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Maximal Strength (maximal + strength)
Selected AbstractsChanges in Muscle Mass, Muscle Strength, and Power but Not Physical Function Are Related to Testosterone Dose in Healthy Older MenJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 11 2008Thomas W. Storer PhD OBJECTIVES: To examine the effect of graded doses of testosterone on physical function and muscle performance in healthy, older men. DESIGN: Randomized, double-blind, placebo-controlled clinical trial. SETTING: General clinical research center. PARTICIPANTS: Community-dwelling healthy men aged 60 to 75 (N=44). INTERVENTION: Monthly treatment with a gonadotropin-releasing hormone agonist plus 25, 50, 125, or 300 mg/wk of intramuscular injections of testosterone enanthate for 20 weeks. MEASUREMENTS: Skeletal muscle mass (SMM) was estimated using dual-energy X-ray absorptiometry. Leg press strength was measured by one repetition maximum, leg power by Nottingham Leg Rig, and muscle fatigability by repetitions to failure in the leg press exercise. Stair climbing, 6-meter and 400-meter walking speed, and a timed-up-and-go (TUG) test were used to assess physical function. RESULTS: Significant testosterone dose- and concentration-dependent increases were observed in SMM (P<.001) and maximal strength (P=.001) but not muscle fatigability. Leg power also increased dose-dependently (P=.048). In contrast, changes in self-selected normal and fast walking speed over 6 or 400 meters, stair climbing power, and time for the TUG were not significantly related to testosterone dose, testosterone concentrations, or changes in muscle strength or power, or SMM. CONCLUSION: Testosterone administration was associated with dose-dependent increases in SMM, leg strength, and power but did not improve muscle fatigability or physical function. The observation that physical function scores did not improve linearly with strength suggests that these high-functioning older men were already in the asymptotic region of the curve describing the relationship between physical function and strength. [source] If bone is the answer, then what is the question?JOURNAL OF ANATOMY, Issue 2 2000R. HUISKES In the 19th century, several scientists attempted to relate bone trabecular morphology to its mechanical, load-bearing function. It was suggested that bone architecture was an answer to requirements of optimal stress transfer, pairing maximal strength to minimal weight, according to particular mathematical design rules. Using contemporary methods of analysis, stress transfer in bones was studied and compared with anatomical specimens, from which it was hypothesised that trabecular architecture is associated with stress trajectories. Others focused on the biological processes by which trabecular architectures are formed and on the question of how bone could maintain the relationship between external load and architecture in a variable functional environment. Wilhelm Roux introduced the principle of functional adaptation as a self-organising process based in the tissues. Julius Wolff, anatomist and orthopaedic surgeon, entwined these 3 issues in his book The Law of Bone Remodeling (translation), which set the stage for biomechanical research goals in our day. ,Wolff's Law' is a question rather than a law, asking for the requirements of structural optimisation. In this article, based on finite element analysis (FEA) results of stress transfer in bones, it is argued that it was the wrong question, putting us on the wrong foot. The maximal strength/minimal weight principle does not provide a rationale for architectural formation or adaptation; the similarity between trabecular orientation and stress trajectories is circumstantial, not causal. Based on computer simulations of bone remodelling as a regulatory process, governed by mechanical usage and orchestrated by osteocyte mechanosensitivity, it is shown that Roux's paradigm, conversely, is a realistic proposition. Put in a quantitative regulatory context, it can predict both trabecular formation and adaptation. Hence, trabecular architecture is not an answer to Wolff's question, in the sense of this article's title. There are no mathematical optimisation rules for bone architecture; there is just a biological regulatory process, producing a structure adapted to mechanical demands by the nature of its characteristics, adequate for evolutionary endurance. It is predicted that computer simulation of this process can help us to unravel its secrets. [source] Exercise Training Improves Aerobic Capacity and Skeletal Muscle Function in Heart Transplant RecipientsAMERICAN JOURNAL OF TRANSPLANTATION, Issue 4 2009M. Haykowsky The aim of this study was to examine the effects of 12 weeks of supervised aerobic and strength training (SET) versus no-training (NT) on peak aerobic power (VO2peak), submaximal exercise left ventricular (LV) systolic function, peripheral vascular function, lean tissue mass and maximal strength in clinically stable heart transplant recipients (HTR). Forty-three HTR were randomly assigned to 12 weeks of SET (n = 22; age: 57 ± 10 years; time posttransplant: 5.4 ± 4.9 years) or NT (n = 21; age: 59 ± 11 years; time posttransplant: 4.4 ± 3.3 years). The change in VO2peak (3.11 mL/kg/min, 95% CI: 1.2,5.0 mL/kg/min), leg and total lean tissue