Friday, June 24, 2016

Not Riding Around the Sea of Galilee

Our family recently took a trip to Israel. In addition to seeing the usual sites, my older son, who organized the trip, had the idea that we should bicycle around the Sea of Galilee. This "sea" is actually a lake, also known as Kinneret, Lake of Gennesaret, or Lake Tiberias (among other names.) It is famous among Christians as a site where many of the important events in Jesus' life took place, lending significant cultural color to the ride. This ride, about 35 miles long, was recommended to my older son by a friend of his who had ridden it a few years before, and gets good reviews on travel websites. Four of us decided to "attempt" this ride; me, my wife, my older son, and my younger son. I put the word "attempt" in quotes as none of us had any doubt but that the attempt would be successful; the distance was short enough that my wife, the weakest rider in the group, should have been able to complete it with no problem. Hah!

The four of us, me, my wife, my older son, and my younger son, in front of the hostel where we rented the bikes.

The travel websites described a traffic-free bike path that covered about 70% of the distance around the lake, with the remaining 30% being ridden on the road, and promised many places where bicycles could be rented. When we arrived in Tiberias, the largest city on the lake, we easily found a bicycle rental place, picked up four rather old and beat-up mountain bikes (all they had), purchased a trail map, and asked the guy who rented us the bikes about the trail. "Just ride down to the lake" he said, "follow the lake, no problem. But be sure to ride it clockwise!" Wrong in every respect, as it happened; he either didn't know what he was talking about and/or didn't care. We did look at the map before we left, and it did show a path along the lake. Getting to the lake was a bit more of a challenge than expected, compounded by completely wrong directions given by various people along the way; it seems Israelis love giving advice whether or not they know anything about the subject at hand. Despite that, we eventually found our way to the lake, and rather than a bicycle path, found beaches, hotels, fast food stalls, boat rentals, and the like. We did our best, travelling on streets and sidewalks next to the lake, until these all led us unavoidably back onto the main highway. That highway features high speed traffic heavy on the trucks, so that riding on it was not entirely pleasant and we kept looking for the promised path.

Eventually my older son found a path which seemed to match what the bike rental guy had told us to expect. It was clearly a designated path, with color coded trail markers. Once we got on it, however, we found it to be more of a hiking than a biking path. Some parts of it were OK, basically dirt roads, but other parts had impassible obstacles (at least to mountain bike novices like us) or loose dirt and sand which brought us to a complete stop, forcing us to walk the bikes. With practice, I got to where I could power my way through these stretches, but only at great expenditure of energy. My wife never could make it through them. Thus, a small number of miles ended up taking us way more hours than we had budgeted and left us a lot more tired than expected. At this point, the path ended. It is possible that, as before, we would be able to rejoin it after a brief ride on the highway. However, the day was already very hot and we were getting tired, so we finally did what we should have done much earlier, we looked at the map carefully. When we did so, we found that there was a completely different path around the lake, one which appeared to be the designated bike path all the travel websites had been talking about. In complete conflict with what the bike renter had told us, this path was some distance from the lake, up in the surrounding hills. To get to it from where we rented the bikes, we would have ridden, not towards but away from the lake, up into the surrounding hills. Realizing this, we crossed the highway, headed off through some farms into the hills, and after a bit of searching, found this other path, also well marked and color coded.

A portion of the map whose cover is at the top of the post. If you look just below the green number 1, you can see a blue highlighted route. That is what we think the correct bike route is. The red line along the shore is the highway which most people ride. Near the top of the picture, just to the left of the highway, you can just see a dotted route. That is the hiking trail on which we attempted to bike.

This was the moment of truth. So far, we had only completed an insignificant fraction of the distance around the lake. Should we turn right, and continue the journey, or turn left, and head back home with our tails between our legs? We chose the latter. Although some of us may have made it around, it was unlikely, given the heat and our exhaustion, that all four of us could. As fate would have it, this new trail was much better than the old; although dirt, it was hard packed and lacked the "beyond technical" features of our previous route. Would we have been able to complete the ride had we taken this path in the first place? This is uncertain at best. The main problem was that this trail travels some distance from the lake and weaves back and forth much more than the highway, so the 35 mile trip around the lake on the highway turns into an 88 mile trip around the lake on the trail. In the second place, even high quality dirt roads are more tiring to ride than pavement. Thirdly, being up in the hills, this route would have inevitably involved significant climbing. We were, however, able manage to drag ourselves home by refueling along the way with many glasses of the delicious, mint-rich Israeli lemonade.

Here we are, stopped by loose dirt and sand.

When we got back, my older son immediately emailed his friend, asking him to comment on our difficulties. His reply: "I rode the highway, dude." Riding the highway would have been somewhat unpleasant and perhaps even a bit dangerous due to the traffic, but on a road bike, the ride would have been the piece of cake we had anticipated, especially if we had started at dawn to avoid some of the heat and traffic. In my judgement, the inner route where we started riding is not a usable bike trail. The little we rode of the outer ride through the hills seemed doable but is very long and may contain unexpected challenges.

