ENDURE | Alex Hutchinson

Read: 1/2022

Fundamental Principles and Summary:

• Our mental limitations hold us back as much (if not more) than our physical limitations.
• Re hydration: the best advice is for runners to drink when they’re thirsty. It’s more important to avoid thirst than to avoid dehydration.
• A good proxy of who worked harder: not finishing time, but cumulative years and volume of training. (214)
• “Run a lot of miles

Some faster than your race pace

Rest once in a while.”

On Physical Limitations:

1. Aerobic capacity (aka VO2 max): analogous to the size of a car's engine.
2. Running economy: efficiency measure like how many miles per gallon a car gets.
3. Lactate threshold: dictates how much of your engine’s power you can sustain for long periods of time.

On VO2 Max:

• Oxygen intake reaches a max point in which no more can be processed. You can still go faster, but your oxygen intake cannot increase. VO2 max is a pure and objective measure of endurance capacity that is (in theory) independent of motivation, weather, etc.
• A general consideration in VO2 max testing is your limit is set by the ability of your heart to pump any more oxygen to your muscles, or your muscles are incapable of extracting any more oxygen from your bloodstream. (41)

On Lactic Acid:

• At higher intensities your muscles demand energy at a rate that aerobic processes cannot match, so your body draws on fast-burning  anaerobic (w/o oxygen) energy sources. The problem is that muscles contracting w/o oxygen generate lactic acid. Your muscles' ability to tolerate high levels of lactic acid (called anaerobic capacity)  is another important determinant of endurance. (24)

On Salt Intake:

• Is an important component in avoiding heat exhaustion. (see story on pg 31)

On Tim Noakes:

• The body does not solely set our limits. Claims the brain alone sets and enforces physical limits during prolonged exercise. (39)
• Examples exist of athletes with memory loss being able to complete impressive endurance feats. (43)
• Claims we are never running as fast as you truly can: if we could, we would literally be able to run ourselves into exhaustion. A “central governor” (the brain), effectively prevents this from happening. (45)
• “The finishing kick” dilemma: if our physiology truly was the sole reason we fatigue and have to slow down during a race, then technically a finishing kick would be impossible. A finishing kick implies that there ‘was more in the tank’ and the only thing holding us back was something other than our pure physiology. (47)
• Most running world records are set on the backs of a fast start, a steady middle segment, and a very fast finish that is on par w/ the opening kilometers or even faster. But the more advance the runners, the less likely they were able to summon a finishing kick. Possibly because their training taught them to dig deeper during the middle segments of the race and truly leave less in the tank for a finishing kick. (51)

Thoughts on Perceived Exertion:

• Perceived exertion is probably the single best indicator of the degree of physical strain. If you feel you can faster, you can. If you feel at your limit, you probably are. (59)
• Anything that moves the ‘effort dial’ (how hard something feels) in your head, will determine how far/fast you can run. A combination of factors at play (dehydration, tired muscles, pounding heart, heavy breathing) contribute to the sense of effort, and anything that decreases an exertion factor will possibly improve performance.
• Personal rating of perceived exertion seems to still be the best way to determine effort, as the brain will ultimately determine how hard it will let you go, and that comes down to how hard it feels the effort is. (211). This is a trainable factor.

• If you can do something to make the perceived effort feel lower, you will be able to go faster.

Thought on Brain Training:

• Your training should be designed to make your mind resistant to fatigue. (boredom resistance).
• Design workouts that make you mentally tough: “Let’s do 10 intervals….. Okay good job, but not good enough, let's do 5 more.” This reframes what the brain thinks is possible.
• Ultimately a breakthrough performance requires your brain allowing your body to do something that it has not yet proven it is capable of doing.

Thoughts on Pacing Tools:

• Using HR monitors and power meters is somewhat like using a speedometer in your car to determine how fast to drive. A great driver does not care what the speedometer says, they are using their sense of feel of the car and the road to determine if they can go faster or need to slow down. This may result in them blowing up, or having the race of their life.

On Pain Tolerance:

• Systematic exposure to intense but intermittent pain during training seems to improve ability to handle discomfort. (87)  Not only that, but within a season an athlete is more able to handle pain during their most fit period of time (peak season) (88)
• High intensity training was critical to improve pain tolerance. Low to moderate intensity training did not move the pain tolerance needle, while high intensity suffering increased pain tolerance by 41%. (88)
• In short, training discomfort prepares you for racing discomfort.

