A stretching program increases the dynamic passive length and passive resistive properties of the calf muscle-tendon unit of unconditioned younger women.
ABSTRACT This study examined the effects of a 6-week stretching program on the dynamic passive elastic properties of the calf muscle-tendon unit (MTU) of unconditioned younger women. After random assignment of 12 women (age 18-31 years) to a stretching group (SG) or to a control group (CG), six subjects in the SG and four subjects in the CG completed the study. For the initial tests, a Kin-Com dynamometer moved the ankle from plantarflexion to maximal dorsiflexion (DF) with negligible surface EMG activity in the soleus, gastrocnemius and tibialis anterior muscles. Angular displacement, passive resistive torque, area under the curve (passive elastic energy) and stiffness variables were reduced from the passive DF torque curves. The SG then completed ten static wall stretches held 15 s each, five times a week for 6 weeks, the CG did not. The tests were repeated and the changes between the tests and retests were examined for group differences (Mann-Whitney U). The SG had significant increases in the maximal passive DF angle (7 degrees +/- 4 degrees ), maximal passive DF torque (11.2 +/- 8.3 N m), full stretch range of motion (23 degrees +/- 24 degrees ), full stretch mean torque (3.4 +/- 2.1 N m), and area under the full stretch curve (22.7 +/- 23.5 degrees N m) compared to the CG (P < or = 0.019). The passive stiffness did not change significantly. The results showed that a stretching program for unconditioned calf MTUs increased the maximal DF angle and length extensibility, as well as the passive resistive properties throughout the full stretch range of motion. The adaptations within the calf MTU provide evidence that stretching enhances the dynamic passive length and passive resistive properties in unconditioned younger women.
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ABSTRACT: The present study determined human skeletal muscle oxygenation dynamics during and after a single bout of self-administered stretching (SAS) of the plantar flexors. Nine healthy recreationally fit men (n = 7; age = 25.7 yrs) and women (n = 2; age = 23.5 yrs) performed two protocols: 1) one bout of SAS for 4 min, and 2) one bout of moderate intensity cycling for 4 min. We used near infrared spectroscopy to measure changes in muscle deoxygenated hemoglobin-myoglobin ([HHb]) and blood volume ([Hbtot]) of gastrocnemius medialis muscle before, during and after stretching. The SAS caused an increase (P < 0.05) in [HHb] during stretching between 60 and 240 s relative to baseline, but not at 30 s. No significant difference was found for [Hbtot] at any time interval during SAS. Furthermore, the increase in local blood flow (suggested by [Hbtot] changes) was found to be significantly increased relative to baseline at 1, 5 and 10 min after SAS, thus providing novel evidence for a post-stretch hyperemia. No significant interaction for [HHb] was found between stretching and cycling conditions, suggesting that the metabolic disturbance during stretching closely resembles moderate intensity exercise. These findings suggest that a single self-administered stretch for 60 s can produce a substantial microcirculatory event and that blood flow may be enhanced for up to 10 min after stretching.Clinical Physiology and Functional Imaging 09/2014; DOI:10.1111/cpf.12205 · 1.33 Impact Factor
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ABSTRACT: Skeletal muscle undergoes continuous turnover to adapt to changes in its mechanical environment. Overload increases muscle mass, whereas underload decreases muscle mass. These changes are correlated with, and enabled by, structural alterations across the molecular, subcellular, cellular, tissue, and organ scales. Despite extensive research on muscle adaptation at the individual scales, the interaction of the underlying mechanisms across the scales remains poorly understood. Here, we present a thorough review and a broad classification of multiscale muscle adaptation in response to a variety of mechanical stimuli. From this classification, we suggest that a mathematical model for skeletal muscle adaptation should include the four major stimuli, overstretch, understretch, overload, and underload, and the five key players in skeletal muscle adaptation, myosin heavy chain isoform, serial sarcomere number, parallel sarcomere number, pennation angle, and extracellular matrix composition. Including this information in multiscale computational models of muscle will shape our understanding of the interacting mechanisms of skeletal muscle adaptation across the scales. Ultimately, this will allow us to rationalize the design of exercise and rehabilitation programs, and improve the long-term success of interventional treatment in musculoskeletal disease.Biomechanics and Modeling in Mechanobiology 09/2014; 14(2). DOI:10.1007/s10237-014-0607-3 · 3.25 Impact Factor
01/2013; 2013:1-8. DOI:10.1155/2013/171809