Sandro Manuel Mueller

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.

One bout of vibration exercise with vascular occlusion activates satellite cells

What is the central question of this study? Acute skeletal muscle satellite cell (SC) activation is associated with skeletal muscle hypertrophy. Although the quantity of SCs has been reported to increase following a single bout of resistance exercise, data on muscle fibre type‐specific SC quantity and/or activation status after a single bout of vibration is presently lacking. What is the main finding and its importance? By determining SCs from muscle biopsies of the vastus lateralis using immunohistochemistry, we conclude that modification of vibration exercise by superimposition of occlusion induced activation and differentiation of SCs in young men, which had not been observed with whole‐body vibration or blood flow restriction alone.

High-intensity interval training with vibration as rest intervals attenuates fiber atrophy and prevents decreases in anaerobic performance.

Aerobic high-intensity interval training (HIT) improves cardiovascular capacity but may reduce the finite work capacity above critical power (W′) and lead to atrophy of myosin heavy chain (MyHC)-2 fibers. Since whole-body vibration may enhance indices of anaerobic performance, we examined whether side-alternating whole-body vibration as a replacement for the active rest intervals during a 4x4 min HIT prevents decreases in anaerobic performance and capacity without compromising gains in aerobic function. Thirty-three young recreationally active men were randomly assigned to conduct either conventional 4x4 min HIT, HIT with 3 min of WBV at 18 Hz (HIT+VIB18) or 30 Hz (HIT+VIB30) in lieu of conventional rest intervals, or WBV at 30 Hz (VIB30). Pre and post training, critical power (CP), W′, cellular muscle characteristics, as well as cardiovascular and neuromuscular variables were determined. W′ (−14.3%, P = 0.013), maximal voluntary torque (−8.6%, P = 0.001), rate of force development (−10.5%, P = 0.018), maximal jumping power (−6.3%, P = 0.007) and cross-sectional areas of MyHC-2A fibers (−6.4%, P = 0.044) were reduced only after conventional HIT. CP, V̇O2peak, peak cardiac output, and overall capillary-to-fiber ratio were increased after HIT, HIT+VIB18, and HIT+VIB30 without differences between groups. HIT-specific reductions in anaerobic performance and capacity were prevented by replacing active rest intervals with side-alternating whole-body vibration, notably without compromising aerobic adaptations. Therefore, competitive cyclists (and potentially other endurance-oriented athletes) may benefit from replacing the active rest intervals during aerobic HIT with side-alternating whole-body vibration. Trial Registration ClinicalTrials.gov Identifier: NCT01875146

Skeletal muscle characteristics and mitochondrial function in Huntington's disease patients

Huntington’s disease (HD) is a hereditary neurodegenerative disorder characterized by hyperkinesia with choreatic movements, cachexia, and impaired cognitive function. HD is caused by the expansion of a CAG repeat in the gene encoding the protein huntingtin, which is also present in peripheral tissues including skeletal muscle. Despite considerable progress in the comprehension of the pathophysiology of HD, the role of huntingtin and according pathomechanisms in peripheral tissues still remain elusive. A possible cause for muscular dysfunction might be metabolic alterations. In particular, impaired mitochondrial function has been proposed to be a major pathogenic factor. Many HD patients suffer from cachexia, which has been related to alterations in energy metabolism and mitochondrial impairment. However, the underlying mechanisms for the muscle atrophy and mitochondrial disturbances are not known, whether they are primary or secondary to the disease. Unraveling these mechanisms may add to a better understanding of the HD pathogenesis and offer new potential therapeutic approaches. We investigated skeletal muscle morphology and mitochondrial function of 10 patients with genetically verified HD (6 men and 4 women, 54 6 7 years), and 11 ageand gender-matched healthy controls (7 men and 4 women, 56 6 14 years). Patients and healthy controls underwent a skeletal muscle biopsy obtained from the vastus lateralis muscle and mitochondrial respirometric measurements. The main finding was a difference in skeletal muscle fiber phenotype in HD patients when compared with healthy controls. Namely, HD patients had a significantly higher proportion of type I fibers than controls (67.1 6 9.2 vs 39.2 6 22.8%; P < .05). In contrast, there was no difference in cross-sectional area of any fiber type between patients and controls. In addition, mitochondrial respiratory capacity specific to complex I (63.9 6 13.1 vs 80.6 6 18.2 pmol O2 mg 21 s) and maximal oxidative phosphorylation capacity (88.9 6 18.7 vs 106.1 6 18.4 pmol O2 mg 21 s) were slightly lower in HD patients when compared with healthy controls (P < .05; Fig. 1A). However, when respiratory capacity was normalized to respiratory capacity of complex IV activity, no difference was observed, although respiratory capacity of complex IV FIG. 1. (A) Mass-specific mitochondrial respiratory capacity and (B) mitochondrial-specific respiratory capacity (normalized to COX) in patients with Huntington’s disease (white bars) and healthy controls (black bars). LN, leak respiration without adenylates; PETF, fatty acid oxidative capacity; PCI, respiratory capacity of complex I; P, oxidative phosphorylation capacity; LOmy, oligomycin-induced leak respiration; E, electron transport system capacity; PCII, respiratory capacity of complex II; ROX, residual oxygen consumption; COX, respiratory capacity of complex IV. Values are mean 6 standard deviation. *P < .050; nPatients 5 10, nControls 5 11.

