QUICK SCI­ENCE

Study iden­ti­fies a pro­tein that can ei­ther build mus­cle or aer­o­bic ca­pac­ity

220 Triathlon Magazine - - CONTENTS -

Sci­en­tists in Amer­ica have iden­ti­fied a new ‘mus­cle switch’ that in­flu­ences the ben­e­fits of ex­er­cise. The team stud­ied ro­dents and then hu­mans over a pe­riod of ex­er­cise and dis­cov­ered that a pro­tein, c-Jun N-ter­mi­nal ki­nase (JNK), stim­u­lates the in­di­vid­ual’s re­sponse to training. If JNK is ac­ti­vated dur­ing ex­er­cise, it drives mus­cle growth; if it’s not, mus­cles im­prove their adap­ta­tion for en­durance and aer­o­bic ca­pac­ity. Key to JNK’s role is its im­pact on the mus­cle sig­nalling path­way myo­statin, with reams of re­search show­ing high lev­els of myo­statin help boost en­durance per­for­mance; low lev­els are as­so­ci­ated more with mus­cu­lar force. The team showed that in­hi­bi­tion of JNK in­creased myo­statin sig­nalling, re­sult­ing in greater en­durance gains. How­ever, lev­els of JNK var­ied be­tween sub­jects, sug­gest­ing dif­fer­ences are down to me­chan­i­cal stress on the mus­cle. This means while some triath­letes might pro­duce high lev­els of JNK from long, slow runs, oth­ers will en­joy greater en­durance gains from in­ter­vals. Ex­pect DNA com­pa­nies to add JNK to their ge­netic list very soon.

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If only per­for­mance im­prove­ment was as sim­ple as flick­ing a switch – well, thanks to a re­cent U.S. study, it looks like it fi­nally is!

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