What's Cool In Road Cycling

Hydration and Anaerobic Performance

Hard to believe, but it used to be prevailing wisdom amongst endurance athletes like marathoners that drinking water during training or racing was a sign of weakness akin to unsportmanslike conduct. We now know that impaired hydration can affect our endurance, but what’s the consensus on anaerobic performance?

Water Water Everywhere…
With my background doing research on the effects of hydration status during exercise in the heat, it is only natural that we return to this topic every summer with the onset of warm weather. We have seen in general the problems brought about by sudden or prolonged heat waves every year in both the athletic and general population. In the former, we’ve seen many examples of athletes succumbing to heat exhaustion, from Gabrielle Andersson-Schiess at the first Olympic women’s marathon in 1984 to Paula Radcliffe at the Athens marathon in 2004. Much more seriously, we’ve witness major increases in deaths coinciding with massive heat waves in Europe (2003) and Chicago (1995).

To counteract the health and performance problems with hyperthermia, the primary approach has been to maintain proper hydration status. Though there remains some dissenters, the majority consensus amongst scientists is that maintaining adequate hydration both prior to and throughout exercise is the best method of preventing performance decrements in the heat. This has been outlined in detail in position statements by the American College of Sports Medicine (ACSM), the pre-eminent international exercise physiology society.

The main mechanism of protection appears to be by keeping blood volume high, thereby decreasing the strain imposed by the heart pumping blood to fuel both the active muscles and the skin to dissipate heat. You’re faced with a double whammy – you’re losing fluid from your blood to sweat, and at the same time your skin blood vessels are opening more and requiring greater blood flow to get rid of the heat produced by exercise. You may have seen this problem happen in the phenomenon of ”cardiovascular drift, where your heart rate rises over time even though you’re riding at the same power output.

Aerobic versus Anaerobic
The major caveat to the above “consensus” statement is that it mainly applies to prolonged endurance exercise, where the exercise is long enough for the above problems of decreased blood volume and increased skin blood flow demands to become important. But what if your main event is a short track event, or even a short age-group criterium? With the events short in overall duration and the focus on brief and very high-intensity efforts, does the same considerations apply?

The research here is much less certain towards the need to maintain full hydration status. My former department boss in my Ph.D. lab, Ira Jacobs, was one of the first to study this topic (2). Using the common anaerobic Wingate test on the cycle ergometer, consisting of 30 s of maximal sprinting, he tested trained athletes during a progressive dehydration to 5% of body weight. No significant impairment in peak power or mean power over the 30 s was observed throughout the dehydration.

The pattern continues with very recent studies. In a study just published in this month’s issue of Med Sci Sports Exerc Cheuvront and colleagues (1) exposed their trained subjects to either: 1) passive heat exposure with hydration maintenance (EU, but elevated core temperature due to heat exposure), or 2) passive heat exposure with dehydration of 2.7% (DH, dehydration + core temperature elevation). They then had the subjects perform 15 s Wingate sprints before the heat exposure, and also at 0, 30, and 60 min afterwards while recovering in a temperate (22oC) room.

Key Findings
No effect from hyperthermia. Core temperature was elevated significantly with both hydration programs, with 0.6 (EU) and 1.0oC (DH) core temperature rises after the 3 h passive rest in the heat. Core temperature dropped back to normal after 60 min rest in a thermoneutral room, though DH remained a bit higher than EU. Regardless, no differences were observed in any power output measures at any timepoint.

No effect from hypohydration Coupled with the above lack of significance with hyperthermia, no significant differences were observed between the two hydration conditions at any timepoint.

(Weight) Cutters
I’ve obviously only discussed two studies here, but the general view to date seems to be that mild to even moderate decreases in body weight does not seem to have a really huge performance impact when it comes to very brief, high-intensity exercise. Weight-cutting athletes in sports like wrestling, boxing, martial arts, and body-building have taken advantage of this for years, often dropping 5+ kg in the days leading up to a weigh-in to make a weight category. Most of this weight loss is primarily water. Then in the short time between weigh-in and competition, they would try to gain back as much weight as possible. Their sport fits the scientific profile quite well, consisting of brief 1-3 min bursts of supramaximal intensity with short recovery breaks.

Cycling Parallels?
Does this have any relevance to cycling? Well, almost all cycling disciplines, excepting some track events, are primarily aerobic and lasts much, much longer than the typical anaerobic test such as the Wingate. However, if you’re a kilo specialist or maybe even a pursuiter, then hydration prior to your event, while still probably a good thing, probably isn’t going to be the make or break for your performance.

The importance of not sacrificing hydration continues to be reinforced in cycling-specific studies. In one interesting twist on this idea, a group of scientists at the Australian Institute for Sport presented an abstract at the recent ACSM conference in Denver on whether mild hypohydration would really impact performance in a simulated road race. The course profile was roughly analogous to a Mont Ventoux stage, where there’s a long flattish run-in leading to a big mountain-top finish, where climbing ability and power-to-weight ratio becomes critical. They had subjects lose weight over the initial part of the test, then rode at a set pace to exhaustion on a simulated hillclimb. Despite a lighter weight and therefore theoretically less power output required to maintain climbing speed, time to exhaustion was the same whether subjects were normally or de-hydrated prior to the hill climb. So the lighter weight did not have any performance benefits, but may lead to problems with thermoregulation and cardiovascular dynamics.

So the ultimate moral of these stories? Unless your name is Chris Hoy and your quads measure near my waist size, then do not toss the bottle away and make sure you stay hydrated!

Hydration Re-Loaded: Reader Questions

Hydration Part 4: Hyponatremia, along with links to the previous three articles

1. Cheuvront, S. N., R. Carter, 3rd, E. M. Haymes, and M. N. Sawka. No effect of moderate hypohydration or hyperthermia on anaerobic exercise performance. Med Sci Sports Exerc. 38:1093-1097, 2006.
2. Jacobs, I. The effects of thermal dehydration on performance of the Wingate anaerobic test. Int. J. Sports Med. 1:21-24, 1980.

About Stephen:
Stephen Cheung is an Associate Professor of Kinesiology at Dalhousie University, with a research specialization in the effects of hydration and thermal stress on human physiology and performance. He can be reached for comments at [email protected].

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