52 more things I learned from a third year of weekly writing

This month marked three years since I started writing articles for RunnersConnect.net investigating what the scientific literature has to say about a wide range of running-related topics, from injuries to training to peak performance on race day.  At the end of each year, I've made a list of one useful tip or interesting fact that I learned from each week's research.  Here are fifty-two more things I learned from reading scientific research this past year, one from each article.  If you want to see all of the material I've written, head on over to the blog section of RunnersConnect! Also feel free to check out the yearly lists from 2013 and from 2012.
1.  Celiac disease, which affects around one percent of the population, can cause a wide range of vague, non-specific symptoms that can interfere with your training, like joint pain, extreme fatigue, weight loss, gastrointestinal problems, and anemia.  Further, even once you've adopted a gluten-free diet, it can take a while for your body to return to normal.
2.  If you choose to eat a vegetarian or vegan diet, you're more likely to have iron-deficiency anemia, amenorrhea (if you are a woman), and insufficiently vitamin B12 levels.  Though it's very possible to have a complete diet as a vegetarian or vegan, you need to take extra care to ensure you get enough protein, vitamin D, and iron, and you should probably take a vitamin B12 supplement or eat foods that are fortified with it.
3.  Scientific findings can run contrary to your own experiences.  The research says it's okay to run when you have a cold, that the speed of your daily runs does not affect your injury risk, and that it's okay to do some running on an injured area, as long as you monitor your pain and stop before it's over 5/10 on the pain scale.  In my own training, I can't get away with any of this! There might be subtle reasons why the findings from one study don't apply to your own experiences.
4.  The faster you run, the greater the proportion of your energy that comes from carbohydrates.  This has some major implications when it comes to running out of fuel in the marathon.  The people most at-risk for "hitting the wall" before the finish of a marathon are very fit runners who can run at a high percentage of their VO2 max, and heavier, overweight runners—especially if their extra weight is not in their legs.
5.  When planning out a fueling strategy for a marathon, you should generally shoot for taking in 60 grams of carbs per hour of running.  If you have had major problems with hitting the wall, you may consider increasing your carb intake to 90 grams per hour.  However, if you've had gastrointestinal problems from trying to refuel, you might want to cut this down to 45 or 30 grams per hour. 
6.  Gels, sports drinks, and energy chews are all equally valid choices for refueling during a long race.  None of them offer a distinct physiological advantage, so feel free to choose whichever suits you best. 
7.  Electrolytes aren't all that important for endurance events.  There's no good evidence that you need to replace the salt you lose in your sweat—it appears that your body intentionally modulates the amount of salt you lose in your sweat to keep the concentration of electrolytes in your blood constant, so there's no need for salt tablets or super-salty sports drinks.
8.  There's no magic formula for carbo-loading.  All you need to do is increase your carbohydrate intake by 50-75% over the last few days leading up to a long race (over 90 minutes), and you don't need to do a "depletion period" prior to it to get the benefits of carbo-loading.
9.  In a marathon, elite Canadian runners consume between 16 and 26 fluid ounces of liquids per hour of running and about 50-75 grams of carbs per hour.  Elites use a combination of gels, solids, and sports drinks according to personal preferences.
10.  When runners collapse after finishing a race, it's usually (though not always) from a sudden drop in blood pressure that's triggered when you stop running.  After laying down for a few minutes and elevating their legs, they'll be fine.  When runners collapse during a race, however, it's much more likely that they're having a medical emergency like hyponatremia or sudden cardiac arrest. 
11.  Some research suggests that taking vitamin C before and after completing an ultramarathon can decrease your risk of getting sick.  Over half of the finishers of a 90km ultramarathon in one study came down with a cold in the weeks following the race!
12.  However, try not to load up on antioxidant supplements in general.  They can inhibit your body's adaptation to exercise: oxidative stress is a big part of improvement! Fruits and vegetables are probably okay, though.

