Mechanical Response Tissue Analysis Research Articles

Musculoskeletal loading from road cycling and distance running on bone bending strength and BMD in athletes

The purpose of this study was to determine whether chronic sport training comprising of low or nonimpact musculoskeletal loading in road cycling (CYC) and distance running (RUN) were associated with tibial and ulnar bending strength and calcaneus and wrist BMD in male athletes. Method. Study subjects included 12 road cyclists (CYC), 12 distance runners (RUN) and 12 physically active nonathletic (CON). Tibial and ulnar bending strength (EI, Nm2) were assessed using a mechanical response tissue analyzer (MRTA), and BMD (g/cm2) of the wrist and calcaneus were assessed using a peripheral X-ray absorptiometry. Group means differences among the study groups were determined using ANCOVA. Results. Ulnar bending strength (EI, Nm2) of CYC were higher than CON (62.0 ± 20 vs 44.7 ± 9 Nm2, p< 0.05), but not RUN. Tibial bending strength (EI, Nm2) of CYC and RUN were not higher than CON. Calcaneus BMD of RUN was higher than CON (0.666 ± 0.07 vs 0.579 ± 0.06 g/m2, p<0.05), but not CYC. Wrist BMD of CYC was not higher than (p = 0.07) RUN and CON. Conclusion. Chronic engagement in CYC training induces osteogenic adaptation for increased ulnar bending strength and RUN training induces increased calcaneus BMD.

Bone bending strength and BMD of female athletes in volleyball, soccer, and long-distance running.

The purpose of the study was to determine whether sports training comprised of (1) high-impact loading sport in volleyball (VOL), (2) odd impact loading sport in soccer (SOC), and (3) low impact sport in distance running (RUN) were associated with tibial bending strength and calcaneus bone mineral density (BMD), and ulnar bending strength and wrist BMD. Female athletes comprised of 13 VOL, 22 SOC, and 22 RUN participated in the study. Twenty-three female non-athletes (NA) served as the comparison group. Tibial and ulnar bending strength (EI, Nm2) were assessed using a mechanical response tissue analyzer (MRTA). Calcaneus and wrist BMD were assessed using a peripheral X-ray absorptiometry. Group means differences among the study groups were determined using ANCOVA with age, weight, height, percent body fat, ethnicity/race, and training history serving as covariates. Tibial EI of VOL (228.3 ± 138Nm2) and SOC (208.6 ± 115Nm2) were greater (p < 0.05) compared to NA (101.2 ± 42Nm2). Ulnar EI of SOC (54.9 ± 51Nm2) was higher (p < 0.05) than NA (27.2 ± 9Nm2). Calcaneus BMD of VOL (0.618 ± 0.12g/cm2), SOC (0.621 ± 0.009g/cm2), and RUN (0.572 ± 0.007g/cm2) were higher (p < 0.05) than NA (0.501 ± 0.08g/cm2), but not different between athletic groups. Wrist BMD of VOL (0.484 ± .06g/cm2) and SOC (0.480 ± 0.06g/cm2) were higher (p < 0.05) than NA (0.443 ± 0.04g/cm2). Female VOL athletes exhibit greater tibial bending strength than RUN and NA, but not greater than SOC. Female SOC athletes exhibit greater ulnar bending strength and wrist BMD than NA.

Association of Osteogenic Adaptation and Sport Training in Distance Running, Soccer and Volleyball

