Saturday, October 25, 2008

The Most Common Ironman Mistake

In Kona this year I met an age-group athlete the day before the race. Nice guy. After the race he wrote me with a question about his race. He also sent me his WKO+ power-data file. You can see it below. What I saw is typical of most Ironman athletes. It’s easy to fix but requires dedication as it isn’t what you want to do in a race. The other chart you see farther down is explained in my answer.

Question: I have been training with power (bike) and GPS (run) throughout this year and have felt as though I had nailed my plan down. On my bike, I did a bunch of rides 4:30-6:00 and was able to maintain 200-220 watts (I usually don’t use normalized power because I can’t see it on my computer). Also, my critical power is around 290. I use the 20 minute all out and the 3 minute all out to calculate this. I had registered for Ironman Florida as well so I really didn’t want to push too hard and have nothing left. I figured I would stay around 200-210-ish to be safe. Coming out of the swim and going to the bike my legs felt pretty tired. I was able to keep the watts up in the beginning but it really felt like I was pushing a lot harder than what my watts were showing. By mile 40 I started cramping in my VMO on both legs. This went on for the next several miles and got worse. At this point all goals went out the window and it was a race of survival at that point. My average power was 169 and normalized power was 179 (which is the lowest long ride I have done in months). I was hoping to finish the bike in 5:30 but only managed 5:57...which I was actually happy with considering the conditions of the race and my body. I felt good from a nutrition standpoint. I think I was a little dehydrated but not by much (i urinated before the bike and 2x on the bike and none on the run). Of course, the bike killed my run as well. I was hoping for a 3:45 run (which I have done before). In my previous ironman races I have been sore for the whole week. Two days after the race I was stiff but not bad and think it may have been due to my flight home more than the race. Four days out I felt great.
I was totally baffled by this result and wondered am I asking too much out of myself? Could the conditions of heat and wind have that much of an effect on my performance or am I missing something here?

Answer: It’s always a bit difficult to draw conclusions from just one piece of data even if it is over nearly 6 hours. Having heart rate in addition to power would have been good to see what you were experiencing effort-wise and to get some idea of what the heat was doing to you, also. I would like have seen how much cardiac drift/decoupling was going on. That can be found on the “graph” view of WKO+ where it says “Pw:HR.” But I’m fairly confident I see the cause of your demise on the bike. It has to do with variability index. I see this a lot and spend months teaching the athletes I train how to control it by working on pacing while staying very focused on power in training and races.

Variability index (VI) is normalized power divided by average power. The resulting ratio should be less 1.05 I’ve found in long course racing. Your average VI for the entire race was 1.08. Much too high. Looking at it by quarters reveals even more. That’s what the chart attached shows. In Q1 VI was 1.08, Q2 it was 1.07 and in Q3 climbing to Hawi and descending it was 1.11. For 84 miles of the race you were averaging 1.09 for VI. It didn’t drop back down into the goal range of less than 1.05 until the final quarter when fatigue set in and forced you to ride steady.

What these VI numbers tell me is that you were surging a lot—in and out of corners in town, into head wind, up and down small hills, when someone passed you or you passed others, etc. Surges sap you of energy very quickly and also play havoc with your gut’s processing of fluid and fuels. Steady state pacing is a far better use of your energy. I expect your long rides did not have nearly this high of a VI. They, just like your race, should have a VI less than 1.05. Until you can do that it is unlikely that you will ever produce your best possible long course ride.

Also attached is a chart from an athlete I used to coach who was the best I’ve ever worked with for low VI scores. Here he does 112 miles in training in 4:44 with a VI of 1.01. He raced exactly the same as he trained. There was never any question that he would have a good IM ride. This is exactly what you need to work on doing also. Make your rides exactly like what you expect to do in the race – as much as possible. Terrain and weather may confound the preparation a little but you need to decide how to handle those also relative to your power. Once you learn to ride this same way you’ll have good races without issues, at least not on the bike.

You mentioned that you didn’t see any way to ride normalized power in the race. Actually, you can. If you ride at a steady power output of VI less than 1.05 the average power on your device will be almost the same as normalized power. In fact, what you should do is to set a race power goal based on the NP from your long rides in the last several weeks before the race. So if you determine that an appropriate NP is, say, 200w then you just ride steadily trying to average 200w. At less than 5% VI your range would wind up being +/- 10w or less. But realize that the goal number you come up with must be based on actual training data, not what you think you are capable of. That’s a whole other discussion.

