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Wednesday, October 26, 2016

Run like a Keyan or maybe better a Kalenjin

Occasionally while  running in the park I will see a T-shirt that says "Run Like a Keynan". A more precise and accurate phrasing might read "Run like a Kalenjin"

Indeed most runners might admire or envy the impressive running speed and endurance that Kenyan runners  have demonstrated

The Kakenjin tribe in Kenya account for only 12% of the total population of the county, but about 75% of the elite Kenyan runners are Kalenjins.

Danish researchers attempted to determine why Kenyans are so good at endurance running events. They found that the Kenyans do not have a higher maximal oxygen uptake (V02Max) nor a higher aerobic threshold than other elite endurance athletes  but that they simply were more efficient runners. This the researcher attributed to their body type, specifically long thin legs.That does not mean that Kalenjins do not have a high 02 max,They certainly do but that is not their distinguishing
characteristic.  Long thin legs and high V02 max and efficiency  seem to be the keys.


Monday, October 10, 2016

Exercise capacity of octogenarians and age related decline in exercise capacity



A great source for information about the exercise capacity of octogenarians is a 2013 article by Scott Trappe and co-authors.( Trappe,S et al , New records in aerobic power among octogenarian lifelong endurance athletes. JAAP, vol 114, no 1, 3-10.) See here.

The authors studied 9 life long and still competitively active  elite endurance athletes and compared their aerobic capacity as well as myocellular markers of oxidative metabolism with 6 age matched healthy non exercisers.

The V02 max (maximal oxygen uptake ) in the group of athletes was 38 plus/minus 2.1 ml/kilo/minute versus 21 plus minus 1 for the sedentary group. The authors reviewed other published data on aerobic capacity in untrained 80 year olds and found:

1) In 195 men  the average V02max was 21 plus/minus 4
2) In  269 women the average V02max was 18 plus/minus 4

These values are comparable to Trappe's non-exercising  subjects while his athletes  were said to have the highest values reported in a group of octogenarians.(There are some individual case reports with value this high and higher-see below)

Having monitored several hundred stress tests using the Bruce protocol I find it helpful to put these 02max values in that context.

The Bruce protocol has 3 minutes stages and after each the treadmill pace and inclination increase:

Stage I 1.7 mph 10% grade using 5 METS  and requiring 17.5 ml 02/kilo/mi

Stage II 2.5 mph 12%                    7 METs                          24.5

Stage III 3.4 mph 14%                    9 METS                        31.5

Stage IV    4,2    mph 16%               13 METS                        45


Stage V    5 mph  18%                     15 Mets                          52

Stage VI     5,5 mph   20%               18 METS                       68



A MET is the resting oxygen uptake of 3.5 ml 02/kilo/min.

Based on these values many or maybe most of the male non athlete   octogenarians would complete Stage I while a number  of the females might not  not.Most of Trappe/s athletes would complete Stage 111 .

One of Trappe 's'subjects was 91 years old , a former Olympic champion  ( ok he is not an octogenarian)  has an amazing  aerobic capacity of 36! He should complete stage 3 and into stage 4.

Using time estimates from Tim Noakes book (footnote 1   ) you can guesstimate  running and marathon times from aerobic capacity or  at least get a estimate of the aerobic capacity that is required to run at a given speed. An  02 capacity of 30-32 would be required to complete the 26.2 marathon in about 5.5 hours.

Ed Whitlock, dob 1931, was the first man to run a marathon in less than 3 hours at age 70 .At age 73 he ran a 2:54 marathon.It probably takes a 02 Max of 60 to run a sub three hour marathon.

There are real life 80 year  people who complete marathons. For example, 4 men all aged 80 finished the Houston Marathon in times ranging from 4:23 to 5:40  in 2016 .The winner in this group probably has a 02 max of about 40 ( using the table from footnote 1).Also there were three 80 year olds who completed the NY City Marathon in 2016 with times ranging from 5:03 to 5:37.

In 2011 Ed Whitlock at age 80 ran the Toronto Marathon in 3:15corresponding to a 02 uptake of 50-53. This is  comparable to the report by Trive Karlsen who measured the max 02 uptake on an 80 year old Norwegian at 50 and claimed a world record for an 80 year old.See here. There are  a few other octogenarians who have run a sub-four hour marathon, Ed Benham ran 3:48 at age 82. and Harold Willson who did 3:58 at age 80 . These are times  probably requiring an 02 Max of around 40.

(See addendum below for update on Ed Whitlock)


In regard to the non superathlete  male octogenarians , their average 21 ml/kilo/min aerobic capacity should allow them to be able to walk at a fifteen minute per mile pace  ( which is a fairly brisk walking  pace) which probably requires about 17 ml  02/kilo/min as does playing double tennis, doing light yard work ,etc. and a lot more than whittling on the park bench.Finishing Stage II suggests adequate 02 capacity to run a fifteen mile. (Walking a fifteen minute mile requires about 70% as much 02 uptake as does running a mile.)

It seems more than reasonable to assume that these octogenarian marathon finishers has in their youth 02 max values just as impressive for their ages then as they are now and likely could have run a marathon in less than 2 1/2 hours.