Purpose: The purpose of the study was to determine whether sports training comprising of 1) high-impact loading sport in volleyball (VOL), 2) odd impact loading sport in soccer (SOC), and 3) low impact sport in distance running (RUN) were associated with weight bearing tibial bending strength and calcaneus BMD, and non-weight bearing ulnar bending strength and distal radius and ulna (wrist) BMD. Method: Female athletes comprised of 13 VOL, 22 SOC and 22 RUN participated in the study. A group of 23 non-athletes (NA) served as the comparison group. Tibial and ulnar bending strength ( EI, Nm 2 ) were assessed using a mechanical response tissue analyzer (MRTA). Calcaneus and wrist BMD were assessed using a peripheral X-ray absorptiometry. Group means differences among the study groups were determined using ANCOVA with weight, height, body mass index, ethnicity/race, and training history serving as covariates, and Tukey post-hoc test to determine the sources of the difference. Results: Tibial EI of VOL (228.3 ±138 Nm 2 ) and SOC (208.6 ±115 Nm 2 ) were higher (p &lt; 0.05) than NA (101.2 ± 42 Nm 2 ), but not RUN (144 ± 110 Nm 2 ). Ulnar EI of VOL, SOC and RUN (43.6 ± 17, 54.9 ± 51, 33.6 ± 15 Nm 2 , respectively) were higher (p &lt; 0.05) than NA (27.2 ± 9 Nm 2 ), not among the athletic groups. Calcaneus BMD of VOL (.618 ± .0.12 g/cm 2 ), SOC (.621 ± .009 g/cm 2 ), and RUN (.572 ± .007 g/cm 2 ) were higher (p&lt;0.05) than NA (.501 ± .08 g/cm 2 ), not among the athletic groups. Wrist BMD of VOL (.484 ± .06 g/cm 2 ) and SOC (.480 ± .06 g/cm 2 ) were higher (p &lt; 0.05) than NA (.443 ± .04 g/cm 2 ). Conclusion: The most effective mode of musculoskeletal loading activity for developing tibial bending strength and calcaneus and wrist BMD is from VOL and SOC training. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Association between body mass index, bone bending strength, and BMD in young sedentary women.

The purpose of this study was to determine whether body mass index (BMI) is a predictor of tibial or ulnar bending strength and bone mineral density (BMD) in sedentary women. Sedentary women (n = 34), age 19-27years, with low BMI (LBMI < 18.5kg/m2, n = 16), and normal or high BMI (NHBMI between 18.5 and 29.9kg/m2, n = 18) participated as study subjects. Study outcomes included tibial and ulnar bending strength (EI in Nm2) using a non-invasive mechanical response tissue analyzer (MRTA); BMD and bone mineral content (BMC) of the whole body (WB), femoral neck (FN), total hip (TH), lumbar spine 1-4 (LS1-4), and ulna; and bone turnover biomarkers. The LBMI group have lower (p < 0.01) body weight [group difference (Δ) = 32.0%], lean mass (LM) (Δ = 23.1%), fat mass (FM) (Δ = 77.2%), and tibial bending strength (Δ = 22.0%), compared to the NHBMI. The LBMI group also have lower (all p < 0.025) BMC in WB (Δ = 19.9%), FN (Δ = 20.1%) and TH (Δ = 19.0%), compared to the NHMBI, not in BMD results. Multivariate regression analysis shows that significant predictors of tibial bending strength are tibia length (adjusted R2 = .341), age (adjusted R2 = .489), ulna BMD (adjusted R2 = .536), and LM (adjusted R2 = .580). BMI was positively correlated with tibial EI (p < 0.05), height, weight, FM, LM, body fat% (all p < 0.01), and BMD of WB, FN, TH, and LS 1-4 (p < 0.05 or < 0.01). Our results show that BMI is not a significant predictor of tibial or ulnar bending strength in young sedentary women.

Effect of 6-month high-impact step aerobics and resistance training on BMD and tibial bending strength in sedentary premenopausal women.

