Effect of 10‐day cast immobilization on sarcoplasmic reticulum calcium regulation in humans

Abstract

This study investigated the effects of 10-day lower limb cast immobilization on sarcoplasmic reticulum (SR) Ca2+ regulation. Muscle biopsies were analysed in eight healthy females for maximal rates of SR Ca2+ release, Ca2+ uptake and Ca2+ ATPase activity at control, during immobilization at day 3 (IM 3), day 6 (IM 6) and day 10 (IM 10). Quadriceps muscle cross-sectional area (CSA) and 1-repetition maximum (1RM) leg extension strength were measured to determine the extent of muscle size and strength adaptations. Muscle CSA and strength decreased following 10 days of immobilization (11.8 and 41.6%, respectively, P < 0.01). A decrease in SR Ca2+ uptake rate (analysed per g wet wt) was found at IM 3 (13.2%, P=0.05), with a further decrease at IM 10 (19.8% from control, P < 0.01). At IM 10, a decrease in SR Ca2+ uptake rate (per mg protein) also occurred (19.9%, P < 0.01). Sarcoplasmic reticulum Ca2+ ATPase activity and rate of Ca2+ release were not altered with 10 days of immobilization. This study observed a decrease in SR Ca2+ uptake rate, muscular atrophy and strength loss over 10 days of immobilization in humans.

Effect of 23-day muscle disuse on sarcoplasmic reticulum Ca2+ properties and contractility in human type I and type II skeletal muscle fibers

“…There is currently very little information in human muscle on whether a period of inactivity alters properties of the SR or myoplasmic [Ca 2ϩ ] handling proteins (50). Some work has been done in rodent, although information is also very limited or conflicting.…”

Morphological Responses of Human Skeletal Muscles to Decreased Mechanical Loading

“…Most of these studies have provided evidence that, on the average, unloading produces significant atrophic changes in all individual muscles of the knee extensors and plantar flexors regardless of the models of unloading, although there were differences between the reports in variables analyzed as the score of muscle size, i.e., ACSA at a single site (Berry, et al, 1993;Thom, et al, 2001;Vandenborne, et al, 1998) and muscle volume (Akima, et al, 1997). As a result of 20 days of bed rest, however, Akima et al (1997) observed greater reductions in the vastus intermedius and vastus medialis muscles and in the semimembranosus among the constituents of quadriceps femoris and hamstrings, respectively.…”

“…Many studies have investigated the influences of decreased mechanical loading on muscle size using various unloading conditions such as bed rest (Abe, et al, 1997;Akima, et al, 1997;Alkner and Tesch 2004 a,b;Berg, et al, 1997;Berry, et al, 1993;Convertino, et al, 1989;Ellis, et al, 1993;Ferrando, et al, 1995;Ferretti, et al, 1997;LeBlanc, et al,1992), immobilization (i.e, suspending or casting lower limbs) (Adams, et al, 1994;Berg, et al, 1991;Dudly, et al, 1992;Hather, et al, 1992;Miles, et al, 1994;Ploutz-Snyder, et al, 1995;Schulze, et al, 2002;Tesch, et al, 2004;Thom, et al, 2001;Vandenborne, et al, 1998) or space flight (Akima, et al, 2000b;LeBlanc, et al, 1995LeBlanc, et al, , 2000. As the profiles of atrophic changes in these conditions, this paper firstly focused on the influences of the duration and mode of decreased mechanical loading on the magnitude of atrophy with relation to muscle-related differences in them.…”

“…F u r t h e r m o r e , s o m e p r e v i o u s s t u d i e s h a v e examined the influences of simulated microgravity on individual muscles consisting of a synergistic muscle such as plantar flexors or knee extensors (Akima, et al, 1997;Berry, et al, 1993;Hather, et al, 1992;Thom, et al, 2001;Vandenborne, et al, 1998). Most of these studies have provided evidence that, on the average, unloading produces significant atrophic changes in all individual muscles of the knee extensors and plantar flexors regardless of the models of unloading, although there were differences between the reports in variables analyzed as the score of muscle size, i.e., ACSA at a single site (Berry, et al, 1993;Thom, et al, 2001;Vandenborne, et al, 1998) and muscle volume (Akima, et al, 1997).…”

Influência do alongamento passivo em três repetições de 30 segundos a cada 48 horas em músculo sóleo imobilizado de ratos

“…Thom et al (13) investigaram os efeitos de 10 dias de imobilização em quadríceps sobre a área de secção transversal, força e a regulação de cálcio no retículo sarcoplasmático através de biópsias musculares em 8 sujeitos saudáveis. Observaram que a área muscular, força e captura do cálcio diminuíram significativamente no perío-do.…”