Skip navigation

Tag Archives: maximal oxygen consumption

Individuals with Down Syndrome, especially as they age, tend to be characterized with obesity, health-related problems from that obesity, poor fitness, a reduced physical work capacity, as well as hyperflexibility and low muscle tone.  In the latest issue of Exercise and Sport Sciences Reviews, Fernhall et al discuss the cardio-vascular impacts of Down Syndrome and the impact of exercise training on this.

 

The authors begin by discussing the low work capacity (i.e. maximal oxygen consumption) of individuals with Down Syndrome (DS):

·      Individuals in their 20’s with DS have a maximal oxygen consumption equivalent to a 60-year old without DS.

·      Maximal heart rates in people with DS are typically 25-30 beats/minute below that of people without DS.

 

What causes these?  The authors note that this is not due to congenital heart disease due to the fact that the studies examining this exclude people with congenital heart disease.  Traditionally this has been thought to be due to a lack of understanding/comprehension and a lack of motivation on the part of people with DS.  However, the authors report that with training individuals with DS can take a maximal oxygen test on a treadmill and produce consistent results, so understanding and motivation are not issues. 

 

Other possibilities are a lack of physical activity or obesity.  Interestingly, the authors report that while the DS population is sedentary it is not more so than the general population.  Based upon the authors’ research, 8-10 hours of week of training still result in unusually low work capacities.

 

In the non-DS population, as we age we tend to accumulate more body mass.  As this happens our work capacity declines.  In the DS population, as they age they also accumulate more body mass but their work capacity remains constant.  According to the authors, maximal oxygen consumption remains in the mid twenties (ml/kg/min) for people with DS between the ages of 9 and 45; whereas for the non-disabled population (on average) it changes from about 45 ml/kg/min to about 35 ml/kg/min over that same age range. 

 

All of this combined suggests that understanding, motivation, obesity, and activity level are not the culprits of the reduced work capacity seen in individuals with DS.  While this is oversimplifying the discussion somewhat, essentially the authors report that a combination of the brain’s control over heart rate and a reduced production of catecholamines (for example, epinephrine) are the likely culprits behind this reduced work capacity.    In other words, due to the brain’s regulation a person with DS has a lower heart rate, which has an impact over their ability to supply oxygen to their body, which reduces their ability to perform long, strenuous exercise.

 

The authors report that exercise helps with this.  I wrote an article a number of years ago about exercise and Down Syndrome, and at the time (and even today) there was little research on this.  The good news is that exercise helps individuals with DS just like it helps individuals without DS.  The challenge is that parents, siblings, caregivers, and individuals working with someone with DS need to be cognizant of these limitations because they impact motivation and require creative ways to address the fitness of a person with DS. 

 

Fernhall, B., Mendonca, G.V., and Baynard, T.  (2013).  Reduced work capacity in individuals with Down Syndrome: A consequence of autonomic dysfunction?  Exercise and Sport Sciences Reviews, 41(3), 138-147.

 

 

Advertisements

Jason Karp had a great article in the November issue of Techniques, which is the publication put out by the U.S. Track & Field and Cross Country Coaches Association. Dr. Karp writes for everything from peer-review journals to coaching publications like Techniques and Track Coach dealing primarily with distance running. I enjoy his writing even though I don’t work with distance runners.

In this article, he is focusing on lessons learned from physiology and how they can be applied to distance running. I’m not going to cover all of these, instead I’m going to focus on one big one (and I’m paraphrasing here), which is that maximal oxygen consumption might be overemphasized both in the lab and in training.

Maximal oxygen consumption has been the measure for distance runners for about forty years now. A lot of training programs are designed with the idea of improving this measure. This is where we get things like long, slow distance running. The idea is to go at a slow, steady state for a long time, which will improve maximal oxygen consumption.

The problem is that maximal oxygen consumption is one of those things that genetics plays a big role in. No amount of training is going to get you to 70+ ml/kg/min unless you have the genetics for it. Some of this training (like long slow distance training) can teach even distance runners to be slow, which is not the intent behind training.

So if maximal oxygen consumption isn’t the smoking gun, what is? According to Dr. Karp, the two important measures might be lactate threshold and running economy. Lactate threshold refers to the fastest speed that can be sustained aerobically. This is important because athletes can have a similar maximal oxygen consumption, but the ones with the greater lactate threshold will be able to run faster.

Running economy is the amount of oxygen consumed at submaximal speeds. In other words, an athlete with a greater running economy does less work at the same speed as another athlete, allowing them to run further and faster.

Karp, J.R. (2011). A faster runner. Techniques, 5(2): 30-39.