The effect of body composition and serum inflammatory markers on the functional muscle–bone unit in premenopausal women

Background/Objectives:A number of recent studies dealing with the relationship between the effects of high body mass (BM) and fat mass (FM) on bone mass and strength exhibit a range of contrasting variations in their findings. These diverse findings have led to an ongoing controversy as to whether high BM and FM positively or negatively affect bone mass and strength. Excessive FM and the associated low-grade inflammation might overturn the higher mechanical stimulus arising from a higher BM. Therefore, we aimed at quantifying the functional muscle–bone unit in premenopausal women with markedly diverging body composition.Subjects/Methods:Sixty-four young women with BMs ranging from 50 to 113 kg and body fat percentages between 20.7% and 51.8% underwent jumping mechanography and peripheral quantitative computed tomography measurements. Maximum voluntary ground reaction force during multiple one-legged hopping (Fm1LH), as well as bone characteristics at 4, 14 and 38% of tibia length, were determined. Body composition was assessed by dual-energy X-ray absorptiometry, and serum inflammatory markers were analyzed from blood samples.Results:Fm1LH predicted volumetric bone mineral content at the 14% site by 48.7%. Women with high body fat percentage had significantly higher Fm1LH, significantly lower relative bone mass, relative bone strength and relative bone area, as well as higher serum inflammatory markers in comparison to women with lower body fat percentage.Conclusions:In conclusion, high body fat percentage was associated with lower relative bone mass and strength despite normal habitual muscle force in premenopausal women, indicating that high body fat percentage compromised the functional muscle–bone unit in these individuals.

Greater blood volume and Hb mass in obese women quantified by the carbon monoxide-rebreathing method affects interpretation of iron biomarkers and iron requirements

Background/objectiveIron deficiency (ID) is common in overweight and obese individuals (OW/OB) but the mechanism is uncertain. Greater blood volume (BV) in OW/OB may increase hemoglobin (Hb) mass and iron requirements, and confound iron biomarkers by hemodilution. Quantification of BV/PV changes in OW/OB is challenging and a formula to estimate BV/PV based on anthropometric indices would be valuable. In normal weight (NW) and OW/OB women, we aimed at: (1) measure BV and assess whether differences in BV affect concentrations and total circulating mass of Hb and iron biomarkers; (2) develop an algorithm describing BV in OW/OB.Subjects/methodsIn a cross-sectional study, we measured BV in NW, OW, and OB non-anemic women (n = 62) by using the carbon monoxide-rebreathing method, body composition by dual energy X-ray absorptiometry, and iron and inflammatory status.ResultsOW and OB women had 11 and 16% higher mean BV and PV compared to NW (P < 0.05), respectively. In OW/OB compared to NW, total circulating masses of IL-6, hepcidin, Hb, and sTfR were higher, while total mass of serum iron was lower (for all, P < 0.05). An equation including height, body mass and lean mass to estimate BV in all BMI groups (R2 = 0.76).ConclusionAn equation based on anthropometric indices provides a good estimate of increased BV in OW/OB women. In OW/OB women, there is an increase in Hb mass that likely increases iron requirements for erythropoiesis and circulating TfR mass. At the same time, higher hepcidin concentrations may lower serum iron mass. Both these mechanisms may increase risk for ID in OW/OB women.