13.  In the ultramarathon, the ideal age for top performances seems to be between your mid-30s and early 40s.  This is a distinctly older age range than is typical for top performers in shorter events, like the 5k, 10k, or even the marathon.
14.  Ultramarathoners generally tend to get the same types of injuries as regular runners, though they appear to get fewer stress fractures in general, though when they do get a stress fracture, it's far more likely to be in the metatarsals than would be typical for a road runner.
15.  Initial findings of a large-scale study of ultramarathons appear to show that long-distance running confers some significant general health benefits.  Ultra runners averaging >40 miles per week spend less time in medical care and have lower rates of virtually all serious medical conditions when compared to the general public.  Hay fever and asthma are more common among ultra runners, though.
16.  Rotating between two different pairs of shoes for your daily run might prevent injuries, though it's too soon to tell for sure—the only study which supports this was a retrospective study, not a randomized controlled trial.
17.  Surprisingly, there isn't any evidence that consuming electrolytes during a workout leads to a performance benefit compared to just plain water.  The benefits of sports drinks in long events appear to be entirely because of their carb content.
18.  Knowing your VO2 max is great if you're a running nerd, but by itself, it isn't a very helpful number.  A more relevant parameter is your vVO2max, or how fast you run when you are at your VO2 max.  This can be determined by physiological testing, but is also pretty easy to predict from your 5k PR.
19.  Your risk of heat illness is much higher for short, continuous all-out races like a 5k or a 10k race.  Counter-intuitively, running longer competitions like a marathon carries a significantly lower risk of heat illness.
20.  Beetroot juice appears to boost performance by about 1% in sedentary or recreationally-active athletes, but does not have any effect in well-trained runners. 
21.  For running in hot weather, you don't need to worry about weighing yourself before and after your run to determine water losses.  Just drink to thirst, and understand that it is perfectly normal and healthy to lose a few pounds of water weight when you run.  It is, in fact, dangerous to replace 100% of your weight losses by drinking water during your run.
22.  Cramping during exercise is not associated with heat or electrolyte levels.  The best weapons against muscle cramps are stretching and a solid warm-up routine with some dynamic exercises.
23.  Taking a swig of pickle juice immediately after a muscle cramp occurs is a very effective way to shorten the duration of a painful cramp, but it has nothing to do with electrolytes.  Instead, it appears to work by sending a "reset" signal to your central nervous system, which stops the neuromuscular "glitch" causing the cramp.
24.  Though there's been only a few studies on the topic, wearing sunscreen doesn't appear to negatively affect your ability to stay cool in the heat, so don't hesitate to put some on for a long run in the summer.
25. In hot and humid weather, women have a slight edge when it comes to heat management because they sweat more efficiently and tend to be smaller in size.  Men, however, have a small advantage in extremely hot, very dry weather. 
26.  Even if you can't make it to Flagstaff for eight weeks of altitude training, you can still take advantage of the "training camp effect" by taking advantage of lower stress levels, better sleep, and an improved diet that tends to happen when you take a break or vacation.
27.  If you control for relative exercise intensities (as a percentage of VO2max), children and teenagers aren't any more susceptible to overheating during exercise in hot conditions than adults. 
28.  You'll start to see the negative effects of high altitude on running performance at about 3,000-4,000 feet above sea level.  If you're traveling to a location above 8,000 feet, you should take a few rest days to acclimate before you work your way into running.
29.  You should not do a hard, continuous workout or a race within the first week of recovering from an illness that included a fever—you run the risk of heat stroke, even in cool conditions.
30.   It takes about three weeks for your performance to return to normal after donating blood.  Donating plasma only affects your performance for a few days.   Donating blood too often can lead to chronically low ferritin levels.
31.  "Altitude masks" which use resistance-breathing mechanisms to try to simulate training or living at altitude aren't worth it—they don't train the same biological pathways as real altitude, and there isn't a body of high-quality research that supports their use.
32.  Despite how often you hear about tracking your resting heart rate (even from me...), it is not a reliable indicator of overtraining, and there's no good research on heart rate response when you're sick either.
33.   A typical GPS watch is accurate to 1% of true distance on a flat, straight path with a clear view of the sky.  In an urban environment, GPS watches are accurate to 3%, and in a heavily-forested area, 6%. 
34.  Foam rolling is a fairly reliable way to reduce muscle soreness after a workout.  For increased efficacy, use a hard-cored roller instead of a pure foam one (or build your own using 3" PVC pipe)
35.  Successful studies on foam rolling prescribe at least two sets of 60 seconds of foam rolling per muscle group—a far more intense rolling session than a typical runner casually lounging around on the foam roller tends to do.  Additionally, they prescribe short, kneading-like motions for each roll, starting at the "bottom" of a muscle group and gradually kneading back and forth up to the "top."  Once you've reached the top, roll back down in one smooth motion and start again.
