Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium.
Med Sci Sports Exerc. 2010 Feb;42(2):402-8. doi: 10.1249/MSS.0b013e3181b0f2e2.
The purpose of this study was to test whether the higher slope of the oxygen uptake/work rate relationship (DeltaVO2/DeltaW) in aerobically trained subjects compared with less trained counterparts during a ramp protocol is related to changes in muscle fiber activation.
Ten cyclists and 10 physically active (PA) students performed two ramp exercises (ramp 25 protocol and relative ramp protocol, leading to exhaustion in 12 min) and a step protocol (20-60-100-140-180-220 W). Pulmonary gas exchange was measured, and muscle fiber activity was recorded with surface EMG of the musculus vastus lateralis. V O2 and integrated EMG (iEMG) were described as functions of work rate up to the gas exchange threshold, and linear regression analysis was used to determine the DeltaVO2/DeltaW and the slope of the iEMG/W relationship (DeltaiEMG/DeltaW).
The statistical analysis revealed a higher DeltaVO2/DeltaW in cyclists compared with PA students in ramp exercises (ramp 25 = 9.98 +/- 0.51 vs 9.18 +/- 0.59 mL x min(-1) x W(-1); relative ramp = 9.87 +/- 0.30 vs 9.16 +/- 0.33 mL x min(-1) x W(-1) in the cyclists and PA students, respectively; P < 0.05) but not in step exercise (9.97 +/- 0.32 and 9.83 +/- 0.37 mL x min(-1) x W(-1) in cyclists and PA students, respectively; P > 0.05). In addition, cyclists demonstrated a higher DeltaiEMG/DeltaW in ramp exercises (0.96 +/- 0.14% x W(-1) and 0.98 +/- 0.14% x W(-1) in ramp 25 and relative ramp, respectively) compared with step exercise (0.75 +/- 0.12% x W(-1), P < 0.05), whereas in the PA students, DeltaiEMG/DeltaW did not differ between the ramp protocol (0.75 +/- 0.10% x W(-1) and 0.70 +/- 0.12% x W(-1) in ramp 25 and relative ramp, respectively) and the step protocol (0.77 +/- 0.17% x W(-1), P > 0.05).
The present study reveals that trained cyclists demonstrate reduced mechanical efficiency in the ramp protocol and that this phenomenon is associated with an "overactivation" of muscle fibers.
本研究旨在测试在斜坡方案中，与训练较少的人相比，有氧训练的受试者的摄氧量/做功率关系（DeltaVO2/DeltaW）斜率较高是否与肌肉纤维激活的变化有关。
10 名自行车运动员和 10 名体能活跃（PA）学生进行了两次斜坡运动（斜坡 25 方案和相对斜坡方案，在 12 分钟内导致疲劳）和一次台阶运动（20-60-100-140-180-220 W）。测量肺气体交换，并使用股外侧肌的表面肌电图记录肌肉纤维活动。V O2 和积分肌电图（iEMG）被描述为工作率达到气体交换阈值的函数，线性回归分析用于确定 DeltaVO2/DeltaW 和 iEMG/W 关系的斜率（DeltaiEMG/DeltaW）。
统计分析显示，与 PA 学生相比，自行车运动员在斜坡运动中具有更高的 DeltaVO2/DeltaW（斜坡 25 = 9.98 +/- 0.51 与 9.18 +/- 0.59 mL x min(-1) x W(-1)；相对斜坡 = 9.87 +/- 0.30 与 9.16 +/- 0.33 mL x min(-1) x W(-1)；P < 0.05），但在台阶运动中则不然（自行车运动员和 PA 学生的分别为 9.97 +/- 0.32 和 9.83 +/- 0.37 mL x min(-1) x W(-1)；P > 0.05）。此外，与台阶运动相比，自行车运动员在斜坡运动中表现出更高的 DeltaiEMG/DeltaW（斜坡 25 和相对斜坡分别为 0.96 +/- 0.14% x W(-1) 和 0.98 +/- 0.14% x W(-1)）（P < 0.05），而在 PA 学生中，斜坡方案中的 DeltaiEMG/DeltaW 与台阶方案（斜坡 25 和相对斜坡分别为 0.75 +/- 0.12% x W(-1) 和 0.70 +/- 0.12% x W(-1)）之间没有差异（P > 0.05）。
本研究表明，训练有素的自行车运动员在斜坡方案中表现出较低的机械效率，这种现象与肌肉纤维的“过度激活”有关。
