Running on Empty: Hydration Lessons from Elite Lightweight Rowers

In the world of weight-categorised sports, being able to compete in a lower weight category can be the difference between becoming champion and ending up at the back of the field. “Making weight” is not easy, and athletes adopt a variety of methods (including dehydrate-rehydrate protocols) to achieve this.

But how can the everyday athlete learn from the painful and sometimes foolish methods used by lightweights? How can these methods help or hinder performance and health?

This year I was part of Adelaide University and South Australia’s lightweight rowing squad and witnessed/experienced some of the difficulties of competing as a lightweight first-hand. Going from a student diet consisting of constant snacking, carb-heavy meals and the “occasional” beer, to a diet fit for an elite athlete needing to lose 6 kg in 6 weeks proved all kinds of difficult!

You quickly get used to the feeling of “running on empty” in sessions and life becomes a constant battle between having enough fuel to train and recover and keeping that fuel clean and correctly portioned to continue to lose weight.



Maximum individual weight (kg)

Maximum crew average weight (kg)








As with many sporting adaptations, lightweight rowing was introduced to increase participation in the sport. The table above shows the weight restrictions for male and female lightweight rowers; athletes must weigh-in below these limits between 1 and 2 hours before they race. This short weigh-in to race time doesn’t allow for the extreme weight cutting seen in boxing or Mixed Martial Arts, meaning rowers have to be exceptionally precise with their rehydration tactics.

In order to train effectively and comfortably, lightweights can sit 6-8 kg over-weight when not competing. In fact, it’s not unusual for athletes to weigh 0.5-1 kg over in the immediate lead-up to racing. In order to race legally and without losing power, many lightweights will dehydrate prior to their weigh-in and then undertake ultra-rapid rehydration between the weigh-in and the gun going off.


How to stay hydrated during lightweight rowing races


A team-mate of mine weighed-in at the final state trials a full 2 kg over-weight, then sweated down to weight within the 1 hour weigh-in window! Safe to say he wasn’t in the best pre-race state, but he got to the start line, and in lightweight racing that counts for a lot!

Lightweights only need to weigh-in once per day of racing, so if your heats and finals are on the same day it’s far better for an athlete to struggle through the heat in a dehydrated state and then fully rehydrate for the final than to not make the weight and not be able to race at all…


Rapid Rehydration – what does the research say?

It’s far too easy to get excited by rapid rehydration and gulp down litres and litres of sports drink. But all this will do is make you feel sick on the start line with a need to pee and a stomach full of unprocessed fluid, which will ultimately limit your performance.

To avoid this, MA Penkman showed that with an appropriate rehydration protocol (see the diagram below), there’s no detrimental effect on 2000-m rowing performance compared with a normal well-hydrated state.

Rehydration protocol for lightweight rowers 

But, when full rehydration to pre-dehydration body weight is not achieved, rowing performance is significantly decreased. This shows that if you’re going into a session/race in a dehydrated state your performance will be compromised, but if you follow a very simple rapid rehydration protocol you can get race ready in less than 2 hours!

This is something I wish I had researched more before my first lightweight trial of the season. Being inexperienced and unfamiliar with how to approach lightweight racing, I had a serious carb and fluid binge, hoping 2 hours would be enough time to process the amount of fuel I’d taken in. Never have I felt sicker on a rowing machine, and if I’d had to back that 2000-m test up with another later in the day I would have been in serious trouble due to what I’d put my body through in that short space of time!


Hydration for lightweight rowers


Rehydration Done Right.

For athletes who don’t have to worry about making weight, it’s far wiser to maintain a proper, stable hydration status rather than rely on rapid rehydration. The National Athletic Trainers Association’s position on fluid replacement states that…

  • Athletes should consume 500-600 ml of water or sports drink 2-3 hours before exercise and 200-300 ml 10-20 minutes before exercise.
  • Fluid replacement should be close to sweat and urine losses and maintain a maximum body mass loss of 2%. This generally requires 200-300 ml approximately every 10-20 minutes during exercise.
  • Pay attention to how much you urinate and sweat in different sessions compared to normal.
  • When rehydrating rapidly, excess urine losses should be compensated for and fluid intake should be increased 25-50%.

Take note of the final point weight category athletes, this means you! If excess water is ingested, the body’s renal system will increase urine flow in an attempt to rapidly clear the “surplus” of fluid. The body will automatically increase fluid output to account for increased fluid input, regardless of the body’s hydration status. This means that the ingested volume of liquid must be increased to account for this.

This being said, the renal response to a large and sudden increase in fluid intake can be exploited by athletes looking for a late drop in weight. I would try and stay well hydrated in the week prior to weigh-in, right up until the evening before where I would cut my fluid intake. Even though fluid intake has been reduced, the body has a bit of a lag in recognising this and will continue to promote a large urine output. Drinks such as diet cola and black tea would also help to make you feel less hungry, but have slight diuretic effects (ie they make you pee more).


A word of warning on hyperhydration.

Hyperhydration can be far more harmful than dehydration. Drinking too much fluid that is low in sodium can cause hyponatremia and this can hamper your performance as well as make you pretty sick.


  • To rehydrate, you often need less fluid than you think.
  • Over-hydrating can lead to major performance decline/health risks.
  • It’s important to hydrate using the correct fluid (ie drinks containing sodium, like Precision Hydration, help you absorb and retain more fluid).

For a Personalised Hydration Strategy tailored to the demands of lightweight rowing and how you sweat, take our free online Sweat Test.


Jim Kay is an undergraduate in Sports and Exercise Science at the University of Bath. He is currently on placement at the South Australian Sports Institute, Adelaide and is a ASCA: Level 1 Strength & Conditioning Coach. He is currently a first reserve for the men’s lightweight coxless four at the Adelaide University Boat Club. 

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