Thursday, October 23, 2008

Llanos Power Hawaii 2008

Here you can see the 2008 Hawaii Ironman power chart for 2nd-place Eneko Llanos. This is from his Power-Tap and found on the Saris website (,guid,983fb23f-1a03-4315-b652-dc71e448b4cd.aspx). The Saris website also offers a summary of his data by quarters in the race. His bike split was 4:33:27, the 6th fastest on the day. The chart is a bit hard to read. The only part that really tells us anything here is the power graph, the yellowish line across the middle. Unfortunately, there was no heart rate data.

What you see here is fairly typical of the pro race among those with the top bike times each year. In the first 20 minutes there is a lot of power variability. Lots of peaks and valleys. He is probably quite excited at this stage of the race having come out of the water in eighth place three minutes back from the leaders. So he was undoubtedly working his way up toward them. Being with the lead group is quite an advantage. This may be partially mental as well as physical. Mental because it seems easier to ride hard when there are others nearby. Riding alone makes it very difficult to keep pushing. And even maintaining a staggered gap on the riders ahead within the rules may still afford some drafting benefit if the wind conditions are right. A group of riders going down the road, even though spread out, can displace and redirect a lot of wind.

Note that power for the first half of the race is fairly steady once beyond those initial 20 minutes spent looping through Kona with several turns. His average power for each of the first two quarters of the bike leg was 286 and 284 watts, respectively. Around the half-way point power begins to fade a bit. In the third quarter he averaged 260 watts and 251 in the fourth quarter. This, again, is typical for the pro race. Llanos is paying the price for having gone out so fast early on. He faded less than many of the others since he split the bike in fifth place among the pro field.

Allowing power to fade a bit may also have to do with anticipating the run. He would like to have something left in his legs now that he’s established his position in the field. And this tactic paid off as he ran a 2:51:49 marathon, the tenth fastest of the day. With a tenth-best run I would not have normally expected him to take second. But that day the early leaders on the bike faded significantly. In fact, among the pro men, of the top 10 fastest bike splits only four made the top 10 overall. Six of the top 10 overall finishers were well outside the top 10 fastest bike splits. For example, ninth-place-overall Michael Lovato had the 25th fastest ride of the day (4:45:21). (Some day I’ll write on this. I once looked at what was the best predictor of a high finish place in various Ironman races. In Hawaii it was clearly the run.)

With an average power of 270 watts and a weight of 72 kilograms (158 pounds) Llanos’ average power-to-weight ratio for the ride was 3.75 w/kg (1.71 w/lb). As you can imagine, that’s quite good for riding 112 miles.

While effective for Llanos and a few others in Kona this year, I would not recommend this way of Ironman racing for most amateurs. First, amateurs are likely to have several other riders near them regardless of how hard they work. In Hawi we saw only a few amateurs riding with no one else nearby. The pros train to race this way – or at least they should. Most amateurs do steady state rides for their longest bike workouts. You should always race the way you train. But given that there is a 15-minute gap between the start of the pros and the age groupers, the amateur leaders out of the water who are contending for a high overall and age-group placement may well want to race much as the pros do. There are very few of these in the race, however.

The average watts per kilogram for the other amateurs should probably be in the range of 2.9 to 3.3 w/kg (1.3-1.5 w/lb). And that’s only for the young males. For every year beyond the age of 35 subtract a half percentage point. Women can lower that by yet another 10 percent. So for a man who weighs 72 kg and is 55 years of age, the estimated Ironman power range would be approximately 188 to 214 watts (72kg x 2.9-3.3 = 209-238w, subtract 10% for 20 years of age = 188-214w). A woman of the same age who weighs 60 kg (132 lbs) may subtract another 10 percent for a ballpark range of 141 to 160 watts.

Now realize that these really are just ballpark estimates and not carved-in-stone, scientifically proven facts that everyone must abide by. It’s merely intended to give you a starting point for determining what your average power should be for the bike portion of an Ironman. Some will find the range too low and for others it will be too high. Extreme heat (as in Hawaii) must also be taken into consideration. Learning to apply all of this is one of the reasons that you train—to narrow down what your targeted power should be.

