Paolo Cerretelli

Changes in force, cross-sectional area and neural activation during strength training and detraining of the human quadriceps

SummaryFour male subjects aged 23–34 years were studied during 60 days of unilateral strength training and 40 days of detraining. Training was carried out four times a week and consisted of six series of ten maximal isokinetic knee extensions at an angular velocity of 2.09 rad·s−1. At the start and at every 20th day of training and detraining, isometric maximal voluntary contraction (MVC), integrated electromyographic activity (iEMG) and quadriceps muscle cross-sectional area (CSA) assessed at seven fractions of femur length (Lf), by nuclear magnetic resonance imaging, were measured on both trained (T) and untrained (UT) legs. Isokinetic torques at 30° before full knee extension were measured before and at the end of training at: 0, 1.05, 2.09, 3.14, 4.19, 5.24 rad·s−1. After 60 days T leg CSA had increased by 8.5%±1.4% (mean±SEM,n=4,p<0.001), iEMG by 42.4%±16.5% (p<0.01) and MVC by 20.8%±5.4% (p<0.01). Changes during detraining had a similar time course to those of training. No changes in UT leg CSA were observed while iEMG and MVC increased by 24.8%±10% (N.S.) and 8.7%±4.3% (N.S.), respectively. The increase in quadriceps muscle CSA was maximal at 2/10 Lf (12.0%±1.5%,p<0.01) and minimal, proximally to the knee, at 8/10 Lf (3.5%±1.2%, N.S.). Preferential hypertrophy of the vastus medialis and intermedius muscles compared to those of the rectus femoris and lateralis muscles was observed. Isoangular torque of T leg increased by 20.9%±5.4% (p<0.05), 23.8%±7.8% (p<0.05) and 22.5%±6.7% (p<0.05) at 0, 1.05 and 2.09 rad·s−1 respectively; no significant change was observed at higher velocities and in the UT leg. Hypertrophy produced by strength training accounts for 40% of the increase in force while the remaining 60% seems to be attributable to an increased neural drive and possibly to changes in muscle architecture.

In vivo human gastrocnemius architecture with changing joint angle at rest and during graded isometric contraction

1. Human gastrocnemius medialis architecture was analysed in vivo, by ultrasonography, as a function of joint angle at rest and during voluntary isometric contractions up to the maximum force (MCV). maximum force (MVC). 2. At rest, as ankle joint angle increased from 90 to 150 deg, pennation increased from 15.8 to 27.7 deg, fibre length decreased from 57.0 to 34.0 mm and the physiological cross‐sectional area (PCSA) increased from 42.1 to 63.5 cm2. 3. From rest to MVC, at a fixed ankle joint angle of 110 deg, pennation angle increased from 15.5 to 33.6 deg and fibre length decreased from 50.8 to 32.9 mm, with no significant change in the distance between the aponeuroses. As a result of these changes the PCSA increased by 34.8%. 4. Measurements of pennation angle, fibre length and distance between the aponeuroses of the gastrocnemius medialis were also performed by ultrasound on a cadaver leg and found to be in good agreement with direct anatomical measurements. 5. It is concluded that human gastrocnemius medialis architecture is significantly affected both by changes of joint angle at rest and by isometric contraction intensity. The remarkable shortening observed during isometric contraction suggests that, at rest, the gastrocnemius muscle and tendon are considerably slack. The extrapolation of muscle architectural data obtained from cadavers to in vivo conditions should be made only for matching muscle lengths.

New aspects of altitude adaptation in Tibetans: a proteomic approach

A prolonged sojourn above 5500 m induces muscle deterioration and accumulation of lipofuscin in Caucasians, probably because of overproduction of reactive oxygen species (ROS). Because Sherpas, who live at high altitude, have very limited muscle damage, it was hypothesized that Himalayan natives possess intrinsic mechanisms protecting them from oxidative damage. This possibility was investigated by comparing the muscle proteomes of native Tibetans permanently residing at high altitude, second‐generation Tibetans born and living at low altitude, and Nepali control subjects permanently residing at low altitude, using 2D gel electrophoresis and mass spectrometry. Seven differentially regulated proteins were identified: glutathione‐S‐transferase P1‐1, which was 380% and 50% overexpressed in Tibetans born and living at high and low altitude, respectively; Δ2‐enoyl‐CoA‐hydratase, which was up‐regulated in both Tibetan groups; glyceraldehyde‐3‐phosphate dehydrogenase and lactate dehydrogenase, which were both slightly down‐regulated in Tibetans born and living at high altitude; phosphoglycerate mutase, which was 50% up‐regulated in the native Tibetans; NADH‐ubiquinone oxidoreductase, slightly overexpressed in Tibetans born and living at high altitude; and myoglobin, which was overexpressed in both Tibetan groups. We concluded that Tibetans at high altitude, and to some extent, those born and living at low altitude, are protected from ROS‐induced tissue damage and possess specific metabolic adaptations.

Proteins modulation in human skeletal muscle in the early phase of adaptation to hypobaric hypoxia.

High altitude hypoxia is a paraphysiological condition triggering redox status disturbances of cell organization leading, via oxidative stress, to proteins, lipids, and DNA damage. In man, skeletal muscle, after prolonged exposure to hypoxia, undergoes mass reduction and alterations at the cellular level featuring a reduction of mitochondrial volume density, accumulation of lipofuscin, a product of lipid peroxidation, and dysregulation of enzymes whose time course is unknown. The effects of 7–9 days exposure to 4559 m (Margherita Hut, Monte Rosa, Italy) on the muscle proteins pattern were investigated, pre‐ and post‐exposure, in ten young subjects, by 2‐D DIGE and MS. Ten milligram biopsies were obtained from the mid part of the vastus lateralis muscle at sea level (control) and at altitude, after 7–9 days hypoxia. Differential analysis indicates that proteins involved in iron transport, tricarboxylic acid (TCA) cycle, oxidative phosphorylation, and oxidative stress responses were significantly (p<0.05) decreased in hypoxia. Parenthetically, hypoxia markers such as hypoxia inducible factor 1 α (HIF‐1α) and pyruvate dehydrogenase kinase 1 (PDK1) were still at the pre‐hypoxia levels, whereas the mammalian target of rapamycin (mTOR), a marker of protein synthesis, was reduced.

Effects ofl-carnitine loading on the aerobic and anaerobic performance of endurance athletes

Summaryl-Carnitine (l-c), a well known physiological carrier across the inner mitochondrial membrane of activated long chain fatty acids and acceptor of acyl groups from acyl-CoA, has been recently synthesised industrially. This has made it possible to study the effects ofl-c loading (4 g·d−1 by mouth over a period of 2 weeks) on the aerobic and anaerobic performance of 6 long distance competitive walkers. As a result of the treatment: 1) mean total, free and esterified seruml-c both at rest and shortly after completing a 120 min walk at about 65% of the individual maximal aerobic power % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqFj0xd9q8as0-LqLs-Jirpepeea0-as0Fb9pgea0db9fr-xfr-x% frpeWZqaaeaabiGaciaacaqabeaadaqaaqaaaOqaaiaacIcaceWGwb% GbaiaadaWgaaWcbaGaam4tamaaBaaameaacaaIYaGaciyBaiaacgga% caGG4baabeaaaSqabaGccaGGPaaaaa!4048!

Muscle lipofuscin content and satellite cell volume is increased after high altitude exposure in humans.

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Long term bed rest with and without vibration exercise countermeasures: Effects on human muscle protein dysregulation

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