How did we mess up this ride so badly? In the first place, I believe that if I don't occasionally underestimate a ride, I am not being adventurous enough in my ride selection. In the second place, we all had a lovely time, saw the Sea of Galilee from an interesting perspective, and got plenty of exercise. Having said all these things, here are what I think to be the reasons:

  1. We unknowingly conflated the advice of my son's friend and the travel websites so as to apply the friends endorsement not the the roads on which he rode, but on trails.
  2. The travel websites seemed more informative than they were. They implied, at least to us, an easy to find, unambiguous, trail system. In fact, the trail system required some significant detective work to use, something which we were lulled into not doing.
  3. The guy who rented us the bikes did us a huge disservice by confidently and insistently giving us advice that could not have been more wrong in every way. Because we believed his advice, we did not do our own due diligence.
  4. None of us are experienced mountain bikers. It is my impression that mountain biking is considerably more difficult per mile than road biking. Because we did not have mountain biking experience, we did not correct for that difficulty.
If we had not made these mistakes, I am not sure what we would have done. We certainly would not have attempted 88 miles on dirt roads with the group we had. If we had studied the map ourselves, would we have nonetheless attempted the inner route? I would like to think we would not have, the map never suggested it as a viable route. Might we have attempted the roads? Perhaps. My son's friend rode them successfully, and there are lots of blog posts and the like on the internet of people doing so. And that makes an interesting point. The bike trail everyone raves about is not really an alternative to the road, but an entirely different ride; much longer, and much farther away from the lake. One can debate the relative virtues of lake vistas from the hills vs riding along the lakeshore, but one cannot say they are the same thing. To be perfectly honest, I suspect if we knew then what we know now, we might have never attempted the ride, and so perhaps we were well served by our ignorance.

I am going to try an experiment with this post, I am going to try including a movie. Here is the our group, heading down the trail:

Tuesday, June 14, 2016

Intervals and Common Sense

The 1969 Great Western Bike Rally, a celebration of moderate exercise.

"There are sadistic scientists who hurry to hunt down errors instead of establishing the truth." - Marie Curie

In my last post, I was a sadistic scientist. There were reasons I for that, but in this post, I'd like to take a more constructive, common-sense approach to understanding the relationship between different kinds of exercise and long term health. Specifically, I would like to address the following questions:
  1. How sure are we that exercise improves long term health?
  2. Is VO2max a good biomarker for the impact of exercise on long term health?
  3. Do the short term impacts of different exercise plans on VO2max accurately predict their long term impacts on VO2max?
  4. What is the value of High Intensity Interval Training (HIIT)?

Last Time on the Zombie Cyclist:

In my last post, I discussed an excellent paper (Gillen et al.) which argued that three 20 second sprints produces the same long term health benefits as 45 minutes of moderate intensity cycling. I used that post to illustrate the limitations that go with a biomarker study (a study where you investigate not what you are interested in, but something easier to measure that you believe is linked to what you are interested in.) In the case of Gillen et al., what they were interested in were the relative long term health benefits of different exercise regimens. Unfortunately, these take decades to measure, so what they studied instead was the effect of different exercise regimens on VO2max, glucose tolerance, and the mitochondrial content of muscle. They examined changes in these three different factors produced by 12 weeks carrying out one of three different exercise plans. The three plans were no exercise (the control group), 45 minutes of moderate intensity cycling done three times a week, and three workouts a week built around three 20 second "all out" sprints. Both exercise groups improved by about the same amount, leading them to conclude that the much shorter sprint workout was as good as the longer moderate exercise workout. At the end of that post, I stated that, based on rigorous scientific criteria, I found the paper interesting but not entirely convincing. As a scientist, my formal reservations about the conclusions of Gillen et al. were two-fold:
1) The three biomarkers chosen have not been demonstrated to be reliable proxies for long term health.
2) It has not been demonstrated that the results observed after 8 and 16 weeks of exercise will continue for the decades relevant to long term health.

My intuition tells me that the biomarkers chosen probably are a good stand-in for whatever effects of exercise contribute to long term health. However, I am less certain that the benefits of Gillen et al.'s specific exercise plans will continue long term. As I will argue below, I personally think more varied exercise plans might a be better long term plan.

Does Exercise Improve Long Term Health?