Most athletes I talk with don’t do this at all. They train using heart rate and assume that will give them the best possible bike split. Whenever you are seeking a specific output (bike split) you should measure output (power) not input (heart rate). Heart rate tells you how hard you’re working (plus a lot of other stuff such as what you had to eat or drink and the weather) while power tells you what you’re accomplishing. This is not to say that heart rate is not valuable information during a race. It is. But it must be compared with power (or pace on the run) to be meaningful. This is another completely different post I’ll do some day.

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Tuesday, October 21, 2008

Foot Strike in Hawaii Ironman

Here are 5 pictures from this month’s Hawaii Ironman. Two of them are heel strikers and three are flat foot strikers. Can you tell which is which? There are two obvious signs. Heel strikers nearly lock the knee of the leading leg while flat foot strikers have a slight bend in that knee. Also, heel strikers’ toes point toward the sky and flat strikers’ feet are parallel with the road surface just before the foot touches down. If you haven’t read my blog on this subject from last year, which is the second-most read of all my posts, go to the second archived article here.

Sunday, October 19, 2008

Back-to-Back Ironman

Question: I just finished Ironman Hawaii and I’m signed up for Ironman Arizona in a few weeks. They’re six weeks apart. I had a decent race in Hawaii but I’ve gone faster. I’d like to have a good race in Arizona. Is it possible? – F.C.

Answer: That’s a tough one. Several years ago I used to say that an athlete should only do one Ironman in a year. But then I coached so many triathletes who insisted on doing two in a year that I changed my mind. They proved to me that it could be done by healthy, well-experienced athletes without breaking down physically or mentally. It seemed reasonable, however, to separate the races by at least 12 weeks to allow for recovery and the rebuilding of fitness.

Then along came a few more athletes I coached who wanted to do Ironman Canada and Ironman Hawaii which are usually separated by about six weeks. With a few individual exceptions, they did quite well with two closely spaced races. Then there are triathletes like Joe Bonness and Petr Vabrousek who have made careers out of several closley spaced Ironman races year in and year out. So now I believe almost anything is possible if the athlete is experienced, fitness is high coming into the first race and he/she is not prone to injury or illness.

Getting back to the gist of FC’s question, successfully training for personally competitive, back-to-back Ironman races depends on several issues:

* How fit you were coming into the first race. The higher your fitness was relative to your all-time fitness, the better the second race is likely to be. (Just a quick reminder that
WKO+ software may be used to quantify fitness, or “CTL” as the software calls it.)

* How experienced you are at the Ironman distance. Having done several Ironman races means you know what it takes for you to have a good race the second time. This usually means long workouts, hill training and tempo sessions.

* How hard you pushed yourself in the first race. If you did it just to finish and didn’t try to find the limits of your fitness then you should bounce back fairly quickly. But if you gave it all you had then having a second race of near the same quality is unlikely.

*How quickly you recover. No matter how hard you pushed yourself in the first race, if you typically recover slowly then set your goals relatively low for the second. You may well need four of the six weeks between IM Hawaii and IMAZ to shed the fatigue before you are able to return to something approaching your normal Ironman training routine. That would likely preclude having a fast second race.

* How motivated you are to train hard again. If you are mentally wasted after the first race and just aren’t stimulated to get back into training again then you are better off just forgetting it.

* How high your goal is for the second race. The higher your goal, the more likely you are to be disappointed. Before setting a goal you should review the previous bullet points.

Again, for most athletes it’s not generally a good idea to do two Ironman races spaced so closely. But you may do fine with it depending on the variables listed here.

Good luck!

Tuesday, October 14, 2008

Seasonal Weight Management

It’s been three days since Ironman Hawaii and my family has joined me in Kauai for a week of vacation. I’m taking 11 days off from any training at all and just enjoying life and being with them 24/7. We’re having a great time. But even though I’m enjoying life I still miss training. I didn’t bring a bike and can’t run any more. I had to stop three years ago because of knee discomfort due to wear and tear to the edges of my right knee meniscus from nearly 50 years of running. Last Thursday I climbed 75 floors in five-floor intervals over a 45-minute period. Since then the most physical thing I’ve done is walk to the beach and sit down. While being so inactive still causes a bit of guilt it’s not nearly as bad as it was 20 years ago when the thought of a day off was repulsive. Being older and more patient now I know that it will all come back soon enough.

