Changes in Electrically Evoked Skeletal Muscle Contractions during 17-day Spaceflight and Bed Rest

Narici, Maco V.; Kayer, B.; Barattini, Paolo; Cerretelli, P.

doi:10.1055/s-2007-972729

Cited by 32 publications

(23 citation statements)

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“…These results from animal models may be analogous to the electrically stimulated plantar flexor torque deficits reported in humans recovering from spaceflight and bed rest (25,26). A previous study reported substantial recovery of rat soleus isometric force, on a per wet mass basis, after 1 wk of standing recovery following 14 days of HU (1).…”

Section: Discussionsupporting

confidence: 70%

“…Because lengthening contractions are a component of normal ambulatory activity, rodents subjected to the hindlimb unloading (HU) model of disuse, and then allowed several days of ambulatory recovery, show signs of contraction-induced muscle damage, including sarcolemma disruption, ultrastructural disorganization, and reductions in force (13,16,19,21,27,41). Likewise, in humans, plantar flexor torque decreases during ambulatory recovery following bed rest and spaceflight (25,26), presumably because of damage to the atrophied antigravity muscles.…”

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confidence: 99%

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Detrimental effects of reloading recovery on force, shortening velocity, and power of soleus muscles from hindlimb-unloaded rats

Widrick

Maddalozzo²,

Hu³

et al. 2008

American Journal of Physiology-Regulatory, Integrative and Comp

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To better understand how atrophied muscles recover from prolonged nonweight-bearing, we studied soleus muscles (in vitro at optimal length) from female rats subjected to normal weight bearing (WB), 15 days of hindlimb unloading (HU), or 15 days HU followed by 9 days of weight bearing reloading (HU-R). HU reduced peak tetanic force (P(o)), increased maximal shortening velocity (V(max)), and lowered peak power/muscle volume. Nine days of reloading failed to improve P(o), while depressing V(max) and intrinsic power below WB levels. These functional changes appeared intracellular in origin as HU-induced reductions in soleus mass, fiber cross-sectional area, and physiological cross-sectional area were partially or completely restored by reloading. We calculated that HU-induced reductions in soleus fiber length were of sufficient magnitude to overextend sarcomeres onto the descending limb of their length-tension relationship upon the resumption of WB activity. In conclusion, the force, shortening velocity, and power deficits observed after 9 days of reloading are consistent with contraction-induced damage to the soleus. HU-induced reductions in fiber length indicate that sarcomere hyperextension upon the resumption of weight-bearing activity may be an important mechanism underlying this response.

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Section: Discussionsupporting

confidence: 70%

mentioning

confidence: 99%

Detrimental effects of reloading recovery on force, shortening velocity, and power of soleus muscles from hindlimb-unloaded rats

Widrick

Maddalozzo²,

Hu³

et al. 2008

American Journal of Physiology-Regulatory, Integrative and Comp

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“…Human subjects show reductions in ankle extensor torque as they resume normal weight-bearing activity after bed rest or spaceflight, presumably as a result of activity-induced muscle damage (16). The high breakage rate of the post-6 h fibers is evidence that muscles are more susceptible to activity-induced damage after ULLS.…”

Section: Discussionmentioning

confidence: 99%

Unilateral lower limb suspension does not mimic bed rest or spaceflight effects on human muscle fiber function

