Monday, June 17, 2013

Taking aerobic training too far.

Alan Couzens, MS (Sports Science)

“There is no secret to balance. You just have to feel the waves” – Frank Herbert
In my last couple of articles for the Endurance Corner website I looked at typical (& atypical) long term physiological development patterns of triathletes.

Pattern 1 (usually young)

-          Young, untrained athlete begins chronic endurance training (often with a view to Ironman) but observes an initial relative strength over shorter distance events.
Pattern 2 (usually older)

-          Older athlete begins chronic endurance training (also often with a view to Ironman) and notices an immediate relative strength over the long stuff.
At first glance it might appear that the old guy has exactly what the young guy wants, i.e. good long duration endurance. However, this ignores one important point…

Fiber type conversion and atrophy of your fast twitch fibers ain’t the same thing!
A natural side effect of the aging process is an atrophy of muscle fiber size (& consequent strength). This is most observed in the larger fast twitch fibers. This leads to the better endurance relative to strength and speed trend that we noted above. Older athletes have less ability to ‘fire’ and to train these fast twitch fibers when they are ‘out of the rotation’.

A too often forgotten truth in endurance training is that it takes a level of anaerobic capacity to fully access an athlete’s aerobic capacity. A specific example of this can be found in the criteria for assessing a ‘true’ VO2max (vs a ‘VO2peak’) is a blood lactate level at or above 8mmol/L. Interestingly, studies on this criteria have found that even 8mmol/L is often insufficient to achieve a VO2 plateau. In other words, to access & train these ‘mixed’ aerobic/anaerobic fibers requires the anaerobic capacity to hit a max lactate of at least 8mmol/L – a capacity that may be missing among older athletes.
Elite long course athletes exhibit a similar pattern as their FT fibers begin to take on ST characteristics. However, the difference is that the total muscle mass recruited (& consequently the total power) over these long durations is preserved & is thus far greater in the elite.

Summarizing the above, a less desirable side effect of the whole aging process for the endurance athlete is that the size of the ‘trainable muscle pool’ is diminished. For this reason, when we see a developing athlete with very strong long duration numbers, we also tend to see an athlete with a blunted training response.

When this athlete is approaching the limits of their genetic potential, this kind of specific adaptation might be a good trade. However, for the athlete who is still improving, taking the wrong turn at this fork in the road can severely compromise their potential.

A visual example of this is shown in the 2 lactate/VO2 curves shown below. Both are very good (but still developing) Ironman athletes with PR’s under 9:30. One is in the 45-49AG, the other is in the 25-29AG. Can you guess which curve belongs to which athlete?

The left side of both curves is very similar. Both exhibit similar power numbers at the aerobic threshold (~2.5 w/kg in this case) & just above it. Unsurprisingly, this translates to a similar performance level over the Ironman distance.
However, beyond this point, the curves start to separate. The increased anaerobic capacity of the younger athlete becomes apparent. This anaerobic reserve translates to a difference in max/peak VO2 numbers of 4ml/kg/min & a difference in peak power output of 1 w/kg.

Also, the older athlete fails to reach a VO2 plateau. Put another way, he lacks the anaerobic capacity to bring in the higher threshold ‘mixed’ muscle fibers to fully tax (/train) the aerobic system. If we extend the older athletes curve to the 8mmol mark we see a similar max power level to the young curve and a VO2 plateau becomes far more likely.
Most importantly, for 2 athletes with further Ironman ambition, the older athlete has an AeT of 56% of their peak power output while the younger has an AeT representing only 44% of their peak power output, i.e. room to grow!

The take home messages from this article…..

1.       Take the time to ‘check in on’ the athlete’s anaerobic capacity during base training. The ability to generate a maximal lactate of at least 8mmol/L (or a CP5 of ~1.15x CP20) should be preserved during general prep. For most athletes this balance will occur naturally with a little bit of ‘spice’ added to a normal base program (as described in the EC article) but for older or higher volume athletes, it may not.

2.       For developing athletes who are lacking this ability, it is a wise investment to insert a block (or 2) of training within the preparation, focused on re-building this anaerobic capacity while maintaining the athlete’s aerobic numbers & total training load. Often an improvement in the training response to the aerobic load will be noticed after a brief ‘switch up’.

Train smart.


Unknown said...

Hi Alan. I realize you wrote this way back in June, but I'm only getting around to reading it now. I'm 55 and have been doing triathlons for 4 years now. I am pretty sure I fall into the category you described. When I do time trials for both running and cycling, my predicted performance for longer duration races ends up being worse than my actual performance. So, I am going to spend some time focused on improving my anaerobic capacity.

I am wondering if there is any relationship to max heart rate and limited anaerobic capacity, i.e., does the fact that I cannot reach my VO2 max plateau also imply that I am not seeing a true max heart rate? I ask because I think my observed max heart rates for running (158bpm) and cycling (150bpm) are pretty low.


Alan Couzens said...

Hi Dan,

Yes, I have seen that, i.e. an improvement in max HR (that goes along with an improvement in max lactate) in some athletes after they complete a cycle of anaerobic work.

Isn't true of all athletes with a low max HR but given what you said about long v short races, may be true in this case.