The evidence supporting massage and other forms of soft-tissue therapy (e.g. myofascial trigger point therapy) and their ability to influence parasympathetic modulation appear to be mounting up (9, 40-53). In other words, massage has been shown to increase parasympathetic activity leading to a reduction in blood pressure (48, 54, 55), heart rate (48), and an increase in heart rate variability (46, 49, 50, 51, 53).
An increase in parasympathetic activity simply relates to an increased state of relaxation, often referred to as a “rest and digest” state. Whilst there is a substantial body of evidence supporting the use of massage to increase parasympathetic modulation, most of this research has been conducted in nursing and therefore outside of the athletic environment.
Neuromuscular Excitability and the H-Reflex
Neuromuscular excitability is measured by assessing changes in the Hoffman reflex (H-reflex) amplitude (30). In fact, this is the same technique used to measure any potentiation effects when attempting to induce post-activation potentiation (56, 57). Massage has been shown to reduce neuromuscular excitability (i.e. the H-reflex), and it is thought to do so by stimulating the sensory receptors and reducing muscle tension (58-61). Having said that, the cutaneous mechanoreceptors were not responsible for the changes in H-reflex amplitude in the calf muscle (60).
As a result, the inhibitory effects of massage may originate from either the muscle or deep tissue mechanoreceptors (30). This is supported by one study which found a greater reduction in H-reflex response with an increasing depth of massage (62). Put simply, massage depth may be an important factor for reducing neuromuscular excitability.
If massage is capable of reducing neuromuscular excitability, then this might be a reason why massage appears to be a useful tool for reducing muscle tension and spasm (cramping) after exercise. However, this is still a matter of speculation and more research is required to understand the relationship between neuromuscular excitability and massage.
Effects on Pain
Massage is commonly used to treat perceptions of pain following exercise (63, 25, 26, 64-66), and there appears to be a substantial body of evidence which supports massage’s effectiveness for reducing pain in various populations. For example, massage has been shown to reduce the perception of pain in the following:
- Endurance athletes (67, 68)
- Patients with metastatic bone pain (when cancer cells spread into bone tissue) (69)
- Patients with a recurrent headache (70)
- Post-operative pain (71-81)
- Back and leg pain in pregnant women (82)
- Children and adolescents with chronic pain (83)
- Children with cancer and “growing pains” (84, 85)
- Myalgia (pain in a muscle or group of muscles) (86-88)
- Adult cancer patients (89, 90)
- Patients with Carpel Tunnel Syndrome (91)
- Patients with lower back pain (92-97)
- Patients with distal radial trauma and those receiving needle insertions (98, 99)
Though massage has been repeatedly shown to reduce the perception of pain in a variety of populations, there are numerous methodological issues with many of these studies due to the complexity of pain science. To provide a little more detail, pain is not a ‘sensation’, but instead, a ‘perception’ manifested and regulated by a complex neuromatrix. However, the concept of pain is far beyond the scope of this article.
Physiological (biochemical substances)
Neurotransmitter substances such as serotonin have been shown to reduce the symptoms of pain (100, 101). Massage has been shown to not only increase the levels of serotonin (102, 25) but also increase dopamine levels – a stress-relieving hormone (102). Thus massage may be an effective tool for relieving pain by increasing both serotonin and dopamine – but to accept this as concrete evidence would be a matter of assumption.
There is a significant amount of research which repeatedly supports the effectiveness of massage for reducing the perception of pain, though the effects appear to be small (30, 63, 103-107), and the mechanisms uncertain.