The conventional thinking is that from about age 45 to age 70 a persons aerobic capacity declines somewhere between 5% and 10 % per decade. Some studies have shown and other studies have presented contradictory evidence  that those who continuously train aerobically  have a lower rate of decline. ( Personal note-A rough calculation based on my marathon times suggest that my decline was slightly over the 10% per decade number)

Some of subjects in the non athletic group had V02 max value approaching the range that have been proposed as a threshold value for independent living(18 ml/kilo/min) and as a threshold for disability assessment ( 15 ml/kilo/min) refs 2 and 3

The lower the 02 max, the higher percentage of it is used  for the typical  activities of everyday life leading to fatigue and predisposition to inactivity and deconditoning. Further the increased oxygen consumption  attendant to trauma , acute illness and surgery may push someone with a 18 -20 02 max over into the disabled category .

addendum: 10/19/2016- Ed Whitlock, now 85 years old, finished a marathon In Toronto in 3 hours and 56 minutes -over a half hour quicker than the previous record for that age for the marathon.

footnotes:

 1.Table 2.3 page 66, Forth Edition of "Lore of Running " Tim Noakes

2 Jackson, AS et al Effect of lifestyle and aging on the longitudinal change in respiratory fitness. Arch Int Med. 2009,169 ,1781

3 Putz, C et al  Incremental shuttle and six minute waking tests in the assessment of functional capacity.in Chronic Heart Failure.Can J Cardiol 2008 24 (2) 131-134

Thursday, October 06, 2016

Exercise intensity and risk of atrial fibrillation-a possible gender specific effect

Dr, S, Moharty  et al have presented a meta-analysis on the relationship between exercise level and risk of atrial fibrillation (AF). In what is the largest data analysis to date on this topic they found that  women's risk of AF is reduced at all levels of exercise while in men low and moderate levels of exercise seem protective risk of AF increases at the highest levels.

The term coined by Jim Manzi,( ref 5)  high causal density, seems appropriate in regard to the etiology of AF. Both inactivity and allegedly " too much exercise" both increase the risk of AF as do aging,obesity, alcohol , hypertension ,  perhaps pericardial fat deposition. and apparently being too tall as well as a number of other putative risk factors.The trick is to figure out what is "too much". Moharty's paper suggests there may be  no "too much" for women ,at least they did not demonstrate a threshold, a claim  which I believe has not been made before.

Reviewing 22 studies (665,750 subjects) they found:

1) In men moderate exercise was protective ,OR .72 , while vigorous exercise increased AF risk with an OR of 3.30 (1.97--4.63). When the authors excluded some small case control studies that had very wide confidence intervals the estimated  risk level was reduced but not eliminated to OR of 2.45 ( 1.1-3.8)


2 )In women moderate exercise was protective with an OR or 0.91 while vigorous exercise seemed even better with an OR of  0.72. So for them more was better without limit?

Previous studies were conflicting with some showing in men the so called J or U shaped curve while others claimed greater physical activity was associated with a lower risk of AF. i.e. a continuing downsloping risk curve as exercise levels increase. Moharty's study indicates that in women the curve is continuously down sloping and supported the existence of a  U-shaped curve in men.

 Intensity levels of exercise in most (all?) of the studies is at best a "coarse grain" indication. Some  of the exercise levels were based on the subjects' declaration of  their exercise level. In Anderson's study of cross country skier exercise  level was defined as finishing one race versus those who finished 5 or more. In some trials AF was self reported, in others AF was  physician confirmed. Often exercise level reflects duration of exercise per week with no consideration of level of intensity of exercise and  some times quantified by number of endurance events completed usually without consideration of intensity, i.e completion times.

The effect of men's age on risk of AF at various exercise levels is also a consideration. At least it seemed to be in Aizer's paper. This was an analysis of AF in men in a post hoc analysis of the randomized aspirin study as part of the Physicians health study. (Ref 1) The only increased AF  risk was shown in men less than age fifty at the highest self reported exercise level.Suggested non-causal explanations for this include survivor effect and the increased risk of so called lone-AF in otherwise healthy runners  usually in a younger or middle aged man 

Another study presented data that suggested increased risk of AF in younger but not older men. This study  by Nikola Drca from Sweden  was a long term followup of 44,000 men with retrospective estimates of their exercise levels. Those 30 year olds who exercised more than 5 hours per week has an increased RR (1.19) but that was not the case for fifty year olds.  Again, could this be a survivor effect or a high number of so-called lone parasympathetic AF in the younger runners? Here we have the relative risk of less than 2, a topic I have ranted about before. An age differential effect was not mentioned in Moharty's paper.

Being the pattern seeking story telling creatures that people are ( ref 4) there are bound to be speculations as to why/how this purported  gender difference could occur. Here is one such such speculation found in a 2011 article by Wilhelm ( ref 3). The authors compared male and female non elite runners and found that the men has subtle changes in diastolic function, slightly large left atria ,changes in heart rate variability and higher BP during exercise, a constellation of findings arguably making male runners, holding training levels constant, more at risk for AF and in fact 4 of the 70 men  studied did have episodes of paroxysmal AF.

How to determine where moderate ends and excessive begins either with group data on for an individual is the problem.

ref
1. Aizer,a et al. Atrial fibrillation is association with different levels of exercise at different ages in men. Heart 2014;100, 1037-1042.

2.Drca, N Atrial fibrillation is associated with different levels of physical activity at different ages in men. Heart, 2014 ,100 (13), p 1037

3. Wilhelm, M et al.Gender Differences of atrial and ventricular remodeling and autonomic tone in non elite athletes.American Coll cardio nov15,2011, vol 108, pg 1489


4."Humans are pattern seeking story telling creatures and are quite adept at telling stories about patterns whether they are true or not.: Usually attributed to  Michael Sherma.The phrase became a theme for Ed Lemer, UCLA economist, in his Book "Macroeconomic Patterns and Stories.


5."Uncontrolled:The surprising payoff of trial-and-error" Jim Manzi ,2012 Basic Books