To determine the effectiveness of 6months of high-impact step aerobics (SA) or moderate-intensity resistance training (RT) on areal bone mineral density (aBMD) and tibial bending strength in sedentary premenopausal women. Sixty-nine women (20-35years old) who were randomly assigned to RT (n = 22), SA (n = 26), or non-treatment control (CON, n = 21) groups completed the study. SA had a minimum of 50 high-impact landings each training session. RT had a periodized lower body resistance training program incorporating eight exercises (65-85% of 1 repetition maximum: 1-RM). Both RT and SA met 3 times weekly. aBMD was assessed using dual X-ray absorptiometry (DXA). Tibial bending strength was assessed using mechanical response tissue analysis (MRTA). Measurements at 6months were compared to baseline using ANCOVA, adjusted for baseline measures and covariates with α = 0.05. Calcaneus aBMD (0.0176 vs -0.0019 or -0.0009g/cm2 relative to RT, p < 0.004, and CON, p < 0.006, respectively), lower leg aBMD (0.0105 vs -0.0036g/cm2, relative to RT, p = 0.02), and lumbar spine 2 (L2) aBMD (0.0082 vs -0.0157g/cm2 relative to CON, p < 0.02) were significantly greater in the SA group after 6months. Tibial bending strength and bone resorption biomarkers were unchanged in all three groups after 6months. Sedentary premenopausal women engaging in 6months of high-impact aerobic exercise improved aBMD in the calcaneus, lower leg, and L2.

Improvements to mechanical response tissue analysis

Cortical Bone Mechanics Technology™ (CBMT) comprises certain improvements over a previous method known as Mechanical Response Tissue Analysis (MRTA). Both methods are dynamic 3-point bending tests intended for measuring the mechanical properties of cortical bone in living people. MRTA presented a theoretical potential for direct measurement of skeletal fragility, but it had acquired a reputation for error and fallen into disuse. We found sources of error in both MRTA data collection and data analysis. We describe here the fundamentals of MRTA, the major sources of error we found in MRTA, and our innovations for avoiding them.•Data collection at many sites across the mid-shaft of the ulna bone in the forearm.•Parameter estimation by fitting analytical complex compliance and stiffness transfer functions to empirical complex compliance and stiffness frequency response functions.•Optimization by selecting results from frequency response functions with the smallest deviations between fits to compliance and stiffness frequency response functions.

Response to "Clinical Evaluation of Bone Strength and Fracture Risk".

We read with great interest the recent review by de Bakker et al that summarized the state of several existing and emerging technologies for estimating bone strength and fracture risk in vivo. Much of their review focused on how well the measurements of selected technologies predicted experimental measurements of bone strength by ex vivo quasistatic mechanical testing (QMT) and on how well they tracked changes in mechanical properties of bone. The authors noted that the association of many common skeletal health measurements (e.g., DXA measures of trabecular bone score and areal and volumetric BMD) are only moderately associated with bone strength. The authors did not include mechanical response tissue analysis (MRTA) in their review. MRTA is a dynamic mechanical bending test that uses a vibration analysis technique to make immediate, direct, functional measurements of the mechanical properties (mass, stiffness, and damping) of long bones in humans in vivo. In this article we note our interest in the ability of MRTA to detect large changes in bone stiffness that go undetected by DXA. We also highlight results of our proprietary improvements to MRTA technology that have resulted in unmatched accuracy in QMT-validated measurements of the bending stiffness and estimates of the bending strength (both R2 = 0.99) of human ulna bones. To distinguish our improved technique from the legacy MRTA technology, we refer to it as Cortical Bone Mechanics Technology (CBMT). Further research will determine whether such CBMT measurements are clinically useful.

Accuracy and reproducibility of bending stiffness measurements by mechanical response tissue analysis in artificial human ulnas

Osteoporosis is characterized by reduced bone strength, but no FDA-approved medical device measures bone strength. Bone strength is strongly associated with bone stiffness, but no FDA-approved medical device measures bone stiffness either. Mechanical Response Tissue Analysis (MRTA) is a non-significant risk, non-invasive, radiation-free, vibration analysis technique for making immediate, direct functional measurements of the bending stiffness of long bones in humans in vivo. MRTA has been used for research purposes for more than 20 years, but little has been published about its accuracy. To begin to investigate its accuracy, we compared MRTA measurements of bending stiffness in 39 artificial human ulna bones to measurements made by Quasistatic Mechanical Testing (QMT). In the process, we also quantified the reproducibility (i.e., precision and repeatability) of both methods. MRTA precision (1.0±1.0%) and repeatability (3.1±3.1%) were not as high as those of QMT (0.2±0.2% and 1.3+1.7%, respectively; both p<10−4). The relationship between MRTA and QMT measurements of ulna bending stiffness was indistinguishable from the identity line (p=0.44) and paired measurements by the two methods agreed within a 95% confidence interval of ±5%. If such accuracy can be achieved on real human ulnas in situ, and if the ulna is representative of the appendicular skeleton, MRTA may prove clinically useful.