mass (0.78 kg, 95% CI: 0.31,1.3 kg and 1.34 kg, 95% CI: 0.34,2.3 kg, respectively), chest-press (10.4 kg, 95% CI: 5.2,15.5 kg) and leg-press strength (34.7 kg, 95% CI: 3.7,65.6 kg) were significantly higher after SET versus NT. No significant change was found for submaximal exercise LV systolic function or brachial artery endothelial-dependent or -independent vasodilation. Supervised exercise training is an effective intervention to improve VO2peak, lean tissue mass and muscle strength in HTR. This training regimen did not improve exercise LV systolic function or brachial artery endothelial function. [source] Randomized double-blind placebo-controlled crossover study of caffeine in patients with intermittent claudication,BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 10 2010A. H. Momsen Background: Intermittent claudication is a disabling symptom of peripheral arterial disease for which few medical treatments are available. This study investigated the effect of caffeine on physical capacity in patients with intermittent claudication. Methods: This randomized double-blind placebo-controlled crossover study included 88 patients recruited by surgeons from outpatient clinics. The participants abstained from caffeine for 48 h before each test and then received either a placebo or oral caffeine (6 mg/kg). After 75 min, pain-free and maximal walking distance on a treadmill, perceived pain, reaction times, postural stability, maximal isometric knee extension strength, submaximal knee extension endurance and cognitive function were measured. The analysis was by intention to treat. Results: Caffeine increased the pain-free walking distance by 20·0 (95 per cent confidence interval 3·7 to 38·8) per cent (P = 0·014), maximal walking distance by 26·6 (12·1 to 43·0) per cent (P < 0·001), muscle strength by 9·8 (3·0 to 17·0) per cent (P = 0·005) and endurance by 21·4 (1·2 to 45·7) per cent (P = 0·004). However, postural stability was reduced significantly, by 22·1 (11·7 to 33·4) per cent with eyes open (P < 0·001) and by 21·8 (7·6 to 37·8) per cent with eyes closed (P = 0·002). Neither reaction time nor cognition was affected. Conclusion: In patients with moderate intermittent claudication, caffeine increased walking distance, maximal strength and endurance, but affected balance adversely. Registration number: NCT00388128 (http://www.clinicaltrials.gov). Copyright © 2010 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd. [source] Neuromuscular function and balance of prepubertal and pubertal blind and sighted boysACTA PAEDIATRICA, Issue 10 2006Arja Häkkinen Abstract Aim: To compare the neuromuscular function and balance of blind prepuberty- and puberty-aged boys to those with normal sight. Methods: Thirty-three prepubertal (aged 9,13 y) and pubertal (aged 15,18 y) blind and sighted boys were tested for muscle mass thickness, electromyography and maximal isometric strength, dynamic explosive actions, and balance. Results: There was no difference in the muscle mass thickness, maximal strength or vertical jump between the blind and sighted boys. However, fitness-ball throwing and five-jump distances were significantly shorter in both blind groups compared to the sighted groups. One-leg stance of the prepuberty-aged sighted boys was 109 (67) s and in blind boys 32 (12) s, and in the puberty-aged boys 120 (57) s and 31 (8) s, respectively. When vision was blocked in the sighted boys, differences between the blind and sighted boys disappeared. Conclusion: The results showed comparable performance between prepubertal and pubertal blind and sighted boys in the static physical fitness tests. However, balance and performance in dynamic multi-joint tests did not improve similarly in the blind groups compared to sighted groups, indicating that maturation, learning and experience by themselves cannot compensate for the loss of sight. [source] Reliability of knee extension and flexion measurements using the Con-Trex isokinetic dynamometerCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 6 2007Nicola A. Maffiuletti Summary The aim of this study was to evaluate the reliability of isokinetic and isometric assessments of the knee extensor and the flexor muscle function using the Con-Trex isokinetic dynamometer. Thirty healthy subjects (15 males, 15 females) were tested and retested 7 days later for maximal strength (isokinetic peak torque, work, power and angle of peak torque as well as isometric maximal voluntary contraction torque and rate of torque development) and fatigue (per cent loss and linear slope of torque and work across a series of 20 contractions). For both the knee extensor and the flexor muscle groups, all strength data , except angle of peak torque , demonstrated moderate-to-high reliability, with intraclass correlation coefficients (ICC) higher than 0·86. The highest reliability was observed for concentric peak torque of the knee extensor muscles (ICC = 0·99). Test,retest reliability of fatigue variables was moderate for the knee extensor (ICC range 0·84,0·89) and insufficient-to-moderate for the knee flexor muscles (ICC range 0·78,0·81). The more reliable index of muscle fatigue was the linear slope of the decline in work output. These findings establish the reliability of isokinetic and isometric measurements using the Con-Trex machine. [source] | ||||||||||