Health benefits of having a fierce personal rivalry
By Dan Kauna, June 8, 2026There is a person in your life who makes you push harder – the gym regular whose lifts are always slightly heavier than yours, the colleague whose work is consistently just sharper than your own.
You may not have named it, but what you have is a rivalry. And science says it is one of the most powerful biological tools available to you.
Rivalry is not the same as ordinary competition. Where competition involves any opponent, rivalry is personal, built through repeated encounters, similarity, and a history of closely fought results.
That is precisely what makes it so potent. Researcher Gavin Kilduff of NYU analysed six years of data from 82 long-distance runners across 112 races and found that running in the presence of a known rival increased a runner’s speed by roughly five seconds per kilometre.
In a 5K, that translates to approximately 25 seconds off your finishing time – a gain that would take weeks of structured training to produce any other way.
“How we behave in competition situations depends on our relationship and history of interaction with our opponent,” Kilduff writes in Social Psychological and Personality Science.
What happens inside your body
The biology behind this is compelling.
When you face a rival (someone whose performance genuinely threatens your sense of standing), your sympatho-adrenal system activates. Heart rate climbs.
Cortisol, the hormone associated with stress arousal and energy mobilisation, rises. Crucially, so does motivational intensity, which translates directly into output.
A peer-reviewed exercise physiology study published in the Journal of Sports Sciences put endurance-trained runners through identical treadmill tests under both competitive and non-competitive conditions and found the results striking: competitive exercise performance was significantly increased by 4.2 per cent, as was peak VO₂ response by 4.4 per cent, with cortisol responses post-exercise significantly elevated in the competitive condition – suggesting that in competitive situations, the motivational state experienced by athletes can enhance performance and lead to increased peak oxygen uptake.
That cortisol spike, which in chronic excess is harmful, is, in short competitive bursts, a feature, not a bug. It primes the body for higher-intensity output, then recedes. Done regularly, the pattern builds physiological resilience.
The rival in the office counts too
The same applies beyond sport. The professional peers whose presentations you study, whose promotions you quietly track; they are triggering the same neurological machinery.
Kilduff’s research found that rivalry increases what psychologists call ‘promotion focus‘: a forward-looking, gain-orientated mindset that drives more creative and persistent effort than anxiety-based motivation.
The sweet spot, research consistently shows, is a rival who is similar to you in ability and context, slightly ahead, and someone you encounter regularly. A distant elite is too remote to activate the circuitry. A clearly weaker opponent does nothing. It is the person one step ahead, in the same lane, who makes your biology work for you.
Pick your rival carefully. Then show up.