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Running on Empty

Posted Oct 12 2010 3:11pm
“Gotta do what you can just to keep your love alive
Trying not to confuse it with what you do to survive” 
~ Jackson Browne, 'Running on Empty'

Once again, last week presented several challenges that affected my ability to maintain the high mileage I had planned on. The result was a humongous difference in my body’s response to the physiological demands of a long run between last Sunday and this past Sunday. Allow me to explain.

My first run following last Sunday’s 20-miler was Tuesday. Monday was a rest day. Following Tuesday’s run, my left IT band was sore, not just after the run, but for a good part of Wed too. After a 2-year battle with IT trouble that I was finally able to resolve early this year, I know not to push it in the early stages of pain. Another rest day Wednesday, with a plan to do some tempo and steady-state drills Thurs and Fri, ending with a 23-miler on Sunday. It would be the highest weekly mileage I’d achieved in my entire running career.

Then came late Wednesday night/early Thursday morning when either my GI tract was hit with major food poisoning or I caught the stomach flu. Not the aching tummy, bloated and cramping kind. The full on deal. I’ll spare you to gory details of that night, but let’s just say by the time I rolled out of bed on Thursday morning, I lost at least a gallon of fluid within a 5 hour period and maybe managed to get 3 or 4 hours of sleep in. I worked from home Thursday and Friday to avoid the embarrassment of dealing with my symptoms in public, barely managing to eat any solid food before Friday night. I was drinking as much fluid as my stomach could tolerate: water, Powerade, Bolthouse protein shakes and eventually some soup. All the while totally stressing myself out about my inability to train and the importance of this next long run. My last chance to get in an LSD before the 3 week taper. Come Saturday, my stomach had probably shrunk to the size of an iPod Nano. It still wasn’t thrilled with solid food but I was certain to stick with high carb, nutrient rich foods and continued with the Powerade and water in an attempt to make up for all that had been lost.


By Saturday night, I was feeling well enough to conquer this long run (or should I clarify I had mentally convinced myself I could do it). Rather than try to run farther than last weekend, my goal would be the same – 20 miles. So what if I have to walk at the end?  I’ll eat and drink a little more often to offset what I’m sure was a great deal of glycogen loss having consumed very few calories Thurs and Fri (not to mention all that I’d lost overnight and into the day on Thursday).

Later that night, I think my logical brain decided it was time to chime in. What will I do if get 10 miles from the car and I’m in such bad shape that I need help? I always carry my phone and extra money with me when I’m running alone outside for emergencies. A) I can take a cab back to the car; B) I can reach 911 with the touch of a button. I decided to get some input from the hubby. It didn’t take long for us to agree that if I was going to try this, I needed to be in as safe an environment as possible. Treadmill it is! I was instantly relieved. The thought of being on the treadmill for 4 hours wasn’t nearly as intimidating as running at the beach seemed. I can do this. I opted for some alternative listening material to mix things up a little bit. I downloaded a podcast that I’d missed the previous week that would take me through the first hour and would start listening to the audiobook version of Born to Run that I’d been meaning to get around to for the remainder of the run.

As you can see, my view from the treadmill isn't exactly scenic, but for me, that white-board can be a great motivator, provides 'in your face' immediate feedback, and when I clear my head, it's a great tool for totally zoning out. The Kings of Leon towel you see hanging over the banister is my attempt at limiting the amount of sweat that flings off my arm and ends up on the family room couch downstairs. So far, so good. :-)

I loaded up the console with a PowerBar, Cliff Shot Blocks, Jelly Belly Sports Beans, Accelerade and water. I was in it for the long haul. The first 3 miles were tough and I was only running an 11:45 pace (my normal long run pace currently), but I'm not even close to giving up yet. Anyone else following The Runners Roundtable podcast series? I listened to Things to Remember and Know on Your Marathon Race. Great panel. Totally recommend it. After an hour (5 miles), I'm finally hitting my stride. I know at this point I'm relying a great deal on fat oxidation for energy (due to this low-intensity pace), but I'm keeping my carb intake up because I know my glycogen stores are limited, and the longer I run, the less glycogen I'll have available for energy. I'm feeling good and really positive. I've got my Garmin


Listening to Born to Run was a great escape. I was able to immerse myself in Mexico's Copper Canyon in search of the Tarahumara Indians. Fascinating. Around mile 10, I am becoming aware of how incredibly thirsty I am. This rarely happens to me and should have been a red flag, but I didn't let it phase me. While I'm trying to keep up with my hydration needs, I'm having difficulty with getting calories in. The Accelerade seems to be going down okay, but a couple bites of PowerBar made me feel instantly full, almost like I was having heart burn. I even had to loosen my Garmin HR monitor strap because it was feeling constricting. I tried a few sports beans. Those seemed to agree with me a little better, but for the most part, my calories (thus carbs and a little protein) were coming from the Accelerade. Tricky balancing act here, but I was doing everything I could to keep the carbs coming in. My calves and hamstrings are aching a little, but nothing I can't handle. It was at this point I remembered the treadmill was set at a 1% grade. For my shorter runs on the treadmill (under 10 miles), I always have the incline set at this level because this grade is generally considered to provide an equal amount of resistance as you would feel during street running. However, 0.5% can be used as well. In hindsight, I should have thought about this earlier, but I so rarely change it (or think about it) unless I'm doing hill work.