On Muscular Contraction:

• Under normal circumstances we can contract our muscles as hard as we physically are capable (when tested against electronic shock contraction- the actual force of contraction was not any higher than willfully contracted muscles, even though the electric shock felt much harder). (107)
• KEY POINT -> During ultra-distance events the muscles typically only lose about 10% of the force producing capacity; the rest is central, reflecting a progressive decline in the brain’s voluntary acitvition of the muscle. (111)  At the point of exhaustion in long distance events, the legs are merely unwilling to go harder, not incapable.
• In shorter events (600-800m run races) EMG signals are continuing to increase to the muscles (we want to go faster) but muscular force is gradually decreasing. This may be an event where the brain is not the limiter but actual muscular ability. (114)

On Vestigial Reflex (dive reflex) (124-125)

• Sensors primarily around the nose trigger a massive peripheral vasoconstriction: blood vessels in your arms/legs squeeze nearly shut, sending blood flooding back to your core (where it maintains crucial oxygen supply to the heart/brain as long as possible).
• Adds validity to splash cold water on your face to calm yourself down, as well as importance before a race to splash cold water on your face before jumping in all the way.
• This falls into a category of reflexes that Tim Noakes called “anticipatory regulation”: your brain uses knowledge that it gathers consciously (impending dive or looming finish line) to deactivate or activate safety mechanisms that are otherwise purley unconscious.

On Altitude and Performance:

• Oxygen supply to the brain seems to be a key detriment to performance, not oxygen supply to the muscle. The brain senses less available oxygen, and reduces effort/energy output in response. (137)
• At altitudes of ~23k ft, lactate levels are less than ½ of their sea-level values, and you won’t be able to raise your lactate levels at all. (138)

• High altitude = low oxygen availability = inability to raise lactate.

• Studies have shown that at altitude muscular contraction is less than at sea level, despite it being too early for muscular fatigue to be a problem. This implies that the brain is reducing the signals to the muscles in an effort to conserve oxygen for itself. (138)

On Heat and Heat Production:

3 Ways we cool ourselves: radiation, convection, and evaporation.

• For every 100 calories burned by the body, 25 are useful calories for work, and 75 are lost as heat. Though this sounds wasteful, this is similar in efficiency of a typical internal combustion engine. (143)
• At rest, ~250milliliters (half a pint) of blood/min flows vessels near your skin, this carries heat away from your core and releases into the environment through radiation (in form of elctromangnetic waves) and convection (as moving air carries it away- like how a fan works in cooling you). Results in our body always giving off heat at a rate of about 100w, which perfectly balances excess heat produced by the basal metabolic reactions that keeps us alive. (144)
• When exercising in warm temps, blood vessels in our skin dilate, allowing up to 8 liters of blood/min (30x increase) to course through and dump heat to the air around you. (opposite happens in the cold).

• You also begin to sweat: transformation of liquid water to vapor as sweat evaporates consumes energy. This has a strong cooling effect on the skin. Evaporation is the process of losing heat through the conversion of water to gas.
• In very hot conditions, if air is comparable to or higher than your skin temp, evaporation is the only effective cooling method we have. (we cannot radiate heat into the environment effectively because the environment is radiating heat into us).
• If it’s so humid that sweat starts dripping off you, then the water cannot turn to gas (and thus cool us), and your internal core temperature will start to inch upwards until you have to stop. (145)

• By training in hot conditions your body adapts and improves its protective responses:

• You sweat more heavily, and start sweating at lower temps.
• Your vessels dilate even wider
• Total volume of blood in your body increases, allowing your heart rate to stay lower during exercise.
• This process in full takes about 2 weeks.

• Head acclimation is important, but it’s still beneficial to attempt to ‘pre-cool’ before events. In studies cyclists were either pre-cooled in cold water (core temp 97), neutral water (core temp 99), or hot water (core temp 101). The pre-cooled group lasted 2x as long on test to exhaustion. Interestingly, the final core temp at failure was all very similar: 104-104.5 degrees, regardless of what group they were in. (147, see study referenced on this page).
• Studies show that a crushed ice slurry of sports drink  could lower core temp by 1degree F and thus improve performance in the heat.

• Possibly due to cooling the brain as the slurry passed through mouth/throat.

• Risks for heat stroke: being heavy; poorly ventilated clothing; pre existing illness; use of certain drugs like amphetamines.

On Cold:

• Because we generate so much heat through the burning of calories (exercise), extreme cold is rarely an issue for endurance athletes if they’re appropriately dressed. (144)
• For athletes, the issue is when intensity of activity changes: when you can no longer maintain the activity level and the furnace turns down… and of course it is made worse if your clothes are wet from sweat and lose their insulation properties. If the furnace turns down, even mildly cold temps can kill someone. (144)

Hydration and Dehydration:

KEY POINT: Best advice now is for runners to drink when they’re thirsty. What matters most is how thirsty you are. It’s more important to avoid thirst than to avoid dehydration. If you’re thirsty, drink. If you crave salt, take some. Even a small splash of water in the mouth can improve performance if you’re thirsty (even though it does not affect hydration levels. It’s more important to arrive at the starting line properly hydrated, than it is to drink during exercise.