Effects of impact‐loaded sport training on bone bending stiffness and BMD in young females (706.16)

BLACKGROUND: Participation in high‐impact loading or odd‐impact loading sports is associated with higher bone mineral density (BMD) and bone mass. OBJECTIVE: The objective of this study is to compare the impact of sport training in long‐distance running, soccer and volleyball practice on BMD and bone bending strength in female athletes, 18‐24 years old.METHODS. 57 trained female athletes participated in this study. They were 22 soccer players (SOC), 22 long‐distance runners (RUN), and 13 volleyball players (VOL). Their ages were 19.1, 20.5 and 21.5 yr for the SOC, RUN and VOL, respectively. Sport training history was: 13, 11 and 10 yr for the SOC, RUN and VOL, respectively. Mean height, weight and BMI were 163 cm (±4.7), 59.8 kg (±4.1) and BMI 22.6 kg/m2 (±1.9), respectively. We also recruited 23 non‐athlete females, age 22.6 ± 0.5 yr, as control subjects. Bone bending stiffness was measured using a Mechanical Response Tissue Analyzer (MRTA, NASA‐ARC, CA), an in vivo technique expressed as EI in Nm2. EI was measured at the ulna and tibia. BMD was measured using a Duel‐Energy X‐ray Absorptiometry (PIXI‐DXA, in g/cm2) at two skeletal sites: heel and wrist.RESULTS. There are no differences in height, weight and BMI between the groups, except that VOL were significantly heavier and taller than the other groups. Tibia EI (TEI) of the RUN (122.7±89 Nm2) were significantly lower (p&lt;0.05) than VOL (228±89 Nm2), but not SOC (152±89 Nm2) and CON (85±89 Nm2). RUN has the lower ulnar EI (UEI=30.7±14 Nm2) relative to SOC (44±14 Nm2) and VOL (44±14 Nm2). VOL has significantly higher TEI (228.3±89 Nm2, p&lt;0.05) compared with SOC, RUN and CON. Heel and wrist BMD of the SOC and VOL are 7% to 9.5% higher (p&lt;0.05) than the RUN and CON.CONCLUSION. Volleyball training exhibited greatest osteogenic adaptation in tibial EI compared with RUN and CON, but not in ulnar EI or heel and wrist BMD. Distance running did not induce high osteogenic adaptation in the tibial EI or heel BMD. The mechanism for these changes in bone EI and BMD is unknown.

Changes in bone fatigue resistance due to collagen degradation

Clinical tools for evaluating fracture risk, such as dual energy X-ray absorptiometry (DXA) and quantitative ultrasound (QUS), focus on bone mineral and cannot detect changes in the collagen matrix that affect bone mechanical properties. However, the mechanical response tissue analyzer (MRTA) directly measures a whole bone mechanical property. The aims of our study were to investigate the changes in fatigue resistance after collagen degradation and to determine if clinical tools can detect changes in bone mechanical properties due to fatigue. Male and female emu tibiae were endocortically treated with 1 M KOH for 1-14 days and then either fatigued to failure or fatigued to induce stiffness loss without fracture. Partial fatigue testing caused a decrease in modulus measured by mechanical testing even when not treated with KOH, which was detected by MRTA. At high stresses, only KOH-treated samples had a lower fatigue resistance compared to untreated bones for both sexes. No differences were observed in fatigue behavior at low stresses for all groups. KOH treatment is hypothesized to have changed the collagen structure in situ and adversely affected the bone. Cyclic creep may be an important mechanism in the fast deterioration rate of KOH-treated bones, as creep is the major cause of fatigue failure for bones loaded at high stresses. Therefore, collagen degradation caused by KOH treatment may be responsible for the observed altered fatigue behavior at high stresses, since collagen is responsible for the creep behavior in bone.

