Reduced Bone Strength and Muscle Force in Women 27 Years After Anorexia Nervosa.

CONTEXT: A substantial body of research findings indicate that muscle mass and bone mass are reduced in populations of anorexic females, even in such populations whose anorexia nervosa had been in remission for longer periods. OBJECTIVE: This study aimed to investigate whether the bone of an anorexia nervosa recovery cohort is adapted to maximal muscle forces and whether there are alterations in the structure of the tibia in this population, as compared with a control group. DESIGN, SETTING, AND PARTICIPANTS: This was a cross-sectional study of 22 women in Switzerland who have remained in stable recovery from anorexia nervosa for an average of 27 years. The measurements were compared with those of an age- and gender-matched control group (n = 73). INTERVENTIONS: There were no interventions. MAIN OUTCOME MEASURES: Bone characteristics of the tibia and maximal voluntary ground reaction force (Fm1LH) were measured. RESULTS: The variability in volumetric bone mineral content (vBMC) at the 14% site was explained by 54.7% on the grounds of Fm1LH (P < .001). Formerly anorexic women had an 11.6% lower Fm1LH (P = .001), a significantly lower vBMC at 4% and 14% of tibia length, and an 11.9% (P = .001) lower body mass than the age- and gender-matched control population. Present body mass of the anorexia group correlated positively with vBMC at the 14% site (P < .001). CONCLUSIONS: Despite the fact that findings reflected an adaptation of bone to the acting forces, most results indicated that the test cohort generally suffered from a secondary bone defect. In addition, maximal muscle force was also impaired in the formerly anorexic women.

The muscle-bone interaction in Turner syndrome.

OBJECTIVES: Turner syndrome (TS) is associated with an increased fracture rate due to reduced bone strength, which is mainly determined by skeletal muscle force. This study aimed to assess the muscle force-bone strength relationship in TS and to compare it with that of healthy controls. METHODS: This study included 39 girls with TS and 67 healthy control girls. Maximum muscle force (Fmax) was assessed through multiple one-legged hopping with jumping mechanography. Peripheral quantitative computerized tomography assessed the bone strength index at the tibial metaphysis (BSI 4) and the polar strength-strain index at the diaphysis (SSI polar 66). The effect of TS on the muscle-bone unit was tested using multiple linear regression. RESULTS: TS had no impact on Fmax (p=0.14); however, a negative effect on bone strength (p<0.001 for BSI 4 and p<0.01 for SSI polar 66) was observed compared with healthy controls. Bone strength was lower in the TS group (by 18%, p<0.01, for BSI 4 and by 7%, p=0.027, for SSI polar 66), even after correcting for Fmax. CONCLUSIONS: Similar muscle force induces lower bone strength in TS compared with healthy controls, which suggests altered bone-loading sensitivity in TS.

Is labral hypotrophy correlated with increased acetabular depth?

Labral hypertrophy is a distinct feature in hip dysplasia. Occasionally, very small, hypotrophic labra are observed. However, there is no literature concerning this pathology. We investigated if the size of the labrum correlated with any radiologic parameters reflecting the amount of acetabular coverage. It was hypothezised that there is a negative correlation between labrum size and acetabular coverage. Labra were categorized into three groups depending on the relation between length of the articular sided surface and height of bony attachment. Labra with a height:length ratio of 2 were classified as hypotrophic, with a height:length ratio of 1 as normal and with a ratio of 0.5 as hypertrophic. Labral cross-sectional areas (CSA) were measured on radial magnetic resonance imaging-arthrography slices using the measuring tool of the PACS system of 20 hips with hypotrophic labra (group 1), 20 hips with normal labral appearance (group 2) and 10 hips with hypertrophic labra (group 3). These values were then analyzed against following parameters: neck-shaft-angle (NSA), lateral center-edge angle (LCE), acetabular index (AI), femoral extrusion index (FEI) and acetabular retroversion index (ARI). Analyses of variance were used to determine differences in mean values between the three groups. Mean labral CSA differed significantly between all groups (group 1: 12.1 ± 2.9 mm(2); group 2: 25.2 ± 6.2 mm(2); group 3: 41.1 ± 12.3 mm(2); P < 0.001). NSA, LCE, AI and FEI all showed a significant difference between group 3 and 1 or 2. The ARI showed no difference between groups. Stepwise linear regression analyses showed a significant correlation between LCE angle and labral CSA with a corrected R (2)-value of 0.301. Labral CSA correlates with the LCE. No statistically significant difference between groups 1 and 2 concerning the LCE, AI or FEI could be identified. Nevertheless, group 1 had the highest mean coverage of all groups, hips with hypertrophic labra the lowest.

Changes in body composition in triathletes during an Ironman race.

