"Never be limited by other people's limited imaginations. If you adopt their attitudes, then the possibility won't exist because you'll have already shut it out." -Mae Jemison, astronaut

Saturday, August 18, 2012

Be Prepared...to cut holes in your shoes?

I'm back in Kent, England, after 3 weeks of amazing training in Canada. I shed a few tears on parting with some of my favourite people and a pretty special place in the world.

Now it's taper time. To compensate for the decrease in hills and distance, I'm putting a little speed into my life. All legal, of course! The speed is a nice way to keep burning a decent number of calories whilst running less (I eat non-stop as it is now) and keeps the legs feeling good.

Coming in for a landing!
Last night I went out to a measured UKA 5k race as part of the "Rye Summer Classic Series." The race was about 45 minutes away on the coast. I wasn't expecting too much of myself for the race, considering I'm enjoying my 2 "bonus" kg this season and haven't been able to do any speed work since before the Bib run in November (due to the compartment syndrome after-effects). It was a highly competitive race, perhaps because of it being an evening race and as there are a few good prizes - including a trip to race in France for the Series winners!

I ran a PB! 20:32 was my fastest ever (track) and I ran 20:10! Naturally, track is slightly slower than road since you have to turn more, but it wouldn't make this much difference. The result was very encouraging towards my hopes of going for 50k W40 records in late November (after more speed work and dropping a kg or two, of course).

For now, I'm back to enjoying my TransAlps prep.

I found a few minutes to poke around the research for any gems.

One paper that's just come out suggests you might want to take a pocket knife to your shoes and carve some holes! This just came out in Medicine & Science in Sports & Exercise (Franz, Wierzbinski & Kram, 2012) and is titled "Metabolic Cost of Running Barefoot versus Shod: Is Lighter Better?" It's been known for a while that every 100g added to shoes increases oxygen uptake during submaximal running by 1%. But there was a question of whether this had anything to do with foot landing/striking patterns - after all, put most people in shoes and they heel strike.

Generally, this might mess with your running speed more than shoe weight!
So, they took "midfoot strikers" (whether shod or not) and compared the power and oxygen costs of running with weight on their feet. The interesting thing was that they made sure all runners were midfoot landers regardless of whether they had shoes on or not and they measured their power and oxygen use when barefoot, when barefoot with lead weights on their feet, and with shoes. They found that there was no advantage in power/oxygen use to being barefoot. In fact, their findings (a 3.3% increase in stride length when shod) suggested that barefooters use shorter, faster strides, which increases oxygen uptake and metabolic power.

They then took their data and worked backwards....at what ideal weight would shoes be (for these 75kg 179cm runners) where the metabolic demand would be lower shod than barefoot? The answer: 129g.

Start trimming!

Be Prepared! Such good advice for an ultra runner.
This got me thinking about other predictors of running performance. So I had a quick scan through some literature on ultrarunners and found several studies looking at predictors for 100mile/24hr-type performance. One study (Knechtle et al, 2009, Br J Sports Med) found that they could not predict runners' distances at the Basel 2007 24hr race by using volume of training, years of running, age, skinfolds, or skeletal muscle mass. The only predictor was marathon time. That's something I was always basically told to discount! Another Knechtle et al study from 2011 (J Strength Cond Res) found that marathon time (sub 3hr 20 noted) and length of longest training run (60km noted) were the two predictors for a 24hr race they analysed. They came up with a lovely equation which I tried using and it was completely inaccurate - on the low side. So much for that.

But I'll stick with my racing flats and speed work, even if I can't get precise predictors. The arrow is wide, but I can see what direction it points ;)

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