The only part of the time off that really bothers me is sense that I’m gaining excess flab. I still have this desire to eat as I do when training 15 or so hours a week. I have to continually remind myself that I’m not hungry. I’m OK with gaining a couple of pounds. That won’t be a problem. More than that and it will be bit of a bother, as my Brit friends say.

I’ve been told that many of the elite Kenyan runners gain in the neighborhood 10 pounds at the ends of their seasons. Maybe at their youthful ages they can get rid of the excess quickly. When younger I could lose a couple of pounds easily. All I had to do was skip dessert. Now at my age 64 I can no longer do that. If I just look at dessert I gain weight, it seems. It’s interesting how the body changes with age. The older athletes I know have pretty much the same issue. I’ve recently been talking with two of them about this. Their seasons are over and they’re cutting back on training stress, as they should be doing. One of them has gained about five pounds. I’ve been coaching him for six years and it seems to have gotten more difficult for him each year. He’ll soon be working with our TrainingBible Coaching nutritionist, Kelly Cawthorn, who specializes in weight management for athletes using a Paleo diet platform.

All of this has to do with power-to-weight ratio. Managing your weight so that you are an optimal mass come race day is critical to success. Of course, this doesn’t mean trying to be excessively skinny, but rather healthfully lean. It’s OK to gain some weight now – just not too much. I like to have the athletes I coach at this lean level by 12 weeks prior to their first A-priority races of the season at the latest. The other part of the equation – power – is also developed during this time. This is largely a muscular training component that starts with weight training and progresses to sport-specific power development in Base 2. I’ll write more on this related subject at a later time

Thursday, October 9, 2008

Kona #12

I’m in Kona this week for Ironman Hawaii even though I have no one competing in it for the first time in many years. Two of the pros I coach, Justin Daerr and Jim Vance, qualified but for personal reasons decided not to race here this year. They will both be doing Ironman Arizona in November instead. That’s good for me since I live just up the road about 15 miles. Both are training quite well and I expect they will also race well.

This is my twelfth trip to Kona for the Ironman. My first was in 1989 which was probably the greatest Ironman triathlon ever. Dave Scott and Mark Allen went shoulder to shoulder for nearly the entire day with Mark taking the lead and the win near the end of the run. I can recall standing at about the 5-mile mark on Ali’i Drive on the old course with sweat pouring out of me as Mark and Dave ran by at sub-6-minute pace. The heat and humidity were unbearable that year. That Marks’ run split is still the fastest ever in Hawaii is a testament to his physical and mental preparation.

On Thursday morning I always do a talk to a group of family physicians there for Dr. John Post’s Orthopedic Update seminar. The bottom line of my talk is that exercise is the most potent medicine these docs can prescribe for their patients. I go through classic research that shows how it prevents or reverses the symptoms of almost every lifestyle disease known to Western society. While a little out of my realm of high-level performance, it is nevertheless a lot of fun. Dr. Post always has some interesting speakers.

A couple of years ago he invited the father and son racing team Dick and Rick Hoyt to talk about their experiences not only in racing but also in dealing with the medical profession. You may know that son Rick has cerebral palsy so Dick pulls him in a raft during the swim, rides a bike with a special seat for his son, and pushes Rick in an oversized “stroller” for the marathon. They didn’t finish the race that year and I believe I saw that they have decided to forego any more Ironman racing since Dick is now in his 60s.

The last two years Dr. Post has invited Bob Scott to speak. Bob is the holder of the 75-79 age group course record at something like 13:27. If Ironman was age-graded I expect that would have won the race when he did it a couple of years ago. That’s a remarkable performance and gives me hope that I can train and race at a high level as I approach my late 60s.

About four years ago Dr. Post invited an athlete whose daughter died as a child. Her dying wish was that her dad would be allowed into the Hawaii Ironman. WTC, the owner of the race at that time, heard of it and gave him a slot. It was a heart-tugging story which the TV coverage featured that year. Even with the death-hardened doctors in attendance, there wasn’t a dry eye in the place when he told his story and how he and his wife worked with the physicians right up until the end.

The Kona trip is a chance for my son, Dirk, and me to represent TrainingPeaks and TrainingBible Coaching by meeting with people in the industry who we talk or trade emails with throughout the year while also making new acquaintances. And this year we’ll wrap it up by spending next week in Kauai with our wives and Dirk’s daughter. It’s a great way to end the season. So I may be away from my computer for a few days. But then again I may change my mind after seeing something that sparks my interest.

