In vivo and in vitro evidence that intrinsic upper‐ and lower‐limb skeletal muscle function is unaffected by ageing and disuse in oldest‐old humans. (28th May 2015)

• Record Type: Journal Article
• Authors: Venturelli, M.; Saggin, P.; Muti, E.; Naro, F.; Cancellara, L.; Toniolo, L.; Tarperi, C.; Calabria, E.; Richardson, R. S.; Reggiani, C.; Schena, F.
• Is Part Of: Acta physiologica. Volume 215:Number 1(2015:Sep.)
• Page Start: 58
• Page End: 71
• Publication Date: 2015-05-28
• Subjects: Physiology -- Periodicals; Physiology -- Research -- Periodicals; 612
• DOI: 10.1111/apha.12524
• Languages: English
• ISSNs: 1748-1708

Abstract

<abstract abstract-type="main" id="apha12524-abs-0001"> <title>Abstract</title> <sec id="apha12524-sec-0001" sec-type="section"> <title>Aim</title> <p>To parse out the impact of advanced ageing and disuse on skeletal muscle function, we utilized both <italic>in vivo</italic> and <italic>in vitro</italic> techniques to comprehensively assess upper‐ and lower‐limb muscle contractile properties in 8 young (YG; 25 ± 6 years) and 8 oldest‐old mobile (OM; 87 ± 5 years) and 8 immobile (OI; 88 ± 4 years) women.</p> </sec> <sec id="apha12524-sec-0002" sec-type="section"> <title>Methods</title> <p> <italic>In vivo</italic>, maximal voluntary contraction (MVC), electrically evoked resting twitch force (RT), and physiological cross‐sectional area (PCSA) of the quadriceps and elbow flexors were assessed. Muscle biopsies of the vastus lateralis and biceps brachii facilitated the <italic>in vitro</italic> assessment of single fibre‐specific tension (Po).</p> </sec> <sec id="apha12524-sec-0003" sec-type="section"> <title>Results</title> <p> <italic>In vivo</italic>, compared to the young, both the OM and OI exhibited a more pronounced loss of MVC in the lower limb [OM (−60%) and OI (−75%)] than the upper limb (OM = −51%; OI = −47%). Taking into account the reduction in muscle PCSA (OM = −10%; OI = −18%), only evident in the lower limb, by calculating voluntary muscle‐specific force, the lower limb of the OI (−40%) was more compromised than the OM (−13%). However, <italic>in vivo</italic>, RT in both upper and lower limbs (approx. 9.8 N m cm<sup>−2</sup>) and Po (approx. 123 mN mm<sup>−2</sup>), assessed <italic>in vitro</italic>, implies preserved intrinsic contractile function in all muscles of the oldest‐old and were well correlated (<italic>r</italic> = 0.81).</p> </sec> <sec id="apha12524-sec-0004" sec-type="section"> <title>Conclusion</title> <p>These findings suggest that in the oldest‐old, neither advanced ageing nor disuse, <italic>per se</italic>, impacts intrinsic skeletal muscle function, as assessed <italic>in vitro</italic>. However, <italic>in vivo</italic>, muscle function is attenuated by age and exacerbated by disuse, implicating factors other than skeletal muscle, such as neuromuscular control, in this diminution of function.</p> </sec> </abstract>