Kohn Tertius A, Essen-Gustavsson Birgitta, Myburgh Kathryn H
Department of Physiological Sciences, University of Stellenbosch, South Africa.
Med Sci Sports Exerc. 2007 Nov;39(11):1977-84. doi: 10.1249/mss.0b013e3181453546.
To determine whether relationships between skeletal muscle hybrid fiber composition and whole-body exercise patterns help to elucidate their transitional capacity or a fine-tuning response to functional demands.
This study investigated hybrid fibers from vastus lateralis biopsies of runners (N= 13) and nonrunners (N = 9) and related hybrid fiber occurrence and distribution of myosin heavy-chain isoforms (MHC) within hybrid fibers to exercise patterns. MHC composition of single fibers was identified by SDS-PAGE.
Runners had more fibers expressing only MHC I, fewer expressing MHC IIx, and fewer IIa/IIx hybrid fibers (P < 0.05). Hybrid IIa/IIx and I/IIa fibers were, respectively, negatively and positively related to training volume or average preferred racing distance (PRDA) in runners (P < 0.05). The relationship between IIa/IIx hybrid fibers and PRDA was more exponential (R(2) = 0.88) than linear (R(2) = 0.69). Only IIa/IIx hybrid fibers correlated negatively with exercise hours in nonrunners (P < 0.05). Their IIa/IIx hybrid fibers had MHC IIa content ranging from 1 to 99%, with most between 41 and 60%. Runners favoring longer distances (PRDA > 8 km or training > 70 km x wk(-1)) had no IIa/IIx hybrid fibers with MHC IIa proportion > 60%. In these runners, MHC I within hybrid I/IIa fibers was skewed toward higher proportions (> 60%), whereas MHC I proportions were skewed oppositely in runners favoring shorter training or racing distances.
Training volume influences both IIa/IIx and I/IIa hybrid fiber proportions in runners, but only the former in nonrunners. Hybrid IIa/IIx fiber proportions were modulated by racing distance. Distinctly different distributions of MHC isoforms within the hybrid fibers were seen in runners favoring longer distances versus those favoring shorter distances.
确定骨骼肌混合纤维组成与全身运动模式之间的关系是否有助于阐明其过渡能力或对功能需求的微调反应。
本研究调查了跑步者（N = 13）和非跑步者（N = 9）股外侧肌活检中的混合纤维，并将混合纤维中肌球蛋白重链异构体（MHC）的混合纤维出现情况和分布与运动模式相关联。通过SDS - PAGE鉴定单根纤维的MHC组成。
跑步者中仅表达MHC I的纤维更多，表达MHC IIx的纤维更少，IIa/IIx混合纤维也更少（P < 0.05）。跑步者中，IIa/IIx和I/IIa混合纤维分别与训练量或平均偏好比赛距离（PRDA）呈负相关和正相关（P < 0.05）。IIa/IIx混合纤维与PRDA之间的关系呈指数关系（R(2) = 0.88），而非线性关系（R(2) = 0.69）。在非跑步者中，只有IIa/IIx混合纤维与运动时间呈负相关（P < 0.05）。他们的IIa/IIx混合纤维中MHC IIa含量在1%至99%之间，大多数在41%至60%之间。偏好较长距离（PRDA > 8 km或训练量> 70 km·wk(-1)）的跑步者没有MHC IIa比例> 60%的IIa/IIx混合纤维。在这些跑步者中，I/IIa混合纤维中的MHC I倾向于更高比例（> 60%），而在偏好较短训练或比赛距离的跑步者中，MHC I比例则相反。
训练量影响跑步者的IIa/IIx和I/IIa混合纤维比例，但仅影响非跑步者的前者。IIa/IIx混合纤维比例受比赛距离调节。在偏好较长距离与偏好较短距离的跑步者中，混合纤维内MHC异构体的分布明显不同。