Wednesday, October 1, 2008

Hydration and Exercise, Part 4

This is the last of a 4-part series on hydration during exercise. Again, I understand that what I’ve been telling you probably contradicts all you’ve been told over the years. I wouldn’t expect you to make a sudden and complete change in how you hydrate during exercise, especially if you’ve had great success in racing. But if you’ve had difficulty with performance in longer events then you may well want to reconsider what you do in this area. Feel free to post your reactions, comments and questions.

Q: What should I drink during a race?
A: It depends on the duration (not necessarily the length) of your race. For shorter endurance events, which I’ve been calling those under four hours, drink either water or a sports drink. Up to about 1.5 to 2 hours, depending on your fitness level, water will do fine. Unless you are in very poor physical condition, it is unlikely that you will bonk (run out of carbohydrate). From this duration up to about 4 hours any sports drink you like the taste of will do the job. Or you may use water and gels. You will need some calories at this duration. Just drink to thirst and you should get both fluid and fuel right. For events lasting longer than about 4 hours I’d recommend separating the hydration and refueling matters. In other words, drink fluids, especially water, to quench thirst using thirst as a gauge of when and how much to drink. You must pay attention to your body to do this. If you become externally focused for long periods of time, which I realize is certainly possible in a race, you are likely to fall behind and mismanage the rate at which you dehydrate. Drinking to an arbitrary schedule in long events is likely to start you down a path toward hyponatremia with performance-detracting symptoms appearing well before you reach the sodium concentration level associated with the condition. Some dehydration is normal and to be expected.

Q: So in long events and workouts what should I use for refueling?
A: Treat refueling as a separate matter from hydration in events longer than about 4 hours. Take in carbohydrate in a form and at a rate you find works for you in training. Again, gels since they are generally easily digested and carried may be a good option for those athletes performing at a relatively high intensity level in four-hour and longer events. If you are familiar with
WKO+ software I’d suggest this is an Intensity Factor (IF) of about 80% or higher. If your intensity is lower and less stressful than that then you may well be able to digest sports bars or real food. The slower you go and the lower the IF, the more options you have for refueling. If you are casually walking a marathon a hamburger with French fries will probably work, although I wouldn’t recommend it!

Q: How much dehydration is acceptable?
A: As mentioned in
Part 1 of this series on hydration, the number keeps rising in the scientific community. A 2% loss of body weight during exercise was once considered to be a critical level with the experts believing this would result in a significant drop in performance. The research does not support this [1,2,3]. Now that level appears to be something more in the range of 4-5% [4] but may be as low as 3% in hot conditions [5]. Other studies of Ironman triathletes found no connection between body weight changes and the finishing times of participants [6,7,8].

Q: Should I drink extra amounts in the days and hours leading up to a race in hot conditions so that I’m hyperhydrated?
A: Your body does not store water like a camel’s does. If you drink an excessive amount, meaning more than necessary to quench thirst, you will soon urinate to remove the excess. And by drinking excessively this you temporarily dilute electrolyte stores. So there is nothing to be gained by drinking copious amounts of fluids the day before or the morning of a race [9]. Thirst is the key. Pay attention to your body.

Q: Should I supplement with sodium capsules during an ultra event?
A: For long events like Ironman triathlons, other similar duration ultra-endurance races and slow marathons I don’t see a reason to do this. Sweating at an average rate of 1 liter per hour with an average sodium loss of 40mmol/l produces a sodium loss of about 920mg per hour, about 1 gram. So taking in 1 gram per hour of sodium for, let’s say, 10 hours means you would take in about 10g and lose about 10g. That 10g represents less than about 8% of an average-sized male’s total sodium stores. But realize that losing 10 liters of water in sweat means a loss of perhaps 20-25% of that athlete’s body fluids. That is a much bigger issue than sodium replacement. So replacing part of this fluid is a far more critical issue than sodium replacement.

It’s also interesting to note that sodium loss is not straight line during exercise. As sodium is lost through sweat the rate at which sodium is lost decreases over time to maintain body fluid homeostasis [10]. In other words, at one hour into an event you may well be losing sodium at a higher rate than you are later in the race even though the sweat rate remains constant.

Q: Is there a downside to taking a sodium supplement during a long race?
A: If you take in a small amount of sodium, let’s say that means less than 1 gram per hour, I suspect there is not a significant impact either way on health or performance.

