Phillips David, Karduna Andrew
1 University of Oregon.
J Appl Biomech. 2017 Jul;33(3):237-240. doi: 10.1123/jab.2016-0224. Epub 2017 Jun 26.
The EMG and load relationship is commonly measured with multiple submaximal isometric contractions. This method is both time consuming and may introduce fatigue. The purpose of this study was to determine if the electromyography (EMG) amplitude from the middle deltoid was reliable during isometric ramp contractions (IRCs) at different angles of elevation and rates of force application. Surface EMG was measured at 3 shoulder elevation angles during IRCs at 4 submaximal levels of maximum voluntary contraction (MVC). Data were reliable in all conditions except during the rate relative to the subjects' MVC at 90° for 30% and 40% MVC. The main effect for angle on EMG amplitude was found to be significant, p < .01. EMG at 90° was greater than at 60° (p < .017) and at 30° (p < .017). The main effect of force level on EMG amplitude was significant, p < .01 and follow-up contrast demonstrated a significant (p < .001) linear increase of EMG amplitude with force level. We conclude that EMG amplitude from IRCs are reliable across all shoulder elevation angles and up to 40% MVC. IRCs are a feasible method for recording EMG at the deltoid.
肌电图（EMG）与负荷的关系通常通过多次次最大等长收缩来测量。这种方法既耗时又可能导致疲劳。本研究的目的是确定在不同抬高角度和力施加速率的等长斜坡收缩（IRC）过程中，三角肌中部的肌电图（EMG）幅度是否可靠。在4个次最大最大自主收缩（MVC）水平的IRC过程中，于3个肩部抬高角度测量表面肌电图。除了在90°时相对于受试者MVC的速率为30%和40%MVC的情况下，所有条件下的数据都是可靠的。发现角度对EMG幅度的主要影响具有显著性，p <.01。90°时的EMG大于60°时（p <.017）和30°时（p <.017）。力水平对EMG幅度的主要影响具有显著性，p <.01，后续对比显示EMG幅度随力水平呈显著（p <.001）线性增加。我们得出结论，在所有肩部抬高角度和高达40%MVC的情况下，IRC的EMG幅度都是可靠的。IRC是一种记录三角肌EMG的可行方法。