36.   Icing is of questionable use for overuse injuries.  Strangely, there isn't a single study that's even investigated ice as a rehab method for an overuse injury.  However, if icing is useful, the best way to go about it is to apply ice for 10min, then take a 10min rest, then reapply for another ten minutes.  Research on ankle sprains found better results from broken-up icing sessions like this compared to a single 20min icing session.
37.  Taking a sauna on a regular basis might boost your blood volume, allowing for up to a 2% performance boost in a race. 
38.  Race conversion charts can be designed to measure one of two things: predicted performance over one race distance based on another, or the relative competitiveness of one performance compared to another.  It's important to recognize the difference!
39.  If you're a "marathon maniac" who does multiple marathons in only a few weeks' time, or an ultramarathon who does multi-day events, proper fueling is essential.  If you don't sustain your energy requirements in your diet during a block of extreme running, your body will start consuming its own muscles and fat reserves.
40.  Running with your head tilted back or too far forward can make the same pace feel harder—generally, you should keep your head and neck relaxed when you run.  But if you're kicking it in at the end of a race, don't worry if you have to throw your head back or tuck your chin down to squeeze out an extra ounce of energy, since it won't have a measurable impact on your real running economy.
41.  If you're running a multi-stage relay event like the Ragnar Relay, fuel up with carbs and protein after each leg.  Shoot for a carb to protein ratio of 3:1 to 5:1.  This should help top up your carbohydrate reserves as fast as possible.
42.  The faster you run, the greater the percentage of your forward motion is generated by your hip extensor muscles become in generating power.  Building glute strength by doing squats, lunges, bounding exercises, and uphill running should improve your ability to run at high speeds.
43.  Stride frequency is not usually a limiting factor when it comes to how fast you can run.  When running at top speed, even a two-year-old has the same stride frequency of a 20-year-old! The reason why adults can run so much faster than children is because they can generate more power each step.
44.  Poor hip flexion and extension range of motion might increase your injury risk.  Doing hip mobility exercises like stretching, the lunge matrix, and hurdle drills can help address this.
45.  In female athletes, poor hip extensor strength and especially an imbalance side-to-side is connected with low back pain.  The biomechanical reasons behind this are not clear, but this connection has been identified in fairly large, well-designed studies.
46.  One of the main reasons runners slow down significantly in old age is because their muscles aren't capable of generating enough power to switch to the "asymmetric" stride pattern that's necessary for optimal efficiency at speeds faster than 8:45 per mile.  To stave off age-related losses in muscle mass and muscular power, older runners should hit the weight room and focus on the major muscles of the legs.
47.  Hip strength programs for rehabbing injuries take an average of three to six weeks to have an effect.  If you're doing a hip strength program for a running injury, be patient! It takes time to increase your hip strength.
48.  Though heavier runners are at a performance disadvantage, there isn't any relationship between your weight and your injury risk.  If anything, runners who are too light—especially women—are at a greater risk of injury.
49.  After a low-risk stress fracture or stress reaction, you can begin to transition back into running with a graduated, pain-monitoring program as soon as you've been pain-free while walking normally (i.e. without a boot or crutches) around and going about your daily activities for several days. 
50.  Because of how low your carbohydrate usage is while at rest, an overnight fast only burns off three or four miles' worth of carbs (150-200 Calories, depending on speed).  Fortunately, it's pretty easy to make up this deficit with a granola bar or a banana and a piece of toast.
51.  Though research is limited, there's nothing to suggest that taking short breaks for a stoplight or to use the bathroom has a negative impact on the benefits of training.  However, if there is a benefit to keeping your heart rate elevated, stopping even for a minute will result in a significant drop in heart rate in a well-conditioned runner.
52.  In one study, the benefits of 150 minutes of weekly training were the same, regardless of whether the training was split into five 30min sessions or two 75min sessions on consecutive days!
I hope you've picked up a tip or two from the research I've done in the past year on such a broad range of topics.  Here's to another year of weekly writings!

About the Author

John J Davis, PhD

I have been coaching runners and writing about training and injuries for over ten years. I've helped total novices, NXN-qualifying high schoolers, elite-field competitors at major marathons, and runners everywhere in between. I have a Ph.D. in Human Performance, and I do scientific research focused on the biomechanics of overuse injuries in runners. I published my first book, Modern Training and Physiology for Middle and Long-Distance Runners, in 2013.

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