Dr. Lim,

My question is about the heart rate vs. power? I’ve noticed that after a series of hard workouts that it becomes more difficult to raise heart rate in the various zones, however, power output (while difficult) is generally maintained. Is this a typical physiological response? If so, it seems counter intuitive; as I would expect heart rate to rise above various zones after a series of hard workouts. Given this situation, is heart rate a valid measurement for training (or racing)?

Thanks,
Bruce

Bruce,

Your observation is quite typical. Heart rate can vary quite a bit for a given power output within a ride and between rides.

Generally speaking, as you become more fit, your heart rate response for a given power output will decrease. Your experience of a blunted heart rate response over several hard days, while not in the same category, may still have several explanations.

First, if you are riding in the heat or if that first hard workout occurred in the heat, it is possible that your body has simply increased its plasma volume. This is an adaptive response that can happen within a day or two after high intensity exercise. As a result, your cardiac output or the total amount of blood ejected by your heart would remain the same despite a lower heart rate.

Another possibility is that after your first hard workout, you are getting better peripheral blood flow to your legs. This can happen after an initial hard bout of exercise as your blood vessels become more sensitive to local factors that cause those vessels to dilate. Thus, you would be able to maintain the same level of oxygen delivery at a potentially lower cardiac output or heart rate.

Another possibility is that your heart is pumping with stronger force allowing the same output at a lower heart rate.

Yet another possibility is that you are producing the same power output using more anaerobic energy sources over the workouts. Temperature is also another important factor.

Ultimately, there are so many factors that can affect your heart rate response for a given power output that it can be a poor or inaccurate measure of exercise intensity. That said, heart rate is not an inaccurate measure of one's response to a given exercise intensity. Although it is difficult to interpret what those changes in heart rate mean, they are worth noting, especially relative to yourself.

Ultimately, the bottom line is that if you can produce the power output, you shouldn't worry too much about whether your heart rate response is high or low, just that it's doing something that is normal for you.

Allen

In the [Stage 4] time trial, it looked like some riders were close to spinning out on the very fast tailwind return section. What kind of gearing were guys running? Should they have taken something a little steeper so as not to run the risk of spinning out? What were the kinds of power seen into and with the wind?

-dB

DB,

The guys were running 56 x 11 as their hardest gear. Generally, speaking if a rider is at a point where they are spinning out that particular gear -- for example -- on a slightly downhill tailwind section -- they can go even faster if they tuck and coast. So we don't often worry about trying to max out the gear past the 56 x 11 unless their are lengthy and extended sections of downhill tailwind. The optimal pacing strategy over undulating terrain occurs when the guys adopt an uneven power profile, going harder over the hills and floating a bit on the descents or fast sections. This pacing strategy also works for head winds (higher power) and tailwinds (lower power). For our riders, they averaged 400 to 500 into the wind but only 350 to 420 with the wind.

Allen

Hello!

Is there a reason why Christian Vandevelde and David Millar did't use their Power Tap Hubs on Stage 9 and 10?

Thanks
Klaus, Austria

Klaus,

Our bikes this year didn't make the minimum weight of 6.8 kg, so the PowerTap, at a 250 gram weight penalty, was sacrificed to save weight for those stages. Normally, this isn't a problem, but we are running some heavier equipment this year for durability and stiffness. The guys are definitely missing the data at times, but the work is done and right now they are primarily focused on doing the best they can and maintaining a level playing field with respect to bike weight. It's an unfortunate compromise for the moment. One that shouldn't be a problem in the future.

Allen

Hi Allen,

I really enjoy your reports. Your know your stuff and know how to write.

Ignore this question if it’s inappropriate. But I think being involved with the cleanest team in the sport, you are uniquely qualified to answer. Besides…curious fans want to know. Can careful analysis and comparison of wattage profiles and VAMs from different races point to oxygen-vector doping or at least suspect one?

Thank you much.
David from NYC.

David,

Theoretically, this is a real possibility and quite similar to the biological passport program, where we look for unusual or statistically unviable changes in one's blood profile or performance. In my mind, this is the ultimate bottom line in detecting doping. The problem is for this to be statistically viable, we would need all the power data from a given athlete. I mean all. Every day of training and every race. This may be possible as the technology improves and something we hope to begin experimenting with next season.

Allen