Q: How do I know if I am dehydrated after a workout or race?
A: Most of the research seems to support the notion that a yellow urine color is a good indicator of significant dehydration [11,12,13,14], but not all of the research is in agreement [15]. While having yellow urine may indicate some level of dehydration, such a color by itself is not proof of dehydration. Metabolites, the end products of metabolism such as urea, are often expelled in the urine and provide color even though you are well hydrated. The same goes for B vitamin supplements. They will provide a bright, yellow color to your urine. The best indicator of dehydration is thirst. It works. Just pay attention.

1. Cheuvront, S.N., R.I. Carter, M.N. Sawka. “Fluid Balance and Endurance Exercise Performance.” Current Sports Medicine Report 2 (2003): 202-208.
2. Food and Nutrition Board of the Institute of Medicine. “Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate.” Washington DC: The National Academies Press, 2005.
3. Oliver, S.J., S.J. Laing, S. Wilson, J.L. Bilzon, N. Walsh. “Endurance Running Performance After 48h of Restricted Fluid and/or Energy Intake.” Medicine and Science in Sports and Exercise 39, No. 2 (2007): 316-322.
4. Slater, G.J., A.J. Rice, K. Sharpe, R. Tanner, D. Jenkins, C.J. Gore, A.G. Hahn. “Impact of Acute Weight Loss and/or Thermal Stress on Rowing Ergometer Performance.” Medicine and Science in Sports and Exercise 37, No. 8 (2005): 1387-1394.
5. Cheuvront, S.N., R.I. Carter, J.W. Castellani, M.N. Sawka. “Hypohydration Impairs Endurance Exercise Performance in Temperate but not Cold Air.” Journal of Applied Physiology 99, No. 5 (2005): 1972-1976.
6. Laursen, P.B., R. Suriano, M.J. Quod, H. Lee, C.R. Abbiss, K. Nosaka, D.T. Martin, D. Bishop. “Core Temperature and Hydration Status During an Ironman Triathlon.” British Journal of Sports Medicine 40, No. 4 (2006): 320-325.
7. Sharwood, K., M. Collins, J. Goedecke, G. Wilson, T. Noakes. “Weight Changes, Sodium Levels, and Performance in the South African Ironman Triathlon.” Clinical Journal of Sports Medicine 12, No. 6 (2002): 391-399.
8. Sharwood, K., M. Collins, J. Goedecke, G. Wilson, T. Noakes. “Weight Changes, Medical Complications, and Performance During an Ironman Triathlon.” British Journal of Sports Medicine 38, No. 6 (2004): 718-724.
9. Sawka, M.N., S.J. Montain, W.A. Latzka. “Hydration Effects on Thermoregulation and Performance in the Heat.” Comp Biochem Physiol A Mol Integr Physiol 128, No. 4 (2001): 679-690.
10. Hew-Butler, T.D., T.D. Noakes, S.J. Soldin, J.G. Verbalis. “Acute Changes in Arginine Vasopressin, Sweat, Urine and Serum Sodium Concentrations in Exercising Humans: Does a Coordinated Homeostatic Relationship Exist?” British Journal of Sports Medicine (Epub ahead of print).
11. Armstrong, L.E., C.M. Maresh, J.W. Castellani, M.F. Bergeron, R.W. Kenefick, K.E. LaGasse, D. Riebe. “Urinary Indices of Hydration Status.” International Journal of Sports Nutrition 4, No. 3 (1994): 265-279.
12. Kavouras, S.A. “Assessing Hydration Status.” Current Opinions in Clinical Nutrition, Metabolism and Care 5, No. 5 (2002): 519-524.
13. Shirreffs, S.M. “Markers of Hydration Status.” Journal of Sports Medicine and Physical Fitness 40, No. 1 (2000): 80-84.
14. Armstrong, L.E., J.A. Soto, F.T. Hacker Jr., D.J. Casa, S.A. Kavouras, C.M. Maresh. “Urinary Indices During Dehydration, Exercise, and Rehydration.” International Journal of Sports Nutrition 8, No. 4 (1998): 345-355.
15. Kovacs, E.M., J.M. Senden, F. Brouns. “Urine Color, Osmolality, and Specific Electrical Conductance Are Not Accurate Measures of Hydration Status During Postexercise Rehydration.” Journal of Sports Medicine and Physical Fitness 39, No. 1 (1999): 47-53.