Monday, September 9, 2019

Don't believe everything that you read.

Leave it to Twitter to get me riled up. A tweet caught my attention a few days ago. It read:

"Greater improvements in cycling performance parameters following HRV-guided vs. block training."

I was intrigued, so I read the abstract. I didn't have access to the peer review journal at the time, but I could see in the abstract, "Between-group fitness and performance were similar after the study."

So I called out the original "tweeter," saying there was no statistically significant difference between the two groups. Claiming one is superior, misrepresents the study's findings. By this point I noticed the individual is a  professor and researcher and maintains a blog devoted to heart rate variability (HRV) research - which surprised me. If he's a professor, surely he understands statistics - I couldn't help but think he was misrepresenting the findings to support his bias in favor of  HRV-guided training...

After I pointed out there was no difference in performance between groups, the tweeter responded with a screen shot of a figure from the paper:


From the figure, yeah - it looks like HRV-guided training does outperform block periodization... but looks can be deceiving. Again, there is no statistically significant difference between the two groups. You can't say that one training method is superior to the other. So that's what I said - Where's the difference?

The original poster, responded:

"One group showed a mean time trial improvement of ~6%, the other, ~3%. If I’m investing the same time and effort into training either way, I’d opt for the method that might give me an extra 3%."

And most people would agree - Who doesn't want an extra three percent?

But it doesn't work that way - we don't know if that 3% difference was due to error or random chance. If the experiment was done again, you may very well find a different result. The difference between the groups was not great enough to be statistically significant. You'd think a PhD educated professor would understand that. And you'd hope he wouldn't misrepresent research to support his own bias for HRV gadgets and training.

This is all public, you can check my Twitter if you have nothing better to do. I don't have any animosity towards the individual, and this is not a critique of HRV-guided or block periodization - I just wanted to take the opportunity to remind people to be critical and don't believe everything that you read.

Bert

Tuesday, September 3, 2019

Different Disciplines, Different Tapers?

When I was at Appalachian State, Dave Morris had us read all about glycogen, glucose and carbohydrate. I still remember reading about how muscle damage can impact muscle glycogen resynthesis. That is - the replenishment of glycogen stores in skeletal muscle following exercise.

Muscle glycogen is a glucose polymer that is stored in muscle cells. When you exercise, particularly at high intensities, it's the primary substrate used to create ATP. Maintaining or preserving glycogen stores can delay fatigue and even preserve economy.

Given glycogen's positive relationship to endurance performance, athletes and coaches often employ tapers in an attempt to maximize glycogen stores prior to competitions. But as Costill et al. noted back in 1990, glycogen resynthesis may be inhibited following muscle-damaging eccentric exercise.

Eccentric exercise is any exercise that involves "active lengthening" of muscle fibers. Sports that include running, and jumping are eccentric dependent. With running - every footstrike requires absorbing an impact through active lengthening of muscle fibers. That lengthening action can damage the muscle. And little by little, as your run progresses, you accumulate more and more muscle damage. It's not necessarily a bad thing - the muscle will repair itself. But the damage may be evident when you're sore the next day. This damage and the subsequent inflammation may inhibit glycogen resynthesis.

When compared to running, cycling and swimming do not rely nearly as heavily on eccentric muscle contractions. That's one reason why cyclists spend so much time on their bikes - fewer eccentric contractions, less muscle damage, less soreness...

So then, how could this knowledge of muscle damage and glycogen resynthesis impact how the runner, cyclist, and multisport athlete approaches a taper?

Perhaps the runner should take a longer or more aggressive taper than the cyclist. This way, the runner would incur less muscle damage as the important competition approaches - ensuring that glycogen resynthesis is not negatively impacted. And the multisport athlete may want to reduce running volume more aggressively than his/her cycling and swimming volume.

If you're interested in reading more about glycogen resynthesis, I recommend you check out this review by Burke et al.

-Bert