Isokinetic Resistance Training Increases Tibial Bending Stiffness in Young Women

Bone mineral content (BMC) and bone mineral density (BMD) are common but imperfect surrogate measures of bone strength. The mechanical response tissue analyzer is a device that measures long bone bending stiffness (EI), which strongly predicts bone breaking strength. We hypothesized that isokinetic resistance training of the knee flexor and extensor muscles would increase tibial EI, BMC, and BMD in young women. Fifty-two women, aged 18-26 years, performed concentric (CON, n = 30) or eccentric (ECC, n = 22) isokinetic resistance training with the nondominant leg three times per week for 20 weeks. Before and after the training period, subjects were tested for CON and ECC peak torque of the knee flexor and extensor muscles with isokinetic dynamometry, tibial BMC and BMD using dual-energy X-ray absorptiometry, and tibial EI using mechanical response tissue analysis. Both training groups increased CON (15-21%) and ECC (17-31%) peak torque vs. the untrained leg. Tibial EI increased in the entire cohort (26%) and in each training group (CON 34%, ECC 16%) vs. the untrained tibia. Tibial BMC and BMD increased in the trained and untrained tibiae, with no significant differences between limbs. No differential tibial EI or bone mineral outcomes were observed between the CON and ECC training groups. In summary, CON and ECC isokinetic resistance training increased tibial EI, but not BMC or BMD, in young women.

A new tool to assess the mechanical properties of bone due to collagen degradation

Current clinical tools for evaluating fracture risk focus only on the mineral phase of bone. However, changes in the collagen matrix may affect bone mechanical properties, increasing fracture risk while remaining undetected by conventional screening methods such as dual energy x-ray absorptiometry (DXA) and quantitative ultrasound (QUS). The mechanical response tissue analyzer (MRTA) is a non-invasive, radiation-free potential clinical tool for evaluating fracture risk. The objectives of this study were two-fold: to investigate the ability of the MRTA to detect changes in mechanical properties of bone as a result of treatment with 1 M potassium hydroxide (KOH) and to evaluate the differences between male and female bone in an emu model. DXA, QUS, MRTA and three-point bending measurements were performed on ex vivo emu tibiae before and after KOH treatment. Male and female emu tibiae were endocortically treated with 1 M KOH solution for 1–14 days, resulting in negligible collagen loss (0.05%; by hydroxyproline assay) and overall mass loss (0.5%). Three-point bending and MRTA detected significant changes in modulus between days 1 and 14 of KOH treatment (−18%) while all values measured by DXA and QUS varied by less than 2%. This close correlation between MRTA and three-point bending results support the utility of the MRTA as a clinical tool to predict fracture risk. In addition, the significant reduction in modulus contrasted with the negligible amount of collagen removal from the bone after KOH exposure. As such, the significant changes in bone mechanical properties may be due to partial debonding between the mineral and organic matrix or in situ collagen degradation rather than collagen removal. In terms of sex differences, male emu tibiae had significantly decreased failure stress and increased failure strain and toughness compared to female tibiae with increasing KOH treatment time.

Isokinetic training increases ulnar bending stiffness and bone mineral in young women

