Therapeutic Effects of Capacitive and Resistive Monopolar Radiofrequency on Muscle Stiffness and Local Hemodynamics of the Rectus Femoris: A Randomized Crossover Study of Female University Soccer Players.
Ryo Sugiyama, Takayuki Miyamori, Masashi Aoyagi and 4 others
A 448-kHz radiofrequency device reduced rectus femoris stiffness in the stretched position immediately after treatment, more than a hot pack or sham.
The effect was gone by 30 minutes. Deep-tissue oxygen levels stayed elevated at 30 minutes only after radiofrequency.
Key findings
1In the stretched position, muscle stiffness was significantly lower immediately after CRMF than after a hot pack or sham. No differences remained at 30 minutes, and no condition-by-time effect was seen in the resting position.
2At 3 cm depth, oxygenated hemoglobin and tissue oxygen saturation were significantly higher after CRMF than after sham at 30 minutes, while the hot pack effect had faded. Immediately post-treatment, both CRMF and hot pack raised oxygenated hemoglobin above sham, but the two were not different from each other.
3No functional outcomes (strength, fatigue resistance, pain, range of motion) were measured; the study reports only physiological markers of stiffness and blood flow.
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What it does not show
All 18 participants were healthy young women with no current muscle injury, so the findings cannot be applied to a patient in the middle of a rectus femoris strain. No functional outcomes (strength, range of motion, pain, fatigue resistance) were measured; the study reports only stiffness and blood-flow numbers. The stiffness effect lasted only 30 minutes, so it is unclear whether repeated sessions or a treatment course would produce a lasting benefit. The examiner who applied the treatment also took the measurements and was not blinded to the condition, and participants could identify the hot pack, so expectancy and measurement bias are possible. Skin and intramuscular temperatures were not measured, so the claim that CRMF heats deeper tissue is inferred, not directly shown. Subcutaneous fat thickness was not measured, which the authors note can affect how heat and ultrasound signals reach the muscle. Menstrual cycle phase and hydration status were not recorded, and the authors acknowledge these could influence the measurements. No a priori sample-size calculation was performed; the post hoc power for the main stiffness interaction was 0.94, but for the resting-position interaction it was only 0.35.
Declared interests
No conflicts of interest were declared. The study was funded by the Institute of Health and Sports Science and Medicine at Juntendo University. The CRMF device used was manufactured by INDIBA (Barcelona, Spain), but no INDIBA employee is listed as an author and no INDIBA funding is named.
The easy way to misread this
Do not read the stiffness reduction as proof that CRMF outperforms a hot pack for treating a muscle strain. All participants were healthy with no current injury, no functional outcomes (strength, range of motion, pain) were measured, and the stiffness effect was gone by 30 minutes. The hemodynamic advantage of CRMF over the hot pack was limited to the 30-minute mark for oxygenated hemoglobin and tissue oxygen saturation; immediately after treatment the two were not different from each other.
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