Tensiomyography detects early hallmarks of bed-rest-induced atrophy before changes in muscle architecture.

In young and older people skeletal muscle mass is reduced after as little as seven days of disuse. The declines in muscle mass after such short periods are of high clinical relevance, particularly in older people who show higher atrophy rate, and a slower, or even a complete lack of muscle mass recovery after disuse. Ten men (24.3± 2.6 years) underwent 35 days of 6° head-down tilt bed rest followed by 30 days of recovery. During bed rest, a neutral energy balance was maintained, with three weekly passive physiotherapy sessions to minimise muscle soreness and joint stiffness. All measurements were performed in a hospital at days 1-10 (BR1-BR10), day 16 (BR16), 28 (BR28) and 35 (BR35) of bed rest, and day 1 (R+1), 3 (R+3) and 30 (R+30) after reambulation. Vastus medialis obliquus (VMO), vastus medialis longus (VML) and biceps femoris (BF) thickness (d) and pennation angle (Θ) were assessed by ultrasonography, while twitch muscle belly displacement (Dm) and contraction time (Tc) were assessed with tensiomyography. After bed rest, d and Θ decreased by 13-17% in all muscles (P<.001) and had recovered at R+30. Dm was increased by 42.3-84.4% (P<.001) at BR35 and preceded the decrease in d by 7, 5 and 3 days in VMO, VML and BF, respectively. Tc increased only in BF (32.1%; P<.001) and was not recovered at R+30. Tensiomyography can detect early bed-rest-induced changes in muscle with higher sensitivity before overt architectural changes and atrophy can be detected

Assessment of Skeletal Muscle Contractile Properties by Radial Displacement: The Case for Tensiomyography

Skeletal muscle operates as a near-constant volume system; as such muscle shortening during contraction is transversely linked to radial deformation. Therefore, to assess contractile properties of skeletal muscle, radial displacement can be evoked and measured. Mechanomyography measures muscle radial displacement and during the last 20 years, tensiomyography has become the most commonly used and widely reported technique among the various methodologies of mechanomyography. Tensiomyography has been demonstrated to reliably measure peak radial displacement during evoked muscle twitch, as well as muscle twitch speed. A number of parameters can be extracted from the tensiomyography displacement/time curve and the most commonly used and reliable appear to be peak radial displacement and contraction time. The latter has been described as a valid non-invasive means of characterising skeletal muscle, based on fibre-type composition. Over recent years, applications of tensiomyography measurement within sport and exercise have appeared, with applications relating to injury, recovery and performance. Within the present review, we evaluate the perceived strengths and weaknesses of tensiomyography with regard to its efficacy within applied sports medicine settings. We also highlight future tensiomyography areas that require further investigation. Therefore, the purpose of this review is to critically examine the existing evidence surrounding tensiomyography as a tool within the field of sports medicine

Odziv sestave telesa, mišične togosti in ravnotežja po 35-dnevni odsotnosti gibanja pri mladih in zdravih preiskovancih

