Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, CANADA.
Med Sci Sports Exerc. 2018 Feb;50(2):334-343. doi: 10.1249/MSS.0000000000001445.
To compare the mechanisms of fatigue and recovery between upper and lower limbs in the same subjects.
Twelve healthy young men performed a 2-min sustained maximal voluntary isometric contraction (MVC) of the knee extensors (KE) and on another day a 2-min MVC of the elbow flexors (EF). Neuromuscular function evaluations were performed with both transcranial magnetic and peripheral stimulations before (PRE), at the end of the 2-min MVC, and five more times within 8 min of recovery.
Decreases in MVC and cortical voluntary activation were approximately 12% (P < 0.001) and approximately 25% greater (P = 0.04) in KE than EF at end of the 2-min MVC. Conversely, twitch response decreased approximately 29% more (P = 0.02) in EF than KE. Changes in motor-evoked potential with fatigue were not different between upper and lower limbs (P > 0.05), whereas the increase in silent period duration was approximately 30% greater in EF than KE (P < 0.05).
Upper and lower limbs presented different magnitudes of total, central and peripheral fatigue. Total neuromuscular fatigue and central fatigue were greater in KE than EF. Conversely, peripheral fatigue and corticospinal inhibition were greater in EF than KE.
比较同一受试者上肢和下肢疲劳和恢复的机制。
12 名健康年轻男性分别进行了 2 分钟持续最大自主等长收缩（MVC）的膝关节伸肌（KE）和另一天的肘关节屈肌（EF）的 2 分钟 MVC。在（PRE）、2 分钟 MVC 结束时以及恢复 8 分钟内的另外 5 次，使用经颅磁刺激和外周刺激进行神经肌肉功能评估。
在 2 分钟 MVC 结束时，MVC 和皮质自愿激活的下降分别约为 12%（P<0.001）和约 25%（P=0.04），KE 比 EF 更大。相反，在 EF 中比 KE 约降低 29%（P=0.02）。疲劳时运动诱发电位的变化在上肢和下肢之间没有差异（P>0.05），而静息期持续时间的增加在 EF 中比 KE 约增加 30%（P<0.05）。
上肢和下肢表现出不同程度的总疲劳、中枢疲劳和外周疲劳。KE 中的总神经肌肉疲劳和中枢疲劳大于 EF。相反，EF 中的外周疲劳和皮质脊髓抑制大于 KE。
