Effect of Capacitive and Resistive electric transfer on changes in muscle flexibility and lumbopelvic alignment after fatiguing exercise

Graduate School of Medicine, Kyoto University

Authors:

Yuki Yokota et al.

Abstract:

Background / Purpose

Inappropriate lumbopelvic alignment—especially excessive anterior pelvic tilt and lumbar lordosis—is a well-known contributor to low back pain (LBP) and anterior cruciate ligament (ACL) injuries. Poor flexibility of the quadriceps, particularly the rectus femoris, can exacerbate these postural imbalances. Since muscle fatigue decreases flexibility and increases stiffness, accelerating recovery is crucial to prevent injury.

This study aimed to determine whether Capacitive and Resistive Electric Transfer (CRet) therapy at 448 kHz can enhance muscle flexibility and restore lumbopelvic alignment after fatiguing exercise, compared with passive rest.

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Methods

A randomized controlled trial was conducted on 22 healthy male participants (mean age 23 years). Subjects were assigned to:

CRet group (n = 11): Received 15 minutes of CRet therapy (5 minutes capacitive, 10 minutes resistive mode) on the quadriceps after fatiguing knee-extension exercise.
Control group (n = 11): Rested passively for 15 minutes.

Fatigue was induced through 10 sets of 10 concentric–eccentric leg extensions at 30% maximal voluntary contraction.
Measurements were taken at baseline, after exercise, and immediately, 15, and 30 minutes post-intervention, including:

Quadriceps flexibility – Ely test
Pelvic tilt – Palpation meter (ASIS–PSIS alignment)
Lumbar lordosis – Spinal Mouse system
Surface temperature – Infrared thermometer

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Results

Flexibility: Both groups showed reduced quadriceps flexibility after exercise (Ely angle ↓ ~6°). However, in the CRet group, flexibility returned to baseline within 30 minutes, while in the control group it remained significantly decreased (p < 0.05).

Pelvic Tilt: Increased anterior tilt immediately after exercise in both groups (+1.9° CRet, +1.4° control). Alignment normalized within 30 minutes in the CRet group but persisted in controls.

Lumbar Lordosis: No significant change in either group.

Temperature: Surface temperature increased by +5.1°C immediately after CRet and remained elevated for 30 minutes (p < 0.01), confirming sustained deep-tissue heating.

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Discussion

The CRet-treated participants recovered muscle flexibility and pelvic balance significantly faster than controls. The authors attributed this to three synergistic effects of radiofrequency stimulation:

Enhanced microcirculation: CRet-induced vasodilation accelerates removal of intramuscular fluid and metabolic waste, reducing stiffness.
Improved tissue extensibility: Deep heating softens collagen fibers, decreasing viscosity and improving stretch tolerance.
Neuromuscular relaxation: Subthermal current reduces α-motor neuron excitability, promoting muscle relaxation.

The faster normalization of pelvic tilt in the CRet group reflects restored quadriceps extensibility, particularly in the rectus femoris, which influences pelvic position through hip flexion control. Though lumbar lordosis did not significantly change, the authors note that unilateral exercise and localized application likely limited global spinal adaptation.

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Conclusion

Fifteen minutes of CRet therapy (448 kHz) applied after fatiguing exercise effectively restored muscle flexibility and normalized anterior pelvic tilt faster than rest alone. The treatment increased muscle temperature by ~5°C and maintained improved circulation for at least 30 minutes post-application.

These findings confirm CRet’s potential as a deep thermotherapy modality for post-exercise recovery, injury prevention, and maintenance of optimal lumbopelvic alignment in athletes and active populations.

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