My training plan calls for hill repeats to help recruit fast-twitch Type IIa muscle fiber. If you are a running nerd like me, you probably already know that that Type I muscle fibers (slow twitch) are associated with endurance while Type II muscle fibers (fast twitch) are used for sprinting. However Type II can actually be broken down further into IIa and IIx. Type IIx is best suited for all out sprints while Type IIa functions more like a combination of Type I and Type IIx: they are fast-twitch like Type IIx but resistant to fatigue like Type I. Since the 5k requires both endurance and speed, this is the ideal muscle fiber for the job.
In the article Solving the 5k Puzzle (the basis for the training plan I created), Pete Magill claims that "The best way to train this intermediate fast-twitch fiber is to run long hill repeats." I will be following the progression of hill repeats laid out in this article.
week 2: 8 x 30s
week 4: 6 x 60s
week 6: 8 x 60s
week 8: 4 x 90s
week 10: 6 x 90s
I decided to aim for my tempo pace (7:00-7:15 per my 5k PR) for this workout. I figured this would be slow enough to allow me to complete the workout without crashing (uphill at 5k pace sounded way too challenging). In the end it didn't matter; 30 seconds is just not long enough to lock into a consistent pace. My paces ranged from 6:44-7:35 (avg 7:07). I'm sure as the climbs get longer and I get a better feel for this type of workout the range will narrow.
The weird part about this run was that it really wasn't a hard run. At all. My last three climbs were actually my fastest. This is due to the long recovery period between each repeat. The article recommends 4-5 minutes of recovery between each repeat! Since the climbs were just 30 seconds long and it was much too cold to walk around for 5 minutes between repeats I cut that down to 3 minutes. In the spirit of following the plan, I will increase recovery to 4 minutes for 60s climbs and 5 minutes for 90s climbs for future workouts.
I won't lie, I'm kind of in disbelief that this workout will be beneficial with such long rest periods, but Magill insists this is the right way to do things:
"Less recovery won't give us a better workout, but it will increase our risk of injury and burnout. Remember that we're targeting a specific muscle fiber type that is recruited during a specific range of effort. Too little recovery forces us to recruit the other type of fast-twitch fiber and/or to burn through our muscle glycogen stores."
I am definitely not an expert when it comes to sports physiology or even a coach. So at this point I will be deferring to the actual experts and having faith in my plan. If you are interested in what else Pete Magill has to say about the 5k, I highly recommend reading Solving the 5k Puzzle. Wikipedia has more information about muscle fiber types (including a pretty cool chart comparing Type I, Type IIa, and Type IIx). Also if anyone is feeling particularly sciency, I came across this article about mice and running and muscle fibers changing from Type IIb to IIa.
PS: Anyone else planning on watching the Olympic Trials Marathon on Saturday? I'll be cheering for the Michigan runners Desi Linden and Dathan Ritzenhein.