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Bone loss in the lower leg during 35 days of bed rest is predominantly from the cortical compartment
Joern Rittweger, Boštjan Šimunič, Giancarlo Bilancio, Natale Gaspare De Santo, Massimo Cirillo, Gianni Biolo, Rado Pišot, Ola Eiken, Igor B. Mekjavić, Marco Narici, 2009, izvirni znanstveni članek

Opis: Immobilization-induced bone loss is usually greater in the epiphyses than in the diaphyses. The larger fraction of trabecular bone in the epiphyses than in the diaphyses offers an intuitive explanation to account for this phenomenon. However, recent evidence contradicts this notion and suggests that immobilization-induced bone loss from the distal tibia epiphysis is mainly from the cortical compartment. The aim of this study was to establish whether this pattern of bone loss was a general rule during immobilization. Wemonitored various skeletal sites with different tissue composition during 5 weeks of immobilization. Ten healthy male volunteers with mean age of 24.3 years (SD 2.6 years) underwent strict horizontal bed rest. Bone scans were obtained during baseline data collection, at the end of bed rest and after 14 days of recovery by peripheral Quantitative Computed Tomography (pQCT). Sectional images were obtained from the distal tibia epiphysis (at 4% of the tibia's length), from the diaphysis (at 38%), from the proximal metaphysis (at 93%) and from the proximal epiphysis (at 98%), as well as from the distal femur epiphysis (at 4% of the femur's length) and from the patella. Relative bone losses were largest at the patella, where they amounted to - 3.2% (SD 1.8%, p < 0.001) of the baseline values, and smallest at the tibia diaphysis, where they amounted to - 0.7% (SD 1.0%, p = 0.019). The relative losses were generally larger from cortical than from trabecular compartments (p = 0.004), and whilst all skeletal sites depicted such cortical losses, substantial trabecular losses were found only from the proximal tibia epiphysis. Results confirm that the differential losses from the various skeletal sites cannot be explained on the basis of trabecular vs. cortical tissue composition differences, but that endocortical circumference can account for the different amounts of bone loss in the tibia. The present study therefore supports the suggestion of the subendocortical layer as a transitional zone, which can readily be transformed into trabecular bone in response to immobilization. The latter will lead to cortical thinning, a factor that has been associated with the risk of fracture and with osteoarthritis.
Najdeno v: osebi
Ključne besede: space flight, simulated microgravity, osteoporosis, exercise, pQCT
Objavljeno: 15.10.2013; Ogledov: 1692; Prenosov: 11
URL Polno besedilo (0,00 KB)

3.
Effects of inactivity on human muscle glutathione synthesis by a double-tracer and single-biopsy approach
Francesco Agostini, Luciano Dalla Libera, Joern Rittweger, Sara Mazzucco, Mihaela Jurdana, Igor B. Mekjavić, Rado Pišot, Luisa Gorza, Marco Narici, Gianni Biolo, 2010, izvirni znanstveni članek

Opis: Oxidative stress is often associated to inactivity-mediated skeletal muscle atrophy. Glutathione is one of the major antioxidant system stimulated, both at muscular and systemic level, by activation of oxidative processes. We measured changes in glutathione availability, oxidative stress induction and atrophy extent mediated by 35-days of experimental bed rest in vastus lateralis muscle of healthy human volunteers. To assess muscle glutathione synthesis, we applied a novel single-biopsy and double-tracer ([2H2]glycine and [15N]glycine) approach based on evaluation of steady-state precursor incorporation in product. The correlations between the traditional (multiple-samples, one-tracer) and new (one-sample, double-tracer infusion) methods were analyzed in erythrocytes by Passing & Bablok and Altman-Bland tests. Muscle glutathione absolute synthesis rate increased following bed rest from 5.5 1.1 to 11.0 1.5 mmol (kg wet tissue / day)-1 (n=9; p=0.02) while glutathione concentration failed to change significantly. Bed rest induced vastus lateralis muscle atrophy, as assessed by pennation angle changes measured by ultrasonography (from 18.6 1.0 to 15.3 0.9 degrees; p=0.01) and thickness changes (from 2.3 0.2 to 1.9 0.1 cm; p<0.001). Moreover, bed rest increased protein oxidative stress, as measured by muscle protein carbonylation changes (from 0.6 0.1 to 1.00 0.1 Oxy RP-1; p<0.04). In conclusion, we developed in erythrocytes a new minimally-invasive method to determine peptide synthesis rate in human tissues. Application of the new method to skeletal muscle suggests that disuse atrophy is associated to oxidative stress induction as well as to compensatory activation of the glutathione system
Najdeno v: osebi
Ključne besede: Antioxidant system, Muscle damage, Oxidative stress, bed rest, muscle glutathione, stable isotopes
Objavljeno: 15.10.2013; Ogledov: 1783; Prenosov: 18
URL Polno besedilo (0,00 KB)

