The data generated in this study suggest that one session of Swedish Massage Therapy caused a relatively large decrease in AVP (as measured by effect size) and relatively small, but consistent decreases in salivary and serum CORT levels. Counter to the working hypothesis, Swedish Massage Therapy did not increase OT nor decrease ACTH, compared to the light touch control condition. Thus, these findings in healthy normal volunteers replicate reports of acute CORT decreases in a variety of pathologic conditions. The rather profound decrease in AVP observed in this study suggests at least one possible mechanism responsible for the mild, yet consistent decrease in serum and salivary CORT levels.42,43
Although these findings represent a relatively detailed preliminary investigation of peripheral peptide measures, the findings may not reflect the central levels nor actions of these hormones.42
A unique feature of this study was the repeated assessment of neuroendocrine hormones at 1, 5, 10, 15, 30, and 60 minutes after the end of the intervention session. The information presented in may prove useful for determining optimum sampling times for future studies. Only the maximum or minimum value for comparison of treatment groups were selected in this preliminary study because it was believed that a broader summary of change during the hour following treatment (such as area-under-curve [AUC]) could miss evanescent, yet biologically meaningful, peaks or troughs in neuroendocrine hormones. Furthermore, one might expect a pattern of brief but potentially meaningful physiologic responses to transient environmental stimuli such as might be produced by other types of massage, or yoga or meditation.
The data presented in demonstrate that a single session of Swedish Massage Therapy leads to a greater increase in circulating of lymphocytes than one session of the light touch intervention. There was a moderate massage versus light touch effect size for the increase in total circulating lymphocytes and cells circulating that are positive for CD25 (the α
chain of the IL-2 receptor) and CD56 (a non-specific marker of NK cells). There was a small–to–very-small effect size for the increase in the number of circulating CD4+ cells and CD8+ cells after a single session of Swedish Massage Therapy. In the majority of the published massage literature investigating the actions of massage therapy on immune function, CD56 staining is used to determine NK cell numbers. However, it has recently become accepted that CD56 can be expressed by other cells as well as NK cells; thus, although the current study’s data do replicate previous reports in the literature, the current authors are hesitant to suggest that this solely reflects an increase in NK cells. In general these preliminary findings in normal volunteers—that circulating T-cells, activated lymphocytes, and CD56-positive staining cells are increased after a single session of Swedish Massage Therapy—support the findings of previous investigators who have been studying subjects with a variety of different pathologic conditions.17–22
However, more extensive flow cytometry studies are needed to clarify these observations. In general, the present findings are consistent with the postulate that the manual techniques used during Swedish Massage Therapy may lead to migration of leukocytes into the general circulation.
The consistently lower levels of whole-blood mitogen-stimulated cytokine production for subjects who received Swedish Massage Therapy compared to light touch was surprising. Swedish Massage Therapy caused an absolute decrease in the mitogen-stimulated production of IL-4, IL-5, IL-10, and IL-13, compared to baseline levels, while production of these four cytokines increased slightly in the light touch group. This is of particular interest, because this absolute decrease in mitogen-stimulated TH-2 cytokine levels after a single session of massage may provide a biologic basis for reports that massage therapy mitigates the symptoms of asthma in children.9,44
Cytokine production levels of IFN-γ
, IL-1β, IL-2, and IL-6 increased relative to baseline levels in both treatment groups, but the increase was smaller for massage than for touch. Only TNF-α
increased more after a session of massage than a session of light touch. In general, Swedish Massage Therapy decreased mitogen-stimulated proinflammatory, TH-1 mediated, and TH-2 mediated cytokine levels, compared to the light touch condition. Most of these differences in mitogen-stimulated cytokine levels were in the moderate-to-large effect-size range. Further work is needed to elucidate the mechanisms responsible for these findings.
As expected, the two groups of healthy normal subjects had similar baseline and postintervention ratings of anxiety, depression, and QoL. This suggests that the differences in biologic findings identified in this study were not the result of baseline or intervention-related differences in psychologic status.
There are always limitations to exploratory studies, and a number of these limitations merit discussion. Given that it was not possible to obtain from the literature a reasonable estimate of expected differences on the biologic measures investigated, this study arbitrarily settled on a sample size of approximately 25 per group. In order to decrease potential biologic heterogeneity, it was decided to study young, healthy adult subjects; thus, the current authors hesitate to extrapolate this study’s findings to children or older adults. It was not possible to control for menses in this pilot analysis, although the phase of each female subject’s menstrual cycle was recorded at the intervention visit, and there were no obvious differences resulting from phase of the menstrual cycle. The use of light touch condition as a control for Swedish Massage Therapy, while perhaps controversial,45,46
allowed comparison and contrasting of the biologic effects of the core massage techniques of effleurage, petrissage, kneading, tapotement, and thumb friction while controlling for other aspects of the intervention, such as disrobing, lying on the table, physical touch, and interaction with the therapist. A different pattern of response might have been observed if another control condition had been used, but the relationship to the specific massage techniques would have been less clear. A possible criticism is that expectancy and credibility of the two interventions were not measured, but, given that the study subjects were normal individuals who were not seeking relief for a pathologic condition, it was decided that measuring these two parameters was not essential for a pilot study. The similarity in postintervention mood anxiety and QoL ratings for the two groups support this contention. Another limitation of this study is the concern that small samples may not be truly representative of the range of subject heterogeneity that can be observed in a larger sample; thus, the current effect-size estimates may be larger than would be observed in a larger replication study.47
However, the consistency of this study’s effect-size findings over a number of independent variables suggests that these biologic differences are likely to be real and replicable in a larger sample. Another possible criticism is the absence of data on sympathetic and parasympathetic tone. Heart rate variability data were collected, but these young, healthy normal subjects did not differ on any of those measures.