27 January 2013

An attempt to run a marathon using SCIENCE: part IV (Cross training)

(I was going to cover muscle recovery in this post, until I realised this would mean getting to grips with ice baths. There's been so much ice outside the house this week, that I couldn't quite contemplate sitting in a bath of it inside. So that's postponed for warmer weather...)  

In the last week and a half, I have been forced to try OTHER sports besides running. This has led me to two conclusions:
  • I am ill-equipped to do other sports.
  • Swimming pool timetables are worse than third-year-of-a-biology-degree revision timetables.
Some people refer to training in other sports besides your "primary" sport as "cross-training". I refer to it as a pain in the bloody backside. It all began with the snow - when it hit a week ago on Thursday, I decided I could probably take a day or two off from running to rest various niggles. By Sunday, the roads were still skating rinks. There was to be no traditional Sunday long run and I had been reduced to pacing around the house like a caged animal. It was time to hit the pool.

The first problem was that I didn't have a swimming costume, which meant swimming in a mismatched bikini that I had to tie on so tightly it hurt. The second problem only became apparent after about four lengths - the stretchy rubber strap on my 15-year-old pair of goggles had stopped being stretchy and pretty much disintegrated as soon as I tried to tighten it. Mr Hayley, who had been cajoled into joining me for a swim, was made to share his pair, which meant stopping to hand them over every four lengths or so.

The ice continued to hang around, leaving me no choice but to persevere with the cross-training regime. I found myself at a 7.00am "group cycling" class, cycling to tracks from Big Willy Style... oh yes. And then back at the pool again on a Saturday morning, only to be told that adults aren't permitted to swim on Saturday mornings. After driving to three different swimming pools, all with similar anti-adult policies, we decided we'd emitted enough carbon for one day and went for a big, fatty-fat-fat breakfast to make up for our disappointment. At least we now have two pairs of goggles and a timetable for every swimming pool within a five-mile radius.

Anyway, this post is primarily about the scientific basis for cross-training, so I'll get on with it. Actually, there seems to be very little to support the idea that cross-training in other sports complements endurance running - at least in terms of performance. This New York Times article summarises the current state of research on cross-training, which is based on a few small studies from the nineties, most of which didn't last longer than a few weeks. The general consensus seems to be that although you can maintain a decent level of fitness by substituting runs for cycling or swimming sessions, the only thing that is going to make you really good at running is doing a lot of running.

In one 1994 review, a researcher at the University of Tennessee concluded that athletes (and ordinary folks) never see any greater benefits from cross-training than they do from their main sports. There may be some transfer of aerobic capacity between running and cycling, but less with swimming. Boo. Another study took the interesting approach of comparing physiological adaptations between runners and cyclists. Intriguingly, an athlete's ability to use oxygen, measured as VO2max (based largely on heart and muscle adaptations, see posts II and III), was specific to their individual sport. So a runner would be able to achieve a higher VO2max on a treadmill, whereas a cyclist would be able to achieve a higher VO2max on a bike. This hints at just how well our bodies are able adapt to different sports. BUT, it turns out triathletes have pretty similar measurements on both treadmill and bike, reflecting the fact that they train regularly on both.

So my cross-training probably hasn't made me any better at running. On the other hand, that wasn't really my expectation. I was trying to ensure that I didn't lose any fitness during my marathon training regime, and to protect a dodgy ankle from pounding on hard ground. My best guess based on limited literature is that my running fitness would take a few weeks to drop off, and that swimming, and certainly cycling, would go some way towards slowing that drop-off. But what about protecting my dodgy ankle? According to the Tennessee guy:
"...cross-training may be an appropriate supplement during rehabilitation periods from physical injury and during periods of overtraining or psychological fatigue"
Okay. Good. But note the "may" in this sentence. It seems common sense to me that if you're reducing your weekly mileage on the roads, you're less likely to get injured (this study on injuries in high school runners and this one on risk factors for running injuries come to tentatively similar conclusions) but I can't find any evidence to suggest that adding cross-training to an already demanding running schedule will stop you doing yourself a mischief. And perhaps surprisingly, this very small study appears to suggest that running and cycling take an equal toll on your feet, thus throwing my early morning Big Willy cycling sessions into jeopardy...

All this contradicts a lot of what I have been reading in marathon training plans, which seem to suggest that cross-training should form a big part of your weekly routine. I'm not convinced it does that much good, besides giving your body a bit of a break from punishing work outs on hard pavements. I think I will continue with one swim a week (not on Saturdays) just to see what happens. But otherwise, how about a leisurely stroll, a lie down on the sofa or a big fatty-fat-fat breakfast?

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