A team of researchers recently found that massage therapy led to improved heart-rate variability—a measure of improved autonomic nervous system development and function—among medically stable preterm male infants in the hospital.
The study, “The effect of massage on heart rate variability in preterm infants,” involved a total of 37 hospitalized, medically stable preterm infants born 29 to 32 weeks gestation. Seventeen of the infants were randomly assigned to the massage group, and the other 20 were randomly assigned to the control group.
“The purpose of our study was to test the effect of massage on heart rate variability (HRV) as the proxy measure of autonomic nervous system (ANS) development and function in preterm infants during four weeks of hospitalization,” state the study’s authors.
Infants in the massage group received 20 minutes of massage therapy twice a day for four weeks, using the Infant Massage USA protocol. This protocol was modified for preterm infants by eliminating abdomen massage.
The routine consisted of six soft-tissue compression strokes from the top of thighs to ankles and feet, chest over ribcage, shoulders down the arms to hands, head from crown to neck, and along the back from the neck to the waist.
Following the massage, range of motion to the arms and legs of each infant was delivered by the massage therapist, using a specific protocol. For each session, the infants were supine.
Those in the control group also were supine but did not receive the massage or range of motion protocol. Instead, the massage therapist stood next to the infant’s bed for 20 minutes twice a day for four weeks.
The main outcome measure in this study was HRV. Electrocardiograph (ECG) data were collected continuously beginning 10 minutes before the massage or control session and continuing throughout the 20-minute session and for 10 minutes after the session ended. This occurred weekly during the four-week study.
From the ECG, researchers extracted data on the frequency domain of HRV, an estimate of the variations between the high-frequency (HF) and low-frequency (LF) regions of the HRV data.
“Increased HRV is demonstrated when a decrease in LF/HF ratio occurs and is indicative of increased parasympathetic activity,” state the study’s authors. “Increased HRV is associated with improved awakenings during supine sleep and may be associated with decreased risk of sudden death.
“Decreased HRV is demonstrated when the LF/HF ratio increases and is indicative of increased sympathetic activity,” the researchers continue. “Decreased HRV is associated with prone sleeping patterns in preterm infants, which may be associated with sudden infant death.”
Results of the research revealed that the LF/HF ratio of preterm infants in the massage group was lower than that of the control infants, pointing to increased parasympathetic activity in the massage infants. In addition, preterm infants in the control group showed a significant increase in LF/HF ratio from weeks zero to four, whereas those in the massage group showed a significant decrease in LF/HF ratio from weeks zero to four.
Among the male infants in the control group, the LF/HF ratio was significantly higher at weeks three and four. Among the male infants in the massage group, the LF/HF ratio was significantly lower at weeks three and four. According to the study’s authors, female infants in both the massage and control groups showed no significant change in LF/HF ratio from weeks zero to four.
“We found significant gender differences with massage males demonstrating improved parasympathetic function over time compared with males in the control group and females in both groups,” state the study’s authors. “Preterm male infants have higher morbidities and mortality than their female counterparts.
“Our work demonstrates that a well-delivered massage intervention may improve the ANS development in preterm male infants who are more vulnerable to stress response,” the researchers continue. “If massage improves the male infant’s ability to respond to stressful events, there may be prolonged effects on minimizing morbidity and chronic disease.”
Authors: S.L. Smith, R. Lux, S. Haley, H. Slater, J. Beechy and L.J. Moyer-Mileur.
Sources: School of Nursing, University of Louisville, Kentucky; Cardiovascular Research and Training Institute, and Division of Neonatology, Department of Pediatrics, University of Utah, Salt Lake City, Utah. Originally published April 26, 2012, in Journal of Perinatology.