Uvod: Problemi sedečega načina sodobnega življenja se kažejo v fizioloških odzivih, tako pri starejših kot tudi pri mlajših ljudeh. Cilj raziskave je bilugotoviti odziv morfoloških in skeletno-mišičnih značilnosti ter izgubo funkcionalnih sposobnosti ohranjanja ravnotežja po 35-dnevni popolni gibalni nedejavnosti in zagotovljeni uravnoteženi prehrani glede na njeno sestavo in preiskovančevo telesno težo. Metode: Deset moških preiskovancev (starih 24,32,6 let) je v bolnišničnem okolju preležalo 35 dni v vodoravnem položaju. Fiziološke odzive telesa smo vrednotili z merjenji telesne, maščobne in mišične mase, mineralne vsebnosti sprednje golenske kosti, togosti trebuha dveh funkcionalno različnih glav antigravitacijske mišice in sposobnost ohranjanja ravnotežja. Rezultati: Preiskovanci so v povprečju značilno izgubili 0,97 % (P=0,001) telesne teže, 4,1 % (P=0,009) mišične mase in 1,7 % (P=0,000) mineralne gostote tibialne kosti ter pridobili 1,4 % (P<0,000) maščobne mase. Mišična togost se je značilno zmanjšala od 8. dne ležanja (P=0,006) dalje pri distalni in že od 1. dneva (P=0,007) dalje pri proksimalniglavi notranje stegenske mišice ter se 14. dan po zaključku BR vrnila v izhodiščno stanje le pri distalni glavi. Po zaključku BR in dan kasneje smo ugotovili značilno izgubo ohranjanja ravnotežja za 9,5 % (P=0,006), in 17,4 % (P=0,000), medtem ko 14. dan po zaključku ležanja ni biloveč značilnih razlik. Zaključek: Povzamemo lahko, da z uravnoteženo prehrano lahko omejimo izgubo telesne teže in pridobivanje maščobne mase, vendar ne moremo zmanjšati izgube mišične mase ter mineralne vsebnosti tibialne kosti. Ugotovili smo, da se mišična togost zmanjšuje v dveh časovno zakasnjenih procesih. Sposobnost ohranjanja ravnotežja je zmanjšana v vsaj prvih 24 urah po zaključku ležanja.Introduction: Sedentary lifestyle causes morphological in physiological changes in both elderly and young people. Horizontal bed rest (BR) is one of the most widely used models for studying the effects of spaceflight, physical inactivity and sedentarism on human body. Our aim was to determine morphological and musculoskeletal changes, and changes in functional balance occurring as a result of total 35-day physical inactivity in persons eating nutritionally well balanced diet adjusted to individual body weight. Methods:Ten healthy young males (age 24.3 2.6 years) were submitted to a 35-day horizontal bed rest in strict hospital environment. Body mass, fat mass, muscle mass, tibial bone mineral content, muscle belly stiffness and postural stability were monitored prior to, during and after bed rest. Results: Body mass dropped by 1 % (P=0.001), muscle mass by 4.1 % (P=0.009) and tibial bone mineral content by 1.7 % (P=0.001), whereas fat mass increasedby 1.4 % (P=0.001). There was a significant decrease in belly muscle stiffness: in the distal head of the vastus medialis muscle it declined from the eighth day of bed rest (P=0.006), and in the proximal head from the very first day of inactivity (P=0.007). After the recovery phase, muscle stiffness returned to baseline levels in the distal head of the vastus medialis only. Postural stability deteriorated by 9.5 % (P=0.000) immediately after bed rest and by 17.4 % (P=0.000) at the first day of recovery. Fourteen days following the period of bed rest no significant postural stability loss was observed. Conclusions: Maintaining nearly neutral energy balance reduces body mass drop and fat mass gain, yet fails to preserve muscle mass or decrease tibial bone loss. The observed decrease in muscle belly stiffness varies among different muscles and occurs during two different phases of cessation and regaining of physical activity. Stance stability tests have proved an effective tool for evaluating postural stability in healthy young men submitted to bed rest

Single muscle fibre contractile properties differ between body-builders, power athletes and control subjects

What is the central question of this study? Do the contractile properties of single muscle fibres differ between body-builders, power athletes and control subjects? What is the main finding and its importance? Peak power normalized for muscle fibre volume in power athletes is higher than in control subjects. Compared with control subjects, maximal isometric tension (normalized for muscle fibre cross-sectional area) is lower in body-builders. Although this difference may be caused in part by an apparent negative effect of hypertrophy, these results indicate that the training history of power athletes may increase muscle fibre quality, whereas body-building may be detrimental. We compared muscle fibre contractile properties of biopsies taken from the vastus lateralis of 12 body-builders (BBs; low- to moderate-intensity high-volume resistance training), six power athletes (PAs; high-intensity, low-volume combined with aerobic training) and 14 control subjects (Cs). Maximal isotonic contractions were performed in single muscle fibres, typed with SDS-PAGE. Fibre cross-sectional area was 67 and 88% (P < 0.01) larger in BBs than in PAs and Cs, respectively, with no significant difference in fibre cross-sectional area between PAs and Cs. Fibres of BBs and PAs developed a higher maximal isometric tension (32 and 50%, respectively, P < 0.01) than those of Cs. The specific tension of BB fibres was 62 and 41% lower than that of PA and C fibres (P < 0.05), respectively. Irrespective of fibre type, the peak power (PP) of PA fibres was 58% higher than that of BB fibres (P < 0.05), whereas BB fibres, despite considerable hypertrophy, had similar PP to the C fibres. This work suggests that high-intensity, low-volume resistance training with aerobic exercise improves PP, while low- to moderate-intensity high-volume resistance training does not affect PP and results in a reduction in specific tension. We postulate that the decrease in specific tension is caused by differences in myofibrillar density and/or post-translational modifications of contractile proteins