Widrick

Trappe

Romatowski

et al. 2002

Journal of Applied Physiology

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. Unilateral lower limb suspension does not mimic bed rest or spaceflight effects on human muscle fiber function. J Appl Physiol 93: 354-360, 2002. First published April 5, 2002 10.1152/japplphysiol.01245. 2001.-We used Ca 2ϩ -activated skinned muscle fibers to test the hypothesis that unilateral lower leg suspension (ULLS) alters cross-bridge mechanisms of muscle contraction. Soleus and gastrocnemius biopsies were obtained from eight subjects before ULLS, immediately after 12 days of ULLS (post-0 h), and after 6 h of reambulation (post-6 h). Post-0 h soleus fibers expressing type I myosin heavy chain (MHC) showed significant reductions in diameter, absolute and specific peak Ca 2ϩ -activated force, unloaded shortening velocity, and absolute and normalized peak power. Fibers obtained from the gastrocnemius were less affected by ULLS, particularly fibers expressing fast MHC isoforms. Post-6 h soleus fibers produced less absolute and specific peak force than did post-0 h fibers, suggesting that reambulation after ULLS induced cell damage. Like bed rest and spaceflight, ULLS primarily affects soleus over gastrocnemius fibers. However, in contrast to these other models, slow soleus fibers obtained after ULLS showed a decrease in unloaded shortening velocity and a greater reduction in specific force. muscle atrophy; muscle disuse; muscle damage; weightlessness HUMANS EXPOSED TO SPACEFLIGHT experience skeletal muscle atrophy, particularly of the antigravity, postural muscles of the lower limbs and back (8). Efforts to understand the mechanisms underlying the adaptations of skeletal muscle to microgravity have been hindered by the limited number of human spaceflights and by the expense and logistical problems associated with studying humans in space. An alternative approach has been to use ground-based models of nonweight bearing that mimic the effects of spaceflight. The most commonly used ground-based model of spaceflight has been bed rest. This model appears to induce adaptations in muscle cells that are similar to those experienced during spaceflight (25-27). However, although ground-based bed rest eliminates or reduces many of the problems associated with human spaceflight, the procedure is still relatively expensive and logistically complex.An alternative ground-based model of non-weight bearing is unilateral lower limb suspension (ULLS). In this model, as originally described by Berg et al. (2), the treatment limb is flexed and suspended above the ground by the use of a shoulder harness. Subjects ambulate using crutches and are thus able to participate in most of their routine daily activities. The procedure reduces many of the expenses and logistical issues associated with bed rest studies, induces atrophy of the extensor muscles that comprise the treatment limb, and results in a decline in the voluntary neuromuscular strength of these muscle groups (1-3, 5, 11). Consequently, the procedure has been proposed as an alternative ground-based model of spaceflight (2, 5).In previous work, our laboratory reported t...

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“…There is evidence that the peak force of limb skeletal muscles is significantly reduced with periods of inactivity and the extent of decline is muscle specific. 14,20,33,61 For example, Skylab 2, a 28-day mission, showed a greater decline in thigh versus arm and extensor versus flexor torque. The peak extensor torque of the thigh muscles declined by 20% compared with a 10% loss in thigh flexor and arm extensor muscle groups.…”

Section: Muscle Forcementioning

confidence: 99%

Skeletal Muscle Adaptations with Age, Inactivity, and Therapeutic Exercise

Thompson¹

2002

J Orthop Sports Phys Ther

104

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One of the remarkable features of skeletal muscle is its adaptability. Skeletal muscle adaptations are characterized by modifications of morphological, biochemical, and molecular variables that alter the functional attributes of specific skeletal muscle fiber types. Skeletal muscle adaptation is diverse and the magnitude of change is dependent on many factors, such as activity pattern, age, and muscle fiber type composition. The adaptation of skeletal muscle in the adult population is well described. In contrast, the adaptation of skeletal muscle in the older population is less documented, especially in the area of inactivity-induced alterations. Age-related changes in skeletal muscle may play a significant role in the magnitude of change with inactivity and influence the rehabilitation process for the older adult.A consistent feature of age and inactivity is limb muscle atrophy and the loss of peak force and power. Differences exist in the rate and mechanisms of muscle wasting and in the susceptibility of a given fiber type to atrophy. Most likely, the rapid muscle wasting might be in part due to a decrease in protein synthesis coupled with an increased degradation. Besides the quantitative change in muscle mass, age and inactivity induce important qualitative changes in the structure of key skeletal muscle proteins that are manifested in alterations in contractile properties.Therefore, the purpose of this clinical commentary is to identify the major effects of age and inactivity on skeletal muscle structure and function, and discuss potential therapeutic interventions. Special emphasis will be placed on how alterations in muscle structure affect function and on the cellular and molecular mechanisms of the age-related and inactivity-induced muscle changes.

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Changes in Electrically Evoked Skeletal Muscle Contractions during 17-day Spaceflight and Bed Rest

Cited by 32 publications

References 0 publications

Detrimental effects of reloading recovery on force, shortening velocity, and power of soleus muscles from hindlimb-unloaded rats

Detrimental effects of reloading recovery on force, shortening velocity, and power of soleus muscles from hindlimb-unloaded rats

Unilateral lower limb suspension does not mimic bed rest or spaceflight effects on human muscle fiber function

Skeletal Muscle Adaptations with Age, Inactivity, and Therapeutic Exercise

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