Venturelli M, Saggin P, Muti E, Naro F, Cancellara L, Toniolo L, Tarperi C, Calabria E, Richardson R S, Reggiani C, Schena F
Department of Biomedical Sciences for Health, University of Milan, Milan, Italy.
Department of Neurological, and Movement Sciences, University of Verona, Verona, Italy.
Acta Physiol (Oxf). 2015 Sep;215(1):58-71. doi: 10.1111/apha.12524. Epub 2015 May 28.
To parse out the impact of advanced ageing and disuse on skeletal muscle function, we utilized both in vivo and in vitro 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.
In vivo, 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 in vitro assessment of single fibre-specific tension (Po).
In vivo, 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, in vivo, RT in both upper and lower limbs (approx. 9.8 N m cm(-2) ) and Po (approx. 123 mN mm(-2) ), assessed in vitro, implies preserved intrinsic contractile function in all muscles of the oldest-old and were well correlated (r = 0.81).
These findings suggest that in the oldest-old, neither advanced ageing nor disuse, per se, impacts intrinsic skeletal muscle function, as assessed in vitro. However, in vivo, 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.
为了剖析衰老和废用对骨骼肌功能的影响，我们运用体内和体外技术，全面评估了8名年轻女性（YG；25±6岁）、8名最年长的可活动女性（OM；87±5岁）和8名不可活动女性（OI；88±4岁）的上下肢肌肉收缩特性。
在体内，评估股四头肌和肘屈肌的最大自主收缩（MVC）、电诱发静息抽搐力（RT）和生理横截面积（PCSA）。对股外侧肌和肱二头肌进行肌肉活检，以辅助体外评估单纤维比张力（Po）。
在体内，与年轻女性相比，OM和OI下肢MVC的丧失[OM（-60%）和OI（-75%）]比上肢更明显（OM = -51%；OI = -47%）。考虑到仅在下肢明显的肌肉PCSA减少（OM = -10%；OI = -18%），通过计算自主肌肉比力，OI下肢（-40%）比OM下肢（-13%）受损更严重。然而，在体内，上下肢的RT（约9.8 N m cm-2）以及体外评估的Po（约123 mN mm-2）表明，最年长者所有肌肉的内在收缩功能得以保留，且两者相关性良好（r = 0.81）。
这些发现表明，在最年长者中，衰老和废用本身均不会影响体外评估的骨骼肌内在功能。然而，在体内，肌肉功能会因年龄而减弱，并因废用而加剧，这表明在这种功能减退中涉及骨骼肌以外的因素，如神经肌肉控制。
