Ex­tra miles could pre­vent in­jury

Do the num­bers to run fur­ther and in­jury-free

Runner's World (UK) - - In This Issue - BY ALEX HUTCHINSON Alex Hutchinson is a for­mer elite ath­lete and the author of Which comes first, car­dio or weights? ( Wil­liam Mor­row)

IF YOU GET IN­JURED, you must be run­ning too much, right? Maybe not. Re­cently, sports sci­en­tists have been re­think­ing this be­lief. In some cases, hard train­ing may act as a ‘vac­cine’ against in­juries by tough­en­ing up your body, so do­ing too lit­tle can be as risky as do­ing too much. That doesn’t mean you should crank up your mileage im­me­di­ately. In­stead, fo­cus on the bal­ance be­tween how much you’re run­ning now and how much run­ning you’ve done over the past month. By track­ing this ‘acute-to-chronic’ ra­tio, you guard against the twin per­ils of too much and too lit­tle.


The acute-to-chronic train­ing ra­tio com­pares your mileage for the last week with your av­er­age weekly mileage for the last four weeks. If you’ve run 50, 40, 50 and 60 miles in the past four weeks, your ra­tio is 60 (last week’s mileage) di­vided by 50 (av­er­age of last four weeks). That’s 1.2. Re­cent stud­ies show in­jury risk climbs when this ra­tio ex­ceeds 1.2, and in­creases sig­nif­i­cantly when it ex­ceeds 1.5. This is a more so­phis­ti­cated ver­sion of the old 10 per cent rule: if you in­creased your mileage by 10 per cent each week for four weeks, you would end up with a ‘safe’ acute-to-chronic ra­tio of 1.15. But by look­ing back for four weeks in­stead of one, the ra­tio pro­tects you from over­do­ing it after pe­ri­ods of missed or re­duced train­ing, which leave you more vul­ner­a­ble when you re­sume your rou­tine.


How much you run isn’t the only fac­tor that af­fects in­jury risk – hard work­outs take a greater toll on your body than easy runs do. You can ac­count for this by cal­cu­lat­ing a train­ing load ra­tio. After each run, rate the in­ten­sity of the ses­sion on a scale from one to 10. Then mul­ti­ply that rat­ing by the du­ra­tion of the run in min­utes to get a more com­pre­hen­sive mea­sure of train­ing load. For ex­am­ple, a 40-minute run at an ef­fort level of six would pro­duce a train­ing load score of 240. Now calculate your acute-to-chronic ra­tio but us­ing weekly to­tals of train­ing load in­stead of miles.

Some GPS watches and heart-rate mon­i­tors calculate a train­ing score for each work­out based on du­ra­tion and av­er­age heart rate or speed in­stead of sub­jec­tive ef­fort. These are also good op­tions for track­ing acute-to-chronic ra­tio, if you stick to one mea­sure for con­sis­tency.


You can think of a ra­tio of 1.2 as an am­ber light and 1.5 as a red light. But ev­ery run­ner is dif­fer­ent, so what ap­plies to the ‘av­er­age’ run­ner may not ap­ply to you. This ap­proach will be most valu­able if you keep track of your chang­ing ra­tios over sev­eral years while mak­ing note of in­juries – not just ma­jor ones, but also mi­nor pains. Even­tu­ally, you’ll dis­cern patterns that tell you which ra­tios your body can tol­er­ate and which ra­tios trig­ger prob­lems.

The ob­vi­ous time to be care­ful is when you’re push­ing your mileage or in­ten­sity; keep­ing the ra­tio low will help you do it safely. But watch for patterns at the low end, too. You might find, for ex­am­ple, that when­ever you let your mileage drop be­low 20 miles for two weeks in a row, your acute-to-chronic ra­tio spikes a few weeks later when you get back to nor­mal train­ing – and that you of­ten get in­jured as a re­sult. You can’t al­ways avoid in­juries, but by look­ing for patterns, you can at least avoid mak­ing the same mis­take twice.

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