%), and fat mass (1%); heel BMC was best predicted by LBM (50%) and height (3%), accounting for 53% of the variance. CONCLUSION The findings of this study suggest that lean body mass is the primary determinant of bone mass in Chinese adolescents. Menarche is also an important contributor in girls, whereas age and sports team participation are secondary predictors of bone mass in boys.

The 17β-hydroxysteriod dehydrogenase 1 (17β-HSD1) gene encodes the 17β-HSD type 1 enzyme that catalyzes the reaction converting estrone to estradiol. PURPOSE: This investigation was conducted to test the hypothesis that the A/A genotype of 17β-HSD1 would be associated with elevated levels of bone mineral density (BMD) and serum estradiol (E2) in college-aged young women. METHODS: Forty-six young women aged 21.0±3.0 years (X±SD) participated in this investigation. 17β-HSD1 genotype was determined by PCR as A/A, A/G, or G/G. BMD was assessed at the spine (SP) and proximal femur (femoral neck (FN), total hip (TH)) by dual energy x-ray absorptiometry (DXA). In the subjects who ovulated, fasting serum E2 was determined by radio-immuno assay (RIA) on samples obtained on day 22 of the menstrual cycle. Weekly physical activity patterns during the year prior to testing were based on data derived from questionnaires. BMD and E2 differences between women of the differing genotypes were determined by multivariate analysis of variance (with ethnicity, weight, gynecologic age and normalized minutes of physical activity as the covariates for BMD). RESULTS: Results are presented below as X±SD. *Significant difference between the group homozygous for the A allele (N = 11) and the group including those heterozygous or homozygous for the G allele (N = 35, p < 0.05).TableWhile luteal phase E2 concentrations did not differ between the genotypes, BMD was significantly greater in those homozygous for the G allele. CONCLUSION: The above results suggest 17β-HSD1 genotypes may be an important determinant of BMD in young women. Supported by USC James H. Zumberge Faculty Research and innovation Fund, USC MFWA Research Fund, and BCRP 1KB-0060

Strength has been shown to decline in both males and females with age. Studies have suggested that muscle quality (MQ), defined as force or torque/unit muscle mass also decreases with age. PURPOSE: To determine the effects of age on MQ in active older male and female athletes. We hypothesized that by using chronically active older subjects we would be able to distinguish between the influence of age versus the influence of sedentary lifestyle on muscle strength relationships. METHODS: Fifty-four master athletes (17 female and 37 male) were separated into tertiles: 45 – 54 years = 1st tertile (7 female and 8 male), 55 – 64 years = 2nd tertile (5 female and 14 male), and 65+ = 3rd tertile (5 female and 15 male). Maximal isometric knee extension strength at 60° (0* = full extension) was obtained on a KinCom dynamometer (Chattecx Corp., Hixson, TN). Muscle mass was obtained from a duel energy x-ray absorptiometer (DXA) using the whole body scan mode. Right lower extremity lean mass was used for calculating MQ. Muscle Quality was defined as maximal right leg isometric extension torque (Nm)/right leg lean mass (g). RESULTS: Factorial ANOVA demonstrated no differences for MQ between groups by gender (F = 0.22, NS). Significant differences for MQ were found between groups by age (F = 5.759, p < 0.006). Fishers LSD revealed significant differences between the oldest tertile and the two younger tertiles (3rd < 1st & 2nd). However, regression analysis revealed a significant age related decline in MQ in females (R = −0.627, p = 0.007), but not in males (R = −0.283, p = 0.090). CONCLUSION: These findings support the contention that MQ declines with age. However, we conclude that this decline is more apparent in females and that the age at which changes in MQ occur is most likely after the age of 65.

This study examined the relationships between high-intensity resistance exercise and bone mass in postmenopausal women and serum reproductive-hormone levels and bone-mass changes in response to resistance exercise. Women 45–65 years old were assigned to an exercise or a control group. They trained 3 times weekly for 18 weeks at 90,70, and 80% of their 1-RM. Groups were not different in age, height, body mass, muscle strength, or lean body mass. Initial muscle strength increased significantly in the training group. Total hip and intertrochanter bone-mineral density (BMD) increased in the training group. Estradiol, testosterone, osteocalcin, and CrossLaps concentration did not change in either group. Serum estradiol was significantly related to change in BMD at the hip, femoral neck, and intertrochanter, as well as change in lean mass. Results suggest that high-intensity resistance exercise can increase BMD of the hip and that serum estrogen concentrations might influence bone and muscle adaptations to resistance exercise in postmenopausal women.

The cytochrome P450c17α (CYP17) gene encodes the enzyme cytochrome P450c17α that is important in estrogen biosynthesis. PURPOSE: This investigation was performed to test the hypothesis that the A2/A2 polymorphism of the CYP17 gene would be associated with elevated levels of bone mineral density (BMD) and serum concentrations of estradiol (E2) in college-aged young women. METHODS: Fifty-five young women aged 20.7±2.8 years (X±SD) participated in this investigation. CYP17 genotype was determined via PCR as A1/A1, A1/A2, or A2/A2. BMD of the spine (SP), proximal femur (total hip (TH)) and for the whole body (WB) was assessed by dual energy x-ray absorptiometry (DXA). In the ovulatory subjects, fasting serum E2 (day 22) was determined by radio-immuno assay (RIA). Questionnaires were utilized to derive weekly physical activity patterns during the year prior to testing. Multivariate analysis of variance was utilized to determine significant differences in BMD and E2 between women of the differing genotypes (with ethnicity, weight, gynecologic age and normalized minutes of physical activity as the covariates for BMD). RESULTS: Results are presented below as X±SD.TableNeither luteal phase E2 concentrations nor BMD at any site differed when comparisons were made between the groups of women with different genotypes. CONCLUSION: These results suggest that CYP17 gene polymorphisms are not important in the determination of BMD in college-aged women. Supported by USC James H. Zumberge Faculty Research and Innovation Fund, USC MFWA Research Fund, and BCRP 1KB-0060

Research addressing the role of lifestyle and environmental factors on bone development during times of peak bone acquisition in adolescence is limited. Although the relationship between cigarette smoking and bone loss during adulthood is well established, the effect of smoking and second-hand-smoke on bone mass in adolescents is unknown. The high prevalence of smoking among the adults living in China, and the adolescent period being a critical time for both bone accretion and smoking initiation, were the incentives for this investigation. To determine whether these factors were detrimental to the adolescent skeletal system, we measured cortical (forearm) and trabecular (os calcis) bone mineral density (BMD) and content (BMC) using peripheral dual energy x-ray absorptiometry (DXA) in 466 girls and boys ages 10 to 16 years and living in Wuhan, China. In 166 girls, forearm BMC was best predicted by body mass index (24%), age (5%), and menarche (2%) for a combined variance of 31%, while 8% of the variance in os calcis BMC was predicted by body mass index (BMI) alone with no contribution by age or menarche. In 300 boys, a total of 24% of the variance in forearm BMC was explained by BMI (18%) and age (6%); os calcis BMC was only predicted by BMI (21%). The addition of active cigarette smoking and second-hand-smoke into the multiple linear regression models for forearm and os calcis bone mineral contant did not make significant contributions to the variances in either girls or boys. The reasons may have been due to the low levels and duration of tobacco use and exposure among the adolescents we studied. Selecting an older sample of adolescents who smoke more frequently and for a long duration may have uncovered a different relationship. Nevertheless, this was the first study that investigated the role of smoking and second-hand-smoke on bone mass during adolescence.