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Friday, December 04, 2009

Another Article Debunking Lactic Acid Myth - Sodium-Potassium Pump!

I found this article in the latest email newsletter from www.roadbikerider.com (whom i thought i'd unsubscribed from, but then a couple weeks ago started getting newsletters again..) There was actually an interesting article, progressing the ideas of what causes muscle fatigue (aka not lactic acid, see here for an article i put together a while back on the subject, and how lactic acid ISN'T a bad thing.)

Read on, discussion welcome!
Does Interval Training Improve Endurance?

No doubt about it, according to a new study published in the November issue of the Journal of Applied Physiology and reported by cycling physician Gabe Mirkin, M.D., in his weekly ezine (available at http://www.drmirkin.com).

We're pleased because the findings underscore a training approach long promoted by RBR's Coach Fred Matheny. Here's an overview:

Dr. Jens Bangsbo of the University of Copenhagen asked competitive distance runners to reduce their mileage by 25% but add 8-12 half-minute sprints 2 or 3 times per week. They also ran fast repeats of 0.6-0.8 miles (1-1.3 km) 1 or 2 times per week.

Meanwhile, a control group of runners continued what was basically long, steady distance training.

After 6-9 weeks, the control group showed no improvement. Runners in the intervals group, however, improved both their 3-km (1.8-mile) and 10-km (6.1-mile) race times by more than 3%. Half of them ran their best times ever, even though they'd been racing for more than 5 years.

That's remarkable improvement after only about 2 months of interval training.

Two years earlier, Dr. Mirkin reports, Dr. Bangsbo had done ground-breaking research supporting the theory that exhaustion of the "sodium-potassium pump" (not lactic acid buildup) is the major cause of muscle fatigue during exercise.

Now in his new study, Dr. Bangsbo shows how interval training improves a muscle's capacity to pump potassium back inside muscle cells during exercise. This helps athletes run or ride faster even in very long events such as marathons and multi-day bike rides.

Dr. Mirkin explains that a muscle can contract only if it has an electrical charge across the muscle cell membrane. This electrical charge comes from having sodium primarily outside the cell and potassium primarily inside the cell. These higher concentrations are maintained by the sodium-potassium pump in the cell membranes.

Dr. Bangsbo showed that during rapid contractions, muscle cells lose potassium so fast that it's doubled outside cells in less than a minute. The pump is overwhelmed. This reduces the electrical charge between the inside and outside, so muscle cells contract with much less force until finally they cannot contract at all. 

Now here's the good news. Repeated muscle contractions can increase the ability of the pump to put potassium into cells. The greater the force on a muscle during training, the more effectively the pump can do this. It's why a training plan that increases the number of intense efforts will give an athlete greater endurance.

How to Apply these Facts

You cannot gain maximum endurance just with continuous steady exercise, says Dr. Mirkin. It's also a message found in various RBR training eBooks written by Coach Fred, Coach David Ertl and Arnie Baker, M.D.

To improve your sodium-potassium pump, you need to put some serious force on your muscles. And probably the "easiest" way to do it is with interval training (although hard climbing and time trialing can work too).

Of course, Dr. Mirkin cautions, intense exertion can kill a person who has blocked heart arteries. You should get your physician's permission before increasing hard efforts.

Once cleared, you can do intervals on the road or on a trainer. There are 2 basic types for this discussion:

---short intense efforts of 30 seconds or less

---long intense efforts of 2 minutes or more

"Intense" is for you to decide. It's possible to ride as hard as you can for half a minute, but the effort can't be quite as great when going longer.

Dr. Mirkin recommends 30-second intervals once or twice a week. Do 6, 8, 10 or more sprints during a session, then follow with a short, easy recovery day.

Because long intervals of 2+ minutes are more stressful, you can't do as many during a workout or do them as often. You may need 2 days of easy riding for recovery.

Rest Intervals

Athletes usually learn their ideal between-effort rest interval through experience, notes Dr. Mirkin.

You may want to rest until your pulse drops enough for you to begin to feel comfortable. Or until you're able to slow your breathing rate towards normal, or until your muscle discomfort begins subsiding. But don't wait for complete recuperation before going again.

Between interval workouts, if it takes longer than 2 days to recover you are probably riding too intensely, doing too many repetitions, or your rest intervals are too short.

Weekly Training Plan

In Dr. Mirkin's view, based on Dr. Bangsbo's research and his own cycling experience (he's 74 and a dedicated roadie), a weekly endurance training program should include a good amount of relatively slow miles, 1 or 2 workouts with numerous short intervals, and perhaps one workout that includes several long intervals.

So that's that - something new for me.

Have a good weekend of riding!


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    Dave Shishkoff
    aka Dave Noisy
    Victoria, BC

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