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Kinesiology for the Future
2012, druge monografije in druga zaključena dela

Najdeno v: osebi
Ključne besede: kinesiology, bicycle safety, traffic safety, bicycle helmets, traffic accidents, injury prevention
Objavljeno: 15.10.2013; Ogledov: 2088; Prenosov: 17
URL Polno besedilo (0,00 KB)
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6.
Skeletal muscle oxidative function in vivo and ex vivo in athletes with marked hypertrophy from resistance training
Desy Salvadego, R. Domenis, Stefano Lazzer, Simone Porcelli, Joern Rittweger, Giovanna Rizzo, I. Mavelli, Boštjan Šimunič, Rado Pišot, Bruno Grassi, 2013, izvirni znanstveni članek

Opis: Oxidative function during exercise was evaluated in 11 young athletes with marked skeletal muscle hypertrophy induced by long-term resistance training (RTA, body mass 102.67.3 kg, meanSD) and 11 controls (CTRL, body mass 77.86.0). Pulmonary O2 uptake (V'O2) and vastus lateralis muscle fractional O2 extraction (by near-infrared spectroscopy) were determined during an incremental cycle ergometer (CE) and one-leg knee-extension (KE) exercise. Mitochondrial respiration was evaluated ex vivo by high-resolution respirometry in permeabilized vastus lateralis fibers obtained by biopsy. Quadriceps femoris muscle cross sectional area, volume (determined by magnetic resonance imaging) and strength were greater in RTA vs. CTRL (by ~40%, ~33% and ~20%, respectively). V'O2peak during CE was higher in RTA vs. CTRL (4.050.64 L min-1 vs. 3.560.30); no difference between groups was observed during KE. The O2 cost of CE exercise was not different between groups. When divided per muscle mass (for CE) or quadriceps muscle mass (for KE) V'O2peak was lower (by 15-20%) in RTA vs. CTRL. Vastus lateralis fractional O2 extraction was lower in RTA vs. CTRL at all work rates, both during CE and KE. RTA had higher ADP-stimulated mitochondrial respiration (56.723.7 pmolO2s-1mg-1 ww) vs. CTRL (35.710.2), and a tighter coupling of oxidative phosphorylation. In RTA the greater muscle mass and maximal force, and the enhanced mitochondrial respiration seem to compensate for the hypertrophy-induced impaired peripheral O2 diffusion. The net results are an enhanced whole body oxidative function at peak exercise, and unchanged efficiency and O2 cost at submaximal exercise, despite a much greater body mass
Najdeno v: osebi
Ključne besede: skeletal muscle, hypertrophy, mitochondrial respiration, oxidative metabolism, exercise
Objavljeno: 15.10.2013; Ogledov: 1727; Prenosov: 10
URL Polno besedilo (0,00 KB)

7.
Gibalna kompetenca
Rado Pišot, 2012, objavljeni povzetek znanstvenega prispevka na konferenci (vabljeno predavanje)

Najdeno v: osebi
Ključne besede: gibalna kompetenca, gibalni razvoj
Objavljeno: 15.10.2013; Ogledov: 2453; Prenosov: 85
URL Polno besedilo (0,00 KB)

