Dads-to-be, take note! You may be more useful in the labour room than you realise, as a study has found that holding your partner's hand synchronises your heart and respiratory rates and dissipates her pain.
The study of 22 couples is the latest in a growing body of research on "interpersonal synchronisation," the phenomenon in which individuals begin to physiologically mirror the people they are with.
"The more empathic the partner and the stronger the analgesic effect, the higher the synchronisation between the two when they are touching," said Pavel Goldstein from University of Colorado at Boulder in the US.
Scientists have long known that people subconsciously sync their footsteps with the person they are walking with or adjust their posture to mirror a friend's during conversation.
Recent studies also show that when people watch an emotional movie or sing together, their heart rates and respiratory rhythms synchronise.
When leaders and followers have a good rapport, their brain-waves fall into a similar pattern. And when romantic couples are simply in each other's presence, their cardiorespiratory and brain-wave patterns sync up, research has shown.
The latest study, published in the journal Scientific Reports, is the first to explore interpersonal synchronisation in the context of pain and touch.
The researchers hope it can inform the discussion as health care providers seek opioid-free pain relief options.
Goldstein recruited 22 long-term heterosexual couples, aged 23 to 32, and put them through a series of tests aimed at mimicking that delivery-room scenario.
Men were assigned the role of observer; women the pain target. As instruments measured their heart and breathing rates, they: sat together, not touching; sat together holding hands; or sat in separate rooms.
Then they repeated all three scenarios as the woman was subjected to a mild heat pain on her forearm for two minutes.
As in previous trials, the study showed couples synced physiologically to some degree just sitting together. However, when she was subjected to pain and he could not touch her, that synchronisation was severed.
When he was allowed to hold her hand, their rates fell into sync again and her pain decreased.
"It appears that pain totally interrupts this interpersonal synchronisation between couples. Touch brings it back," Goldstein said.
Goldstein's previous research found that the more empathy the man showed for the woman (as measured in other tests), the more her pain subsided during touch. The more physiologically synchronised they were, the less pain she felt.
It is not clear yet whether decreased pain is causing increased synchronicity, or vice versa, researchers said.
"It could be that touch is a tool for communicating empathy, resulting in an analgesic, or pain-killing, effect," said Goldstein.
The study did not explore whether the same effect would occur with same-sex couples, or what happens when the man is the subject of pain.