Numerous studies have investigated the effects of physical activity on bone health; however, little is known about the effects of isokinetic strength training on bone. While bone mineral density (BMD) is widely used to assess bone health and fracture risk, there are several limitations of this measure that warrant new technology development to measure bone strength. The mechanical response tissue analyzer (MRTA) assesses bone strength by measuring maximal bending stiffness ( EI). We hypothesized that isokinetic strength training of the elbow flexors and extensors would increase ulnar EI, BMD, and bone mineral content (BMC) in young women. Fifty-four women trained the nondominant arm 3 times per week for 20 weeks; 32 trained concentrically (CON) and 22 trained eccentrically (ECC). Subjects were assessed for the following variables pre- and post-training: CON and ECC peak torque of the elbow flexors and extensors with isokinetic dynamometry, ulnar mineral content and density using dual-energy X-ray absorptiometry, and ulnar EI using MRTA. Isokinetic training increased CON (17%) and ECC (17%) peak torque, even when controlling for changes in the untrained arm. Eccentric training increased CON and ECC peak torque while CON training improved CON peak torque only. Isokinetic training increased ulnar EI 28%, which was statistically greater than the untrained arm. Ulnar EI increased 25% with CON training and 32% with ECC training. Both training modes resulted in greater EI gains compared to the untrained limb. Isokinetic training increased ulnar BMC (2.7%) and BMD (2.3%), even when controlling for untrained ulna changes. Both training modalities resulted in BMC and BMD increases; however, only CON training yielded gains when controlling for changes in the untrained limb. In conclusion, isokinetic strength training increases ulnar EI, BMC, and BMD in young women; no statistical differences were noted between CON and ECC training modes.

Relationship Among MRTA, DXA, and QUS Revisited

Inexpensive, commercially produced devices that directly measure bone strength in vivo are not currently available. Mechanical response tissue analysis (MRTA), a unique prototype device, is an in vivo vibrational test that measures transverse bending stiffness (a measure of whole bone strength expressed as the product of estimated Young's modulus of elasticity and cross-sectional moment of inertia, EI, Nm2) at ulna midshaft. We compared speed of sound (SOS; [m/s]) in ulna cortical bone using a commercially available axial transmission quantitative ultrasound (QUS) device with EI using MRTA. Dual-energy X-ray absorptiometry (DXA) was used to provide an estimate of ulna size (cm2), bone mineral content (BMC; [g/cm]) and areal bone mineral density (BMD; [g/cm2]). The objective of the study was to determine if ulna SOS--alone or in combination with BMD from DXA--was correlated with ulna EI, thus becoming a surrogate measure of transverse bending stiffness, and thus whole bone strength. Data were collected from 138 female volunteers (18-86 yr). EI and SOS were significantly correlated, r = +0.218, p = 0.01, but r2 was very low, 4.8%. SOS and total ulna BMD were combined to estimate elastic modulus, which correlated with EI, r = +0.377, p < 0.0001; however, the correlation was not significantly better than with SOS alone. We conclude that axial transmission QUS is not a strong surrogate in vivo technique for estimating transverse bending stiffness.

Ulnar and tibial bending stiffness as an index of bone strength in synchronized swimmers and gymnasts

The purpose of this study is to compare a mechanical property of bone in world-class female athletes with different loading histories. Bone bending stiffness or EI (E is the modulus of elasticity and I, the moment of inertia) was measured noninvasively with the mechanical response tissue analyzer, that analyzes the response of bone to a vibratory stimulus. We evaluated the ulna, ulnar width, wrist density and tibia in 13 synchronized swimmers (SYN), eight gymnasts (GYM) and 16 untrained women (UNT) of similar age. Muscle strength in the flexors and extensors at elbows and knees was measured in the athletes. SYN were taller than GYM or UNT (168 +/- 0.7 vs. 152 +/- 1.1 or 157 +/- 1.2 cm, P < 0.01). Ulnar EI, Nm(2), was similar in SYN and GYM (41 +/- 5.4 vs. 42 +/- 4.2, NS) and 50% higher than in UNT (27 +/- 2.1, P < 0.05). Ulnar EI, Nm(2) was related to ulnar width (r = 0.497, P < 0.002, n = 37) but not to wrist density. Tibial EI, Nm(2), in SYN and GYM (270 +/- 42 vs. 285 +/- 49, NS) was similar and more than twice as high as in UNT (119 +/- 6; p < 0.05). Knee flexor strength measured at 60 degrees s(-1) and elbow extensor strength at 200 degrees s(-1) correlated with tibial EI (r = 0.44 and 0.41, P < 0.05). In spite of different loading histories, the tibiae and ulnas of world-class athletes showed similar high values for bending stiffness that exceeded values in untrained women. EI in the ulna could be related to bone width and in the tibia, to muscle strength.

