期刊
AMERICAN JOURNAL OF PHYSICAL MEDICINE & REHABILITATION
卷 88, 期 12, 页码 973-978出版社
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1097/PHM.0b013e3181c1eda5
关键词
Electrotherapy; Electrical Stimulation; Quadriceps Femoris; Knee Extension
Objective: To investigate the effects of medium frequency burst-modulated alternating current on the current amplitude necessary to produce maximally tolerated electrically stimulated quadriceps femoris isometric knee extension torque. Design: Ten healthy volunteers participated in this study. Neuromuscular electrical stimulation was applied to the quadriceps femoris at two different carrier frequencies: 2500 and 5000 Hz. All subjects received both frequencies in a random order. Maximum voluntary isometric contraction torque of knee extension was measured. The current amplitude (in milli-amperes) required to produce maximally tolerated isometric contraction knee extension torque at both carrier frequencies was recorded. Results: The mean maximally tolerated isometric contraction torque (in %maximum voluntary isometric contraction) was 37.6% (SD, +/- 20.9) for 2500 Hz and 37.2% (SD, +/- 20.9) for 5000 Hz. These values were not significantly different (P = 0.944). However, the mean current amplitude required to produce maximally tolerated isometric contraction torque with 2500 Hz was 91.9 (SD, +/- 23.1) mA and with 5000 Hz K was 167.4 (SD, +/- 34.5) mA (P < 0.001). Conclusions: A carrier frequency of 2500 Hz is nearly twice as efficient for generating quadriceps femoris knee extension torque as one at 5000 Hz. Using lower medium frequency burst-modulated alternating current carrier frequencies will allow lower current amplitudes to be used to generate maximum-tolerated contraction torque, and will limit the possibility of reaching the upper limits of current amplitude on an electrotherapeutic device before reaching an individual's maximum tolerable contraction torque.
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