Being in a relationship can completely change a person’s life.  They alter their routine, try different activities, and spend more time with that one other person.  Hopefully, they also show an improvement in mood.  However, according to a recent study published on PLOS One, walking speed varies for males depending on the nature of the relationship they have with those they are walking with.

Research has already established that individuals each have an optimal walking speed, which is the pace at which they can walk and minimize the energy expended to reach the necessary distance.  Optimal walking speed varies with mass and lower limb length, showing an overall variance between males and females.  Even with an optimal speed, there are still choices being made about the appropriate speed at which to walk in a given situation.

When a romantic partner is also the walking partner, researchers found that males significantly altered their walking pace.  Specifically, males slowed down by an average of seven percent.  This slowing is more pronounced and is statistically significant than walking with other acquaintances, male or female.  The Los Angeles Times points out that women do not change their pace.  In fact, there was hardly any change from their optimal walking pace whether they were walking with a romantic partner or with friends.

Researchers theorize that these findings may be related to the need to procreate.  Optimal walking speed is about maximizing the efficient use of energy.  If a man continues to walk at his optimal pace and the woman has to expend more energy to keep up, could have greater reproductive success.  Natural instinct to improve the chances of producing offspring leads men to unconsciously slow down.  Considering evolution, this makes sense because in more dangerous societies, burning calories unnecessarily could jeopardize the woman and her offspring.

If males and females are walking together, the males are much more likely to bear the energetic burden in order to walk with the females because of the biological differences between men and woman.  From an energetics perspective, this is the expected outcome since the female reproductive system is sensitive to even the slightest energetic disturbances.  If a female is in a state of negative energy balance, ovarian function may be stifled.  This would eliminate the possibility of conceiving until energy balance is restored by either expending less energy or consuming more energy.  Concern for energy balance and its impact on the reproductive system is understandably linked to relationship status, though this is not a conscious change but a possible remnant of evolution.