Effects of high-velocity, low-amplitude spinal manipulation on strength and the basal tonus of female pelvic floor muscles.

OBJECTIVE Spinal manipulation with high-velocity and low-amplitude (HVLA) manipulation is frequently used for the treatment of lumbopelvic pain; however, the effect on the pelvic floor has been poorly studied in the past. The objective of this study was to quantify the intravaginal pressure (IVP) and the basal perineal tonus (BPT), measured in terms of pressure, before and after the HVLA manipulation in patients without neuromuscular and skeletal dysfunctions. METHODS In this experimental, noncontrolled, nonrandomized study, IVP was obtained through a perineometer introduced into the volunteers' vagina while in dorsal horizontal decubitus. Forty young, healthy university volunteer women with no history of vaginal delivery participated. All voluntary contractions of the perineal muscles were measured in 3 different ways: phasic perineal contraction (PPC), tonic perineal contraction, and perineal contraction associated to accessory muscles. New pressure measurements were obtained immediately after the HVLA manipulation on the volunteers' sacrum. The pressures were registered and transcribed directly to a personal computer with specific software. RESULTS The average IVPs obtained in millimeters of mercury before and after the HVLA manipulation were 56.01 (+/-25.54) and 64.65 (+/-25.63) for PPC, 445.90 (+/-186.84) and 483.14 (+/-175.29) for tonic perineal contraction, and 65.62 (+/-26.56) and 69.37 (+/-25.26) for perineal contraction associated to accessory muscles, respectively. There was significant statistical variation only for PPC (P = .0020) values. The BPT increased regardless of the type of contraction (P < .05). CONCLUSION High-velocity and low-amplitude manipulation of the sacrum was associated with an increase of PPC and of BPT in women who had no associated osteoarticular diseases. These preliminary discoveries could be helpful in the future study of the treatment of women with perineal hypotony.