Effect of low-frequency acupuncture on muscle and fascia stiffness: examination with or without intervention

Abstract

Background: Low-frequency acupuncture is used to maintain skeletal muscle flexibility and improve joint range of motion; however, its definite effects are unclear. This study aimed to determine the effects of low-frequency acupuncture on muscle and fascial stiffness and ankle dorsiflexion range of motion.

Methods: The participants included 12 randomly selected healthy adults. The medial head of the gastrocnemius muscle was selected as the target muscle, and changes in hardness and dorsiflexion range of motion of the ankle joint in the deep fascia, muscle, and deep intermuscular fascia of the same region were measured before and after low-frequency acupuncture intervention. Acupuncture needles were inserted until they passed through the deep intermuscular fascia and electrically stimulated at a frequency of 2 Hz for 15 min. The 12 right legs were the intervention legs, and the 12 left legs were the non-intervention legs.

Results: In the intervention leg, hardness increased in the deep fascia immediately after low-frequency acupuncture, but decreased in all regions (deep fascia, muscle, and deep intermuscular fascia) after 15 min. The rate of change in hardness was the greatest in the muscles and deep intermuscular fascia. Additionally, the ankle's dorsiflexion range of motion increased after 15 min. In contrast, the non-intervention leg showed no significant changes in stiffness or ankle dorsiflexion angle.

Conclusions: Low-frequency acupuncture may decrease muscle stiffness and improve fascial gliding. The change in hardness tended to be greater in the deeper areas.

Keywords: ankle dorsiflexion; fascia; low-frequency acupuncture; muscle; needling; shear wave elastography; ultrasound.

Figure 1

(A) A marker (6.5 cm × 1.0 cm) aligned with the ultrasound probe placed at the proximal 30% site of the lower leg length (lateral knee joint cleft to external capsule). (B) Lower extremity position during measurement and low-frequency electroacupuncture.

Figure 2

Ultrasound measurements. The image in (A) is an ultrasound image of the medial head of the gastrocnemius muscle. The image in (B) is an ultrasound image showing measurement of the shear wave velocity of muscle and fascia in the long axis. The image in (C) shows confirmation of the acupuncture needle insertion depth. The presence or absence of DIF passage was determined using an ultrasound imaging device to confirm the following two points: (1) the DIF flexed during acupuncture and (2) the acupuncture point was visible under the DIF. The dotted square line indicates the area where the acupuncture needle was inserted. DIF, deep intermuscular fascia.

Figure 3

Shear wave velocity of the deep fascia (DF), muscle, and deep intermuscular fascia (DIF). Measurements were obtained before (PRE), immediately after (POST), and 15 min after the acupuncture plus low-frequency electrical stimulation. *Significantly different from PRE (P < 0.05). †Significantly different from POST (P < 0.05).

Figure 4

Rate of change in shear wave velocity after acupuncture plus low-frequency electrical stimulation. The rate of change was calculated at the deep fascia (DF), muscle, and deep intermuscular fascia (DIF). (A) Rate of change from PRE to POST. (B) Rate of change from POST to 15 min. (C) Rate of change from PRE to 15 min. *Significantly different from PRE (P < 0.05).

Figure 5

Changes in the maximum dorsiflexion range of motion of the ankle joint. The changes were measured from before (PRE) to 15 min after the acupuncture plus low-frequency electrical stimulation. *Significantly different from PRE (P < 0.05).