THE CLINIC
It Is The Heat—And The Humidity
This question about summer weather's impact on a runner has interested me for some time:
A runner runs 5 miles at 6 a.m. one day with cloudy skies, an 80-degree temperature and 80 percent humidity. That same runner a few days later runs 5 miles at 4 p.m. under sunny skies with a 95-degree temperature and 50 percent humidity. Which of the two external weather conditions is more taxing on the runner assuming the exact same running route and running pace? Why?
Paul Scelsi
Dallas, TX
Musclar contractions, as you probably are aware, generate heat that must be released into the environment; if not, internal core temperature will increase and eventually threaten health and possibly even life (see A Summer Scorcher [LINK]). High ambient heat and humidity make it more difficult to dissipate this heat. The primary factors that affect body core temperature are reflected in the composite temperature known as the Wet Bulb Globe Temperature (WBGT). This index integrates humidity, air temperature and the temperature of the globe into a single value. It is determined with the use of specialized instruments that are commercially available. However, the risk of a heat-related illness can be assessed by simply combining the influence of ambient temperature and relative humidity (both readily available from local weather stations).
Thus to answer your question, the relative risk of running in the a.m. with the cloud cover, an 80-degree temperature and 80 percent humidity would be moderate to high. Doing that same run on the same course at the same pace on a sunny day in the late afternoon with an ambient temperature of 95 degrees and 50 percent humidity would be very high. For more information, see the American College of Sports Medicine Guidelines for Exercise Testing and Prescription, 7th ed., Lippincott, Williams and Wilkins, Appendix E. In either case it would be critical to stay hydrated but I would advise you to run in the a.m. under these conditions or inside in a controlled environment.
For a fluid-need calculator go to www.gatorade.com/hydration/fluid_loss_calculator/.
Tom LaFontaine, PhD, ACSM RCEP, FACSM
Muscle Cramping in Endurance Races
I am a 54-year-old male runner and triathlete. Despite what I believe has been adequate training, hydration and sodium intake I still get severe cramping during my races. I rarely get the cramps during training. Yesterday I did a half-Ironman race in Cambridge, MD. The weather was perfect. It was overcast and not very warm. I stayed with my race plan to keep my cadence on the bike at 90 to 105, with my heart rate at 70 to 80 percent of maximum. I was comfortable until mile 38, and then suddenly my medial vastas and adductors started to cramp. This slowed my pace.
When I got off the bike as I dismounted I got severe cramps in both hamstring and adductors. I walked the best that I could and after two miles I was able to run the rest of the race. I did walk through the water stops for 10 to 20 seconds. My medial quads were painful through the whole run. This is a typical experience that I have. I have been doing all distances of triathlon as well as marathons for 17 years. It seems that during the longer races I have the most trouble. I am not sure if my training is incorrect, my salt intake too low or my calories insufficient. I am just not sure where to go from here. I have been reluctant to use salt tablets during these events. I have had my bike fitted. I have calculated out my calorie requirement and my hydration needs. Please help.
Ed Dzielak, DO
Scranton, PA
This is a tough but common problem. You are correct in re-evaluating all aspects of your training and racing. Hydration and electrolytes are always potential sources of cramping, especially in longer events. Although dehydration is a concern, hyponatremia is commonly seen in Ironman events. (I have not seen data on half-Ironman races.) It is easy to take in excess fluids while on the bike. Weighing yourself prior to and following workouts can give you a good ballpark of your fluid intake. Obviously, this will vary depending on the weather conditions.
Another big issue is the exercise intensity during a race. Do you ride at the same intensity during training, especially after swimming? Many athletes perform short and fast, and then long and slow, workouts but never workout at race pace. Incorporating workouts at race pace may be helpful.
What is your caloric intake during a race? By the time you get off of the bike, you have been exercising for hours and your glycogen stores will be low unless you have ingested adequate calories while on the bike.
Although training for a triathlon is time intensive, you may consider adding in core and leg strengthening exercises. Each of the activities involves a limited motion of the hips; strength deficits are fairly common. Weakness causes the muscles to fatigue, leading to cramping with continued exercise.
Lastly, don't be hesitant to supplement electrolytes during a race (certainly after testing this during training). There are a number of capsules available that are easy to tolerate (I've used them during 100-mile runs). There is a new electrolyte strip called Endurolyte that dissolves in your mouth—you may want to try it.
Cathy Fieseler, MD
Tyler, TX
Recurrent cramping tends to be a phenomenon that is a bit perplexing and probably multifactorial. There is much debate about the role of sodium and other electrolytes but sodium loss in sweat/inadequate sodium intake is most likely part of the puzzle. Muscle fatigue with an aberrant spinal cord reflex preventing activation of golgi tendon organs in the muscle also leads to hyper-stimulation without down regulation. Other things to consider: whether you taking a statin drug; metabolic or mitochondrial myopathies (maybe some genetic variant of one of these); sickle cell trait; thyroid disease?