By mile 12, my calves are burning and it's almost like they're losing elasticity. Come on Vera, you can do this. You have more to give. Maybe I should take the incline down. No, that's cheating - I told myself. You wouldn't have this option on the road so it's not an option here. At 13.25 miles, I bring the incline down to 0.5% and feel a slight sense of relief in my calves, but there's no doubt I'm feeling a lot worse here than I did at the end of the 20-miler last weekend. I'm getting surges of energy here and there, but they don't last long. Mile 14 passes. I don't even know what's going on in the book. I'm totally in my head, fighting with my brain in a last attempt to convince myself I could keep going. Mile 15 was close to being excruciating. My calves are on fire and I can barely keep up with the belt. I hit the 15 mile mark and try to keep walking slowly to cool down, but now my calves are cramping and seizing. I have to get off this thing.  I tried to walk downstairs to get some salt but I can't do it. Hubby to the rescue! I downed two salt packets straight with a little Accelerade to wash it down and within about 10 minutes, the burning and aching sensations are gone. Immediate thoughts? I failed. The truth? I ran 15 miles in sub-optimal physiological conditions. Some coaches even advocate the inclusion of training sessions in glycogen depleted states to get the body prepared for what's to come at the end of a marathon or other long distance endurance event. Yeah, that's pretty much what I was feeling like at the end of this TM run.


Photo credit
So what do I think happened and how did I convince myself I could pull off 20 miles under these conditions? Delusional thinking of course! While we’re at it, let’s throw in some denial and outright stubbornness. My thinking:  If I could maintain a low intensity session, I could burn more fat for energy for a longer period of time, sparing glycogen utilization so more would be available later in the run. Reality check: Not being properly hydrated and having sub-optimal glycogen levels (See Figure 7 in this link) are both physiological stressors that cause your body to work harder to maintain your pace/workload. Proof? My average Heart Rate was consistently 5-7 bpm higher for the first 10 miles relative to last week, and over 10 bpm higher in the last 5 miles, even though my pace was exactly the same (and presumably doing the same amount of work). The concept the above image portrays is one known as the Crossover Concept, as published by George Brooks in 1994  and is generally accepted as scientific truth in the academic world. The basic idea is that the harder you work, the more carbohydrates (CHO) contribute to the energy demands. Unless you're in a full on sprint, the breakdown of fat is always a source of energy, as seen in the Crossover Concept. (I should point out here that other theories state the breakdown of fat does continue to contribute energy even at a maximum effort due to the breakdown of triglycerides in your muscle.) In addition to the effect of increasing exercise intensity on your reliance for glucose, the duration of exercise increases your body's utilization of glucose.

J Appl Physiol 87: 124-131, 1999


Photo Credit
Where are you getting this glucose? Your blood (the plasma part to be exact), your liver, and your muscles. Unlike the very limited glycogen-storing capacity of the human body, our fat stores are almost colossal in comparison. In healthy lean athletes, Dr Tim Noakes explains in  Lore of Running  "....fat is the largest energy store in the body... as much as 9kg even in relatively lean...[athletes]. By comparison, the carbohydrate stores are quite trivial, at most 600 to 700g." Higher levels can be achieved with carb-loading and high-intensity endurance training.  Whoa. 

So what's the deal with fat? Why can't we rely on that to go the distance? Two reasons: 1) the metabolic cycle that turns fat into usable energy is very slow in comparison to the breakdown of sugar (this is why you hear fitness experts say it takes about 20 minutes to 'start burning stored fat'). When you need a lot of energy and/or need energy quickly, it can't keep up with your increasing energy demands; 2) the breakdown of glucose provides more energy per liter of oxygen you're breathing in relative to the energy you would get from the breakdown of fat (at the same rate of oxygen consumption). 

Here's another interesting fact: Did you know that for every molecule of glycogen you lose, you also lose about 3 molecules of water along with it? Another source of dehydration! This was evident on the scale when I weighed myself Friday morning to find I’d lost 1.5% of my body weight in under 40 hours. You can see an illustration of the effects of different exercise intensities on glycogen utilization over time in a  previous post . The point here is, as endurance athletes, we've got enough challenges with maintaining what little stored sugar we have during distance events without the added effects of poor nutrition, dehydration and pre-exercise glycogen depletion when the need for sugar is increasing with each passing minute of your endurance event.
To wrap up, let’s put all of this into perspective. I started off dehydrated. I did not have enough time to properly re-hydrate or re-fuel my body from it’s energy-depleted state. Not ingesting enough carbs or calories basically means I was on a calorie-restricted, low-to-moderate carbohydrate diet for over 48 hours (see aforementioned Figure 7 in link above to see how this aspect affects performance) leading up to about 26 hours prior to attempting the 20-miler. The longer (and harder) you exercise, the more glucose your body uses. I started off depleted, was unable to stomach as many carbs as I had planned on ingesting during the run, and I was working about ~10% harder to maintain the same pace I did during last weeks long run. Somebody call Rachael Ray. I've got a recipe for disaster! It's a miracle I made it as far as I did with no major repercussions. Including ending with a pain-free and happy IT band.
Oh ya, one last little reminder of this LSD treadmill adventure through Copper Canyon: forgetting to use Body Glide on my lower back. Ouch!

Gotta do what you can to keep this love alive, right? I think I did my part this weekend. :-)

Three Saturdays to race day!

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