Relationship Among MRTA, DXA, and QUS

Dual-energy X-ray absorptiometry (DXA) and quantitative ultrasound (QUS) are the accepted modalities for the evaluation of fracture risk in the clinical setting. However, neither method provides a direct measurement of bone mechanics. In this study, we investigated a prototype device, known as a mechanical response tissue analyzer (MRTA), which provides direct mechanical measurements of mechanical properties of bone. A total of 56 healthy volunteers (20 men and 36 women) between the ages of 18 and 83 were recruited. The MRTA was used to measure the cross-sectional bending stiffness (EI) of the ulna bone. Axial speed of sound (SOS) at the ulna bone was determined by QUS; bone mineral content (BMC) and bone mineral density (BMD) were determined by DXA. Correlations, regression analysis, and analyses of variance (ANOVAs) were used to compare the three modalities. These analyses revealed that although there are strong linear relationships among the data collected by the various technologies, the bone properties reflected by MRTA are not fully explained by DXA and QUS. We conclude that the total information conveyed by MRTA measurements is unique. Further research is needed to delineate the different qualities of bone strength that are captured by MRTA, but not by DXA or QUS.

Influence of Oral Contraceptives on Bone Adaptations to Isokinetic Strength Training in Young Women

0756 PURPOSE: To assess the independent and synergistic effects of oral contraceptive (OC) use on bone mineral density (BMD) and bone mechanical stiffness (EI) in college-aged females after unilateral isokinetic resistance training. METHODS: Forty six females (age 20 ± 1.4 yr, height 163.8 ± 6.2cm, weight 58.9 ± 8.6kg, %fat 27.9 ± 4.8) were categorized as OC users (OC, N = 22) or not (NOC, N = 24) and participated in 32 weeks (3 d/wk) of unilateral arm and leg training, angular velocity 60°/s, using isokinetic dynamometers. BMD and EIMRTA were assessed using dual-energy x-ray absorptiometry (DXA) and mechanical response tissue analysis (MRTA), respectively. RESULTS: Leg and arm muscular strength increased by 16% and 15%, respectively (P < 0.001), beyond the pre- to post-training changes observed in the control limbs. Muscular strength gains were not associated with any consistent changes in either leg or arm EIMRTA, nor did groups using or not using OC respond differently. Both BMD of the tibia for the control leg and for the total body increased by small but significant amounts (1.4% and 0.4%, respectively; P <0.05) in the NOC group. The OC group showed no increase in these two measures, suggesting a potential suppressive effect of OC on bone mass accumulation in these skeletally immature females. However, BMD increased in the ulna bilaterally (P <0.01) and in the total hip of the trained leg only (P <0.05), regardless of OC use. CONCLUSION: These results suggest that oral contraceptives may limit attainment of total body peak bone mass in young adult females. Variable effects on appendicular bone were inconsistent in both control and regions of interest for assessing isokinetic training. Further studies are needed to determine the interactive effects of OC use and isokinetic resistance training on measures of bone strength. Supporting agency: United States Army Medical Research and Materiel Command, Grant #DAMD17-00-1-0114

Decreased ulnar bending stiffness in osteoporotic Caucasian women.

Mechanical response tissue analysis (MRTA) is a noninvasive measure of ulnar bending stiffness in vivo. It is unique in that the mechanical response to the lower range of vibrational frequencies is used to determine the average cross-sectional bending stiffness. The objective of this study was to compare ulnar bending stiffness among normal, osteopenic, and osteoporotic Caucasian women. World Health Organization criteria were used to define cohorts. Ulnar bending stiffness was expressed as the product of Young's modulus of elasticity (E) and the cross-sectional moment of inertia (I) in units of square Newton meters using MRTA. There was no difference in the mean body weight between cohorts but mean age was significantly different (p < 0.0001, analysis of variance): normal women, 34 +/- 12 yr (n = 55); women with age-related/idiopathic osteopenia, 52 +/- l l yr (n = 36(; and women with osteoporosis, 65 +/- 10 yr (n = 24). The mean EI of osteoporotic Caucasian women (25 Nm(2)) was 25% lower than normal subjects (33.1 Nm(2)) (p < 0.0001). However, there was no significant difference between EI of normal women and osteopenic women (30.l Nm(2)). EI was significantly but weakly correlated (i.e., the greatest r(2) value was 37%) to all dual X-ray absorptiometry variables, ulnar width, age, and body weight. In summary, results with MRTA were consistent with previous studies using classical ex vivo biomechanical techniques and in vivo vibrational techniques, showing decreased strength (i.e., bending stiffness) in osteoporotic bone compared with normal bone and a generalized decrease in bending stiffness with increasing age.