8.
Whole muscle contractile parameters and thickness loss during 35-day bed rest
Rado Pišot, Marco Narici, Boštjan Šimunič, Maarten D. de Boer, Olivier Seynnes, Mihaela Jurdana, Gianni Biolo, Igor B. Mekjavić, 2008, izvirni znanstveni članek

Opis: Extended exposure to microgravity leads to significant musculoskeletal adaptations. Contractile parameters of four skeletal muscles (biceps brachii-BB, vastus medialis-VM, biceps femoris-BF and gastrocnemius medialis-GM) were measured in ten healthy males (aged 22.3 +/- 2.2 years) during 35 days of horizontal bed rest by a mechanomyography-based method termed 'tensiomyography' (TMG). Two contractile parameters: contraction time (Tc) and maximal displacement (Dm) were individually measured from electrically evoked maximal single twitch TMG response of all four muscles before and after bed rest. Significant changes in Tc were found after bed rest, as shown by an increase in GM muscle Tc by 18% (p < 0.01). Dm values significantly increased (p < 0.01) after bed rest, by 24, 26 and 30% in the VM, BF and GM muscles, respectively. In the GM, the change in Dm significantly correlated with the decrease in muscle thickness (r = -0.70, p < 0.01). In conclusion, bed rest induced changes in both Dm and Tc of the TMG signal; changes in Dm being inversely related to those of muscle thickness. Amongst the investigated muscles, most affected, in terms of atrophy and mechanical alterations, were those of the lower limbs. The observed increase in Dm may be attributed to a decrease in muscle, as well as tendon stiffness, causing larger muscle fibre and non-contractile tissue oscillations following contraction.
Najdeno v: osebi
Ključne besede: Bed rest, skeletal muscle, muscle contraction, muscle thickness, mechanomyography, tensiomiography, ultrasound
Objavljeno: 15.10.2013; Ogledov: 1841; Prenosov: 9
URL Polno besedilo (0,00 KB)
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9.
Vpliv šole smučanja na nadaljnje ukvarjanje s tem športom
Ana Mašera, 2013, diplomsko delo

Najdeno v: osebi
Ključne besede: alpsko smučanje, šola smučanja, učitelji smučanja, metode učenja, igra
Objavljeno: 15.10.2013; Ogledov: 2102; Prenosov: 35
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10.
Effect of 5 weeks horizontal bed rest on human muscle thickness and architecture of weight bearing and non-weight bearing muscles
Maarten D. de Boer, Olivier Seynnes, Pietro di Prampero, Rado Pišot, Igor B. Mekjavić, Gianni Biolo, Marco Narici, 2008, izvirni znanstveni članek

Opis: The aim of the present study was to investigate the changes in thickness, fascicle length (L f) and pennation angle of the antigravity gastrocnemiusmedialis (GM) and vastus lateralis (VL) muscles, and the non-antigravity tibialis anterior (TA) and biceps brachii (BB) muscles measured by ultrasonography in ten healthy males (aged 22.3 +/- 2.2 years) in response to 5 weeks of horizontal bed rest (BR). After BR, muscle thickness decreased by 12.2 +/- 8.8% (P < 0.05) and 8.0 +/- 9.1% (P < 0.005) in the GM and VL, respectively. No changes were observed in the TA and BB muscles. L f and pennation angle decreased by 4.8 +/- 5.0% (P < 0.05) and 14.3 +/- 6.8% (P < 0.005) in the GM and by 5.9 +/- 5.3% (P < 0.05) and 13.5 +/- 16.2% (P < 0.005) in the VL, again without any changes in the TA and BB muscles. The finding that amongst the antigravity muscles of the lower limbs, the GM deteriorated to a greater extent than the VL is possibly related to the differences in relative load that this muscle normally experiences during daily loading. The dissimilar response in antigravity and non-antigravity muscles to unloading likely reflects differences in loading under normal conditions. The significant structural alterations of the GM and VL muscles highlight the rapid remodelling of muscle architecture occurring with disuse.
Najdeno v: osebi
Ključne besede: muscle, disuse, microgravity, atrophy
Objavljeno: 15.10.2013; Ogledov: 1811; Prenosov: 9
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