Institute of Cardiology of Rio Grande do Sul/University Foundation of Cardiology (IC/FUC), Clinical Research Laboratory, Porto Alegre, Brazil.
Disabil Rehabil. 2011;33(6):486-93. doi: 10.3109/09638288.2010.498551. Epub 2010 Jul 2.
To compare the acute effects of functional electrical stimulation (FES) with 15 and 50 Hertz (Hz) frequencies on muscle strength in patients with heart failure with healthy individuals.
Twenty-two 61.6 ± 1.0 y-old male volunteers were studied: 10 patients with heart failure (functional class II-III) and 12 healthy controls. The isometric muscle peak torque (IMPT) of the quadriceps femoral muscle was measured through a Biodex dynamometer in maximum voluntary contraction (MVC), and under FES of 50 Hz and 15 Hz, which was applied with a 0.4 ms pulse width, 10-s contraction time, 50-s resting time and maximum tolerable intensity.
The IMPT differed in MVC, 50 Hz and 15 Hz FES both in patients (201.9 ± 14, 55.6 ± 13 and 42.1 ± 12 Newton-metre, respectively; p < 0.001) and in controls (179.3 ± 9, 62.4 ± 8 and 52.3 ± 7 Newton-metre, respectively; p < 0.001). There were no differences between the groups. In patients and controls, respectively, the 50 Hz FES corresponded to 27% versus 35% and the 15 Hz to 21% versus 29% of the IMPT generated at the MVC (p < 0.001).
This result can be attributed to the fact that muscle strength is proportional to the stimulation frequency and to the number of recruited motor units. Thus, the higher the frequency, the greater the motor recruiting, producing increased muscle strength.
The IMPT generated by acute 50 Hz application of FES is higher than the one generated by 15 Hz, but it is lower than MVC in controls and patients with heart failure.
比较 15 赫兹和 50 赫兹（Hz）频率的功能性电刺激（FES）对心力衰竭患者和健康个体肌肉力量的急性影响。
研究了 22 名 61.6±1.0 岁的男性志愿者：10 名心力衰竭患者（功能分级 II-III）和 12 名健康对照者。使用 Biodex 测力计测量股四头肌的等速肌肉峰值扭矩（IMPT），分别在最大自主收缩（MVC）、50Hz 和 15Hz 的 FES 下进行测量，FES 的脉冲宽度为 0.4ms，收缩时间为 10s，休息时间为 50s，强度为最大耐受强度。
MVC、50Hz 和 15Hz FES 下的 IMPT 在患者（分别为 201.9±14、55.6±13 和 42.1±12 牛顿米；p<0.001）和对照组（分别为 179.3±9、62.4±8 和 52.3±7 牛顿米；p<0.001）中均存在差异。两组之间没有差异。在患者和对照组中，50Hz FES 分别对应于 MVC 产生的 IMPT 的 27%和 35%，15Hz 对应于 21%和 29%（p<0.001）。
这一结果可以归因于以下事实：肌肉力量与刺激频率和募集的运动单位数量成正比。因此，频率越高，募集的运动单位越多，产生的肌肉力量越大。
急性 50Hz 应用 FES 产生的 IMPT 高于 15Hz，但低于对照组和心力衰竭患者的 MVC。
