Abstract: BACKGROUND: In recent years, magnetic stimulation therapy can activate the classical transient receptor potential channel 1, triggering the calcium-mitochondrial axis to enhance myogenesis and mitochondrial biogenesis in vivo, thereby recapitulating physiological adaptations related to exercise-induced metabolic responses. As an emerging technique for promoting muscle function, magnetic stimulation has gained widespread attention and validation in the rehabilitation of muscular diseases due to its advantages of being non-invasive, passive, and safe. However, there is a lack of clinical studies on the therapeutic efficacy of this technique in the treatment of disuse-induced muscle atrophy.
OBJECTIVE: To investigate the therapeutic effect of exercise therapy combined with magnetic stimulation on the recovery of muscle strength and locomotor ability in patients with disuse-induced muscle atrophy after Achilles tendon rupture.
METHODS: Sixteen patients were recruited for long-term bed rest after unilateral Achilles tendon rupture of the lower limb, which triggered disuse-induced muscle atrophy of the lower limbs. These patients were randomly divided into a control group and an experimental group, with eight cases in each group. The control group received traditional exercise rehabilitation therapy, including joint mobility training, muscle strength training, soft tissue stretching training, three times a week; the experimental group was subjected to medical magnetic physical factor stimulation (intensity 1.5 mT, frequency 3 300 Hz, once for 10 minutes every 48 hours) based on the exercise training. The total length of the trial was 4 weeks. All subjects were tested for maximum voluntary contraction force of the lower limbs and gait speed indexes (including the Timed Up and Go Test, the 5 Times Sit-to-Stand Test, and the 6-Meter Walking Test) before and after the intervention. Changes in these indexes were observed.
RESULTS AND CONCLUSION: (1) After 4 weeks of intervention, 16 subjects completed the trial. In the experimental group, the maximum voluntary contraction force of the lower limb on the affected side (P=0.001) and the discrepancy rate of maximum voluntary contraction force between the healthy and affected sides decreased significantly (P=0.001); both changes were significantly better than those in the control group. (2) In terms of gait speed indexes, the experimental group showed significant improvement in the Timed Up and Go Test (P=0.038), the 5 Times Sit-to-Stand Test (P=0.050), and the 6-Meter Walking Test (P=0.025) after intervention. (3) Inter-group comparisons revealed that the experimental group showed significant improvements compared with the control group in the following parameters: maximum voluntary contraction of the affected lower limb (P=0.003), discrepancy rate of maximum voluntary contraction between the unaffected and affected sides (P=0.004), Timed Up and Go Test results (P=0.019), and 6-Meter Walking Test results (P=0.011). The above data confirmed that after 4 weeks of low-frequency pulsed magnetic field (1.5 mT, 3 300 Hz) combined with exercise therapy, patients with postoperative disuse-induced muscle atrophy after Achilles tendon rupture had a significantly better improvement than the control group in the maximum voluntary contraction force of the affected limb, Timed Up and Go Test results, and 6-Meter Walking Test results, which could indicate that magnetic stimulation combined with exercise therapy can produce synergistic enhancement effects on isometric muscle strength and lower limb motor function. Therefore, the combination of magnetic stimulation and exercise therapy can be considered as a novel approach for the recovery of disuse-induced muscle atrophy.

Key words: magnetic stimulation, exercise therapy, achilles tendon rupture, disuse-induced muscle atrophy, skeletal muscle function recovery, classical transient receptor potential channel 1