Michael Mosley

Focus-Science and Technology - - CONTENTS - DR MICHAEL MOSLEY Michael is a science writer and broad­caster, wwho presents Trust Me, I’m m ADoc­tor on BBC Twwo. His lat­est book is The Clever Guts Diet (££8.99, Short Books).

Is run­ner’s high a real thing?

Spring is the time when fair-weather run­ners like me pull our train­ers out of hi­ber­na­tion, dust them down and re­luc­tantly start run­ning again. I say ‘re­luc­tantly’ be­cause I don’t en­joy run­ning. I do it be­cause I re­alise it is good for my lungs, my heart and my brain. I also do it be­cause I am wor­ried that soon I won’t be able to keep up with my wife. But I don’t, at any point, get plea­sure from it. I cer­tainly don’t ex­pe­ri­ence the in­tense plea­sure that many avid run­ners de­scribe as ‘run­ner’s high’.

I was cu­ri­ous about what was go­ing on, so as part of a re­cent pro­gramme for BBC One, The Truth About Get­ting Fit, I de­cided to find out more.

For a long time, the pos­i­tive feel­ings that run­ners de­scribe has been put down to en­dor­phins. These are pep­tides that our bod­ies pro­duce which ac­ti­vate opi­oid re­cep­tors in the brain. But phys­i­ol­o­gist Dr Saoirse O’Sul­li­van be­lieves a dif­fer­ent brain sig­nal may be re­spon­si­ble: a class of chem­i­cals called en­do­cannabi­noids. These mol­e­cules are neu­ro­trans­mit­ters that are sim­i­lar in struc­ture to the main chem­i­cal in cannabis. They bind to cannabi­noid re­cep­tors through­out the body, in­clud­ing the brain.

To see if en­do­cannabi­noids re­ally do rise in the blood of run­ning en­thu­si­asts, we asked O’Sul­li­van to help us do an ex­per­i­ment which, as far as we could find out, had never been done be­fore. We got a small group of en­thu­si­asts to go for a short run, only half an hour, out­doors. Pre­vi­ous ex­per­i­ments have in­volved much longer runs in a lab set­ting.

So what did we find? Well, once their blood was an­a­lysed it was clear that even a short run had had a strik­ing ef­fect. “When you came back from the run, you had, on av­er­age, 30 per cent more en­do­cannabi­noids in your blood than you did be­fore you set off,” O’Sul­li­van told our vol­un­teers. “So that ex­er­cise, short though it was, re­ally does seem to have led to a big in­crease in en­do­cannabi­noids.”

One of our run­ners, a wo­man who suf­fers from se­vere bouts of de­pres­sion, had a par­tic­u­larly marked re­sponse. She is aware of the pro­found ef­fect run­ning has on her mood and has been us­ing it as a form of self­med­i­ca­tion for some years now. She is a keen marathon run­ner and is now pro­gress­ing to run­ning ul­tra marathons.

So even a short, easy run can bring some peo­ple a nat­u­rally pro­duced chem­i­cal high. But why do we have this sys­tem at all? O’Sul­li­van be­lieves the re­lease of en­do­cannabi­noids may be a way for our bod­ies to en­cour­age us to keep fit. “We know that we’re men­tally and phys­i­cally health­ier when we ex­er­cise. So the body hav­ing an im­me­di­ate re­ward sys­tem for ex­er­cise would seem like a good evo­lu­tion­ary thing,” she says.

That still doesn’t ex­plain why some peo­ple get a run­ner’s high while oth­ers don’t. The next step would be to take a group of peo­ple who don’t en­joy run­ning, like me, make us run and see what ef­fect, if any, that has on our en­do­cannabi­noid lev­els. It could be we don’t pro­duce as much, it could be we don’t have such sen­si­tive re­cep­tors, or it could be we don’t push our­selves hard. I’m up for find­ing out. Any other ex­er­cise sloths care to join me?

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