Friday, May 7, 2010

Is your workout effective? Part 1: Anaerobic Workouts

When I was younger I would often wonder if my workouts were effective at making me faster. Now I've been running long enough and read enough that I know when the workout is done if it was effective or not.

Anaerobic workouts are workouts run faster than a pace you can maintain for about one hour. This is often called speed work, repetitions or intervals. In general this is 5k race pace, 10k race pace, mile race pace, or 3k race pace type of running. What is occuring is that lactic acid is accumulating in your legs faster than it is being flushed out. Now lactic acid alone is not a bad thing. For a trained person the body will respond to lactic acid by working to use it and flush it out so that it is possible to maintain a fast pace longer.

The goal of anaerobic workouts are two things:
  1. Teach your body to accumulate lactic acid and flush it out so that you can maintain a fast pace longer by flushing more of the lactic acid out as it comes in. This is accomplished running intervals and repetitions where it is usually possible to run farther than the race distance at race pace. For example 6 x 1000 meters at 5k pace.
  2. Teach your body to use as much aerobic respiration as possible so that there is less accumulation of lactic acid. This is accomplished through long repetitions or short tempos. For example a 5k tempo at 10k pace. Every distance event from the 1500 meters on up is mostly aerobic.
Anaerobic workouts should feel like your legs are going faster than your lungs can handle. Near the end of the workout your legs should get heavy like they are made of lead. There comes a point when your legs have accumulated so much lactic acid that your speed slows down considerably because you can not accumulate any more lactic acid. This is "hitting the wall" in the shorter events. I have had a particularly hard time in the past with the 5k. I would often get two miles in at the pace I thought I should be running and then my legs were just too heavy and I slowed down. In my best races the feeling of too heavy legs to push any harder came in the last 400 meters. At that point there is so little left that it is not hard to get to the finish.

Lydiard suggested running anaerobic repetitions on a loop that you didn't know the distance, didn't time them, and not even counting how many you did. The reason being that you keep doing the workout until you get that feeling of lead legs like you encounter in a race. Fartleks are run on the same principle. (Fartlek is Swedish for "speed play" which means periods of fast running and periods of slower running.)

Now one final consideration of anaerobic workouts is race specific endurance. This is also known as sharpening. These are the workouts done in the last month or two before the goal race. For these workouts running on a track or loop of a known distance and timing them is important. These workouts are used to judge what pace you should be racing at your goal event. That is to say that if you can not run 4 x 400 at 65 seconds in practice chances are low that you will run 4:20 for a mile. Although factors such as running alone versus in a pack, running on dirt instead of a rubber track, running at altitude, and even accumulated stress such as weekly mileage can be taken into account when deciding on race pace and how much race pace specific work needs to be completed.

The feelings that should occur during these workouts are something along the lines of very heavy legs, hard breathing, and a generally unsustainable feeling of running. Anaerobic workouts are like a slow sprint that keeps going. It starts out feeling awesome to run as fast you are running. However it soon enough becomes a difficult endeavor. The fun wears off as breathing becomes harder and your legs get heavy. The workout has accomplished it's goal when so much lactic acid has accumulated in the legs that it can not be flushed out in a reasonable time. For example, if the workout is 400 meters hard and 200 meters jog repeated, the first few will feel easy, then several will go by with a sort of glaze without talking or much thinking, then near the end the last 50-100 meters of the 400s will feel harder. The last 400 of the workout ends with the legs more heavy than any of the previous 400s. However, the actual time of the 400 may range from the fastest of the session to the slowest by a few seconds.

The workout should not be extended to the point where the pace is more than 5% slower than desired. In fact, any more than 2% slow, excepting for weather and other conditions, is cause for concern. Sometimes a workout needs to end early when the paces are just not being hit. Stress, lack of sleep, and other emotional factors can greatly affect running. 

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