PURPOSE: Triathletes lose body mass during an Ironman triathlon. However, the associated body composition changes remain enigmatic. Thus, the purpose of this study was to investigate Ironman-induced changes in segmental body composition, using for the first time dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT). METHODS: Before and after an Ironman triathlon, segmental body composition and lower leg tissue mass, areas and densities were assessed using DXA and pQCT, respectively, in eight non-professional male triathletes. In addition, blood and urine samples were collected for the determination of hydration status. RESULTS: Body mass decreased by 1.9 ± 0.8 kg. This loss was due to 0.4 ± 0.3 and 1.4 ± 0.8 kg decrease in fat and lean mass, respectively (P < 0.01). Calf muscle density was reduced by 1.93 ± 1.04 % (P < 0.01). Hemoglobin, hematocrit, and plasma [K(+)] remained unchanged, while plasma [Na(+)] (P < 0.05), urine specific gravity and plasma and urine osmolality increased (P < 0.01). CONCLUSIONS: The loss in lean mass was explained by a decrease in muscle density, as an indicator of glycogen loss, and increases in several indicators for dehydration. The measurement of body composition with DXA and pQCT before and after an Ironman triathlon provided exact values for the loss in fat and lean mass. Consequently, these results yielded more detailed insights into tissue catabolism during ultra-endurance exercise.

Side-to-side differences in the lower leg muscle-bone unit in male soccer players.

PURPOSE: To characterize side-to-side differences in the lower leg muscle-bone unit between the nondominant leg (NL) and the dominant leg (DL) using maximum voluntary forefoot ground reaction force (Fm1LH) during multiple one-legged hopping (m1LH) and tibial bone mass and geometry measured by peripheral quantitative computed tomography (pQCT). METHODS: Sixty-six male high-level soccer players (age range = 12-18 yr) performed m1LH to determine Fm1LH acting on the forefoot during landing for the NL and DL separately. pQCT scans were obtained to assess bone structural variables at 4%, 14%, 38%, and 66% tibia length and calf muscle cross-sectional area at the 66% site. RESULTS: First, participants displayed significant (P < 0.05) side-to-side differences in bone mass and geometry at 4%, 14%, and 38% (but not at the 66% site) of tibia length, with higher values in NL relative to DL (+0.7% to +5.6%), most evident at the 14% site. Second, no asymmetries were found for Fm1LH between the two legs (P = 0.442). Third, the relationship between Fm1LH and vBMC 14% was strong for both NL and DL (R2 = 0.48 and R = 0.54, respectively), but side-to-side differences in Fm1LH (ΔFm1LH) and side-to-side differences in vBMC 14% (ΔvBMC 14%) were not related (R2 = 0.04). CONCLUSIONS: Contrary to expectations from the mechanostat theory, ΔFm1LH and ΔvBMC 14% did not differ in proportion to each other. It seems that playing soccer is a well-balanced activity with respect to Fm1LH. However, the NL contributes to the supporting of the action of the DL, meaning that the loading experienced by the tibia might be more pronounced for the NL relative to the DL, leading to the observed higher bone strength values for the NL.

Maximum ground reaction force in relation to tibial bone mass in children and adults.

PURPOSE: The purpose of the study was to assess maximum voluntary forefoot ground reaction force during multiple one-legged hopping (F m1LH) and to determine the correlation between tibial volumetric bone mineral content (vBMC, a valid surrogate of bone strength) and F m1LH. METHODS: One hundred eighty-five females (8-82 yr old) and 138 males (8-71 yr old) performed multiple one-legged hopping to measure F m1LH acting on the forefoot during landing. Peripheral quantitative computed tomography scans were obtained to assess vBMC at 4%, 14%, 38%, and 66% of tibia length and calf muscle cross-sectional area at the 66% site. RESULTS: In all 323 participants, F m1LH corresponded to 3-3.5 times body weight, and F m1LH predicted vBMC 14% by 84.0% (P < 0.001). vBMC 14% was better correlated with F m1LH than with the calf muscle cross-sectional area in both males (R2 = 0.841 vs R2 = 0.724) and females (R2 = 0.765 vs R2 = 0.597). F m1LH and vBMC14% both increased during growth and afterward remained constant or decreased with age but never increased above the values reached at the end of puberty. F m1LH decreased by 23.6% between 21-30 and 61-82 yr in females and by 14.0% between 31-40 and 51-71 yr in males. vBMC 14% decreased by 13.7% in females between 21-30 and 61-82 yr but remained unchanged in adult males. CONCLUSIONS: Multiple one-legged hopping yields the highest (i.e., maximum) ground reaction force relative to other jumping maneuvers. Because bone strength is strongly governed by maximum muscle force, the concurrent assessment of peripheral quantitative computed tomography-derived bone strength and F m1LH might represent a new approach for the operational evaluation of musculoskeletal health.