• Historically advice has been all over the place: century ago the running advice was to not drink during a marathon, by 1996 it was drink early and often to replace all water lost through sweating. (161)
• Dehydration is a greater concern in longer races: you have more time to sweat.
• Heatstroke is more common in shorter races- due to body temp primarily determined by metabolic rate (how hot the engine is running). (165)
• For most races some fluid loss is necessary, we simply cannot consume enough liquids. Gastric emptying rate of 1.3 liters/hr max for most men, while fluid loss can be 3 liters/hr.
• In most events from running, cycling, triathlon, etc, the fastest finishers tend to be the most dehydrated. (168)
• The body doesn’t monitor fluid levels, it monitors “plasma osmolality”, which is the concentration of small particles like sodium and other electrolytes in your blood. (170).
• Our ancestoral history required us to be able to handle bouts of dehydration for periods at a time. (ultimately it’s not big deal).
• Remember that when conducting long workouts or races you use up fat and carbohydrate stores, which has mass, and once it’s used it is not there anymore. Which means that some of the body weight loss from a workout is not just fluid. (171)
• 2013 meta-analysis showed that in real world conditions a fluid loss of less than 4% very unlikely to impair performance. (173)
• The weight loss via dehydration may be a performance benefit late in the race. I.e. Haile Gebrselassie would lose almost 12lbs during a race, making him that much lighter and faster. (176)
• Your brain registers thirst, not dehydration, and that is what causes your brain to start slowing the body down.

On Fueling: (chap 10)

Endurance performance depends not just on how much fuel is in the tank, but also what types you have stores, where it’s stored, and how quickly you can access it.

• The more fit you are, the higher % of fat you burn at any given speed. This is due to simply maintaining a given speed gets easier the fitter you are, and no matter how fit you are you’ll burn the same fat-carb mix at any given relative intensity. (181)
• Biopsy studies confirm that the amount of glycogen you can stuff into your muscles is a pretty good predictor of how long you’ll last on a test to exhaustion. (181)

• Muscles not the only source of glycogen: liver is another (storing 400-500 cal for use throughout the body, compared to 2k for fully loaded leg muscles. When you eat a morning breakfast you’re mostly topping off your liver glycogen that was depleted while sleeping (liver depleted because it fuels the energy-hungry brain while sleeping).

• Swishing a CHO mixture in your mouth is enough for the brain to think that fuel is on the way, and that results in a performance benefit. This may also explain why CHO offers a boost to performance almost instantaneously. (190)

• Mostly beneficial if you are already low on CHO stores (almost no benefit registered if you’re topped on fuel).

Low Carb/High Fat Considerations:

• Explorers on low carb (or no carb) diets (eating reindeer during an 11month trip) would go through a 2-3 week adjustment of low energy and apparent weakness, but soon adapt and often be as strong as ever. (184)

• The trick is the fat- not the lean meat. ~¾ of their calories came from fat, and they were fine.

• Adequate salt intake is very important on low carb diets. (186)
• See study on pg 186 re fat adapted cyclists.
• Even the leanest athlete carries around 30k cal of fat (most carry 100k), and if you could access those fat stores while exercising at moderately high intensity, you could in theory go long enough that sleep deprivation would be a bigger problem than bonking).

• It does seem sprint ability is hindered on LCHF diets (important detriment for sprints/accelerations).

• If your primary focus is on covering the greatest distance possible, then LCHF and the ability to access as much of your fat stores as possible is a considerable advantage. (188)
• If your goals involve racing, the key fuel concern may not be how much you burn but how fast, and how quickly you can refill those reservoirs as you race.
• Glucose combined with fructose = faster absorption.
• In theory the math for fueling is simple: the # of cal you need to ingest is the difference between how many you already have stored in your body and how many you want to burn. In practice, it appears to be much more complicated. (189)
• Athletes on LCHF diets adapted in amazing ways over a 3wk intervention diet. The problem was that fat-adapted athletes became less efficient, requiring more oxygen to sustain their race pace. This is the consequence of the metabolic reactions required to transform either fat or CHO into ATP (ATP is the final form of fuel the muscles use for muscular contractions). For low intensity activities the loss of efficiency is no problem, for a 10k race it’s a huge detriment.

Metabolic Flexibility:

• Best approach to racing/fueling seems to be using a “metabolic flexibility” approach in which you train yourself to use CHO for high intensity activity, and fat stores for long aerobic activities. (193)
• Study repeated just 3x, over 6 days total had athletes do a “sleep low” approach of conducting a CHO depleting workout in the evening, eating a low CHO meal, then the next morning another CHO depleted moderate workout in the morning before breakfast improved 20k performance in a time trial by 3%. (196)
• “You train to burn fat, but you race on carbs.” (198)

On Racing:

• Perfect pacing may not be the best way to compete. The “Kenyan” way is to go out  very fast, settle in, then kick at the end. This gives you the opportunity to have a breakthrough race.

• The Kenyans wake up and firmly believe that ‘today will be my day’, and run with the leaders because they think they can beat them. If they can’t, they regroup and try again the next day. The belief in themselves often become self-fulfilling prophecy. (250)

• A perfectly paced race may result in better results on average, but you’re effectively pre-determining how good your day can be. (249)

On Placebo Effect:

• If it results in an improvement in performance, does it matter that it is a placebo? (251)
• In short, if you think it works, then go for it.