I recommend training and racing with Gatorlytes or Endurolytes as directed by manufacturers. Maintain your hydration and review your nutritional intake with a sports nutritionist. Stretch at the first warning sign of cramping. If this persists consider thyroid testing. Consider muscle biopsy by a specialist who knows the proper laboratory tests for these myopathies.
Fred H. Brennan, Jr., DO, FAOASM, FAAFP
My thought on cramping is that it is primarily due to muscle overuse and/or fatigue. There also may be a component just related to the mental stress of racing. I know we always talk about and look for electrolyte problems and dehydration, and these issues can certainly cause cramping to occur, but it is usually obvious when these occur. It certainly does not sound like these were issues for you. Even so, I wouldn’t hesitate to experiment with taking some electrolyte replacement tablets during your next long event (try them a couple of times in training first, to make sure you tolerate them okay), and see if that helps.
My first suggestion would be to look at your training (and I assume you have already done this); especially at race-specific training. Have you done bricks at race intensity, with shorter duration? I have found that doing workouts like bike-run-bike-run-bike-run-bike, where each bike segment is 5 to 10 miles, and each run 1 to 2 miles, both at race pace or even faster, to be highly effective. Or if the cramps are mainly in longer races perhaps you would benefit from longer bricks, such as 15 to 20 miles bike, 3 to 5 miles run; repeated 2 to 3 times. Tough workouts, but I have found that one or two of these workouts leading up to a race are worth the effort.
Another thought: was the course hillier than you are accustomed to? Perhaps this could be additional stress on you muscles that would lead to overuse and cramping. One other suggestion would be to work on specific training for the areas affected by the cramps, and try to improve strength and flexibility in these areas. So, specific adductor and vastas medialis resistance training for improved strength may help reduce cramping. I also wonder why the cramps occurred in your adductors and medialis, as these are not the typical muscles I would expect to be overworked.
My totally anecdotal comment is that I have occasionally experienced cramping in these areas in triathlons, even as I exit the water and start the bike. My conclusion has been that somehow wearing a wetsuit makes these muscles work more during the swim, thereby leading to fatigue. I’m not sure what the solution for this is; probably working on specific muscle conditioning as I mentioned above. Hopefully this will help you figure out what is causing the cramps and enable you to race cramp-free!
Mark Elderbrock, MD
Knowing Your Maximal Oxygen Consumption is Good for Your Health
How beneficial is a baseline VO2 max and at what interval is it typically repeated?
Ben Pearl, DPM
When you say “baseline” I'm assuming you mean VO2 max in an untrained, sedentary state although you could mean baseline such as in an endurance athlete at the start of periodized training for an upcoming season as well. I'm going to summarize several facts about VO2 max below.
1. VO2 max is considered by most exercise physiologists to be the best measure of cardiorespiratory capacity;
2. VO2 max is defined as the maximal amount of oxygen that a person can take in (respiration), transport (cardiac output), and use (cellular respiration) during maximal exhaustive aerobic exercise;
3. 50 percent of VO2 max is determined by the ability of the heart to pump blood and 50 percent is due to the ability of the exercising tissues to use oxygen;
4. the formula for VO2 max is HR x Stroke Volume x A-V Oxygen difference;
5. VO2 max is typically highest on the treadmill (or cross-country skiing) with the highest value recorded to my knowledge being 92 mls/kg/min (typical expression in order to correct for differences in bodyweight referred to as relative VO2 max);
6. Lance Armstrong was measured at 84 mls/kg/min and Jim Ryun at 82 mls/kg/min. Interestingly, Ryun's VO2 max was 65 mls/kg/min after a year without training. This suggests his VO2 max (82) increased from his baseline (65) by 25 percent;
7. The Heritage Study showed that among previously sedentary twins, after 16 weeks of training, VO2 max increased from about 5 percent to 50 percent, with an average of around 25 to 30 percent; thus it is presumed that VO2 max can be increased from baseline by 25 to 30 percent. Knowing your baseline VO2 max can give you an idea of your personal genetic limit. Note that this assumes optimal nutrition and bodyweight. Since VO2 max is expressed in milliliters per kilogram per minute, bodyweight becomes critical to optimization of the value;
8. VO2 max is one of four or so parameters that predict performance among homogenous populations (such as elite runners), along with running efficiency, anaerobic or lactate thresholds, and blood status;
9. one of the best reasons for knowing VO2 max is for health status. For example, in one study 100 percent of cardiac patients with a VO2 max greater than 32 mls/kg/min were alive after three years, whereas 70 percent of those with a VO2 max of less than 22 mls/kg/min had expired. Kavanaugh in Toronto found similar results among 12,000 cardiac patients;
10. a VO2 max of less than 85 percent of the VO2 max predicted for your age, gender, height and weight suggests cardiac dysfunction;
11. in men and women who do not have coronary artery disease, VO2 max is an excellent predictor of longevity and survival;
12. VO2 max is an excellent predictor of surgery outcomes, transplant outcomes and other procedures.
The bottom line is that VO2 max is an excellent measure to predict both performance and health outcomes.
Tom LaFontaine, PhD, ACSM RCEP, FACSM
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