Noninvasive determination of bone mechanical properties using vibration response: A refined model and validation in vivo

Accurate non-invasive mechanical measurement of long bones is made difficult by the masking effect of surrounding soft tissues. Mechanical response tissue analysis (MRTA) offers a method for separating the effects of the soft tissue and bone; however, a direct validation has been lacking. A theoretical analysis of wave propagation through the compressed tissue revealed a strong mass effect dependent on the relative accelerations of the probe and bone. The previous mathematical model of the bone and overlying tissue system was reconfigured to incorporate the theoretical finding. This newer model (six-parameter) was used to interpret results using MRTA to determine bone cross-sectional bending stiffness, EI MRTA. The relationship between EI MRTA and theoretical EI values for padded aluminum rods was R 2 = 0.999. A biological validation followed using monkey tibias. Each bone was tested in vivo with the MRTA instrument. Postmortem, the same tibias were excised and tested to failure in three-point bending to determine EI 3-PT and maximum load. Diaphyseal bone mineral density (BMD) measurements were also made. The relationship between EI 3-PT and in vivo EI MRTA using the six-parameter model is strong ( R 2 = 0.947) and better than that using the older model ( R 2 = 0.645). EI MRTA and BMD are also highly correlated ( R 2 = 0.853). MRTA measurements in vivo and BMD ex vivo are both good predictors of scaled maximum strength ( R 2 = 0.915 and R 2 = 0.894, respectively). This is the first biological validation of a non-invasive mechanical measurement of bone by comparison to actual values. The MRTA technique has potential clinical value for assessing long-bone mechanical properties.

Noninvasive assessment of ulnar bending stiffness in women

The load-carrying capacity of cortical bone is closely related to its geometry and to its fundamental material properties, including mineral content (BMC). Together these determine the bending stiffness EI, where I is the cross-sectional moment of inertia and E is Young's modulus of elasticity. To assess the relationship of BMC and bone width (BW) to EI in healthy women, we used mechanical response tissue analysis (MRTA), a noninvasive method that involves analysis of tissue responses to ulnar vibration. A total of 48 healthy women were enrolled into an older (64 +/- 1y, n = 25) and a younger (25 +/- 0.6y, n = 23) group. BMC and BW of the dominant ulna were measured by single-photon absorptiometry (SPA). EI was determined by MRTA. BMC (0.75 +/- 0.02 versus 0.63 +/- 0.02 g/cm), BMC/BW (0.75 +/- 0.02 versus 0.63 +/- 0.02 g/cm2), and EI (27.7 +/- 1.3 versus 21.3 +/- 1.1 N.m2) were significantly greater (p less than 0.005) in the young subjects. BW did not change with age (1.00 +/- 0.01 versus 1.01 +/- 0.01 cm). In young women, simple correlations of BMC and BW with EI were both significant. By multiple regression analysis only BW independently predicted EI (EI = -0.35 + 39.1 x BMC, R2 = 0.52). In older women BMC and BW correlated with EI, but in multiple regression only BMC was significant (EI = -34.5 + 62.1 x BW; R2 = 0.45). When this analysis of older women included only those whose BMC values were within 2 SD of the young mean, BMC remained the only significant predictor of EI.(ABSTRACT TRUNCATED AT 250 WORDS)