The influence of exercise on longevity and health has been extensively studied and the benefits appear to be substantial. Men in their 50's have a 42% chance of living to 85 if they exercise regularly compared to 23% if they don't. (For comparison, the numbers for not smoking are 37% vs 18% if you do and of not being obese are 35% vs 13% if you are.) Yes, yes, we have all heard about the curmudgeon who never exercises and drinks a quart of whisky and smokes two packs of cigarettes a day and is 97 years old; it can be done, 18% is not 0%. But there is no escaping the fact that your odds are a lot better if you take care of yourself. Such studies are (almost?) always observational, and so there is the theoretical possibility that the people who choose to exercise make that choice because they are different to begin with, that it is this pre-existing difference that is responsible for their longevity, and that they would have lived to a ripe old age even if they had not exercised. This is not as far-fetched as it may seem. Some people are healthier than others for a whole range of reasons. Healthier people live longer and feel better. Because they feel better, they might be more likely to exercise. This kind of ambiguity is present in all observational studies. That duly noted, I think the benefits of exercise are broadly accepted nonetheless, and that this acceptance is due to the large number of studies that have been done, the consistency of all the evidence, the substantial size of the effect, and the intrinsic plausibility of the conclusion. Thus, I will answer this question with a strong YES.

Is VO2max a Good Biomarker for Exercise?

VO2max varies enormously between people, but most of this difference is genetic. No matter how much you exercise, you can never catch up with someone who has "good genes." (The good news is that VO2max is not the most important determinant of who is a fast cyclist, and the parameters that are, are more trainable.)

Most studies of exercise and aging work by assembling a group of people, determining how much they exercise, and then revisiting them some years later to see if they are still alive. There are two ways that "how much they exercise" is commonly determined. The first is to ask people. This is unreliable because people may not accurately remember or they may exaggerate. To get around these problems, the other way is to measure how much they have been exercising by measuring their VO2max. Because VO2max does increase with exercise, people who exercise will, on the average, have a higher VO2max. But this is only true on the average. Because VO2max is determined more by genetics than exercise, many people who exercise will have lower values for VO2max than many people who do not. However, since the whole study is based on statistics, the group who has a higher average VO2max will, on the average, have exercised more. The fact that VO2max does work as a stand-in for exercise despite the problem of genetic variability raises an interesting question; what if what is important for longevity is VO2max, not exercise? Because exercise increases VO2max, it will increase longevity, but will people who inherit a high VO2max but do not exercise live longer or shorter lives than those who exercise but have genetically low VO2max? I don't know the answer to this question, nor do I even know if the answer is known.

The scientific community believes that the important variable is exercise with VO2max being a biomarker for exercise, so for the remainder of this post, let's assume that is correct. What this may mean is that someone who inherits a high VO2max does not live longer as a result. This then begs the question, does the VO2max you get from high intensity interval training get you the same benefit as the VO2max you get from exercising at a more moderate level for a longer time? Without being the least bit sadistic, I am at least somewhat skeptical that it does. Does that mean Gillen et al. is wrong, or at least unreliable? One of the most important ways scientists avoid being mislead is to look at the same question as many ways as possible, and that is one of several reasons I like Gillen et al.; they did look at the effect of HIIT on VO2max but they also looked at the effect of HIIT on muscle mitochondria and on glucose tolerance. It is much less likely that they were mislead by all three of these biomarkers than by any one, making me significantly more enthusiastic about Gillen et al.'s conclusions.

Am I Sold on HIIT?

Yes and no. When I first started thinking about training five years ago, I was skeptical of the value of any kind of brisk training, intervals included. I now believe intervals, and short, fast (high intensity) intervals in particular are good for health and will improve my performance in most kinds of rides (group rides, long rides, etc.) Even five years ago, I rode intervals now and then because pretty much all training programs included them, but I was unenthusiastic and often skipped them. Going forward, I am going to make a real effort to include at least one set of intervals every week. Further, I had been favoring longer intervals and longer kinds of brisk rides (30 minute time trials) believing they were better for building endurance. I am now going to include shorter, faster intervals. A few weeks ago, for the first time, I tried 20 second intervals as describing in Gillen et al. and found I reached heart rates significantly higher than I usually do. I had been skeptical that such a short interval would last long enough to bring up my heart rate, but it turns out I was wrong.

So that is the yes part, what about the no? I am not prepared to replace all my other riding with high intensity intervals. Even if all I was interested in was health I would not do so. I believe that the mechanism by which exercise improves health is complex and that our understanding has just scratched the surface of that complexity. The exercise community has embraced the value of a diverse exercise program for millennia, and although I will always follow science when it successfully overturns tradition, I don't think the weight of scientific evidence about exercise and health is sufficient to do that here.


  1. "The exercise program that you do is always superior to the one you don't do." - my younger son
  2. If I were betting on the long term prospects of folks who do a small amount of very high intensity exercise versus a group that follows a more conventional moderate exercise program, I'm not sure how I would bet, but I definitely would bet against a third group that did no exercise at all.
  3. If there was a fourth group who mixed it up, did some long, slow bike rides, did some sprints, lifted some weights, and did some yoga, I would bet on them over any of the above three groups.
  4. I am who I am. I am probably not going to lift weights. I am definitely not going to do yoga. But I do plan to mix up my cycling; to ride long when I can, to ride intervals when I am inspired, and to keep doing 45 minute rides at a moderate level of intensity when I can think of nothing better to do. Do I think this is optimum? Nope. Do I think it is better than nothing? Yep. Do I think I will actually do it? I hope so.