Effect of 5 weeks horizontal bed rest on human muscle thickness and architecture of weight bearing and non-weight bearing muscles

Abstract

The aim of the present study was to investigate the changes in thickness, fascicle length (L (f)) and pennation angle (theta) of the antigravity gastrocnemius medialis (GM) and vastus lateralis (VL) muscles, and the non-antigravity tibialis anterior (TA) and biceps brachii (BB) muscles measured by ultrasonography in ten healthy males (aged 22.3 +/- 2.2 years) in response to 5 weeks of horizontal bed rest (BR). After BR, muscle thickness decreased by 12.2 +/- 8.8% (P < 0.05) and 8.0 +/- 9.1% (P < 0.005) in the GM and VL, respectively. No changes were observed in the TA and BB muscles. L (f) and theta decreased by 4.8 +/- 5.0% (P < 0.05) and 14.3 +/- 6.8% (P < 0.005) in the GM and by 5.9 +/- 5.3% (P < 0.05) and 13.5 +/- 16.2% (P < 0.005) in the VL, again without any changes in the TA and BB muscles. The finding that amongst the antigravity muscles of the lower limbs, the GM deteriorated to a greater extent than the VL is possibly related to the differences in relative load that this muscle normally experiences during daily loading. The dissimilar response in antigravity and non-antigravity muscles to unloading likely reflects differences in loading under normal conditions. The significant structural alterations of the GM and VL muscles highlight the rapid remodelling of muscle architecture occurring with disuse.

Skeletal muscle adaptations to physical inactivity and subsequent retraining in young men

“…A decrease in pennation angle (θ), due to muscle atrophy, is commonly interpreted as a decrease in the number of fascicles in parallel (Kawakami et al, 1993). Reductions in θ seen after only short durations of ULLS or bed rest (~8-13% in the vastus lateralis muscle after 23 to 35 days, (de Boer et al 2007(de Boer et al & 2008 indicate that substantial muscle remodelling occurs with few days of muscle unloading.…”

“…A decrease in pennation angle (θ), due to muscle atrophy, is commonly interpreted as a decrease in the number of fascicles in parallel (Kawakami et al, 1993). Reductions in θ seen after only short durations of ULLS or bed rest (~8-13% in the vastus lateralis muscle after 23 to 35 days, (de Boer et al 2007(de Boer et al & 2008 indicate that substantial muscle remodelling occurs with few days of muscle unloading.In line with the decrease in pennation angle, a reduction in muscle fascicle length of ~8% was also found after 23 days ULLS (de Boer et al, 2007). Such a decrease implies a loss of sarcomeres in series and a consequential increase in sarcomere excursion during shortening of the whole muscle, shifting the operating muscle length towards a less favourable portion of its length-tension curve.…”

High sodium chloride intake exacerbates immobilization-induced bone resorption and protein losses

“…travelers as well as in immobilized subjects, are associated with alterations in protein turnover (1,2,11,15,41,44,66). Specific disuse-induced changes include a negative nitrogen balance, a decrease in whole body protein synthesis, and an increase in lower-limb proteolysis leading to decreased amounts of contractile protein in skeletal muscle (11,20,44,57,67).…”

Confiabilidade das medidas de arquitetura do músculo Vasto Lateral pela ultrassonografia

“…O VL é um músculo penado, superficial e de arquitetura pouco complexa (BLAZEVICH 2007a). Dessa forma, é frequentemente analisado em estudos com US (KAWAKAMI et al, 2001;KUBO et al, 2003;REEVES et al, 2004;KAWAKAMI, et al, 2006;MAGANARIS et al, 2006; BLAZEVICH et al, 2007a;BLAZEVICH et al, 2007b; BRANCACCIO et al, 2008;DE BOER et al, 2008;REEVES et al, 2009; BLAZEVICH et al, 2009).…”

“…O arranjo estrutural das fibras musculares é um importante parâmetro funcional para a análise da mecânica da unidade músculo-tendínea (DE BOER et al, 2008, LIEBER, 2010. A organização dessas fibras é denominada arquitetura muscular e ocorre a nível macroscópico, influenciando a capacidade de geração de força do músculo.…”