Myocellular characteristics in rheumatoid arthritis and osteoarthritis patients

Duijnisveld et al. have published an interesting study on the regenerative potential of muscle satellite cells in chronic inflammation in this journal [1]. They showed that muscle stem cell populations obtained from M. vastus medialis of patients with rheumatoid arthritis (RA) and osteoarthritis (OA) exhibited similar myogenic purity, viability, growth speed, differentiation, and maximum proliferative capacity. Based on these findings in vitro, the authors hypothesized that circulating inflammatory factors in RA negatively influence the regenerative potential of satellite cells and muscle strength in vivo. We aimed to verify whether these results obtained from vastus medialis muscles also apply to a muscle typically involved in the disease process of RA, namely M. interosseus dorsalis manus 1. For this purpose, we obtained intraoperative muscle biopsies from the M. interosseus dorsalis manus 1 of five RA (57.2 ± 11.1 years old) and four OA (60.7 ± 12.1 years old) patients and tested whether satellite cell numbers, myofiber sizes, and proportions were different between RA and OA patients. There was no difference in muscle fiber type distribution between RA and OA patients (Table 1). Myofiber cross-sectional area (CSA), myonuclear domains, the number of Pax7 cells, and the number of proinflammatory macrophages (CD68) were not different between RA and OA patients. There was a tendency for increased myonuclear number in myosin heavy chain (MyHC)-1 fibers in RA patients compared with OA patients, while there was no difference in myonuclear number in MyHC-2 fibers between the groups. MyHC-2 fiber CSAs in M. interosseus dorsalis manus 1 were significantly larger than MyHC-1 CSAs in RA and OA patients (Table 1). Our results point towards similar muscle characteristics between RA and OA patients in the highly affected M. interosseus dorsalis manus 1. Moreover, we found that most values for RA patients seemed to be higher when compared with OA in this preliminary dataset. Notably, there was a tendency for increased myonuclear number in MyHC-1 fibers in RA patients. Our results from a severely affected skeletal area are in line with previous studies investigating other skeletal sites. In M. vastus medialis, MyHC-2 CSAs were significantly larger than MyHC-1 CSAs in RA patients [2] and no significant differences in satellite cell numbers between RA and OA patients were present [3]. Based on our results from a small patient sample, the hypothesis that chronic systematic inflammation negatively influences the regenerative potential of satellite cells and myonuclei number cannot be confirmed, but it warrants further investigation.

Alterations in bone mineral density and lower extremity lean mass after hip arthroscopy in a professional female Ironman triathlete: a case study

IntroductionFemoroacetabular impingement is a pathomechanical condition of the hip, which is often treated through arthroscopic techniques. The ensuing immobilization period is associated with decreases in muscle mass and bone mass. To date, minimal knowledge is present about the development of tissue mass during the considerably short rehabilitation period before returning to competition in elite endurance athletes.Case descriptionBefore and after surgery, a professional female Ironman triathlete underwent dual-energy X-ray absorptiometry and peripheral quantitative computed tomography measurements.Discussion and evaluationAreal bone mineral density (aBMD) of the proximal femur and lower extremity lean mass decreased in the surgically treated lower extremity during the two-month period of immobilization after the hip arthroscopy. These losses were compensated for after only six weeks of rehabilitation. A similar progression of aBMD values was observed in the lumbar spine. The adaptational pattern in volumetric BMD (vBMD) and volumetric bone mineral content (vBMC) of the tibiae were more complex, but attained pre-immobilization values for most variables also after six weeks of rehabilitation. All other variables attained pre-immobilization values no later than nine months after the surgical intervention.ConclusionsThe athlete showed a high plasticity of bone and lean tissue with an optimal short- and midterm outcome. Following a two months immobilization period after a hip arthroscopy, aBMD, vBMD and vBMC achieved pre-surgical levels after four months of rehabilitation in a female Ironman triathlete. A nine-month follow-up measurement confirmed the safety of the fast return to sport.